Mohaka River Catchment State and Trends of River Water Quality and Ecology

October 2015 HBRC Report No. RM 14-12. Plan Number 4644.

Environmental Science - Water Quality and Ecology

October 2015 HBRC Report No. RM 14-12. Plan Number 4644.

Prepared By: Dr Adam Uytendaal Dr Andy Hicks Heli Wade Dan Fake Oliver Wade (Estuarine and Coastal Quality)

Reviewed By: Stephen Swabey – Manager – Environmental Science

Approved By: Iain Maxwell – Group Manager – Resource Management

Contents

Executive summary ...... 9

1 Introduction ...... 12 1.1 Description of the surface water system of the Mohaka Catchment ...... 12 1.2 Water Conservation (Mohaka River) Order 2004 ...... 12 1.3 Characteristics of the Upper, Middle and Lower Zones of the Mohaka River ...... 13 1.3.1 River characteristics of the Upper Zone, from the source to upstream of the Ripia River ...... 14 1.3.2 River characteristics of the Middle Zone, from the Ripia River to upstream of the Waipunga River ...... 15 1.3.3 River characteristics of the Lower Zone, from the Waipunga River to the coast ...... 15

2 Surface water quality of the Mohaka River catchment ...... 16 2.1 Long-term SoE monitoring data ...... 16 2.1.1 Water quality guidelines relevant to the Mohaka catchment ...... 17 2.1.2 Data summaries and visualisation ...... 20 2.1.3 Trend analyses ...... 21 2.1.4 Nutrients - total nutrients ...... 22 2.1.5 Nutrients - dissolved nutrients ...... 29 2.1.6 Toxicity – nitrate nitrogen and ammoniacal nitrogen ...... 34 2.1.7 Water clarity – black disc and turbidity ...... 37 2.1.8 Bacteriological water quality – E. coli ...... 45 2.1.9 Biological indicators – Macroinvertebrate Community Index ...... 48 2.1.10 Biological indicators – periphyton biomass ...... 52 2.1.11 Dissolved oxygen ...... 54 2.1.12 Compliance with NOF attribute bands under the NPS FW (2014) ...... 60 NOF attribute band – E. coli ...... 60 NOF attribute band – nitrate-nitrogen ...... 61 NOF attribute band – ammonia ...... 62 NOF attribute band – dissolved oxygen ...... 63 NOF attribute band – periphyton ...... 63 NOF attribute band summary ...... 64 2.1.13 Compliance with HBRC Regional Resource Management Plan (2006) surface water quality Environmental Guidelines ...... 65 2.2 Mohaka Catchment Concurrent Gauging Study ...... 68 2.3 Effects of Taharua River outflows on water quality of the upper Mohaka River ...... 74 2.3.1 Invertebrate drift and trout growth potential study ...... 75 2.3.2 Mohaka River longitudinal survey ...... 77 Dissolved inorganic nitrogen ...... 79

Mohaka River Catchment

Dissolved reactive phosphorus ...... 80 Water clarity ...... 81 Algal biomass and algal visual cover ...... 82 Phormidium ...... 84 Macroinvertebrate Community Index ...... 86 Macroinvertebrate biomass ...... 87 Longitudinal survey summary ...... 90 2.3.3 Recent nitrogen and phosphorus trends in the Taharua Catchment ...... 91 2.3.4 Possible targets for nitrogen loads from the Taharua Catchment ...... 98 2.4 Land intensification in the upper Rangitaiki catchment – potential impacts on the upper Waipunga River ...... 104 2.5 Nutrient limitation and Nutrient Diffusion Substrate studies ...... 106 2.6 25 years of monitoring data from the Mohaka River at State Highway 5 and State Highway 2...... 108 2.6.1 Trend analysis of NIWA NRWQMN data ...... 108 2.6.2 Time series analysis of DIN and DRP concentrations at Glenfalls ...... 110 2.7 The near-shore coastal environment...... 113

3 Native fish distribution in the Mohaka River ...... 114 3.1 Fish surveys in the Mohaka Catchment ...... 114 3.2 Native fish distribution and volcanism ...... 114 3.3 Pressures on native fish species ...... 116 3.4 Distribution of koura ...... 116

4 Upper Mohaka and Taharua trout habitat assessments – comment from Glen Mclean ...... 116

5 Summary and conclusion ...... 117

References ...... 120

Appendix A Site metadata and flow statistics for water quality monitoring sites ...... 123

Appendix B Summary statistics by flow ...... 125 All flows ...... 125 Less than three times median flow ...... 130 Less than median flow ...... 135 Less than lower quartile flow ...... 140

Appendix C Trend analysis results for water quality variables ...... 145

Appendix D Regional ranking tables for select water quality variables ...... 154 Regional SoE sites ranked by median total nitrogen 2009-2013 ...... 155 Regional SoE sites ranked by median total phosphorus 2009-2013 ...... 156

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Regional SoE sites ranked by median dissolved inorganic nitrogen 2009-2013 ...... 157 Regional SoE sites ranked by median dissolved reactive phosphorus 2009-2013 ...... 158 Regional SoE sites ranked by median nitrate 2009-2013 ...... 159 Regional SoE sites ranked by median black disc clarity 2009-2013 ...... 160 Regional SoE sites ranked by median turbidity 2009-2013 ...... 161 Regional SoE sites ranked by median E. coli 2009-2013 ...... 162 Regional SoE sites ranked by median MCI 2009-2013 ...... 163 Regional SoE sites ranked by median Total Phosphorus 2009-2013 ...... 164

Appendix E NPS-FW (2014) NOF attribute tables ...... 165 Periphyton NOF attribute table ...... 165 Nitrate NOF attribute table ...... 166 Ammonia NOF attribute table ...... 167 Dissolved Oxygen NOF attribute table ...... 168 Escherichia coli NOF attribute table ...... 169

Appendix F Mohaka catchment NOF periphyton compliance table ...... 170

Appendix G Nutrient and sediment loads and yields for long-term SoE monitoring sites ...... 171

Appendix H MfE benthic cyanobacteria alert-level framework ...... 172

Tables Table 1-1: Catchment characteristics of the major Mohaka River catchment zones. 14 Table 2-1: Summary of water quality guidelines for attributes observed in the Mohaka catchment. 18 Table 2-2: HBRC Regional Resource Management Plan (2006) water quality limits - “Environmental Guidelines – Surface Water Quality”. 19 Table 2-3: Trend analysis results for TN and TP for SoE monitoring sites of the Mohaka catchment. 28 Table 2-4: Trend analysis results for DIN and DRP for SoE monitoring sites of the Mohaka catchment. 34

Table 2-5: Trend analysis results for nitrate-nitrogen (NO3-N) for SoE monitoring sites of the Mohaka catchment. 37 Table 2-6: Trend analysis results for black disc clarity and turbidity for SoE monitoring sites in the Mohaka catchment. 45 Table 2-7: Trend analysis results for E. coli for SoE monitoring sites of the Mohaka catchment. 48 Table 2-8: MCI quality classes as defined by Stark and Maxted (2007). 49 Table 2-9: NPS-FW (2014) NOF bands for the E. coli attribute for Mohaka River catchment monitoring sites. 61 Table 2-10: NPS-FW (2014) NOF bands for the nitrate Attribute States for nitrate toxicity for Mohaka River catchment monitoring sites. 62 Table 2-11: NPS-FW (2014) NOF bands for the ammonia toxicity attribute for Mohaka River catchment monitoring sites. 63

Mohaka River Catchment 5

Table 2-12: NPS-FW (2014) NOF band summary for freshwater river attributes for Mohaka River catchment monitoring sites for the period 2009 to 2013. 64 Table 2-13: Comparison of measured dissolved oxygen, black disc, dissolved reactive phosphorus and ammoniacal nitrogen levels with HBRC RRMP (2006) Environmental Guideline levels. 66 Table 2-14: Comparison of measured DO, BD clarity and DRP values with HBRC RRMP (2006) Environmental Guideline levels. 67 Table 2-15: Past and present flow conditions for each of the Longitudinal Surveys. 78 Table 2-16: Proximity to the Taharua River at Twin Culverts surface water monitoring site, mean water residence time and depth of bores included in Figure 2-50. 94 Table 2-17: Trend analysis results for DRP and Nitrate-nitrogen for the Taharua River at Twin Culverts and Wairango SoE monitoring sites. 97 Table 2-18: Annual total nitrogen loads measured in-stream in the Taharua River. 101 Table 2-19: Annual total nitrogen loads measured in-stream in the Taharua River. 102 Table 2-20: Regression coefficients for relationships between DIN concentration and distance downstream of the Taharua confluence. 103 Table 2-21: Estimated DIN concentration at sites downstream of the Taharua River confluence based on average DIN reduction rates measured during the four longitudinal surveys and hypothetical DIN concentrations in the Mohaka River D/S of Taharua. 103 Table 2-22: Trend analysis results for, Black Disc, TP, DRP, TN and DIN for the Mohaka River at State Highway 5 (Glenfalls) NIWA NRWQMN monitoring site. 109 Table 2-23: Trend analysis results for, Black Disc, TP, DRP, TN and DIN for the Mohaka River at State Highway 2 (Raupunga) NIWA NRWQMN monitoring site. 109

Figures Figure 1-1: The Mohaka River at Willowflat carrying an elevated suspended sediment load during high flow conditions...... 16 Figure 2-1: Long-term SoE monitoring sites of the Mohaka catchment referred to in this report.17 Figure 2-2: Total nitrogen (TN) levels at SoE monitoring sites...... 24 Figure 2-3: Total phosphorus (TP) levels at SoE monitoring sites...... 25 Figure 2-4: 5 year median total nitrogen (TN) levels at SoE monitoring sites including trend direction...... 26 Figure 2-5: 5 year median total phosphorus (TP) levels at SoE monitoring sites including trend direction...... 27 Figure 2-6: Dissolved inorganic nitrogen (DIN) levels at SoE monitoring sites...... 30 Figure 2-7: Dissolved reactive phosphorus (DRP) levels at SoE monitoring sites...... 31 Figure 2-8: 5 year median dissolved inorganic nitrogen (DIN) levels at SoE monitoring sites including trend direction...... 32 Figure 2-9: 5 year median dissolved reactive phosphorus (DRP) levels at SoE monitoring sites including trend direction...... 33

Figure 2-10: Nitrate - nitrogen (NO3-N) levels at SoE monitoring sites...... 35

Figure 2-11: 5 year median nitrate-nitrogen (NO3-N) levels at SoE monitoring sites, including trend direction...... 36 Figure 2-12: Council staff measuring black disc sighting distance in the field...... 38 Figure 2-13: Water clarity measured as black disc horizontal sighting distance for SoE monitoring sites...... 39

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Figure 2-14: Water clarity measured as turbidity (NTU) for SoE monitoring sites...... 40 Figure 2-15: 5 year median Black Disc (BD) water clarity levels at SoE monitoring sites including trend direction...... 41 Figure 2-16: 5 year median turbidity levels at SoE monitoring sites including trend direction...... 42 Figure 2-17: The relationship between black disc sighting distance and turbidity for several mainstem Mohaka River SoE monitoring sites across the Mohaka catchment...... 43 Figure 2-18: Bacteriological water quality levels measured as E. coli counts (Colony Forming Units / 100ml) at SoE monitoring sites...... 46 Figure 2-19: 5 year median E. coli levels at SoE monitoring sites including trend direction...... 47 Figure 2-20: MCI levels measured at SoE monitoring sites...... 50 Figure 2-21: 5 year median Macroinvertebrate Community Index (MCI) levels at SoE monitoring sites...... 51 Figure 2-22: Periphyton biomass levels measured at SoE monitoring sites...... 53 Figure 2-23: Photos of excessive filamentous green algae growth in the Ngaruroro River at Whanawhana after extended periods of low flow...... 54 Figure 2-24: Schematic of the major processes influencing dissolved oxygen concentration in rivers...... 55 Figure 2-25: Dissolved oxygen % saturation at SoE monitoring sites...... 56 Figure 2-26: Dissolved oxygen concentration at SoE monitoring sites...... 57 Figure 2-27: 5 year median dissolved oxygen % saturation levels at SoE monitoring sites...... 58 Figure 2-28: 5 year median dissolved oxygen concentration levels at SoE monitoring sites...... 59 Figure 2-29: Locations of Mohaka Catchment Concurrent Gauging study sites...... 68 Figure 2-30: Mohaka Catchment Concurrent Gauging study results for Total Nitrogen (TN) concentration...... 70 Figure 2-31: Mohaka Catchment Concurrent Gauging study results for Total Phosphorus (TP) concentration...... 70 Figure 2-32: Mohaka Catchment Concurrent Gauging study results for DIN concentration...... 71 Figure 2-33: Mohaka Catchment Concurrent Gauging study results for DRP concentration...... 71 Figure 2-34: Mohaka Catchment Concurrent Gauging study results for Total Nitrogen (TN) instantaneous yield...... 73 Figure 2-35: Mohaka Catchment Concurrent Gauging study results for Total Phosphorus (TP) instantaneous yield...... 73 Figure 2-36: Comparison of Mohaka River water quality upstream and downstream of the Taharua River confluence...... 74 Figure 2-37: Locations of longitudinal survey study sites...... 77 Figure 2-38: Mohaka River flows around the time the longitudinal surveys were carried out...... 78 Figure 2-39: Mohaka River Longitudinal Survey results for Dissolved Inorganic Nitrogen (DIN). ... 80 Figure 2-40: Mohaka River Longitudinal Survey results for Dissolved Reactive Phosphorus...... 81 Figure 2-41: Mohaka River Longitudinal Survey results for water clarity (black disc)...... 82 Figure 2-42: Mohaka River Longitudinal Survey results of algal biomass...... 83 Figure 2-43: Mohaka River Longitudinal Survey results for PeriWCC...... 84 Figure 2-44: Mohaka River Longitudinal Survey study results of Phormidium (cyanobacteria) cover...... 85 Figure 2-45: Mohaka River Longitudinal Survey study results of Macroinvertebrate Community Index (MCI)...... 86

Mohaka River Catchment 7

Figure 2-46: Mohaka River Longitudinal Survey study results of Quantitative Macroinvertebrate Community Index (QMCI)...... 87 Figure 2-47: Mohaka River Longitudinal Survey study results of EPT taxa biomass for Survey 1. .. 89 Figure 2-48: Time series of nitrate-nitrogen concentration measured in the headwaters of the Taharua River at the Wairango monitoring site...... 91 Figure 2-49: Time series of nitrate-nitrogen concentration measured in the headwaters of the Taharua River at the Twin Culverts monitoring site...... 92 Figure 2-50: Time series of nitrate-nitrogen concentration measured in the headwaters of the Taharua River at the Twin Culverts monitoring site and nitrate-nitrogen concentration measured in groundwater bores in the local area...... 93 Figure 2-51: Time series of dissolved reactive phosphorus concentration measured in the headwaters of the Taharua River at the Wairango monitoring site...... 95 Figure 2-52: Time series of dissolved reactive phosphorus concentration measured in the headwaters of the Taharua River at the Twin Culverts monitoring site...... 96 Figure 2-53: Relationship between total nitrogen (TN) concentration in the Mohaka River downstream of Taharua River confluence and the Mohaka River upstream of Taharua River confluence...... 98 Figure 2-54: Relationship between total nitrogen (TN) concentration in the Mohaka River downstream (D/S) of Taharua River confluence and the Taharua River at Red Hut monitoring site...... 99 Figure 2-55: Relationship between Taharua River total nitrogen (TN) concentration (measured at Red Hut) and the Mohaka River D/S Taharua River confluence dissolved inorganic nitrogen (DIN) concentration...... 100 Figure 2-56: Total nitrogen (TN) concentration measured in the Taharua River at Red Hut...... 101 Figure 2-57: Linear regression of reductions in dissolved inorganic nitrogen (DIN) for the Mohaka River Longitudinal Surveys...... 102 Figure 2-58: Dairy farming in the headwaters of the Waiarua Stream (left) and production forestry (mid ground) in the headwaters of the Waipunga River (right)...... 104 Figure 2-59: Time series of nitrate-nitrogen concentration measured in the headwaters of the Waipunga River at two sites...... 105 Figure 2-60: Time series of nitrate-nitrogen concentration measured in the headwaters of the Taharua River at the Twin Culverts monitoring site compared with nitrate-nitrogen concentration in the upper Waipunga River at the Waiarua River monitoring site. . 106 Figure 2-61: Nutrient diffusing substrate (NDS) results for the Mohaka River upstream of the Taharua River April 2011...... 107 Figure 2-62: Time series of Dissolved Inorganic Nitrogen (DIN) concentration measured in the Mohaka River at State Highway 5 at the NIWA NRWQMN site...... 111 Figure 2-63: Time series of Dissolved Reactive Phosphorus (DRP) concentration measured in the Mohaka River at State Highway 5 at the NIWA NRWQMN site...... 112 Figure 2-64: Time series of DIN:DRP ratios measured in the Mohaka River at State Highway 5 at the NIWA NRWQMN site...... 112 Figure 3-1: Fish species diversity of the Mohaka River catchment...... 115

8 Mohaka River Catchment

Executive summary This report summarises state and trends in river water quality and ecology across the Mohaka River catchment. The report is one of six State of Environment (SoE) reports for the Hawke’s Bay region summarising river water quality and ecology data. The reports form the detailed regional 5 yearly review of surface water quality and ecology and are an update from the previous round of reports completed in 2009.

The six SoE reports cover the following river catchments and water management zones:

o (A) Porangahau River/Southern Coastal o (B) Tukituki River o (C) TANK (Tutaekuri River, Ahuriri Estuary, Ngaruroro River, Karamu Stream) o (D) Mohaka River (bordered in black) o (E) Waikari River/Esk River/Aropoanui River o (F) Wairoa River/Northern Coastal

Mohaka River Catchment

The Mohaka River is a large river approximately 160 km in length with its headwaters originating in the Kaimanawa Forest Park. It discharges to sea near the Mohaka Settlement 22 km southwest of Wairoa. The river has a catchment of 2440 km2 and is highly valued for its scenic, cultural, and recreational qualities. The river has a mean annual flow of 80 m3/s (cubic metres per second) measured at Raupunga making it Hawke’s Bay’s second largest river.

A Water Conservation Order (WCO) is in place on the Mohaka River (SR 2004/397) under the Resource Management Act 1991. This conservation order was granted in 2004 to protect the outstanding characteristics and features of the Mohaka River.

Water quality monitoring in the Mohaka River catchment has been carried out by HBRC since 1980 as part of the State of the Environment (SoE) programme. Emerging water quality issues in the Taharua sub-catchment, located in the upper Mohaka catchment, have resulted in the Mohaka catchment becoming the subject of a special investigation programme, with monthly sampling occurring at key sites since 2008.

Generally, the Mohaka catchment has not been subject to intensive land-use pressures. However, land-use in the Taharua sub-catchment affects the overall trophic state of water quality of the upper catchment. In the lower catchment, concerns have been expressed by the community about impacts from forestry on Mohaka waterways including soil erosion, phosphorus loss and generation of excessive woody debris, particularly around harvesting operations.

Most of the Mohaka catchment has excellent nutrient water quality, with very low levels of nitrogen and low to moderate levels of phosphorus, compared to natural background levels. Stream ecological health is also very good with macroinvertebrate communities dominated by pollution sensitive taxa.

Overall, the following conclusions can be drawn from the data, analysis and information presented in this report:

. Most sampling sites across the Mohaka River have excellent water quality.

. Overall, based on macroinvertebrate assessments, the ecological health of the Mohaka River is excellent.

. The results show periphyton biomass levels to be in excellent condition throughout the upper and middle catchment, based on measurements taken by HBRC over the course of the SoE monitoring program.

. Current water quality issues upstream of the Ripia River are largely due to intensive farming on free draining pumice soils in the Taharua sub-catchment.

. The effects of Taharua outflows on water quality downstream can be summarised as follows:

− Nitrogen contributed from the Taharua River dominates the in-stream nitrogen levels of the upper Mohaka River.

− Dissolved Inorganic Nitrogen (DIN) concentrations increase markedly downstream of the Taharua confluence and remain elevated for over 60 km downstream.

− Dissolved Reactive Phosphorus (DRP) concentrations, although showing slight elevation downstream of the Taharua confluence, return to very low levels after approximately 15 km.

10 Mohaka River Catchment

. Changes in water quality at surface water monitoring sites in the Taharua River can be summarised as follows:

− Over the last 10 years, there have been significant increases in nitrate-nitrogen concentrations measured at the Wairango and Twin Culverts SoE monitoring sites, which relate to land-use changes and historical farming practices.

− Improved farming practices over the last 6 years appear to have improved nitrate-nitrogen concentrations measured in-stream (and in groundwater monitoring wells) at the Wairango and Twin Culverts monitoring sites.

− Nutrient mitigation measures undertaken over recent years have improved in-stream DRP concentrations.

. Reductions in water clarity are the most significant change in water quality through the lower zone.

Mohaka River Catchment 11

1 Introduction

1.1 Description of the surface water system of the Mohaka Catchment The Mohaka River is a large 7th order river, according to the Strahler ordering system (Strahler, 1952), approximately 160 km in length, with its headwaters in the Kaimanawa Forest Park. It discharges to sea near the Mohaka Settlement 22 km southwest of Wairoa. The river has a catchment area of 2440 km2 and is highly valued for its scenic, cultural, and recreational qualities. The river has a mean annual flow of 80 m3/s (cubic metres per second) measured at Raupunga, making it Hawke’s Bay’s second largest river (Stansfield, 2008).

The river is a single-thread gravel-bed river situated in incised river valleys, gorges and discharging as a braided river over a coastal marginal floodplain. It has good quality in-stream habitat for most of its length, with regular riffles, pools and bends and a predominantly, large cobble/cobble streambed. Riparian margins are well protected in the upper reaches, where the river flows through the Kaweka Forest Park, with few breaks in vegetation cover or signs of erosion. The lower reaches are characterised by less riparian protection, with intermittent patches of stream bank erosion.

Generally, the Mohaka catchment has not been subject to intensive land-use pressures. However, land-use in the Taharua sub-catchment affects the overall trophic state of water quality of the upper catchment. Concerns have been expressed by the community about impacts from forestry on Mohaka waterways including soil erosion, phosphorus loss and generation of excessive woody debris, particularly around harvesting operations.

1.2 Water Conservation (Mohaka River) Order 2004 A Water Conservation Order (WCO) is in place on the Mohaka River (SR 2004/397) under the Resource Management Act 1991. This conservation order was granted in 2004 to protect the outstanding characteristics and features of the Mohaka River, including:

. “an outstanding trout fishery in the main-stream upstream of the State Highway 5 bridge and in the tributaries; and

. “outstanding scenic characteristics in the Mokonui Gorge [also known as the Maungataniwha Gorge]; and

. “outstanding scenic characteristics in the Te Hoe Gorge; and

. “an outstanding amenity for water-based recreation from the State Highway 5 bridge to Willow Flat”.

The Water Conservation (Mohaka River) Order states that no water permit may be granted under the Resource Management Act 1991 to dam the Mohaka or its tributaries, unless the effects of the dam on water levels only occur downstream of the Te Hoe Gorge. A permit is required to carry out activities that may affect the outstanding characteristics or features that are valued in the Mohaka River catchment.

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The key water quality attributes identified for the WCO were:

1. The outstanding trout fishery in the main stem of the Mohaka River and in its tributaries. The evidence identified for this included the following:

a. High catch rates of large fish b. Variety of river settings and fishing challenges for both novice and expert fishers c. Accessibility d. Popularity e. National and international reputation f. Year round fishing g. Ability of the river to rapidly clear (of sediment) after rain h. Presence of brown & rainbow trout i. Compatibility with other recreational activities

2. The outstanding amenity for water-based recreation upstream of Willowflat, for which the evidence was:

a. The Mohaka is the only significant river offering multi-day river-based trips in the North Island that has not been modified by hydro-electric power developments b. There are multiple convenient access points c. River flows through papa [mudstone] gorges with large house-sized boulders and highly demanding rapids for experienced canoeists d. Highly valued because it provides grade 4 and 5 water which can only be found on a few rivers in NZ e. Does not suffer from low flow in summer

1.3 Characteristics of the Upper, Middle and Lower Zones of the Mohaka River The catchment characteristics of the Mohaka River are summarised in Table 1-1. The geology attributes in Table 1-1 are drawn from the River Environment Classification system (REC), which maps physical characteristics of New Zealand rivers (Snelder et al., 2010). This information reflects underlying geology and source of river water. The summary descriptions of geology derived from the REC cover a wide range of lithologies. Some of these geological definitions include several types of rock, which behave differently when weathered and transported to the river. For example, mudstone when weathered, produces significant concentrations of suspended sediment in rivers, but calcareous sandstone and limestone will produce, when weathered, a lower volume of larger quartz grains, and less suspended sediment. The effects of geological variation cannot be considered in this work, since insufficient spatial detail is available in the ecological observations. Spatial variability of geology will be examined in future work.

Included here are the proportions of individual land cover types in the catchment, derived from the Land Cover Database (New Zealand) version 3 (LCDB3).

Three arbitrary Mohaka River catchment zones have been identified in this report - the “upper zone”, “middle zone” and “lower zone” (shown as A, B and C in Figure 2-1). The zones partition the catchment into areas of similar recreational value, geology and topography, water quality characteristics and river uses.

Mohaka River Catchment 13

Table 1-1: Catchment characteristics of the major Mohaka River catchment zones. Information has been taken from the River Environment Classification (REC), the Land Cover Data Base (New Zealand) version 3 (LCDB3) and AGRIBASE. Zone Source of flow Geology Land cover/land use (REC) (REC) (LCDB3/AGRIBASE)

Upper Zone Cool wet climate with Volcanic acidic 63% Arable 0% flow Hard sedimentary 37% Dairy 5.2% originating from hill Sheep/Beef 7.2% country OR Deer 0.1% Cool extremely wet Forestry 5.7% climate with source of Native bush 81% flow originating from mountain country Middle Zone Cool wet climate with Volcanic acidic 76% Arable 0.2% flow Hard sedimentary 19% Dairy 0% originating from hill Miscellaneous 4% Sheep/Beef 26.5% country Soft sedimentary 1% Deer 1.2% Forestry 24.2% Native bush 47.8% Lower Zone Cool wet or warm wet Volcanic acidic 59% Arable 0.2% climate with flow Hard sedimentary 28% Dairy 0.3% originating from Miscellaneous 7% Sheep/Beef 9% lowland country Soft sedimentary 6% Deer 0.8% Forestry 21.9% Native bush 67.2%

1.3.1 River characteristics of the Upper Zone, from the source to upstream of the Ripia River The upper zone of the Mohaka River catchment, upstream of the Ripia River tributary, is prized for its naturalness and its pristine wilderness. It is valued for recreational fishing and its clear, cool waters that originate from the Kaimanawa Ranges and Kaweka Ranges forest parks.

According to the River Environment Classification (REC) system (Table 1-1) most of the upper zone catchment can be described as ‘cool wet climate’, with water originating from hill country, or ‘cool extremely wet climate’ from mountain sources (Snelder et al., 2010). Rivers in this part of the catchment are either low- or medium-order streams with high- or medium-gradient valley landforms. The geology of the upper zone catchment is characterised by acid volcanic or hard sedimentary rocks. The LCDB3 shows native or indigenous forest and pastoral activities such as sheep, beef or deer, with some exotic forestry. (Table 1-1).

The upper zone has the highest proportion of dairying land-use, with Taharua dairy farms covering approximately 5% of the area. With the exception of dairying, all land-uses in the upper zone are low intensity and are unlikely to experience nitrogen leaching.

14 Mohaka River Catchment

1.3.2 River characteristics of the Middle Zone, from the Ripia River to upstream of the Waipunga River Mohaka River flows downstream of the Ripia River confluence are larger than upstream. The increased flows in this middle zone of the river make it more morphologically diverse and energetic with greater occurrence of large boulders, rapids, chutes and plunge pools. The Ripia River is a 5th order tributary of the Mohaka River, with its headwaters near the upper Rangitaiki River catchment on Lochinver Station. The habitat in the middle catchment is less wild then in the upper zone, but is still considered natural. The middle zone is valued for its water based recreation opportunities, including fishing, camping, kayaking and rafting.

According to the REC (Table 1-1), the middle zone of the catchment experiences ‘cool wet climate’ with flow originating from hill country. The rivers in this section of the catchment are either low- or medium-order streams, with high- or medium-gradient valley landforms. The middle zone of the catchment includes acid volcanic or hard sedimentary rocks, with occasional miscellaneous soft sedimentary deposits. The dominant LCDB3 land cover is native or indigenous forest, covering almost half of this zone of the catchment. Sheep/beef and production forestry are the two other significant land-cover types, each covering about a quarter of the land in this part of the catchment (Table 1-1).

1.3.3 River characteristics of the Lower Zone, from the Waipunga River to the coast The lower zone of the Mohaka River catchment, downstream of the Waipunga River, is very dynamic morphologically and is valued for its natural character. The Te Hoe Gorge is prized for its scenic character and the stretch of water from State Highway 5 down to Willow Flat is also noted in the Water Conservation Order (SR2004/397) as having outstanding water-based recreation and it is especially prized for kayaking and rafting (Booth et al., 2012).

The upper part of the lower catchment zone has ‘cool wet climate’ with most flow originating from hill country, according to the REC. The main land cover here is indigenous forest on hard sedimentary to acid volcanic rocks, with medium- to high-gradient streams and medium- to high-gradient valley landforms.

The altitude of the upper part of the lower catchment zone is typically 300 m to 600 m above sea level, although mountain parts of the catchment are situated at a higher altitude, typically 900 m to 1300 m above sea level. Here the climate is considered ‘cool and extremely wet’. The geology consists of hard sedimentary or acid volcanic rocks. Native bush is the dominant land cover identified in the LCDB3, on about two-thirds of the land, followed by production forestry at about 21% of land use (Table 1-1). Sheep/beef is of similar significance as in the upper zone (Table 1-1). All land-uses are relatively low intensity (Menneer et al., 2004) and pose little risk in relation to nitrogen leaching.

The lower part of the lower zone (downstream of the Te Hoe confluence) is quite different to the rest of the Mohaka catchment, as it has cool wet or warm wet climate with lowland source of flow. The land cover is mainly pasture or exotic forestry. The geology of this section is also different, with acid volcanic and soft sedimentary rocks (Table 1-1).

The increased prevalence of soft-sedimentary rocks compared to the upper catchment causes naturally higher suspended sediment loads in this zone of the river, observed as increased turbidity and reduced water clarity during times of increased flow (Figure 1-1).

Mohaka River Catchment 15

Figure 1-1: The Mohaka River at Willowflat carrying an elevated suspended sediment load during high flow conditions. The soft sedimentary rock typical of the river valley in the lower Mohaka River is visible in the background and foreground of the picture.

2 Surface water quality of the Mohaka River catchment

2.1 Long-term SoE monitoring data Water quality monitoring in the Mohaka River catchment has been carried out by HBRC since 1980 as part of the State of the Environment (SoE) programme. The SoE monitoring programme was undertaken on a quarterly basis until June 2012, when monthly sampling began across the whole region.

Emerging water quality issues in the Taharua catchment in the early 2000’s have resulted in the Mohaka catchment becoming the subject of a special investigation programme, with monthly sampling occurring at key sites in this catchment since 2008. Over this time a total of 45 sites have been sampled. Of these, 13 are currently sampled as part of the SoE monitoring programme. Figure 2-1 shows the location of the SoE monitoring sites that are reported on in this section. (See Appendix A for a detailed monitoring site listing).

Water quality parameters routinely measured across SoE monitoring sites include the following field-based measurements:

. Turbidity (NTU) . Visual clarity (as black disc sighting distance) . Dissolved oxygen (mg/l) . Conductivity (S/cm) . pH . Water temperature (oC)

16 Mohaka River Catchment

Visual periphyton assessments were introduced to the programme in 2011 and are undertaken at most sites, subject to flow conditions and substrate type. Water samples are collected at each site and analysed for total and dissolved nutrients (nitrogen and phosphorus), suspended solids, and faecal bacteria (as E. coli).

Periphyton biomass estimates (as chlorophyll-a) are made from rock scrapes at the Mohaka River upstream and downstream of the Taharua River confluence and at the Mohaka downstream of the Ripia River confluence.

Particular effort has been made to investigate the effects of dairy conversions in the Taharua catchment on water quality, nuisance periphyton growth and visual water clarity in the upper Mohaka River.

Figure 2-1: Long-term SoE monitoring sites of the Mohaka catchment referred to in this report. Three arbitrary Mohaka River catchment zones have been included in this report being the “upper zone” (A), “middle zone” (B) and “lower zone” (C). Characteristics of each of the zones is provided in Section 1.3.

2.1.1 Water quality guidelines relevant to the Mohaka catchment Environmental guidelines are often used to describe the general state of a natural resource, even though they may not be directly applicable in a regulatory context. These guidelines are not intended to provide limits for the quality of freshwater bodies. In the following analysis the guidelines are discussed to provide context for the observations made in the Mohaka catchment.

Table 2-1 outlines several relevant ‘trigger values’ and suggested water quality limits that are included in graphical summaries throughout Section 2. The various trigger values, guidelines and limits are discussed in the following paragraphs.

Mohaka River Catchment 17

The ANZECC (2000) guidelines are used to indicate environmental conditions in “baseline” (essentially unaffected) or “pseudo-baseline” (lightly impacted) catchments (Davies-Colley, 2000). The ‘trigger’ values are based on water quality conditions taken from sites from the NIWA National River Water Quality Monitoring Network (NRWQMN) (Davies-Colley, 2000). The trigger values relate to 80th percentile or 20th percentile values for the data range taken from the NRWQMN.

The main aim of the ANZECC guidelines is ‘to provide an authoritative guide for setting water quality objectives required to sustain current, or likely future, environmental values for natural and semi-natural water resources in Australia and New Zealand’ (ANZECC 2000).

In the development of the ANZECC (2000) trigger values, Davies-Colley (2000) states: ‘running medians of water quality data measured in monitoring programmes may be compared with these trigger values. If the median value of a water quality variable for a particular site exceeds the trigger value, then it is intended to “trigger” a response on the part of water managers, which might be to initiate special sampling or carry out an investigation of reasons for the degraded water quality.’

The Biggs (2000) NZ periphyton guidelines are used nationally to set limits around periphyton biomass as well as identifying possible values for setting nutrient limits or targets to manage nuisance periphyton growth.

The Hickey (2013a) Nitrate Protection Guidelines represent the most up-to-date assessment of nitrate toxicity and provide guidance around nitrate concentration thresholds, both as annual median and annual concentration peaks (95th percentile), for managing nitrate toxicity risk.

Hay et al. (2006) identified several limits for the protection of trout fisheries in their report ‘Water quality guidelines to maintain trout fishery values’. The report was produced on behalf of Horizons Regional Council in the development of their One Plan.

The MfE/MoH (2003) ‘microbiological water quality guidelines for marine and freshwater areas’ are used extensively to assess ‘risk’ in relation to contact recreation and exposure to bacteria present in aquatic environments.

The HBRC (2006) Regional Resource Management Plan (RRMP) identifies several water quality targets for nutrients and other water quality variables, including the limit for dissolved oxygen saturation (Table 2-2). This limit also aligns with the limit identified in the RMA 1991 for the protection of trout fisheries.

Table 2-1: Summary of water quality guidelines for attributes observed in the Mohaka catchment. Variable1 Guideline / Trigger Source TN – ANZECC Lowland 0.614 mg/l ANZECC (2000) TN – ANZECC Upland 0.295 mg/l ANZECC (2000) TP – ANZECC Lowland 0.033 mg/l ANZECC (2000) TP – ANZECC Upland 0.026 mg/l ANZECC (2000)

DIN/NOx-N - Tukituki Plan Change 6 0.800 mg/l HBRC (2014)

DIN/NOx-N – ANZECC Lowland 0.444 mg/l ANZECC (2000)

DIN/NOx-N – Periphyton growth 20 day accrual < 0.295 mg/l Biggs (2000)

DIN/NOx-N – ANZECC Upland 0.167 mg/l ANZECC (2000)

1 TN = total nitrogen; TP = total phosphorus; DIN = dissolved inorganic nitrogen; NOx-N = oxides of nitrogen or nitrate/nitrite- nitrogen; DRP= dissolved reactive phosphorus; NO3-N = nitrate – nitrogen; Clarity = black disc sighting distance; E. coli = faecal bacteria levels measured as E. coli in colony forming units (CFU) / 100ml; MCI = Macroinvertebrate Community Index; DO% saturation = % dissolved oxygen saturation.

18 Mohaka River Catchment

Variable1 Guideline / Trigger Source DRP – Periphyton growth 20 day accrual < 0.010 mg/l Biggs (2000) DRP – ANZECC Lowland 0.010 mg/l ANZECC (2000) DRP – ANZECC Upland 0.009 mg/l ANZECC (2000)

NO3-N Toxicity ‘90% species protection’ < 3.8 mg/l Hickey (2013)

NO3-N Toxicity ‘95% species protection’ < 2.4 mg/l Hickey (2013)

NO3-N Toxicity ‘99% species protection’ < 1.0 mg/l Hickey (2013) Clarity – contact recreation > 1.6 m ANZECC (2000); HBRC RRMP (2006) Clarity – ‘Significant’ trout fishery > 3.5 m Hay and Hayes (2006) Clarity – ‘Outstanding’ trout fishery > 5.0 m Hay and Hayes (2006) E. coli – Contact recreation (health) Red alert > 550 (CFU/100ml) MfE/MoH (2003) E. coli – Contact recreation (health) Amber alert > 260 (CFU/100ml) MfE/MoH (2003) Periphyton biomass - biodiversity < 50 mg/m2 Biggs (2000) Periphyton biomass – aesthetic/recreation < 120 mg/m2 Biggs (2000) Hay and Hayes (2006); MCI ‘Outstanding’ trout fishery; Excellent quality > 120 Stark and Maxted (2007) Hay and Hayes (2006); MCI ‘Significant’ trout fishery; Good quality > 100 Stark and Maxted (2007) DO % saturation – protection of trout fisheries > 80% RMA (1991); HBRC RRMP (2006)

Table 2-2: HBRC Regional Resource Management Plan (2006) water quality limits - “Environmental Guidelines – Surface Water Quality”. The table has been taken from Table 7, page 99, Section 5.4 of the RRMP. Variable Guideline2 The temperature of the water should be suitable for Temperature sustaining the aquatic habitat The concentration of dissolved oxygen should exceed Dissolved oxygen 80% of saturation concentration The concentration of ammoniacal nitrogen (NH4-N) Ammoniacal nitrogen should not exceed 0.1 mg/l The concentration of dissolved reactive phosphorus Dissolved reactive phosphorus should not exceed 0.015 mg/l In areas used for recreation, the horizontal sighting Clarity range of a 200mm black disc should exceed 1.6m

2 These guidelines apply after reasonable mixing and disregarding the effect of any natural perturbations that may affect the water body, as set out in Policy 72 of the HBRC RRMP (2006) that states that the guidelines for the variables included in Table 2-2 apply “at or below median flows”.

Mohaka River Catchment 19

2.1.2 Data summaries and visualisation Box plots have been used throughout Section 2.1 to summarise water quality data. The sites are ordered from right to left in ascending order based on distance from the sea along the river channel. Sites are grouped by their position in the same major sub-catchment. For example, the Waipunga River confluence is closer to the sea than the Ripia River confluence, so Waipunga River SoE monitoring sites appear to the right of the Ripia River monitoring sites in the graph.

KEY POINT: Box plots graph data as a box representing statistical values. The lower boundary of each box indicates the 25th percentile, a line within the box marks the median, and the higher boundary of each box indicates the 75th percentile. The line at the end of the whiskers (error bars) above and below the box indicate the 90th and 10th percentiles respectively.

Catchment maps have been used to spatially represent changes in water quality data based on the median value of observations taken over the last 5 years for the water quality variable in question (from January 2009 to December 2013). The catchment maps include arrows indicating the direction of statistically significant trends, with blue arrows for improvement and red arrows for deterioration of the variable in question. Sites without an arrow did not exhibit a statistically significant trend. Six sites have no trend results because they did not contain the required 8 years of record between 2004 and 2013. These sites are identified on each of the catchment water quality maps.

Tables of summary statistics are presented in Appendix B, to provide additional context to the changes in water quality variables under differing flow conditions. For example, the levels of faecal bacteria in rivers during high flows may not be relevant for bathing, because people will not be swimming during high flows. The conditions most likely to be experienced by bathers can be found in the < Lower Quartile Flow table (i.e. low flows).

20 Mohaka River Catchment

Box plots, catchment water quality summary maps and statistical summaries of water quality variables all use the last 5 years of data to represent current conditions throughout the catchment. Data obtained from sites during all flow conditions was used for these comparisons.

2.1.3 Trend analyses Trend analysis of environmental monitoring data is important because environmental characteristics may exhibit trends which indicate particular issues are changing in significance. For example, if nitrate concentrations are increasing or decreasing at a particular site, the cause and significance of these changes may need to be identified.

Trend analyses in this report use non-parametric statistical approaches similar to those used in recent nationwide water quality analyses undertaken for the LAWA project (Ballantine, 2012), which involved seasonal Kendall trend tests. Some sites had a long term monthly record, whereas others only had monthly sampling for the latter part of the record. For these latter sites, a quarterly sampling interval was applied to the entire time period using median quarterly values, to avoid biasing the trend analyses to the latter part of the period. January was used as the ‘start’ month, i.e. the seasons were: Jan-Mar; Apr-Jun, Jul-Sep; Oct-Dec, to be consistent with the LAWA project.

In some reporting of trend analyses, adjustment of the results is made to accommodate variation in river flow. This is known as flow adjustment. Flow adjustment is not completed on data hosted by LAWA when undertaking trend analyses, and there currently is no industry standard for flow adjustment for trend analyses in water quality. For these reasons, no flow adjustment was undertaken for the trend analyses presented here.

The seasonal Kendall tests help identify whether variability in the data is randomly distributed, or whether a significant trend exists over time. For example, did most of the higher ranked values occur in the last few years, or did higher values occur randomly over time? It was decided that a ‘significant’ trend existed where there was a less than 5% probability that the observed data was obtained by chance.

To estimate the strength of trends over time, a Theil-Sen slope estimator was used. The non-parametric Theil- Sen slope estimator estimates the median slope amongst lines through all pairs of points in the dataset. This approach is effective at estimating the true slope in water quality data series because it is less sensitive to outliers.

The values derived from the Theil-Sen slope estimator are referred to as “Percent Annual Change” (PAC). A trend in PAC was considered meaningful if the PAC was greater than 1% per year. For some variables, such as black disc distance, an increase in observed values is improvement (e.g., we can see further in the water). For other variables such as phosphorus concentration, an increase in observed values represents a deterioration (i.e. there is more phosphorus in the water).

In all tables that present trend results, the changes are represented in bold when they are significant (i.e., p value is less than 0.05). Given a significant trend for a particular variable, the PAC is highlighted in blue if there was a significant improvement in the water quality variable, and highlighted in red if there was a significant deterioration in the water quality variable.

The discussion around improvement and deterioration does not relate to natural enrichment of streams and rivers that occurs from the headwaters of the catchment to the coast, but instead to short-term site-specific increase or decrease in a water quality variable. The only explanation in these situations is likely to be an anthropogenic influence.

Mohaka River Catchment 21

The full details of trend analyses are presented in Appendix C, and a summary of trend results is presented in the sections on water quality variables that follow.

Only trend results for sites with eight or more years of data are presented in the body of the report. Results of trend analyses for sites that contain less than eight years of data are presented in Appendix C, and the different time period noted.

2.1.4 Nutrients - total nutrients Nitrogen (N) and phosphorus (P) are key ‘growth limiting’ nutrients that influence the growth rate and biomass of algae (or periphyton) and aquatic plants. Low availability of these two nutrients often limits plant biomass development (Mathieson et al., 2012).

Eutrophication is the term used to describe the enrichment of water bodies by inorganic plant nutrients such as nitrate or phosphate. Eutrophication may occur naturally, but is often the result of human activity. Land- use change and intensification often give rise to elevated levels of nitrogen and phosphorus, particularly in areas where appropriate farming practices are not followed. Nuisance periphyton growth can be managed by reducing or eliminating inputs of N and P from point-source discharges and/or diffuse sources such as discharges from land-use (Biggs, 2000).

KEY POINT: Dissolved inorganic nitrogen (DIN) and dissolved reactive phosphorus (DRP) are dissolved inorganic forms of the nutrients nitrogen (N) and phosphorus (P) respectively. N and P are the two key macronutrients required for growth of plants and algae, occurring in all living cells – for example being key elements in proteins and DNA. DIN includes nitrate, nitrite and ammonia. DRP includes phosphate. Although numerous other forms of nitrogen and phosphorus exist and are commonly referred to in the field of water quality (e.g., organic and particulate forms), it is the dissolved forms DIN and DRP that are most readily available for uptake by plants and are thus most relevant for assessing effects on nuisance growths in rivers. The terms total nitrogen (TN) and total phosphorus (TP) refer to the sum total of all forms of N and P respectively in a sample. TN and TP are most relevant for assessments in lakes and coastal waters. At sufficiently elevated concentrations, nitrate and ammonia forms of nitrogen have toxic effects on aquatic biota (and on humans in the case of nitrate). This effect is independent of their significance as plant nutrients (Norton, 2012).

Figure 2-2 and Figure 2-3 are box-plots of total nitrogen (TN) and total phosphorus (TP) concentrations for SoE monitoring sites across the Mohaka catchment. ANZECC trigger levels have been included on the plots for upland (> 150 m altitude) and lowland sites (< 150 m altitude). However, there are only two sites - the Mohaka at Willowflat and Mohaka at Raupunga - that are classified as ‘lowland’ sites according to the ANZECC guidelines.

With the exception of the Taharua River, TN concentrations in the Mohaka catchment are generally at or below ANZECC trigger values (Figure 2-2). There is a significant increase in TN concentrations in the Mohaka River downstream of its confluence with the Taharua River. This is discussed in more detail in Section 2.3. TN levels are lower from the confluence with the Taharua River towards the sea (Figure 2-4), with sites in the lower catchment showing TN concentrations well below the lowland ANZECC (2000) guidelines.

These lower downstream TN concentration are caused by in-stream uptake by algae (attenuation) combined with dilution effects from tributary inflows to the Mohaka River with very low concentrations of nitrogen such as the Ripia, Waipunga and Te Hoe rivers (Figure 2-2 and Figure 2-4).

22 Mohaka River Catchment

The only other monitoring site outside the Taharua River sub-catchment that shows elevated TN levels is the Waiarua Stream at State Highway 5. This site is in the headwaters of the Waipunga River and is influenced to a limited degree by intensive land-use in the Rangitaiki Plains (discussed in more detail in Section 2.4).

Downstream towards the confluence of the Waipunga and Mohaka rivers, TN concentrations in the Waipunga River are quickly diluted by tributary inflows such as those from the upper Waipunga River, Okeke Stream and the Mokomokonui River.

Although not included in the list of long-term monitoring sites presented in Figure 2-2, the Waipunga River upstream of the Mohaka River had low TN concentrations (average 0.15 mg/l TN) measured during the Concurrent Gauging Study (discussed in Section 2.2), suggesting that the Waiarua Stream has minimal influence on the lower Waipunga River and Mohaka River.

Monitoring sites in the lower Mohaka River, such as the Mohaka at Willowflat and Mohaka at Raupunga have median TN concentrations well below the ANZECC (2000) guideline level for lowland streams (blue line in Figure 2-2). If TN concentrations remain at current levels in the lower Mohaka River, there would be minimal eutrophication risk in the near-shore coastal environment.

The TN concentrations in the lower Mohaka are comparable to the Ngaruroro River at Whanawhana (Figure 2-2), which has very low TN levels for a lowland river, since it is in a near-natural condition.

Mohaka River Catchment 23

Figure 2-2: Total nitrogen (TN) levels at SoE monitoring sites. SoE sites for the Mohaka River upstream (U/S) Taharua confluence and the Ngaruroro River at Whanawhana (shaded) are included as Upland (U) and Lowland (L) reference sites for comparison purposes. As a consequence, the first of these sites appears twice in this chart. The blue line relates to the ANZECC (2000) ‘Upland’ TN trigger value; the red line the ANZECC (2000) ‘Lowland’ TN trigger value.

By contrast, total phosphorus (TP) concentrations are low in the upper and middle catchment but increase towards the sea (Figure 2-3 and Figure 2-5). Unlike TN, TP concentrations in the upper catchment are well below the ANZECC (2000) guideline level for upland rivers, and although higher than values expected in pristine natural catchments, are still very low. Flow received from the Taharua River slightly increases TP concentrations in the Mohaka River, but this is quickly attenuated by in-stream processes such as nutrient uptake and associated growth of algae. Phosphorus trends in the Taharua River and their effects on the upper Mohaka River are discussed in more detail in Section 2.3.

The increase in TP in the lower catchment rivers is caused by the higher levels of phosphorus contributed to the river associated with suspended sediments eroded from catchment soils and rocks. The rocks of the lower catchment are different to the upper catchment, with more soft-sedimentary rocks present. Additional sediment mobilised by land clearance and land-use practices increases the levels of associated phosphorus in rivers. However, where more soft sedimentary rocks are found, natural suspended sediment concentrations and associated nutrients are higher than in hard-sedimentary rocks that dominate the upper catchment. Very high flows (not often measured) result in disproportionate spikes in concentrations of particulate phosphorus resulting in the extended ‘whiskers’ in Figure 2-3. This is prominent in the lower catchment where high flows interact with the soft sedimentary geology resulting in increased sediment and particulate phosphorus load. The distribution of samples is skewed towards lower flows and associated lower

24 Mohaka River Catchment

concentrations (where there is a flow/concentration relationship). This is not as prominent for the ‘dissolved’ nutrients that do not have a strong flow/concentration relationship.

Figure 2-3: Total phosphorus (TP) levels at SoE monitoring sites. SoE sites for the Mohaka River U/S Taharua confluence and the Ngaruroro River at Whanawhana (shaded) are included as Upland (U) and Lowland (L) reference sites for comparison purposes. The blue line relates to the ANZECC (2000) ‘Upland’ TP trigger value; the red line the ANZECC (2000) ‘Lowland’ TP trigger value.

Despite the elevated TP concentrations in the lower Mohaka River, these concentrations are unlikely to have an impact on the near-shore coastal environment. TP concentrations at the Mohaka near-shore coastal SoE water quality monitoring site (located approximately 1 km off the mouth of the Mohaka River) are 0.016 mg/l on average and are low and comparable or lower than concentrations at the majority of near-shore coastal SoE sites in Hawke’s Bay. Elevated nutrient concentrations in the coastal environment are typically expressed by blooms of phytoplankton. Chlorophyll a concentrations are measured as a proxy for phytoplankton at near-shore coastal SoE sites. Chlorophyll a concentrations at the Mohaka near-shore coastal SoE site are 0.95 mg/m3 on average and are comparable or lower than at other HBRC coastal monitoring sites suggesting the current nutrient concentrations are not promoting excessive algal growth.

TP concentrations in the lower Mohaka River are high compared to the Ngaruroro River at Whanawhana lowland reference site (Figure 2-3). TP concentrations are also considerably higher than dissolved reactive phosphorus (DRP) discussed in the next section (Section 2.1.5; Figure 2-7). This means that high TP in the lower Mohaka is due to increased levels of particulate P associated with the increased sediment load that is present in the lower Mohaka River.

Mohaka River Catchment 25

Figure 2-4: 5 year median total nitrogen (TN) levels at SoE monitoring sites including trend direction. Arrows indicate direction of significant trends, with blue arrows for improvement and red arrows for deterioration of the variable in question. Sites without an arrow did not exhibit a statistically significant trend. Trend results for sites 1, 4, 6, 7, 9 and 14 are not presented because they did not include the required 8 years of record between 2004 and 2013.

Figure 2-5: 5 year median total phosphorus (TP) levels at SoE monitoring sites including trend direction. Arrows indicate direction of significant trends, with blue arrows for improvement and red arrows for deterioration of the variable in question. Sites without an arrow did not exhibit a statistically significant trend. Trend results for sites 1, 4, 6, 7, 9 and 14 are not presented because they did not include the required 8 years of record between 2004 and 2013.

The Taharua at Henry’s Bridge (Hnrys Br) monitoring site includes a shorter time-series of data compared to the other Taharua River monitoring sites. This shorter time series is likely to have affected the pattern of TP through time (Figure 2-3) at this site compared to the monitoring site upstream at Twin Culverts (Twn Culv) and downstream at Poronui Station (Poronui Stn) Since extreme events, particularly high flow events, experienced at other sites were not therefore recorded.

Table 2-3 summarises the results of trend analysis carried out on TN and TP across all SoE monitoring sites of the Mohaka catchment. For a full summary of trend analysis results refer to Appendix C. Several significant trends are apparent in the dataset.

From the data, it is notable that the Taharua River at Wairango and Taharua River at Twin Culverts monitoring sites have experienced increases in TN at the same time as decreases in TP. The situation of opposing trends in these two nutrients may be caused by different processes causing nutrient loss from the land. Phosphorus typically enters waterways attached to sediment particles in overland flow, but nitrogen often enters waterways as nitrate dissolved in water draining from the soil horizon.

The different pathways by which the two nutrients move means that changes to land-use practices may affect rates of nutrients lost in different ways. For example, reduction of sediment erosion in streams by riparian management can rapidly decrease phosphorus loss, but these approaches would be unlikely to reduce rates of nitrogen loss by a similar magnitude.

The timeframe over which these losses occur is also different for each nutrient: Phosphorus is lost to streams through sediment transported in overland flow, so its transport rate is rapid. Conversely, because nitrogen is concentrated at the root zone by percolating soil water, then typically transported through groundwater, it may take several years for it to travel to the river. An example of the significance of these differing transport pathways to patterns of nutrients observed in stream, changes in the concentration of nitrate-nitrogen in the Taharua River are discussed in more detail in Section 2.3.3.

Table 2-3: Trend analysis results for TN and TP for SoE monitoring sites of the Mohaka catchment. In all tables that present trend results, the changes are represented in bold when they are significant (ie, p value is less than 0.05). Given a significant trend for a particular variable, the Percent Annual Change (PAC) is highlighted in BLUE if there was a significant improvement in the water quality variable, and highlighted in RED if there was a significant deterioration in the water quality variable. Only trend results for sites with eight or more years of data are presented. Results of trend analyses for sites that contain less than eight years of data are presented in Appendix C.

Total Nitrogen Total Phosphorus Percent Percent Site Trend Trend Median Annual Median Annual p value p value Change Change Taharua River at Wairango 3.100 0.004 2.3 0.020 0.026 -2.5 Taharua River at Twn Culv 3.330 0.000 3.4 0.021 0.039 -2.8 Taharua River at Poronui Stn 1.559 0.000 3.9 0.022 0.409 -0.8 Ripia River U/S Mohaka River 0.165 0.003 -5.0 0.013 0.014 -6.0 Mohaka River at SH5 (NIWA) 0.314 0.000 3.3 0.011 0.191 -1.8 Waiarua Stream 0.610 0.115 1.9 0.017 0.002 -4.0 Waipunga River at Pohokura Rd 0.333 0.004 -5.3 0.019 0.124 -2.4 Mokomokonui River 0.138 0.878 0.1 0.019 0.012 -2.7 Mohaka River at Willowflat 0.300 0.357 1.3 0.032 0.586 2.6 Mohaka River at Raupunga 0.256 0.395 2.2 0.022 0.501 3.4 Mohaka River at Raupunga (NIWA) 0.228 0.240 1.1 0.018 0.813 0.0

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The opposing directions in trends for both TN and TP in adjacent sites at the Waiarua Stream upstream of SH5 and the Waipunga River at Pohokura Rd are discussed in more detail in Section 2.4.

Other notable trends in the data include that the Ripia River and the upper Waipunga River (at Pohokura Road) both show significant decreasing trends in TN; and that the Mokomokonui River, with both very low nitrogen concentrations but elevated phosphorus concentrations, is nevertheless showing a significant decreasing trend in TP.

2.1.5 Nutrients - dissolved nutrients Dissolved inorganic nitrogen (DIN) and dissolved reactive phosphorus (DRP) concentrations were also examined at SoE monitoring sites across the Mohaka catchment.

As discussed in the ‘Key Point’ on Page 22, DIN and DRP are important because they represent the two most significant nutrients that stimulate or limit periphyton growth, since they are immediately available to fuel biological growth (they are ‘bioavailable’) to algae and plants. By contrast, forms of nitrogen and phosphorus such as organic nitrogen and particulate phosphorus, are not immediately available to algae and plants and need to decompose through processes such as re-mineralisation to become bio-available.

In situations where other growth constraints such as long periods of low flow and high light availability are less significant, increases in DIN and DRP supply can lead to increased periphyton growth and eutrophication of a waterway. For this reason, setting nutrient concentration guidelines or standards is generally used as a way to guide the actions necessary to maintain periphyton growth to acceptable levels. However, because DIN and DRP are immediately available to plants, they can be removed from the water rapidly (e.g., during summer low flows). This means that concentrations of DIN and DRP at times provide a poor indicator of eutrophication.

The pattern of DIN concentration throughout the Mohaka catchment follows a very similar pattern to that of TN and the discussion around TN (Section 2.1.4) is directly relevant to DIN (Figure 2-6).Tukituki Plan Change 6 (TTPC6) DIN limits and ANZECC trigger levels have been included on the plots for upland (> 150 m altitude) and lowland sites (< 150 m altitude). The Mohaka at Willowflat and Mohaka at Raupunga sampling sites are the only sites classified as ‘lowland’. Also included is the

Notable aspects of the data include the following (see Figure 2-6 and Figure 2-8):

. The Ripia River, the Mokomokonui River and the Mohaka River upstream of the Taharua River have very low concentrations of DIN. Algal growth in these rivers would be strongly limited by the availability of either or both of DIN and DRP.

. The Taharua River has highly elevated levels of DIN. Mixing of Taharua River water with Mohaka River water downstream of the confluence results in significant increases in DIN concentration downstream in the Mohaka River (discussed in detail in Section 2.3.2).

. The Taharua River at Wairango and Twin Culverts have the highest recorded median DIN concentrations in the Hawke’s Bay region (see Appendix D).

. All other SoE monitoring sites, with the exception of the Waiarua Stream, have DIN concentrations typically less than 0.3 mg/l, a level that is likely to begin to limit periphyton growth rates (Biggs, 2000) (orange line on Figure 2-6).

Mohaka River Catchment 29

Figure 2-6: Dissolved inorganic nitrogen (DIN) levels at SoE monitoring sites. SoE sites for the Mohaka River U/S Taharua confluence and the Ngaruroro River at Whanawhana (shaded) are included as Upland (U) and Lowland (L) reference sites for comparison purposes. The blue line relates to the ANZECC (2000) ‘Upland’ DIN trigger value; the orange line the Biggs (2000) suggested limit for DIN for periphyton growth management for a 20 day accrual period; the red line relates to the ANZECC (2000) ‘Lowland’ DIN trigger value.

The pattern of DRP concentrations (Figure 2-7) across the catchment are different to those of TP. DRP in the upper Taharua River (Wairango and Twin Culverts) is higher than the ANZECC (2000) Upland River guideline levels and also higher than typical natural catchments. However, the DRP levels are lower than in other rivers in other extensively3 and intensively farmed catchments in the region such as tributaries of the lower Ngaruroro River, the lower Tutaekuri River, the Esk River and Karamu Stream catchments (refer to Appendix D). The long-term mean DRP levels are also below HBRC RRMP (2006) guidelines (see Section 2.1.12).

DRP levels in the Taharua are lower downstream than upstream (Figure 2-9), being lowest at the Red Hut monitoring site just upstream of the confluence with the Mohaka River. However, outflows from the Taharua River elevate DRP concentrations in the Mohaka River immediately downstream of the confluence.

As with TP, DRP concentrations are higher in the lower catchment than in the upper catchment, but not to the same degree as with TP. This confirms that most phosphorus in the lower catchment is particulate phosphorus associated with suspended particles (Appendix B).

With the exception of the Taharua at Wairango and Twin Culverts monitoring sites, it is notable that DRP concentrations in the Mokomokonui River are higher than most other sites in the catchment. This contrasts with DIN concentrations (Figure 2-6), which are extremely low. The source of this elevated DRP is not clear:

3 Extensive farming or extensive agriculture (the opposite of intensive farming) is an agricultural production system that uses small inputs of labour, fertilisers, and capital, relative to the land area being farmed. Extensive farming most commonly refers to sheep and cattle farming in areas with low agricultural productivity, but can also refer to large-scale growing of grain crops.

30 Mohaka River Catchment

It may be derived naturally from the catchment or may be due to land-use impacts. The dominant land-use in this catchment is forestry, and it is possible that phosphorus is being mobilised during forest rotations. It is also of note that very low DIN concentrations at this site may severely limit plant and algae growth, so that there is little uptake of DRP from the water column.

Figure 2-7: Dissolved reactive phosphorus (DRP) levels at SoE monitoring sites. SoE sites for the Mohaka River U/S Taharua confluence and the Ngaruroro River at Whanawhana (shaded) are included as Upland (U) and Lowland (L) reference sites for comparison purposes. The blue line relates to the ANZECC (2000) ‘Upland’ DRP trigger value; the red line the ANZECC (2000) ‘Lowland’ DRP trigger value and the Biggs (2000) suggested limit for DRP for periphyton growth management for a 20 day accrual period.

Table 2-4 summarises the results of trend analysis carried out on DIN and DRP across long-term SoE monitoring sites of the Mohaka catchment. For a full summary of trend analysis results refer to Appendix C.

Several significant trends are apparent in the dataset. As with TN and TP, over the period of data used in the trend analysis, the Taharua at Wairango monitoring site shows opposing trends for DIN and DRP, with significant increases in DIN while DRP is decreasing significantly. In Section 2.3.3, recent shifts in the direction of the trend in DIN, going from increasing to decreasing, are discussed for the Taharua sites.

It is notable that the decreasing trends in TP in the Mokomokonui River are also evident for DRP whereas the decreasing trends in TN and TP evident for the Ripia River are not as strong for DIN and DRP. The opposing DIN trends apparent in the Waiarua Stream upstream of SH5 and the Waipunga River at Pohokura Rd are discussed in more detail in Section 2.4.

Mohaka River Catchment 31

Figure 2-8: 5 year median dissolved inorganic nitrogen (DIN) levels at SoE monitoring sites including trend direction. Arrows indicate direction of significant trends, with blue arrows for improvement and red arrows for deterioration of the variable in question. Sites without an arrow did not exhibit a statistically significant trend. Trend results for sites 1, 4, 6, 7, 9 and 14 are not presented because they did not contain the required 8 years of record between 2004 and 2013.

Figure 2-9: 5 year median dissolved reactive phosphorus (DRP) levels at SoE monitoring sites including trend direction. Arrows indicate direction of significant trends, with blue arrows for improvement and red arrows for deterioration of the variable in question. Sites without an arrow did not exhibit a statistically significant trend. Trend results for sites 1, 4, 6, 7, 9 and 14 are not presented because they did not contain the required 8 years of record between 2004 and 2013.

Table 2-4: Trend analysis results for DIN and DRP for SoE monitoring sites of the Mohaka catchment. In all tables that present trend results, the changes are represented in bold when they are significant (ie, p value is less than 0.05). Given a significant trend for a particular variable, the Percent annual Change (PAC) is highlighted in BLUE if there was a significant improvement in the water quality variable, and highlighted in RED if there was a significant deterioration in the water quality variable. Only trend results for sites with eight or more years of data are presented. Results of trend analyses for sites that contain less than eight years of data are presented in Appendix C, and the different time period noted. DIN DRP Percent Percent Site Trend Trend Median Annual Median Annual p value p value Change Change Taharua River at Wairango 2.940 0.000 2.5 0.016 0.025 -2.5 Taharua River at Twn Culv 3.223 0.000 3.9 0.014 0.102 -2.6 Taharua River at Poronui Stn 1.460 0.000 4.8 0.011 0.065 -3.1 Ripia River U/S Mohaka River 0.103 0.324 -3.6 0.007 0.136 -4.1 Mohaka River at SH5 (NIWA) 0.240 0.000 4.2 0.005 0.935 0.0 Waiarua Stream 0.492 0.001 3.7 0.007 0.155 -3.0 Waipunga River at Pohokura Rd 0.245 0.011 -8.0 0.007 0.424 -4.8 Mokomokonui River 0.048 0.580 0.8 0.014 0.032 -3.2 Mohaka River at Willowflat 0.182 0.233 1.6 0.008 1.000 0.0 Mohaka River at Raupunga 0.170 0.618 0.6 0.009 0.958 0.0 Mohaka River at Raupunga (NIWA) 0.142 0.140 1.6 0.008 0.542 0.0

With the exception of a single sample collected on 22 November 2012 that showed very low levels of nutrients, there is no data available on the Inangatahi Stream that flows from Puketitiri, through production forest to enter the Mohaka River upstream of State Highway 5. Parts of this stream catchment may be affected by intensive land-use in the Puketitiri area, but the extent to which this affects water quality of the Inangatahi Stream and Mohaka River downstream of its confluence is unknown. Although water quality measured at the NIWA Mohaka River at Glenfalls site is excellent, it is likely that the effects of the Inangatahi Stream on Mohaka River water quality are minimal.

2.1.6 Toxicity – nitrate nitrogen and ammoniacal nitrogen At high concentrations, nitrate can be toxic to aquatic animals (Hickey & Martin, 2009). The ANZECC (2000) nitrate toxicity guidelines were reviewed by NIWA for Environment Canterbury in 2009 (Hickey & Martin, 2009). Chronic toxicity thresholds derived in the 2009 review were based largely on aquatic species from outside New Zealand, although some of the species are now resident in New Zealand. No native New Zealand species were included in the 2009 review (Hickey, 2013b).

To assist with the development of a set of robust nitrate toxicity concentration guidelines, NIWA was engaged by HBRC in 2012/2013 to undertake the following:

. Nitrate toxicity trials using several New Zealand native species, including Inanga, Deleatidium mayfly and early life stages (eggs and early life stages) of New Zealand strains of introduced rainbow trout; . Update the Hickey and Martin (2009) guidelines by including recent international data as well as data derived from the New Zealand trials; . Support the development of nitrate-nitrogen toxicity guidelines applicable to the Hawke’s Bay region.

DIN (discussed in the previous section) is made up of nitrate-nitrogen (NO3-N), nitrite-nitrogen (NO2-N) and ammoniacal-nitrogen (NH4-N). Nitrate-nitrogen is the dominant component of DIN in areas affected mainly

34 Mohaka River Catchment

by diffuse-source discharges and in catchments with limited areas of wetland with anoxic soils, as in the Mohaka catchment. Nitrate-nitrogen concentrations in Mohaka streams (Figure 2-10 and Figure 2-11) are similar to DIN concentrations (Figure 2-6 and Figure 2-8) with nitrate-nitrogen contributing to over 95% of the dissolved inorganic nitrogen.

All monitoring sites outside the Taharua River catchment have nitrate-nitrogen concentrations well below any toxicity threshold (Figure 2-10). In the case of the Taharua River, monitoring sites in the upper catchment (Wairango and Twin Culverts), exhibit nitrate-nitrogen values between the Hickey (2013) 90% and 95% species protection levels as defined by ANZECC (2000) (refer to the NOF nitrate summary in Section 2.1.12 for further discussion on species protection and nitrate toxicity). In a regional context, the Taharua at Wairango and Twin Culverts record the highest median nitrate-nitrogen concentrations for the period 2009 to 2013 in Hawke’s Bay (refer to Appendix D).

Recent reductions in nitrate-nitrogen values at these two sites have brought them below the 95% species protection level. The current nitrate-nitrogen concentrations are likely to pose minimal risk to the two species of fish currently known to be present in the Taharua River - brown trout (Salmo trutta) and longfin eel (Anguilla dieffenbachii).

Figure 2-10: Nitrate - nitrogen (NO3-N) levels at SoE monitoring sites. SoE sites for the Mohaka River U/S Taharua confluence and the Ngaruroro River at Whanawhana (shaded) are included as Upland (U) and Lowland (L) reference sites for comparison purposes. The blue, orange and red lines relate to the Hickey (2013) nitrate toxicity limits for 99%, 95% and 90% species protection respectively.

Trend analysis of the Mohaka SoE monitoring sites shows nitrate-nitrogen trends are essentially the same as those of DIN as DIN is predominantly made up of nitrate-nitrogen (Table 2-5).

Mohaka River Catchment 35

Figure 2-11: 5 year median nitrate-nitrogen (NO3-N) levels at SoE monitoring sites, including trend direction. Arrows indicate direction of significant trends, with blue arrows for improvement and red arrows for deterioration of the variable in question. Sites without an arrow did not exhibit a statistically significant trend. Trend results for sites 1, 4, 6, 7, 9 and 14 are not presented because they did not contain the required 8 years of record between 2004 and 2013.

The trends in the Taharua monitoring sites are discussed in more detail in Section 2.3.3. The trends in the Waiarua Stream upstream of SH5 and the Waipunga River at Pohokura Rd are discussed in more detail in Section 2.4.

Table 2-5: Trend analysis results for nitrate-nitrogen (NO3-N) for SoE monitoring sites of the Mohaka catchment. In all tables that present trend results, the changes are represented in bold when they are significant (ie, p value is less than 0.05). Given a significant trend for a particular variable, the percent annual change (PAC) is highlighted in BLUE if there was a significant improvement in the water quality variable, and highlighted in RED if there was a significant deterioration in the water quality variable. Only trend results for sites with 8 or more years of data are presented. Results of trend analyses for sites that contain less than 8 years of data are presented in Appendix C, and the different time period noted. Nitrate Percent Site Trend Median Annual p value Change Taharua River at Wairango 2.900 0.000 2.6 Taharua River at Twn Culv 3.200 0.000 3.9 Taharua River at Poronui Stn 1.440 0.000 4.9 Ripia River U/S Mohaka River 0.079 0.179 -4.9 Mohaka River at SH5 (NIWA) No Data Waiarua Stream 0.470 0.001 4.3 Waipunga River at Pohokura Rd 0.220 0.029 -8.1 Mokomokonui River 0.036 1.000 0.0 Mohaka River at Willowflat 0.166 0.302 1.4 Mohaka River at Raupunga 0.145 0.842 0.7 Mohaka River at Raupunga (NIWA) No Data

2.1.7 Water clarity – black disc and turbidity Water clarity is measured as the proportion of light transmitted through water. The concept has two important aspects, which are (1) visual clarity (sighting range for humans and aquatic animals), and (2) light penetration for growth of aquatic plants (Davies-Colley & Smith, 2001; Davies-Colley et al., 2003).

Water clarity is of considerable importance for the protection of contact recreation values, because it is perceived by recreational water users to directly affect the aesthetic quality of the water. In addition, adequate visual clarity allows swimmers to estimate depth and identify subsurface hazards (ANZECC 2000).

Changes (generally reductions) of water clarity can also affect the foraging ability of fish, such as trout, by reducing their ability to see food drifting in the water column (Shearer & Hays, 2010). Trout are visual predators and drift feeding is their predominant foraging behaviour in most rivers (Hay et al., 2006). Reduced visual clarity (or equivalent increases in water turbidity), reduces foraging efficiency (i.e. more energy is spent consuming the same amount of prey, or fewer prey are consumed).

Water clarity is measured using a black disc. The measurement consists of measuring the horizontal distance that a black disc of standard size can be distinguished under water (Figure 2-12). Where the size of streams allow, black disc measurements are carried out routinely on a monthly basis across all HBRC SoE monitoring sites.

Mohaka River Catchment 37

The ANZECC (2000) and the HBRC (2006) Regional Resource Management Plan (RRMP) defines a minimum water clarity of 1.6 m for contact recreation waters. However, to maintain the foraging efficiency of drift feeding trout, Hay et al. (2006) recommend a minimum water clarity of 5 m for ‘outstanding trout fisheries’ and 3.5 m for ‘significant trout fisheries’.

Figure 2-12: Hawke's Bay Regional Council staff measuring black disc sighting distance in the field.

Both the Mohaka River upstream of the Taharua River and the Taharua River at Wairango have excellent water clarity with black disc sighting distances often being greater than 4 m, with measurements of up to 8 m being recorded at times (Figure 2-13). Water clarity declines downstream towards the sea (Figure 2-15). Clarity is generally very good to good at times through the middle Mohaka, but is typically below the ANZECC (2000) threshold for contact recreation of 1.6 m in the lower river. As discussed previously in relation to total phosphorus (Section 2.1.7), the lower Mohaka River contains significant levels of suspended sediment leading to reductions in water clarity and increased turbidity.

Even in pristine catchments water clarity is reduced at times of elevated flow. Figure 2-13 includes data collected at all flows so it is difficult from the figure to judge what water clarity for a site would nominally be under low flow conditions. To best understand water clarity under low flow conditions, refer to Appendix B, and the summaries at less than median flow and less than lower quartile flow.

38 Mohaka River Catchment

Figure 2-13: Water clarity measured as black disc horizontal sighting distance for SoE monitoring sites. SoE sites for the Mohaka River U/S Taharua confluence and the Ngaruroro River at Whanawhana (shaded) are included as Upland (U) and Lowland (L) reference sites for comparison purposes. The blue line relates to the Hay and Hayes (2006) ‘Outstanding trout fishery’ limit; the orange line the ‘Significant trout fishery’ limit. The red line relates to the ANZECC (2000)/ HBRC RRMP (2006) recreational amenity limit.

Figure 2-14 shows turbidity measurements across SoE monitoring sites throughout the Mohaka catchment. Turbidity is a measurement of the degree of light scattering of the water and is caused by suspended particles present in the water column. The greater the concentration or number of suspended particles the higher the turbidity.

Mohaka River Catchment 39

Figure 2-14: Water clarity measured as turbidity (NTU) for SoE monitoring sites. NTU stands for Nephelometric Turbidity Units. SoE sites for the Mohaka River U/S Taharua confluence and the Ngaruroro River at Whanawhana (shaded) are included as Upland (U) and Lowland (L) reference sites for comparison purposes. The blue line relates to the ANZECC (2000) ‘Upland’ turbidity trigger value; the red line the ANZECC (2000) ‘Lowland’ turbidity trigger value.

Figure 2-14 has a logarithmic axis on the turbidity axis (y-axis). The figure is plotted in this way to accommodate the extreme range of turbidity measurements that are typical of sites when measurements are included across all flow conditions.

There is a direct relationship between water clarity, as measured using a black disc, and turbidity (Figure 2- 17); the higher the turbidity the lower the water clarity. At very low turbidity levels a small increase in turbidity results in a large decrease in black disc. Turbidity readings less than 1 NTU are typically required to result in black disc distances greater than 3.5 m, distances seen as being optimal for drift feeding trout (Hay et al. (2006). Such turbidity readings reflect very low numbers of suspended particles present in the water column, and even very minor increases, whether due to natural geological effects such as the presence of soft-sedimentary geology like mudstone or papa rock, or minor disturbance of the catchment resulting in increased sediment transport, will result in minor increases in turbidity and rapid reductions in water clarity. Rainfall events and associated runoff mobilises sediment in the catchment and results in significant increases in turbidity with readings of 500 NTU or greater being typical of flood events.

40 Mohaka River Catchment

Figure 2-15: 5 year median Black Disc (BD) water clarity levels at SoE monitoring sites including trend direction. Arrows indicate direction of significant trends, with blue arrows for improvement and red arrows for deterioration of the variable in question. Sites without an arrow did not exhibit a statistically significant trend. Trend results for sites 1, 4, 6, 7, 9 and 14 are not presented because they did not contain the required 8 years of record between 2004 and 2013.

Figure 2-16: 5 year median turbidity levels at SoE monitoring sites including trend direction. Arrows indicate direction of significant trends, with blue arrows for improvement and red arrows for deterioration of the variable in question. Sites without an arrow did not exhibit a statistically significant trend. Trend results for sites 1, 4, 6, 7, 9 and 14 are not presented because they did not contain the required 8 years of record between 2004 and 2013.

The pattern of change in turbidity across the Mohaka catchment is opposite to that of water clarity (black disc), since low visual clarity is caused by high turbidity. Low turbidity readings are typical of the upper and middle Mohaka River SoE monitoring sites but high turbidity readings are typical of monitoring sites in the lower river (Figure 2-16). There is a significant increase in turbidity of around 4 to 5 NTU downstream of the Waipunga River confluence where higher levels of suspended particles are in the water column, from this monitoring site downstream to the coast.

Figure 2-17: The relationship between black disc sighting distance and turbidity for several main-stem Mohaka River SoE monitoring sites across the Mohaka catchment. Data has been taken from the Mohaka D/S Ripia, SH5, Willow Flat and Raupunga monitoring sites.

Table 2-6 summarises trend analysis results for black disc clarity and turbidity. In the case of the Taharua River at Wairango, the results of the analysis are unexpected, because black disc distances increase, indicating better water clarity, while turbidity increases at the same time, indicating poorer water clarity. This may indicate that anomalies exist in the dataset. An alternative explanation is that changes in other components of the water column – such as dissolved colour – affect black disc clarity and turbidity independently. Dissolved colour could have reduced at this, site leading to an improvement in black disc sighting distance but this change may have coincided with an increase in suspended particulate matter that results in an increase in turbidity.

The potential causes of the significant increasing trend in turbidity at 8 of the 11 long-term monitoring sites is not clear. This is particularly the case for the increase in turbidity at monitoring sites in the lower Mohaka River at Willowflat and Raupunga. The percent annual changes (PAC) at these sites for the HBRC data are high (16% to 19% increase per year) reflecting significant increases in turbidity over time. However it cannot be assumed that this is a problem caused by human activities that needs to be addressed.

Mohaka River Catchment 43

The Raupunga site has two data series, one collected by NIWA (for the full trend analysis period from January 2004 to December 2013), and one collected by HBRC, which ended in September 2012. The NIWA dataset was monthly throughout the period, and no significant trend is evident in the monthly data. The HBRC data was initially collected quarterly, and these data contained a strong significant deteriorating trend. If the trend was an ongoing problem caused by human activities, it would be expected that both datasets would show a similar pattern, but they do not. Alternative explanations for these patterns could include:

. The trend in water quality between January 2004 to September 2012 (HBRC data series), could have been different to the trend in water quality between January 2004 to December 2013 (NIWA data series).

. HBRC data for the analysis period January 2004 to August 2009 was collected on a quarterly basis, and monthly from August 2009 onwards. Trend analysis on HBRC data was therefore carried out on quarterly data for the whole data period (see Section 2.1.3). NIWA data was collected monthly from January 2004 to December 2013. Trend analysis on NIWA data was carried out on monthly data for the whole data period. Trend analysis on the monthly samples will provide a more robust result than trend analysis on quarterly samples (Scarsbrook & McBride, 2007).

. HBRC shifted from lab measured turbidity to field measured turbidity in early 2010. The change in method could affect turbidity baselines resulting in a shift that is independent of environmental conditions. This then confounds trend analysis results.

The NIWA Raupunga dataset is more robust, because it was collected monthly over the full period, and so should take precedence over the HBRC Raupunga dataset. Given that the trend seemed to have flattened out (it was no longer positive nor negative) by the end of the record (NIWA dataset), it could be concluded there has not been a significant trend in turbidity from January 2004 to December 2013. However, the significant fluctuations in turbidity evident at Raupunga warrant further investigation to identify their cause.

Also of interest is that turbidity showed a strong and significant trend at Raupunga and Willowflat, but the reduction in black disc (BD) distance was not significant. This may be attributed to turbidity being relatively high in the lower Mohaka River (HBRC median 8.6 NTU and 7.9 NTU for Willowflat and Raupunga; Table 2-6) and at these turbidity levels, BD distance is short (HBRC median 0.4 m and 0.5 m for Willowflat and Raupunga; Table 2-6). At elevated turbidity levels, a moderate change in turbidity will result in only a small change in an already very low BD (Figure 2-13). Thus, trends in black disc may have been evident (PACs of -7.4 and -4.3), but not statistically significant (p values > 0.05). The lack of evidence for reductions in black disc trend at the NIWA Raupunga site (PAC = 0.0) also confirms that there is a difference between the HBRC and NIWA data series.

The Mohaka River at Willowflat and Raupunga record some of the lowest median BD distances, highest median turbidity and highest 75th percentile suspended solids levels in the region (Appendix D). The values recorded for these variables at these two sites are more similar to monitoring sites from the north of the region, than the south of the region. The northern sites have more prevalent soft sedimentary mudstone (papa), compared to the catchments to the south.

At sites other than Raupunga and Willowflat increasing trends in turbidity probably truly reflect an increase in suspended sediment. This includes the Mohaka River at SH5, which is a NIWA site with a robust dataset underpinned by monthly data. The trends of decreasing BD and increasing turbidity in the Taharua at Poronui are also of note, since they have occurred despite recent improvements in riparian fencing throughout the Taharua catchment upstream of this site. These catchment works should have reduced fine-grained sediment received by the stream, so understanding the causes of degrading turbidity at sites throughout the Mohaka catchment is a high priority and warrants further targeted investigation.

44 Mohaka River Catchment

Table 2-6: Trend analysis results for black disc clarity and turbidity for SoE monitoring sites in the Mohaka catchment. In all tables that present trend results, the changes are represented in bold font when they are significant (ie, p value is less than 0.05). Given a significant trend for a particular variable, the Percent Annual Change (PAC) is highlighted in BLUE if there was a significant improvement in the water quality variable, and highlighted in RED if there was a significant deterioration in the water quality variable. Only trend results for sites with eight or more years of data are presented. Results of trend analyses for sites that contain less than eight years of data are presented in Appendix C, and the different time period noted. Black Disc Turbidity Percent Percent Site Trend Trend Median Annual Median Annual p value p value Change Change Taharua River at Wairango 4.1 0.002 5.2 0.6 0.010 7.9 Taharua River at Twn Culv 3.0 0.231 2.0 0.8 0.049 4.9 Taharua River at Poronui Stn 1.5 0.040 -4.9 1.7 0.039 5.6 Ripia River U/S Mohaka River 2.3 0.355 4.2 1.2 0.459 3.3 Mohaka River at SH5 (NIWA) 2.8 0.380 1.3 1.1 0.043 3.8 Waiarua Stream 1.5 0.331 2.0 2.1 0.003 6.2 Waipunga River at Pohokura Rd 1.3 0.487 -3.4 1.9 0.031 6.5 Mokomokonui River 2.6 0.507 2.0 1.4 0.434 2.9 Mohaka River at Willowflat 0.4 0.176 -7.4 8.6 0.034 16.0 Mohaka River at Raupunga 0.5 0.143 -4.3 7.9 0.038 18.9 Mohaka River at Raupunga (NIWA) 0.9 0.979 0.0 4.5 0.187 2.4

2.1.8 Bacteriological water quality – E. coli Escherichia coli (commonly abbreviated E. coli) levels have been routinely monitored throughout the Mohaka catchment as an indicator of microbiological water quality. E. coli is a bacterium commonly found in the lower intestine of warm-blooded animals and is an important indicator of the presence of pathogens of faecal origin in the water. E. coli is used to assess the level of health risk to water users having direct contact with water.

The 2002 microbiological water quality guidelines (MfE/MoH, 2003) define a three-mode risk management system for recreational freshwaters: Acceptable/Green (E. coli < 260 colony forming units CFU/100 ml); Alert/Amber (E. coli 260 CFU/100 ml to 550 CFU/100 ml) and Action/Red (E. coli > 550 CFU/100 ml).

The red mode indicates an unacceptable level of health risk to contact recreational water users such as swimmers. These are single-value criteria, designed to trigger further investigation and additional sampling (amber mode) and positive action to identify the source(s) of contamination and warn recreational users (red mode). The 260 CFU/100 ml to 550 CFU/100 ml amber level has been used in this report to assess suitability for swimming at all river flows.

Figure 2-18 and Figure 2-19 show E. coli levels at monitoring sites across the Mohaka catchment. There are typically very low levels of bacteria at all monitoring sites, with peak levels (represented by 90th percentile whiskers in Figure 2-18) being well within the acceptable/green level. This is also the case for sites in the Taharua catchment that are in close proximity to dairy farms. In fact the Taharua sites rate very well on a regional basis: Their median E. coli values are in the best 20% of regional sites (refer to Appendix D).

A recent report on water quality in the Tukituki catchment (Uytendaal & Ausseil, 2013) concluded bacteriological water quality to be good at the Tukituki at Red Bridge based on the routine SoE monitoring data. This site has higher E. coli levels than the Mohaka River SoE monitoring sites.

Mohaka River Catchment 45

Figure 2-18: Bacteriological water quality levels measured as E. coli counts (Colony Forming Units / 100ml) at SoE monitoring sites. SoE sites for the Mohaka River U/S Taharua confluence and the Ngaruroro River at Whanawhana (shaded) are included as Upland (U) and Lowland (L) reference sites for comparison purposes. The blue line relates to the MfE and MoH (2003) amber alert level.

Table 2-7 summarises trend analysis results of E. coli or bacteria levels across SoE monitoring sites of the Mohaka River catchment. Generally most sites show no significant increase in E. coli numbers and that levels are therefore remaining very low.

The exceptions to this general rule are the Mokomokonui River and the Mohaka River at Willowflat. Both sites returned a significant increasing trend in E. coli. The median E. coli levels remain very low at these sites in the green ‘acceptable’ band, and even high values recorded at these sites are well below the ‘amber’ alert level of 260 CFU/100 ml (Figure 2-18). The risk for contact recreation is negligible as a consequence. However, since both sites have increasing trends in bacteria levels, continued scrutiny and future trend analysis will be important to undertake.

46 Mohaka River Catchment

Figure 2-19: 5 year median E. coli levels at SoE monitoring sites including trend direction. Arrows indicate direction of significant trends, with blue arrows for improvement and red arrows for deterioration of the variable in question. Sites without an arrow did not exhibit a statistically significant trend. Trend results for sites 1, 4, 6, 7, 9 and 14 are not presented because they did not contain the required 8 years of record between 2004 and 2013.

Table 2-7: Trend analysis results for E. coli for SoE monitoring sites of the Mohaka catchment. In all tables that present trend results, the changes are represented in bold when they are significant (ie, p value is less than 0.05). Given a significant trend for a particular variable, the Percent annual Change (PAC) is highlighted in BLUE if there was a significant improvement in the water quality variable, and highlighted in RED if there was a significant deterioration in the water quality variable. Only trend results for sites with eight or more years of data are presented. Results of trend analyses for sites that contain less than eight years of data are presented in Appendix C, and the different time period noted. E. coli Percent Site Trend Median Annual p value Change Taharua River at Wairango 8 0.865 0.0 Taharua River at Twn Culv 11 0.144 3.8 Taharua River at Poronui Stn 8 0.145 8.9 Ripia River U/S Mohaka River 7 0.408 5.2 Mohaka River at SH5 (NIWA) 20 0.715 -2.1 Waiarua Stream 8 0.595 2.0 Waipunga River at Pohokura Rd 4 0.511 0.0 Mokomokonui River 5 0.018 10.1 Mohaka River at Willowflat 8 0.014 18.2 Mohaka River at Raupunga 14 0.083 8.3 Mohaka River at Raupunga (NIWA) 16 0.951 0.0

2.1.9 Biological indicators – Macroinvertebrate Community Index Macroinvertebrate communities are commonly used as state indicators of water quality and ecosystem health. The macroinvertebrate community of a stream adjusts to conditions in the aquatic environment, including naturally induced changes and stressors affecting ecosystem health. The macroinvertebrates collected at a site are exposed to changes in conditions at that site for periods of months, to a year or even several years, depending on their life cycle. The community composition changes as sensitive species experiencing stress are lost, which leads to a community dominated by more tolerant species. Both human activities and natural changes such as drought and floods, or natural variations in stream bed substrate type and water temperature may affect macroinvertebrate communities. Assessing the composition of macroinvertebrate communities provides a long-term and integrated view of “water quality”.

The Macroinvertebrate Community Index (MCI) was developed by Stark (1985) as a biomonitoring tool to assess stream health based on the presence or absence of certain invertebrate species. A higher MCI score indicates more pollution ‘intolerant’ or sensitive species to be present indicating better water quality. The MCI of a site can be used to assess the likely level of ecosystem degradation. The MCI also has the potential to provide an indication of the relative availability of trout food species since many taxa that score highly in the MCI are also important prey for drift feeding trout (Hay et al. (2006). As an indicator the MCI signals changes in the stream environment that may warrant further investigation.

The MCI summarises the complexity of stream health including habitat and water quality and provides a single numeric value that can be affected by a wide range of factors. The MCI is the most commonly used

48 Mohaka River Catchment

indicator of macroinvertebrate community health in large-scale monitoring and reporting in New Zealand, such as State of the Environment monitoring and reporting undertaken by Regional Councils and TLAs4.

The quality classes indicated by the MCI score are included in Table 2-8.

Table 2-8: MCI quality classes as defined by Stark and Maxted (2007).

≥120 Excellent quality, clean water 100-119 Good quality, possible mild pollution 80 – 99 Fair quality, probable moderate pollution < 80 Poor quality, probable severe pollution

Figure 2-20 and Figure 2-21 summarises MCI scores for the Mohaka catchment SoE monitoring sites. The results show in-stream macroinvertebrate communities to be in good to excellent condition throughout the catchment.

The exceptions to this are occasional MCI scores from the Taharua River at Wairango that are less than 100; and MCI scores at the Taharua River at Red Hut that typically are between 85 and 90, reflecting ‘fair quality’ (Table 2-8).

The results for the Taharua at Red Hut suggest declining water quality but are misleading because the site has little habitat preferred by species that contribute to higher MCI scores such as riffles or runs dominated by a gravel or cobble river bed. By contrast, the Taharua River at Red Hut has slow flowing water with a fine sand/silt bed. Water nutrient levels are much lower at the Red Hut monitoring site compared to sites such as the Taharua River at Twin Culverts (which returns an MCI score typically between 105 and 125). The high MCI scores at Twin Culverts may be because the monitoring site has a dominance of riffle/run habitat with clean, silt free gravel or cobble bed.

There is a statistically significant reduction in MCI scores between the Mohaka River upstream and downstream of the Taharua River confluence monitoring sites. This change is likely to be caused by periphyton biomass increases downstream of the Taharua confluence that reduce habitat quality and change food resources. These two factors have the capacity to degrade the quality of the macroinvertebrate community. This is discussed in more detail in Section 2.3.

Sites such as the Ripia River, the Mohaka River downstream of the Ripia River confluence, and the Mokomokonui River consistently return very high MCI scores of around 130, reflecting a macroinvertebrate community of pollution sensitive taxa. These scores compare favourably to some of the higher scores measured in other rivers throughout the region. This indicates that the middle Mohaka has a macroinvertebrate community in excellent health.

MCI scores for the lower Mohaka River monitoring sites are significantly lower than scores in the middle and upper catchment. The two main reasons for this would be potential reductions in the quality of riverbed substrate due to increased sediment loss from the lower catchment smothering the bed of the river as well as temperature effects, with monitoring data showing the lower river being warmer than the upper and middle sections of the river with water temperatures over summer months often recorded over 22oC and up to 25oC. Some temperature sensitive species, such as some stonefly (plecopteran) and mayfly (ephemeroptera) species are lost from the macroinvertebrate community when water temperature is higher

4 Territorial Local Authorities

Mohaka River Catchment 49

than 19oC. For example, in a study of 88 New Zealand rivers, Quinn and Hickey (1990) found stoneflies to be largely restricted to rivers with a maximum temperature below 19°C, while mayfly biomass was lower at sites with a maximum temperature of 21.5°C.

MCI scores for the lower Mohaka River are typically between 100 and 120, with some scores being greater than 120, which indicate a healthy macroinvertebrate community. The Mohaka River scores also compare favourably to the lower Ngaruroro River at Whanawhana (Figure 2-20), which is a site with excellent water quality for a lowland river system.

Figure 2-20: MCI levels measured at SoE monitoring sites. SoE sites for the Mohaka River U/S Taharua confluence and the Ngaruroro River at Whanawhana (shaded) are included as Upland (U) and Lowland (L) reference sites for comparison purposes. The blue line relates to the Hay et al. (2006) ‘Outstanding trout fishery’ limit or the Stark and Maxted (2007) ‘Excellent health’ indicator level; the orange line the ‘Significant trout fishery’ limit or ‘Good health’ indicator level.

On a regional basis, a number of Mohaka River catchment sites rank very favourably for median MCI scores, particularly the Mokomokonui River with the second highest median MCI score. The middle Mohaka River sites and the Ripia River rank highly also and sit in the top 10% of median MCI scores for the region (refer to Appendix D).

The effects of Taharua River outflows on the macroinvertebrate community of the upper Mohaka River are discussed in detail in Section 2.3.

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Figure 2-21: 5 year median Macroinvertebrate Community Index (MCI) levels at SoE monitoring sites.

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2.1.10 Biological indicators – periphyton biomass Aquatic plants such as algae or periphyton are natural components of riverine environments. Periphyton is the brown or green slime or filamentous material coating stones, wood, or other stable surfaces in streams and rivers. It is a living community composed of a large number of different algae species. Being the main primary producers in streams and rivers, periphyton communities are fundamental to the functioning of the aquatic ecosystem (Biggs & Kilroy, 2000). However, abundant growths can be problematic, affecting both human use of the river and ecological values (Mathieson et al., 2012). As a result, excessive growths are often termed “nuisance growths”.

Excessive periphyton growth can have detrimental effects on benthic habitat quality and macroinvertebrates, which can in turn affect native fish and trout growth since macroinvertebrates are a food source for native fish and trout. Excessive growth can also cause wide daily variation in pH and dissolved oxygen concentrations, which can also have detrimental effects on aquatic life (Biggs, 2000). This is distinct from benthic cyanobacteria such as Phormidium that can be hazardous as this species can produce toxins.

Excessively long filamentous algae and thick mats are unsightly and can also have a direct effect on the amenity/aesthetic values of a river, as well as on the quality of the fishing experience for the angler (by fouling fishing lures and lines) (Biggs, 2000; Wilcock et al., 2007).

Since periphyton and algae respond to changes in nutrient availability in streams, periphyton biomass or algal biomass limits are used to assess the effects of increased in-stream nutrient concentrations. Biggs (2000) developed the ‘New Zealand Periphyton Guidelines’, a document that identifies suitable limits of in-stream periphyton biomass and cover to support biodiversity and recreational amenity values. The guideline values are as follows:

. A maximum biomass of 120 mg chlorophyll a/m2 of filamentous algae for the protection of aesthetic/recreation values, trout habitat and angling; and

. A maximum periphyton biomass of 50 mg chlorophyll a/m2 for the protection of aquatic biodiversity values.

Figure 2-22 summarises periphyton biomass measurements for the Mohaka catchment SoE monitoring sites. The results show periphyton biomass levels to be in excellent condition throughout the upper and middle catchment, based on measurements taken by HBRC over the course of the SoE monitoring program. Biomass levels are typically below the 50 mg/m2 Biggs (2000) ‘biodiversity’ threshold and, with the exception of one or two measurements in the lower Mohaka River at Willow Flat and Raupunga, all measurements are below the 120 mg/m2 threshold.

There is a significant increase in periphyton biomass in the Mohaka River downstream of the Taharua River confluence (discussed in more detail in Section 2.3), but biomass levels are still below the ‘biodiversity’ guideline level of 50 mg/m2 at the HBRC monitoring site located approximately 500m downstream of the confluence. There are at times localised high biomass on the rock shelf directly below the confluence possibly associated with high supply of DIN and/or DRP and/or low grazing pressure.

The Taharua River rarely has high algal biomass, which is typical of the pumice dominated geology found in the Taharua River. Pumice rolling down the bed of the river scours attached periphyton off the river bed, even under low flow conditions.

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All other sites have appropriate levels of periphyton, with the exception of occasional high biomass levels in the lower Mohaka River at Willowflat and Raupunga. Despite limiting DIN and DRP concentrations at these sites, it is likely that increasing light intensity and water temperature in these broad lowland reaches provides favourable conditions for periphyton growth. This occurs in rivers such as the Ngaruroro River at Whanawhana that has low nutrient concentrations (Figure 2-23), particularly during periods of extended low flow. Overall, the periphyton biomass at lower Mohaka sites is typical of a healthy, upland and lowland river systems, with levels typically comparable to the reference site examples provided in Figure 2-22.

Figure 2-22: Periphyton biomass levels measured at SoE monitoring sites. SoE sites for the Mohaka River U/S Taharua confluence and the Ngaruroro River at Whanawhana (shaded) are included as Upland (U) and Lowland (L) reference sites for comparison purposes. The blue line relates to the Biggs (2000) ‘Biodiversity’ protection limit; the red line the ‘Recreational amenity’ limit for filamentous algae.

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Figure 2-23: Photos of excessive filamentous green algae growth in the Ngaruroro River at Whanawhana after extended periods of low flow. Nutrient concentrations at this site are low. Photo taken March 2013.

2.1.11 Dissolved oxygen Dissolved oxygen is a vitally important component in the life supporting capacity of freshwater ecosystems. Humans absorb oxygen from the air through their lungs, while aquatic organisms absorb oxygen from the water through their gills. Fish, invertebrates and other organisms are stressed when insufficient oxygen is dissolved in the water.

Various elements of aquatic systems either consume and/or produce oxygen. Plants and algae growing in the water produce oxygen as a by-product of photosynthesis. This supplements oxygen passively diffusing into the water from the atmosphere or being infused by turbulence or aeration in steeper or fast flowing streams, a process known as re-aeration (Figure 2-24). However, plants and algae also use oxygen when they respire, as do animals, fungus and bacteria living in the water. The breakdown of organic matter by aerobic micro- organisms also consumes oxygen and is termed the ‘biochemical oxygen demand’ (BOD). This process also occurs in the sediments and is termed the ‘sediment oxygen demand’ (SOD) as shown in Figure 2-24.

In un-shaded streams with high nutrient inputs, excessive growth of plants and algae results in extremely high dissolved oxygen levels during the day, then extremely low dissolved oxygen levels during the night or early morning, when these plants and algae consume more oxygen than the waterway is capable of supplying. The low dissolved oxygen conditions mean there is little oxygen for fish and other organisms to use. Figure 2-24 is a schematic of the major processes that influence oxygen concentration in rivers and streams.

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Figure 2-24: Schematic of the major processes influencing dissolved oxygen concentration in rivers. DO = dissolved oxygen; BOD = biochemical oxygen demand; SOD = sediment oxygen demand (Davies-Colley et al., 2013).

A waterway with dissolved oxygen levels consistently below 5.0 mg/l is unable to support sensitive species and the ecological integrity of these systems will be compromised. Dissolved oxygen levels that are greater than 8.0 mg/l are typically capable of supporting the full range of aquatic organisms (MfE, 2013).

Colder water can hold more oxygen than warmer water. When water temperature is greater than 27oC it cannot hold more than 8.0 mg/l of oxygen. Un-shaded systems that overheat during the day can also be depleted of oxygen.

The detrimental effects of increasing water temperature on trout are two-fold. First as water temperature increases, trout oxygen requirements also increase as they become more active (Elliott, 1994). At the same time, increasing water temperatures decrease the oxygen-carrying capacity of water.

Rainbow trout are more sensitive to low dissolved oxygen concentrations than most New Zealand native fish species (Dean & Richardson, 1999). Free swimming trout can tolerate DO concentrations of 5 to 5.5 mg/l, but the saturation should be at least 80% (Hay et al., 2006). The RMA Schedule 3 states that “The concentration of dissolved oxygen shall exceed 80% saturation concentration” in Class AE (Aquatic Ecosystems), F (Fishery) and FS (Fish Spawning) waters”.

Dissolved oxygen levels throughout the Mohaka catchment should not pose any risk to native species. As stated previously, rainbow trout are typically more sensitive to low dissolved oxygen levels than native fish. Research into the oxygen requirements of native fish is limited, but Dean and Richardson (1999) demonstrated that 7 native species of fish were less sensitive to low levels of DO than juvenile rainbow trout. This included longfin elvers and juvenile torrentfish, which are the life stages of species we may expect to be particularly sensitive given their preference for fast water habitats with typically higher DO concentrations. Landman et al. (2005) more recently found that the whitebait stage of inanga was more sensitive than juvenile rainbow trout (parr). The contrast of inanga sensitivity between Landman et al. (2005) and Dean and Richardson (1999) was thought to be related to experimental conditions that denied inanga the opportunity for aquatic surface respiration. When dissolved oxygen levels are low, inanga are able to obtain oxygen directly from the air which allows them to survive in low oxygen waters (Urbina et al., 2011). Although more research into the effects of low oxygen on native fish communities would be beneficial, a common assumption in New Zealand is that if conditions satisfy the oxygen requirements of the well-studied rainbow

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trout, they should by default satisfy the requirements of native species (Dean & Richardson, 1999; Franklin, 2013). This assumption has been adopted here.

The ANZECC (1992) guidelines recommend a minimum DO concentration of 6 mg/l and 80% saturation. Hay et al. (2006) suggests these limits should be seen as short-term exposure levels (i.e. occurring only for a few days), as data suggests that long-term exposure to DO levels of 6 mg/l can impair the growth of salmoniids, which include trout species (CCME, 1997).

In river reaches where substantial upwelling of potentially low-oxygen or anoxic groundwater occurs, in- stream dissolved oxygen concentrations after mixing may also be low. Likewise, in wetland systems where bacterial respiration levels are high, oxygen levels can be very low. This is consequence of natural background conditions and is independent of anthropogenic (human) influences.

Figure 2-25: Dissolved oxygen % saturation at SoE monitoring sites. SoE sites for the Mohaka River U/S Taharua confluence and the Ngaruroro River at Whanawhana (shaded) are included as Upland (U) and Lowland (L) reference sites for comparison purposes. The red line relates to the RMA (1991) Schedule 3 lower limit of 80% for supporting salmoniid (trout) fisheries.

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Figure 2-26: Dissolved oxygen concentration at SoE monitoring sites. SoE sites for the Mohaka River U/S Taharua confluence and the Ngaruroro River at Whanawhana (shaded) are included as Upland (U) and Lowland (L) reference sites for comparison purposes. The red line relates to the ANZECC (1992) guideline minimum DO concentration of 6 mg/l.

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Figure 2-27: 5 year median dissolved oxygen % saturation levels at SoE monitoring sites.

Figure 2-28: 5 year median dissolved oxygen concentration levels at SoE monitoring sites.

2.1.12 Compliance with NOF attribute bands under the NPS FW (2014) The National Policy Statement for Freshwater Management 2014 (NPS-FM (2014)) sets out the objectives and policies for freshwater management under the Resource Management Act 1991. The NPS-FM (2014) came into effect on 1 August 2014 and is one of the initiatives developed as part of the Government’s Fresh Start for Fresh Water programme of water reform.

Sitting within the NPS-FW (2014) is a National Objectives Framework (NOF) aimed at providing “an approach to establish freshwater objectives and national values, and any other values that: a) is nationally consistent; and b) recognises regional and local circumstances.” (Objective CA1).

Appendix 2 of the NOF outlines a number of attribute tables. An attribute “is a measureable characteristic of freshwater, including physical, chemical and biological properties, which supports particular values”. Currently, specific to rivers, under the NPS-FW (2014) the NOF includes attributes for periphyton (as chla/m2), nitrate-nitrogen (mg/l), ammoniacal-nitrogen (mg/l), dissolved oxygen (mg/l – applicable to downstream of point-source discharges only), and E. coli (E. coli/100ml - for secondary contact recreation only). Targets have been proposed within the NOF attributes that include “national bottom lines” (D band) – thresholds of water quality attributes that good management should prevent waterways from crossing. Essentially a “bottom line” is the minimum water quality level that all water bodies must achieve.

Each attribute table (see Appendix E) sets out the attribute and the unit in which it is to be measured. It then sets out A, B, C and D states and defines these in narrative and numeric terms. The numbers associated with most of the attributes relate to contaminant load. The higher the contaminant load, the lower the water quality state with A being the highest/best quality and D being below the national bottom line.

NOF attribute band – E. coli Where adequate monitoring data exists, NOF attribute states have been calculated and summarised for all monitoring sites across the Mohaka catchment and presented in the following tables being Table 2-9 (E. coli), Table 2-10 (nitrate) and Table 2-11 (ammonia) along with a general summary of overall bands in Table 2-12.

All sites throughout the Mohaka catchment are in the A band for median E. coli levels at flows less than 3 times the median for years analysed from 2009 to 2013 (Table 2-9). The median value relates to secondary contact recreation values defined under the NPS-FW 2014 as: “Secondary contact means people’s contact with fresh water that involves only occasional immersion and includes wading or boating (except boating where there is a high likelihood of immersion)”. In areas where the community values activities that result in more frequent immersion in water such as swimming, white-water rafting or water skiing, the NPS-FW (2014) states that “the risk of infection will be no more than moderate”. In these areas a more stringent 95th percentile value may be used to assess risk of infection (NPS-FM (2014)). In relation to the 95th percentile, only one site recorded a value outside of the minimum acceptable state for full immersion activities, being the B band, this being 3927 for the Ripia River. This result is an outlier and high for this site.

The A band compliance across all sites for secondary contact and A or B band compliance across all sites except one for full immersion activities shows an excellent level of compliance for E. coli across the Mohaka catchment and as defined by the NPS-FW (2014) “people are exposed to a low risk of infection from contact with water during activities”.

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Table 2-9: NPS-FW (2014) NOF bands for the E. coli attribute for Mohaka River catchment monitoring sites.

NOF banding legend A band B band C band D band

E. coli (CFU/100ml) Medians 95th percentile5 Site 2009 2010 2011 2012 2013 2009 - 2013 Mohaka Rv U/S Taharua Rv 2 1 1 3 11 55 Taharua Rv at Wairango 7 5 7 8 7 57 Taharua Rv at Twin Culv 10 12 6 13 10 270 Taharua Rv at Henry's Br NA NA NA 12 6 86 Taharua Rv at Poronui Stn 7 9 10 12 16 82 Taharua Rv at Red Hut 13 23 16 13 9 93 Mohaka Rv D/S Taharua Rv 6 8 8 9 6 118 Ripia Rv U/S Mohaka Rv 10 9 1 11 10 3927 Mohaka Rv D/S Ripia Rv 5 6 2 10 10 250 Mohaka Rv at SH5 (NIWA) 11 24 21 32 15 35 Waiarua Strm 8 6 20 5 10 12 Waipunga Rv at Pohokura Rd 3 4 4 3 3 35 Mokomokonui Rv 7 8 5 4 17 294 Mohaka Rv D/S Waipunga Rv 2 7 14 11 8 80 Mohaka Rv at Willowflat 14 20 14 10 NA 58 Mohaka Rv at Raupunga 19 21 7 11 NA 332 Mohaka Rv at Raupunga (NIWA) 6 48 15 13 28 55

NOF attribute band – nitrate-nitrogen The nitrate attribute aims to manage against chronic toxicity risk to aquatic animals. Chronic exposure typically includes a biological response of relatively slow progress and long continuance, often affecting a life stage (Hickey, 2013b). Such a response may be reduced growth rate or reduced gonad development when compared to optimum growth conditions (a control). It does not relate to acute toxicity effects that result in the death of an animal. The narratives for each nitrate attribute band are included in Appendix E. Further reading on nitrate toxicity and guidelines for New Zealand can be found in Hickey (2013a); Hickey (2013b).

Median and 95th percentile nitrate-nitrogen concentrations for all Mohaka catchment sites outside of the Taharua catchment are in the A band for years 2009 to 2013. The narrative for this band states there is “unlikely to be effects even on sensitive species” (NPS-FW (2014); Appendix E). The A band reflects extremely a low level of risk to any aquatic species. For the Taharua catchment, the two upper sites with the highest nitrate-nitrogen concentrations, being Wairango and Twin Culverts, are in the C band for both median and 95th percentile nitrate-nitrogen concentrations. The exception is for the 95th percentile concentration for Wairango for 2013 that goes from the C band (2009 to 2012) to the B band. The narrative for the C band states that there is “potential for growth effects on up to 20% of species (mainly sensitive species such as fish). No acute effects” (NPS-FW (2014); Appendix E). The remaining Taharua sites, being Henry’s Bridge, Poronui and Red Hut, all fall within the B band. The narrative for the B band states that there is “some growth

5 For relevance to total immersion activities (swimming), the time period for 95th percentile calculations has been restricted to 1 November to 30 April at flows less than median flow. Activities such as white-water rafting may be undertaken at any time of the year under any flow conditions. To see 95th percentiles for E coli at all times and flow conditions for Mohaka catchment monitoring sites refer to Appendix B.

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effects on up to 5% of species” (NPS-FW (2014); Appendix E). For a more detailed discussion of the likely risk of chronic nitrate toxicity effects at the elevated nitrate-nitrogen concentrations typical of the upper Taharua refer to Hickey (2013b).

Table 2-10: NPS-FW (2014) NOF bands for the nitrate Attribute States for nitrate toxicity for Mohaka River catchment monitoring sites. NOF banding legend A band B band C band D band

Nitrate-nitrogen toxicity (mg/l) Median 95th Percentile Site 2009 2010 2011 2012 2013 2009 2010 2011 2012 2013 Mohaka Rv U/S Taharua Rv 0.03 0.03 0.03 0.02 0.02 0.19 0.07 0.27 0.05 0.07 Taharua Rv at Wairango 2.90 3.45 3.55 3.30 2.60 3.80 4.38 3.90 3.90 2.80 Taharua Rv at Twin Culv 3.60 3.70 3.90 3.60 3.20 3.70 4.09 4.73 3.90 3.69 Taharua Rv at Henry's Br NA 1.48 NA 2.15 2.30 NA 1.48 NA 2.50 2.50 Taharua Rv at Poronui Stn 1.55 1.69 1.77 1.64 1.61 1.90 2.20 2.30 1.95 2.00 Taharua Rv at Red Hut 1.20 1.26 1.28 1.33 1.53 1.50 1.67 1.81 1.77 1.83 Mohaka Rv D/S Taharua Rv 0.50 0.66 0.57 0.55 0.71 1.16 1.02 1.06 0.96 1.08 Ripia Rv U/S Mohaka Rv 0.07 0.08 0.07 0.09 0.03 0.21 0.17 0.17 0.14 0.15 Mohaka Rv D/S Ripia Rv 0.24 0.24 0.32 0.27 0.24 0.34 0.41 0.54 0.40 0.49 Mohaka Rv at SH5 (NIWA) 0.24 0.27 0.30 0.29 0.27 0.32 0.34 0.46 0.37 0.42 Waiarua Strm 0.46 0.54 0.59 0.58 0.60 0.50 0.63 0.64 0.63 0.72 Waipunga Rv at Pohokura Rd 0.27 0.23 0.22 0.17 0.07 0.33 0.30 0.24 0.20 0.08 Mokomokonui Rv 0.10 0.02 0.09 0.03 0.02 0.22 0.04 0.22 0.05 0.08 Mohaka Rv D/S Waipunga Rv 0.22 0.22 0.26 0.21 0.22 0.32 0.37 0.56 0.26 0.47 Mohaka Rv at Willowflat 0.15 0.17 0.19 0.16 NA 0.32 0.34 0.32 0.21 NA Mohaka Rv at Raupunga 0.16 0.18 0.18 0.18 0.01 0.41 0.35 0.31 0.29 0.02 Mohaka Rv at Raupunga (NIWA) 0.15 0.21 0.15 0.16 0.11 0.39 0.44 0.34 0.63 0.40

NOF attribute band – ammonia The ammonia attribute aims to manage against chronic ammonia toxicity risk to aquatic animals. The attribute bands for a site are based on annual median and maximum concentrations (Appendix E). Median ammonia concentrations for all Mohaka catchment monitoring sites are in the A band for years 2009 to 2013 (Table 2-11). The A band reflects an extremely low level of risk to ammonia toxicity for any aquatic species with a narrative that states “no observed effect on any species tested”. Annual maximum numbers fluctuate more than medians and have some sites, such as the Ripia River and the Mohaka River D/S Waipunga, oscillating between the A and B band. The B band narrative states that ammonia “starts impacting occasionally on the 5% most sensitive species” (NPS-FW (2014); Appendix E).

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Table 2-11: NPS-FW (2014) NOF bands for the ammonia toxicity attribute for Mohaka River catchment monitoring sites. NOF banding legend A band B band C band D band

Ammonia toxicity (mg/l) Medians Maxima Site 2009 2010 2011 2012 2013 2009 2010 2011 2012 2013 Mohaka Rv U/S Taharua Rv 0.002 0.003 0.002 0.003 0.003 0.011 0.016 0.003 0.025 0.025 Taharua Rv at Wairango 0.003 0.006 0.002 0.002 0.002 0.027 0.018 0.035 0.025 0.025 Taharua Rv at Twin Culv 0.003 0.006 0.002 0.002 0.002 0.012 0.020 0.019 0.055 0.005 Taharua Rv at Henry's Br NA 0.018 NA 0.014 0.003 NA 0.018 NA 0.025 0.025 Taharua Rv at Poronui Stn 0.004 0.002 0.002 0.002 0.004 0.013 0.013 0.012 0.025 0.006 Taharua Rv at Red Hut 0.002 0.005 0.002 0.004 0.004 0.007 0.028 0.003 0.025 0.080 Mohaka Rv D/S Taharua Rv 0.003 0.003 0.002 0.004 0.004 0.013 0.022 0.003 0.025 0.025 Ripia Rv U/S Mohaka Rv 0.008 0.003 0.004 0.004 0.005 0.013 0.050 0.007 0.060 0.025 Mohaka Rv D/S Ripia Rv 0.003 0.005 0.003 0.003 0.006 0.009 0.048 0.007 0.008 0.025 Mohaka Rv at SH5 (NIWA) 0.003 0.003 0.003 0.005 0.004 0.017 0.011 0.005 0.010 0.015 Waiarua Strm 0.002 0.003 0.002 0.002 0.003 0.026 0.009 0.003 0.025 0.025 Waipunga Rv at Pohokura Rd 0.003 0.004 0.002 0.003 0.025 0.008 0.024 0.003 0.025 0.100 Mokomokonui Rv 0.003 0.005 0.003 0.003 0.003 0.003 0.016 0.003 0.025 0.025 Mohaka Rv D/S Waipunga Rv 0.004 0.015 0.003 0.004 0.007 0.028 0.052 0.010 0.025 0.198 Mohaka Rv at Willowflat 0.004 0.006 0.004 0.005 NA 0.006 0.063 0.026 0.006 NA Mohaka Rv at Raupunga 0.005 0.008 0.005 0.011 0.025 0.012 0.043 0.038 0.025 0.025 Mohaka Rv at Raupunga (NIWA) 0.006 0.004 0.006 0.008 0.008 0.017 0.015 0.020 0.029 0.022

NOF attribute band – dissolved oxygen Continuous dissolved oxygen data has been collected from the Taharua River at Henry’s Bridge from 22nd of November 2014 to the present date (data not presented in this report). For the summer period of 2014/15, the minimum instantaneous dissolved oxygen concentration reached was 8.6 mg/l. This places the Taharua at Henry’s Bridge in an ‘A’ band for dissolved oxygen. With the exception of the Taharua at Wairango monitoring site that typically has lower dissolved oxygen concentrations than the Taharua at Henry’s Bridge (Figure 2-26; based on spot measurements), all other monitoring sites across the Mohaka catchment have comparable or higher dissolved oxygen concentrations. Technically the NOF dissolved oxygen attribute only relates to sections of streams and rivers downstream of point source discharges (Appendix E).

NOF attribute band – periphyton For calculating the NOF periphyton attribute band, monthly measurements collected over a minimum of three years are stipulated (Appendix E). For the period 2009 to 2013, no sites in the Mohaka catchment meet this requirement. Six sites in the Mohaka River have periphyton biomass measurements made nominally on a monthly basis (Table 2-12). The remaining sites either have intermittent, annual or no measurements of periphtyon biomass. NOF bands for periphyton have been calculated for all sites with at least five data points for the period running 2009 to 2013 (Appendix F). Caution must be given to sites with few data points.

For periphyton, with the exception of the lower Mohaka River at Willowflat and Raupunga, all sites with sufficient data to calculate a NOF band are currently sitting as an A band.

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NOF attribute band summary Table 2-12 provides an overall summary of NOF attribute bands for all monitoring sites across the Mohaka catchment. Overall, with the exception of nitrate levels in the upper Taharua River, the ‘A’ NOF attribute band dominates across the Mohaka catchment reflecting an excellent level of compliance againmst the most stringent NOF band. Table 2-12 uses the median values for ammonia, nitrate and E. coli.

Table 2-12: NPS-FW (2014) NOF band summary for freshwater river attributes for Mohaka River catchment monitoring sites for the period 2009 to 2013. The Taharua at Henry’s Bridge is the only site with continuous dissolved oxygen data for which a NOF band may be calculated. For periphyton, sites with NOF bands in BOLD (6 sites) have sufficient data for the NOF bands to be determined. The remaining 3 sites with NOF bands have five observations collected on an annual (summer) basis. The bands for these sites should be treated with caution. The remaining sites have fewer than 5 observations or no data (NA).

NOF band summary Escherichia Dissolved Site Ammonia Nitrate Periphyton coli Oxygen Mohaka Rv U/S Taharua Rv A A A NA A Taharua Rv at Wairango A C A NA NA Taharua Rv at Twin Culv A C A NA NA Taharua Rv at Henry's Br A B A A NA Taharua Rv at Poronui Stn A B A NA B Taharua Rv at Red Hut A B A NA NA Mohaka Rv D/S Taharua Rv A A A NA A Ripia Rv U/S Mohaka Rv A A A NA A Mohaka Rv D/S Ripia Rv A A A NA A Mohaka Rv at SH5 (NIWA) A A A NA NA Waiarua Strm A A A NA NA Waipunga Rv at Pohokura Rd A A A NA NA Mokomokonui Rv A A A NA A Mohaka Rv D/S Waipunga Rv A A A NA A Mohaka Rv at Willowflat A A A NA B Mohaka Rv at Raupunga A A A NA B Mohaka Rv at Raupunga (NIWA) A A A NA NA

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2.1.13 Compliance with HBRC Regional Resource Management Plan (2006) surface water quality Environmental Guidelines Two types of data summary have been prepared to compare existing water quality values to RRMP (2006) Environmental Guideline values:

(1) For samples collected between 2009 and 2013 at flows less than median flow, comparison of mean DO saturation, mean black disc clarity, mean DRP, and mean/max ammoniacal nitrogen (a toxicant) with RRMP (2006) guideline values (Table 2-13)

(2) For samples collected between 2009 and 2013 at flows less than median flow, the total number of samples taken and the number of samples being non-compliant with RRMP (2006) Environmental Guideline levels (Table 2-14).

Surface water quality compliance throughout the Mohaka River is very good when mean values (Table 2-13) are compared to Environmental Guideline values listed in the HBRC Regional Resource Management Plan (2006).

Dissolved oxygen levels are fully compliant at all sites with the exception of the Taharua River at Wairango monitoring site. Dissolved oxygen levels are quite low at this site with the mean of samples being less than the RRMP (2006) guideline value of 80% (Table 2-13) and only 25% of samples having readings greater than 80% saturation (Table 2-14). As discussed in Section 2.1.11, this site is heavily influenced by groundwater upwelling, with the groundwater having very low dissolved oxygen concentrations. This results in lower in- stream dissolved oxygen concentrations compared to sites elsewhere.

Black disc water clarity has the poorest level of compliance with RRMP guideline levels. Although most sites are compliant when mean black disc clarity is compared to the RRMP guideline level of 1.6m (Table 2-13), four sites have around 50% or less of observations that are compliant (Table 2-14). The sites with the poorest level of compliance are the Mohaka River at Willowflat and Mohaka River at Raupunga. These sites have mean black disc clarity measurements of 0.85 m and 1.00 m respectively (Table 2-13). Both these sites have statistically significant deteriorating trends in black disc clarity (Section 2.1.7) and warrant further investigation to determine the reason for trending reductions in water clarity. As discussed in Section 2.1.7, the soft sedimentary geology that is common in the lower catchment could lead to natural reductions in water clarity. However, this alone does not fully explain why these sites have become worse over time.

Mean DRP levels are compliant across all sites (Table 2-13). Only two sites, the Taharua at Wairango and the Taharua at Twin Culverts have measured results greater than the RRMP (2006) guideline level of 0.015 mg/l. These two sites have statistically significant improving trends in DRP.

All sites are fully compliant for ammoniacal nitrogen (NH4-N) with maximum concentrations being well below the RRMP (2006) guideline of 0.1 mg/l (Table 2-13).

Although not summarised in Table 2-13 and Table 2-14, recorded water temperatures were all below the 25oC indicator level identified on page 103 of the HBRC RRMP (2006).

Overall the level of compliance with RRMP (2006) Environmental Guideline levels is very high for the Mohaka catchment.

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Table 2-13: Comparison of measured dissolved oxygen, black disc, dissolved reactive phosphorus and ammoniacal nitrogen levels with HBRC RRMP (2006) Environmental Guideline levels. The data summarised in the table is for samples taken between January 2008 and December 2013 during times that flows in the river were below median flow as prescribed in Policy 72 of the HBRC RRMP (2006). Green cells are compliant, red cells are non-compliant.

Site name Mean of DO Mean of Black Mean of DRP Mean / Max of (%) Disc Clarity (mg/l) NH4-N (mg/l) (m) Mohaka River U/S Taharua River 96.9 5.68 0.003 0.007 / 0.025 Taharua River at Wairango 76.8 6.07 0.015 0.010 / 0.044 Taharua River at Twin Culverts 91.1 4.51 0.011 0.001 / 0.028 Taharua River at Henrys Bridge 94.2 4.04 0.009 0.005 / 0.005 Taharua River at Poronui Station 97.0 2.32 0.009 0.009 / 0.029 Taharua River at Red Hut 98.7 2.70 0.006 0.009 / 0.031 Mohaka River D/S Taharua River 100.8 2.95 0.004 0.008 / 0.025 Ripia River U/S Mohaka River 102.2 3.56 0.005 0.007 / 0.022 Mohaka River D/S Ripia River 102.2 2.77 0.004 0.007 / 0.045 Mohaka River at SH5 103.2 4.06 0.004 No Data Waiarua Stream 95.0 2.26 0.005 0.005 / 0.005 Waipunga River at Pohokura Rd 101.0 1.76 0.006 0.006 / 0.020 Mokomokonui River 99.7 3.55 0.013 0.005 / 0.010 Mohaka River at Willowflat 102.0 0.85 0.005 0.007 / 0.036 Mohaka River at Raupunga 108.1 1.00 0.005 0.007 / 0.036 HBRC RRMP (2006) guideline level 80% 1.6 m 0.015 mg/l 0.100 mg/l Number of sites compliant 15 / 16 14 / 16 16 / 16 15 / 15 % site compliance 94% 88% 100% 100%

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Table 2-14: Comparison of measured DO, BD clarity and DRP values with HBRC RRMP (2006) Environmental Guideline levels. The data summarised in the table if for samples taken between January 2009 and December 2013 at times that flows in the river were below median flow as prescribed in Policy 72 of the HBRC RRMP (2006). Sites with more than 80% of observations being compliant with guideline levels are shaded GREEN; between 50% and 80% compliant are shaded ORANGE; and less than 50% compliant are shaded RED.

Site name Dissolved Oxygen Saturation Black Disc Clarity Dissolved Reactive Phosphorus Samples at Samples Samples Samples at Samples Samples Samples at Samples Samples < median < 80% < limit < median < 1.6m > limit < median > 0.015 < limit flows saturation flows flows mg/l Mohaka River U/S Taharua River 30 1 97% 30 0 100% 38 0 100% Taharua River at Wairango 28 21 25% 27 0 100% 29 13 55% Taharua River at Twin Culverts 28 2 93% 24 0 100% 28 7 75% Taharua River at Henrys Bridge 11 1 91% 8 0 100% 16 0 100% Taharua River at Poronui Station 16 1 94% 18 3 83% 18 0 100% Taharua River at Red Hut 25 0 100% 25 4 84% 31 0 100% Mohaka River D/S Taharua River 34 0 100% 34 6 82% 39 0 100% Ripia River U/S Mohaka River 16 0 100% 17 1 94% 24 0 100% Mohaka River D/S Ripia River 28 1 96% 28 6 79% 29 0 100% Mohaka River at SH5 34 0 100% 34 2 94% 34 0 100% Waiarua Stream 15 1 93% 18 8 56% 23 0 100% Waipunga Rv at Pohokura Rd 9 0 100% 11 7 36% 16 0 100% Mokomokonui River 15 0 100% 16 2 88% 17 0 100% Mohaka River at Willowflat 15 1 93% 16 14 13% 18 0 100% Mohaka River at Raupunga 15 0 100% 17 13 24% 24 0 100%

2.2 Mohaka Catchment Concurrent Gauging Study In 2012, water quantity and quality was measured concurrently across the Mohaka catchment - ie, water quality and flow were measured across all sites on the same day. Five ‘Concurrent Gauging Study’ runs were completed encompassing 17 sites from the upper, middle and lower catchment. Of these 17 sites, 8 were current SoE sites along with an additional 9 previously un-sampled sites. Samples were analysed for total and dissolved nutrients and suspended solids. Figure 2-29 shows the location of the Concurrent Gauging Study sites.

Figure 2-29: Locations of Mohaka Catchment Concurrent Gauging study sites. Three arbitrary Mohaka River catchment zones have been included in this report being the “upper zone” (A), “middle zone” (B) and “lower zone” (C). Characteristics of each of the zones is provided in Section 1.3. Site names in the figure legend include the distance from the monitoring site to the sea.

The main objectives of the study were to measure flow and nutrients across a wide spatial gradient of the catchment under varying flow conditions from low flows to moderate/high flows. Sampling all sites on the same day allows direct comparisons to be made between sites because temporal variability across sites is reduced. The data collected allows both nutrient concentrations, and – when concentrations are combined with flow - nutrient yields to be compared across the catchment.

Including long-term SoE monitoring sites with new sites allows the newly monitored sites to be benchmarked against the long-term datasets of the SoE monitoring sites.

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Although they include limited historical information on flow and water quality, the following four key sites were included in the concurrent gauging study:

(1) The upper Ripia River (Lochinver Station)

(2) The Okeke Stream (tributary of the Waipunga River)

(3) The Waipunga River upstream of the confluence with the Mohaka River

(4) The Te Hoe River upstream of the confluence with the Mohaka River

Patterns in the concurrent gauging data closely follow patterns evident in the long-term SoE monitoring data. The Taharua catchment recorded the highest nitrogen concentrations -- both total and dissolved - of any monitoring sites in the catchment. Similarly, phosphorus concentrations are low in the upper catchment and increase as one travels towards the coast.

The inclusion of the (upper) Ripia River at Lochinver and the Okeke Stream (upper Waipunga River tributary) sampling sites is useful, since these sites may be impacted by land-use practices in the local and adjacent stream catchments. Both these sites are close to the Taharua River and Rangitaiki Plains and could be affected by nitrate enriched groundwater sourced from either the Taharua or the Rangitaiki Plains aquifers.

In the case of the upper Ripia River site, the upstream catchment has been cleared in a similar way to the Taharua River catchment. Figure 2-30 and Figure 2-32 show that the upper Ripia River monitoring site on Lochinver Station shows higher nitrogen levels compared to catchments with little or no land-use change. TN and DIN concentrations are low compared to the Taharua River monitoring sites and are marginally lower than the Waiarua Stream monitoring site (State Highway 5). These values are typical of a stream draining a catchment dominated by sheep and beef grazing land-uses.

However, the Okeke Stream has quite elevated levels of both TP and DRP (Figure 2-31 and Figure 2-33), despite being dominated by native vegetation and having extremely low concentrations of TN and DIN (Figure 2-30 and Figure 2-32). In this case most TP is DRP. At this stage the reasons for this are not clear.

As with the Waiarua Stream (upper Waipunga River) and the monitoring site in the lower Waipunga River upstream of the Mohaka River confluence, the influence of any nitrogen enrichment in the upper catchment is not detectable at the downstream monitoring sites. Nitrogen levels are those that would be expected of a pristine catchment dominated by native vegetation with little or no intensive land-use.

Not surprisingly, the Te Hoe River has very low nitrogen concentrations. The Te Hoe River catchment is dominated by native bush and production forest that is likely to leach very low levels of nitrogen. The concentrations in the river are comparable to those of a near-natural catchment. Contrastingly, phosphorus concentrations were elevated in the Te Hoe River and comparable to those recorded in the lower Mohaka River at SoE monitoring sites. It is unclear whether the elevated P concentrations, either total and dissolved, are due to natural background geological effects or if recent production forest rotations in the lower Te Hoe River catchment could be contributing to short-term elevations in mobilised phosphorus.

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Figure 2-30: Mohaka Catchment Concurrent Gauging study results for Total Nitrogen (TN) concentration.

Figure 2-31: Mohaka Catchment Concurrent Gauging study results for Total Phosphorus (TP) concentration.

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Figure 2-32: Mohaka Catchment Concurrent Gauging study results for DIN concentration.

Figure 2-33: Mohaka Catchment Concurrent Gauging study results for DRP concentration.

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Nutrient yields are a further source of information. Calculation of nutrient yields helps standardise the contribution of nutrients from the catchment upstream of a site and allows for identification of catchments contributing disproportionately to nutrient loss. Typically more intensive land-uses result in higher nutrient yield.

NOTE: Yields calculated and reported on in Figure 2-34 and Figure 2-35 are ‘attenuated’ yields. ‘Attenuated’ in-stream load and yield means that the nitrogen has been attenuated between leaving the surface of the catchment and being measured in the river. Nitrogen attenuation occurs by processes taking place as it travels from below the root-zone, through sub-surface flowpaths to the stream. These processes include denitrification, which is a significant process involving bacterial conversion of nitrate to nitrogen gas. They do not represent the nutrient loss from the ‘farm gate’.

Nutrient yields are calculated by multiplying the measured nutrient concentration with measured flow for each site on a given sampling date. This gives the mass or ‘load’ of nutrient being transported in the river at the time of sampling. The load is then divided by the upstream catchment area to standardise loads across catchments giving a nutrient ‘yield’ per unit of catchment area. Yields are reported as kilograms per hectare per year (kg/ha/yr) (Figure 2-34 and Figure 2-35).

In catchments other than the Taharua catchment, attenuated nutrient yields measured during the concurrent gauging study are generally very low, with TN yields being 5 kg N/ha/yr or less (Figure 2-34). If it is assumed that there is 50% attenuation of nitrogen from the root-zone to what is measured in-stream, then the nitrogen loss from the landscape upstream of the sampling sites would be 10 kg N/ha/yr or less. This is typical of catchments with low intensity land-use (Hamilton, 2005; Menneer et al., 2004; MfE, 2007).

The level of attenuation between what is lost from the root zone to what is measured in-stream is yet to be determined for the Taharua catchment. The free draining pumice soils may result in fully oxidised groundwater that would provide little attenuation through denitrification of groundwater as it travels through the aquifer and is discharged to the stream. There may therefore be very little attenuation of nitrogen in the Taharua catchment. If this is the case then root zone nitrogen yields upstream of the Henrys Bridge sampling site, based on the instantaneous yields calculated from the Concurrent Gauging study may vary anywhere from 20 to 40 kg N/ha/yr.

Annual TN yields for the Taharua at Red Bridge, Twin Culverts and Wairango monitoring sites, based on long- term SoE monitoring data are presented in Section 2.3.4. Nutrient and sediment yields for remaining SoE monitoring sites are summarised in Appendix G.

The Inangatahi Stream was not included in the concurrent gauging run. As mentioned previously, data on water quality entering the Mohaka River from this catchment is sparse with a sample being collected on one occasion only. A targeted investigation looking at benchmarking the water quality of the Inangatahi Stream is warranted.

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Figure 2-34: Mohaka Catchment Concurrent Gauging study results for Total Nitrogen (TN) instantaneous yield.

Figure 2-35: Mohaka Catchment Concurrent Gauging study results for Total Phosphorus (TP) instantaneous yield.

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2.3 Effects of Taharua River outflows on water quality of the upper Mohaka River Taharua River outflows affect nutrient levels, water clarity and algal biomass in the upper Mohaka River. SoE monitoring data from the Mohaka River was examined for sites located upstream and downstream of the confluence of the Mohaka and Taharua rivers, for in-stream nutrients (A and B), algal biomass (C) and water clarity (D) (Figure 2-36).

Changes in the four parameters examined (Figure 2-36) demonstrate the effect that Taharua outflows have on water quality, particularly as it relates to nitrogen (as DIN in Figure 2-36 A) and water clarity (as black disc in Figure 2-36 D), and are statistically significant with a Mann-Whitney test significant at P << 0.001. Interestingly, despite a significant increase in periphyton biomass downstream of the Taharua confluence, periphyton biomass on 42 of the 45 occasions it was measured remains below the Biggs (2000) 50 mg/m2 biodiversity guideline at the HBRC monitoring site 500m downstream of the confluence (Figure 2-36 C).

Figure 2-36: Comparison of Mohaka River water quality upstream and downstream of the Taharua River confluence. A: Dissolved inorganic nitrogen (DIN); B: Dissolved reactive phosphorus (DRP); C: Algal biomass (Chla); D: Water clarity (black disc).

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Over recent years, several additional studies have been undertaken to better understand the effect Taharua outflows have on stream ecosystem function of the upper Mohaka River, particularly as it relates to macroinvertebrate and periphyton communities.

Unpublished work was undertaken by HBRC in February 2012 on the benthic ecology of the upper Mohaka River upstream and downstream of the Taharua River confluence. The study compared periphyton and macroinvertebrate community structures at three sites upstream and three sites downstream of the Taharua confluence.

The study showed evidence for eutrophication in the Mohaka River downstream of the confluence of the Taharua, causing a change to the benthic structure of periphyton and macro-invertebrate communities. Analysis of variance (ANOVA) in this data showed:

. a significant increase in nitrogen (nitrate), periphyton measured as chlorophyll a, and ash free dry weight (AFDW) downstream of the confluence,

. no difference in phosphorus between impact and control sites, and

. a significant reduction in sensitive macro-invertebrate taxa downstream.

Multi-Dimensional Scaling (MDS) plots of periphyton and macro-invertebrate community data showed a clear separation between impact and control sites. Species driving the changes were:

. a significant shift in species composition of the periphyton community from a community typical of oligotrophic (very low nutrient) conditions to one more typical of mesotrophic (mildly nutrient enriched) conditions,

. a higher abundance of Deleatidium mayfly at upstream control sites,

. a higher abundance of the snail Potamopyrgus, the caddis fly Aoteapsyche, the chironomid Maoridiamesa, the crane fly Aphrophila and the diptera Muscidae at sites downstream of the confluence.

The results of the 2012 study confirmed earlier work carried out by HBRC in 2007 and 2008 and published in Stansfield (2008).

2.3.1 Invertebrate drift and trout growth potential study An extensive study took place in 2009 of the potential effect of dairy farming in the Taharua River catchment on macroinvertebrate drift and associated trout growth potential in the Taharua and Mohaka rivers (Shearer & Hays, 2010).

Two 'affected' sites, located in the Taharua River and the Mohaka River downstream of the Taharua confluence; and one ‘unaffected’ or control site located in the Mohaka River upstream of the Taharua confluence were sampled on three separate occasions for drifting invertebrates. Samplings were undertaken in summer (February 2009), autumn (April 2009) and spring (December 2009). On each occasion macroinvertebrate drift density, biomass and size structure estimates were compared between the sites. Comparisons were also made between sites of predicted gross and net rate of energy intake for drift-feeding trout, using a bioenergetic drift foraging model.

The Cawthron report concluded ‘In autumn and spring we found no significant differences in drift density or biomass between the sites. In summer drift density and biomass at the Taharua site was significantly lower than at the upper Mohaka reference site, with the lower Mohaka intermediary between the two. We found taxonomic and size structural differences in the drift between sites. On all sampling occasions the upstream Mohaka site had the greatest proportion of EPT (Ephemeroptera, Plecoptera and Trichoptera) taxa. The

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highest proportion of mayflies occurred at the upstream Mohaka site at dusk in all three seasons (when trout feeding activity is often at its peak). Small invertebrates (3-6 mm), least preferred by large trout, made up a larger proportion (by density and biomass) of the drift in autumn and spring at the sites influenced by dairying inputs (Taharua and downstream Mohaka sites). In all seasons, the upstream Mohaka reference site had the greatest density and biomass of large invertebrates (>6 mm), which are preferred by trout. An exception was in summer where the density, but not biomass, of large invertebrates was highest at the downstream Mohaka site’.

The Cawthron report also concluded ‘Our results provide evidence for impaired aquatic invertebrate drift and trout growth potential at dairy influenced sites in the Mohaka and Taharua Rivers in summer and to a lesser extent in spring. However, our results should be interpreted with caution as they are based on only three days sampling over three seasons. Moreover, although our results are consistent with effects expected from dairy farming (enrichment and/or siltation) definitively attributing cause to dairy farming is limited by the absence of a reference site in the Taharua and pre-impact data’.

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2.3.2 Mohaka River longitudinal survey In February and May of 2013, February 2014 and January 2015, a longitudinal survey study of in-stream river condition in the Mohaka River was undertaken, from upstream of the confluence with the Taharua River downstream to below the confluence with the Ripia River. The study was completed to determine the downstream extent of adverse effects on in-stream water quality in the Mohaka River from the Taharua tributary. Approximately 15 sites (Figure 2-37) were surveyed on each occasion. The surveys examined nutrients, water clarity, algal biomass and cover, and macroinvertebrate community characteristics.

Mohaka River monitoring sites 1 and 2 are located upstream of the confluence of the Mohaka and Taharua rivers. The remaining sites in the longitudinal study are located downstream of the confluence of the two rivers.

This study was called the ‘Mohaka River longitudinal survey’ as it looked at changes in in-stream water quality and ecology ‘longitudinally’ down the river from sites located upstream of the Taharua River confluence to sites downstream.

Figure 2-37: Locations of longitudinal survey study sites. Three arbitrary Mohaka River catchment zones have been included in this report being the “upper zone” (A), “middle zone” (B) and “lower zone” (C). Characteristics of each of the zones is provided in Section 1.3.

The February 2013, March 2014 and January 2015 surveys (surveys 1, 3 and 4) took place when river flows were low and had been so for at least twenty days, providing an extended period of algal accrual or growth. By contrast, the May 2013 survey (Survey 2) was completed 11 days after a small fresh came through the upper catchment. Flows were moderately higher during surveys 2 and 4 than during surveys 1 and 3 (Figure 2-38 and Table 2-15). The four surveys covered a range of low flow conditions and algal accrual periods,

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providing for a range of in-stream conditions to assess the effects of Taharua River outflows on the upper Mohaka River.

Figure 2-38: Mohaka River flows around the time the longitudinal surveys were carried out. Survey dates shown as red dots. Flow data sourced from the NIWA Glenfalls/McVicars Rd flow monitoring site.

Table 2-15: Past and present flow conditions for each of the Longitudinal Surveys.

Survey number Survey start Flow conditions Flow Mohaka River at Days since last Flow event date during survey SH5 (cumecs) flow event magnitude (cumecs) Survey 1 28/2/2013 Low 8000 24 18800 Survey 2 2/5/2013 Moderate 10700 11 21050 Survey 3 12/3/2014 Very Low 5800 29 24750 Survey 4 15/1/2015 Moderate 12150 28 26700

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Figure 2-39 through to Figure 2-45 detail the results of the four Longitudinal Survey studies for Dissolved Inorganic Nitrogen (Figure 2-39); Dissolved Reactive Phosphorus (Figure 2-40); Black Disc water clarity (Figure 2-41); Algal Biomass (Figure 2-42); PeriWCC (being an index of visual algal cover after Mathieson (2012)) (Figure 2-43); Phormidium (Figure 2-44); MCI (Figure 2-45); QMCI (Figure 2-46); and Ephemeroptera (mayfly), Plecoptera (stonefly) and Trichoptera (caddis fly) Biomass (Figure 2-47).

Significant results from the two surveys include the following:

Dissolved inorganic nitrogen At the time of each of the four surveys, Taharua River inflows to the Mohaka River resulted in substantial increases in Dissolved Inorganic Nitrogen (DIN) concentrations. DIN concentrations upstream of the Taharua confluence ranged from 0.016 to 0.043 mg/l. DIN concentrations then increased between 17 and 60 times downstream of the Taharua River confluence as a result of Taharua River inflows (Figure 2-39) to range from 0.75 to 1.05 mg/l.

Surveys 1 and 3 recorded higher concentrations of DIN downstream of the Taharua confluence than surveys 2 and 4. Surveys 1 and 3 were undertaken at times of lower river flow when compared to surveys 2 and 4 (Table 2-15). The difference in concentration between surveys may be the result of additional water flowing off the Kaimanawa Ranges down the Kaipo and Oamaru rivers, diluting Taharua outflows at times of increased river flow, as was evident for surveys 2 and 4. The increased dilution of DIN enriched water at the confluence of the Mohaka and Taharua rivers resulted in a reduction of around 0.3 mg/l DIN at the monitoring sites downstream of the confluence for surveys 2 and 4.

Also of interest is a slight increase in DIN that occurs approximately 20 km downstream of the Taharua confluence. This increase was evident during three of the four surveys. The cause of this increase is unknown. The site is upstream of the Mangatainoka hot springs in the middle of the Kaweka Forest Park, which is remote from any potential anthropogenic influence. However, the hot springs present in the area indicate that groundwater inflows occur, and it may be that these inflows are nitrate or ammonia enriched, which may consequently increase DIN concentrations, since both nitrate and ammonia contribute to DIN.

All four surveys show DIN concentrations remain well above expected natural background levels for over 50 km downstream.

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Figure 2-39: Mohaka River Longitudinal Survey results for Dissolved Inorganic Nitrogen (DIN). The blue line relates to the ANZECC (2000) ‘Upland’ DIN trigger value; the orange line the Biggs (2000) suggested limit for DIN for periphyton growth management for a 20 day accrual period.

Dissolved reactive phosphorus Changes in dissolved reactive phosphorus (DRP) concentrations in the Mohaka River as a result of Taharua River inflows were comparable across the four surveys with negligible to slight increases in DRP evident (Figure 2-40). DRP concentrations upstream of the Taharua River confluence ranged from 0.002 to 0.004 mg/l compared to concentrations downstream of the confluence that ranged from 0.003 to 0.006 mg/l.

DRP concentrations in Taharua outflows are currently low, but outflows result in a slight increase in DRP directly downstream of the confluence of between 0.001 to 0.003 mg/l 6. The extent downstream of the influence of Taharua outflow on DRP is difficult to discern because the dataset contains significant variability.

Currently periphyton growth rate would be expected to be phosphorus limited in (and immediately downstream of) the Taharua River confluence, because DIN concentrations are elevated.

6 NOTE: In Figure 2-40, DRP concentrations for Survey 1 (A) and Survey 2 (B) are based on ‘uncensored’ data that is the raw results supplied from the lab have been used in the figure. The NATA accredited limit of detection for DRP for the dataset is 0.004 mg/l. The uncensored or raw results are reported below that level. For Survey 3 (C) and Survey 4 (D) improved limits of detection of 0.001 mg/l were available.

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Figure 2-40: Mohaka River Longitudinal Survey results for Dissolved Reactive Phosphorus. The blue line relates to the ANZECC (2000) ‘Upland’ DRP trigger value; the red line the Biggs (2000) suggested limit for DRP for periphyton growth management for a 20 day accrual period.

Water clarity Taharua River outflows had a clear effect on reducing water clarity downstream in the Mohaka River across all four surveys (Figure 2-41) with black disc measurements of 6.5 to 8 m upstream of the Taharua River confluence dropping down to 3.5 to 5.5 m directly downstream of the confluence.

On only one occasion did black disc clarity return to levels comparable to those upstream of the Taharua confluence. This was at a distance of approximately 30 km downstream during Survey 1 and at a time of low flow. For the remaining three surveys, black disc sighting distance dropped by 1 to 3 m downstream of the confluence and then continued to slowly decline with distance downstream. Black disc clarity was typically between 3.5 to 5.5 m for survey sites downstream of the Taharua confluence across all four surveys.

The specific variables causing a reduction in water clarity are yet to be determined. Visual clarity is influenced by several specific attributes present in the water column including suspended sediment, both organic and inorganic, dissolved colour and waterborne algae. HBRC are initiating a targeted study looking at these specific components to better understand what is most influential on water clarity. Continued mitigation works in the Taharua catchment including continued riparian planting and management of point-source and diffuse nutrients are likely to result in improvements in water clarity.

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Figure 2-41: Mohaka River Longitudinal Survey results for water clarity (black disc). The purple line relates to the Hay and Hayes (2006) ‘Outstanding trout fishery’ limit; the blue line the ‘Significant trout fishery’ limit. The red line relates to the ANZECC (2000)/ HBRC RRMP (2006) recreational amenity limit.

Algal biomass and algal visual cover Algal biomass measurements (Figure 2-42) and algal visual cover estimates (as PeriWCC, see below for definition; Figure 2-43), as with water clarity, show quite different patterns across the four surveys.

Survey 1 showed an increase in measured algal biomass as well as algal visual cover (PeriWCC) downstream of the confluence, with biomass levels and visual cover being elevated for around 10 km downstream. Algal biomass results for surveys 2 and 3, although elevated directly downstream of the Taharua confluence, were lower downstream of the Taharua confluence than those measured during Survey 1. There was little evidence of increased biomass downstream for Survey 4. For all surveys, biomass levels dropped back to levels comparable to the upstream sites after approximately 10 km downstream.

With the exception of Survey 1 and the three sites located immediately downstream of the Taharua confluence, algal biomass levels remained well below the Biggs (2000) limits to protect ‘recreational values’ (120 mg/m2) and to protect ‘biodiversity’ values (50 mg/m2) at all sites on all occasions (Figure 2-42).

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Algal visual cover or PeriWCC values generally reflected those of algal biomass measurements with evidence of increased cover at downstream sites in close proximity to the Taharua confluence which then dropped back to comparable levels to those measured upstream within about 10 to 15 km. This pattern is consistent across all four surveys.

NOTE: The PeriWCC is a useful, simplified integrated measure of percentage visual algal or periphyton cover. The PeriWCC, as defined in Mathieson et al. (2012):

“While the New Zealand Periphyton Guideline provides separate aesthetic impact guidelines for identifying nuisance periphyton filamentous (≥30%) and mat (≥60%) cover, a composite cover guideline is also useful for instances where both filamentous growths and mats occur. The threshold for aesthetic nuisance mat cover is twice that for filamentous cover, so the composite weighted composite cover (PeriWCC) can be defined as filamentous + mat/2 with a nuisance guideline of ≥30%”

Figure 2-42: Mohaka River Longitudinal Survey results of algal biomass. The Biggs (2000) limits to protect ‘recreational values’ (120 mg/m2 for filamentous algae) and to protect ‘biodiversity’ values (50 mg/m2) are included on the plot.

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Figure 2-43: Mohaka River Longitudinal Survey results for PeriWCC. PeriWCC is a combined index taking into account percent cover of filamentous algae and % cover of matt algae. The proposed Mathieson et al. (2012) limit of 20% to provide ‘Excellent ecological condition’ is included on the plot.

Phormidium Phormidium is the most common genus of matt forming cyanobacteria in New Zealand (MfE/MoH, 2009) and is part of the natural periphyton community of streams and rivers. Although a natural part of the ecosystem, Phormidium can be hazardous since this species of cyanobacteria can produce toxins. The interim New Zealand Guidelines for Cyanobacteria in Recreational Fresh Waters (MfE/MoH, 2009) state a ‘green’ alert level of 20% cover or less. The alert level framework for benthic cyanobacteria is included as Appendix H.

The guidelines are designed to manage risks to recreational users. They have been designed to protect users from the risks associated with ingestion of and contact with water and Phormidium mats. The levels given in the guidelines are not relevant for addressing risks to dogs that actively seek out and consume cyanobacterial mats (MfE/MoH, 2009). Dogs have proven to be extremely sensitive to the toxins produced by Phormidium. It is very difficult to determine the risks of contact with cyanobacteria, particularly the mat-forming cyanobacteria that occur in rivers. Cyanobacteria do not always produce harmful toxins and it is not clear what triggers toxin production.

Phormidium cover is estimated as part of the algal visual cover assessments used to determine the PeriWCC index and can therefore be analysed and reported on independently of other algae. Figure 2-44 summarises Phormidium cover estimates for the four surveys.

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An increase in Phormidium cover downstream of the Taharua confluence is evident for surveys 1 and 2. Patterns of change are less noticeable for surveys 3 and 4. During the first two surveys, the highest visual cover estimates breached the MfE/MoH 20% green level band for one site during Survey 1 and were close to breaching the 20% level band at two sites during Survey 2. During these times the higher estimates of Phormidium cover were typically observed from the confluence of the Taharua River to around 25 km downstream. For surveys 3 and 4 and sites greater than 25 km downstream for surveys 1 and 2, Phormidium cover typically fluctuates around 5% to 15% cover. Interestingly for Survey 3, the highest Phormidium cover of 22% was observed at the top site above the Taharua River confluence.

Figure 2-44: Mohaka River Longitudinal Survey study results of Phormidium (cyanobacteria) cover. The MfE/MoH (2009) green alert level of 20% cover is included on the figure as the green line.

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Macroinvertebrate Community Index Macroinvertebrate Community Index (MCI) scores and Quantitative Macroinvertebrate Community Index (QMCI) scores for sites sampled revealed some interesting and contrasting patterns across the four surveys (Figure 2-45 and Figure 2-46).

For all four surveys there was a reduction in MCI scores directly downstream of the Taharua River confluence. During surveys 1 and 4, MCI scores were low directly downstream of the Taharua confluence, but were at acceptable levels once more (> 120) less than 5 km downstream, typically fluctuating between 125 and 135 across the remaining survey sites. This is in contrast to surveys 2 and 3, which showed a marked drop in MCI scores downstream of the Taharua confluence – when compared to the upstream sites – for a distance of approximately 15 km. Downstream of this point, MCI scores increased and generally remained above 120.

Figure 2-45: Mohaka River Longitudinal Survey study results of Macroinvertebrate Community Index (MCI). Limits proposed by Hay et al. (2006) to protect trout fishery values are included on the plot.

QMCI scores tend to provide a more robust estimate of macroinvertebrate community health because QMCI takes into account the abundance of particular species. By contrast, MCI is based solely on species presence/absence data.

Patterns in the QMCI scores (Figure 2-46) differed markedly from those of the MCI.

QMCI scores for Survey 1 dropped from an average of 7.1 upstream of the Taharua confluence to around 5.8 directly downstream of the Taharua confluence. Scores then fluctuated between 5 and 6 at most sites moving downstream, with the exception of a few low scores recorded at three sites. The reasons for the low QMCI scores at these sites are not obvious.

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QMCI scores for Survey 2, as with Survey 1, showed a distinct drop from an average 6.5 upstream of the Taharua confluence to around 4.0 directly downstream of the Taharua confluence. QMCI scores then recovered quickly to fluctuate between 5 and 6 from approximately 4 km downstream of the confluence and to be above 7, the level for excellent river health (refer to section 2.1.1 for a summary of QMCI thresholds as they relate to river health and the trout fishery) or the Cawthron ‘Outstanding trout fishery’ limit.

Survey 2 showed less of an effect of outflows from the Taharua. As with Survey 1, QMCI scores for Survey 2 showed a distinct drop immediately downstream of the Taharua confluence but then increased to be above 6 after about 15km km.

Figure 2-46: Mohaka River Longitudinal Survey study results of Quantitative Macroinvertebrate Community Index (QMCI). Limits proposed by Hay et al. (2006) in line with how QMCI relates to trout fishery values are included on the plot.

Macroinvertebrate biomass In early 2015, the Cawthron Institute was contracted by HBRC to undertake calculation and cursory analysis of the macroinvertebrate biomass data collected during the four Longitudinal Surveys. The following summary was provided (Shearer, 2015):

Total macroinvertebrate benthic densities and biomass in the Mohaka River on all the sampling occasions varied from site to site with no apparent longitudinal trend (i.e. increase or decrease) below the confluence with the Taharua Rivers. Densities and biomass of animals were lower directly below the confluence in February and May 2013, but higher on the other two sampling occasions. Overall the total biomass of invertebrates collected in the Mohaka was higher than has been found in two South Island rivers valued for their trout fisheries – the Pomahaka and Waikaia rivers (K. Shearer, unpublished data).

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The energy requirements for drift-feeding fish such as trout increase with size, and the presence of large food items to maintain growth is important, especially during the main growth periods in summer and autumn. Prey longer than 6 mm is generally required to feed a 50 cm fish, because smaller prey are more likely to pass through the mouth and out through the spaces between the gill rakers (Wanowski, 1979).

Results for invertebrate density and biomass by size class suggest the food base for adult trout in the Mohaka River is good throughout its length, with invertebrates larger than 6mm in length representing at least 50% of total biomass at all sites on all sampling occasions (Shearer, 2015).

Benthic invertebrate density and biomass surveys do not indicate whether the animals collected in a sample are available for trout to eat (i.e. they are prone to drifting), nor do they consider the impact of changes in invertebrate community taxonomic composition on fish food availability (Shearer, 2015).

For example, on the February 2013 sampling occasion, the combined biomass of the crane fly larvae Aphrophila, dobsonfly Archichauliodes and fly larvae belonging to the family Muscidae was more prominent in invertebrate size classes >12 mm immediately below the Taharua River confluence than further upstream in the Mohaka. These three taxa were found only in low abundance in invertebrate drift samples collected from the Mohaka 0.4 km downstream of the Taharua confluence in 20097 (Shearer & Hays, 2010). Conversely, mayflies (Deleatidium in particular) greater than 6 mm in length were generally abundant in the benthic samples at sites below the Taharua confluence to at least 24.2 km downstream. Deleatidium are commonly collected in the drift (as was the case in the 2009 study), and are well known to be a staple invertebrate in the diet of drift-feeding trout throughout New Zealand (Shearer, 2015).

Analysis of the taxonomic structure of sampled invertebrates, as well as their density and biomass is beyond the scope of this summary, but warrants attention in further analysis because both size and taxonomic structure have potential food implications for drift-feeding fish. The full implications of any effects of the Taharua River on food potential for drift-feeding fish in the Mohaka River cannot be ascertained until these density and biomass results have been considered in context of invertebrate population structure and propensity of the invertebrates in the benthos to drift (Shearer, 2015).

To further understand the availability of high value invertebrates to support trout, the biomass of Ephemeroptera (mayfy), Plecoptera (stonefly) and Trichoptera (caddisfly) (EPT) taxa was calculated and summarised in Figure 2-47. These taxa are an important food for trout, especially drift-feeding adult trout, because these EPT taxa can reach large sizes and have a greater propensity to drift (K. Shearer, Cawthron, pers. comm. 2015).

As was found with analysis of the total invertebrate biomass across the four surveys (see summary of Shearer’s above), the surveys show no clear patterns in changes in EPT biomass when comparing sites upstream of the Taharua to downstream of the Taharua. With the exception of one site downstream, Survey 1 showed little difference between sites upstream of the Taharua and downstream of the Taharua. This contrasts with Survey 2, which recorded a drop in EPT biomass downstream of the Taharua confluence with a slow recovery downstream. By contrast, surveys 3 and 4 show higher EPT biomass downstream of the Taharua confluence when compared to the upstream sites, with some sites having 2 to 4 times the biomass of EPT taxa to the upstream sites.

With the exception of one site on one occasion, which experienced a 41% contribution of individuals >6 mm to the total EPT taxa biomass, >6 mm animals contribute more than 50% of total EPT taxa biomass, with an overall average contribution of 78% across all sites and survey dates (Figure 2-47). This dominance of larger individuals in the EPT community will support the growth of larger trout.

7 In 2009 drift samples were collected from two sites in the Mohaka River - 2.4 km upstream and 0.43 km downstream of the Taharua River confluence. Drift sampling was undertaken in February, April and December under baseflow conditions.

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Figure 2-47: Mohaka River Longitudinal Survey study results of EPT taxa biomass for Survey 1.

Recently, Stansfield (2013) carried out a detailed study of upper Ngaruroro River macroinvertebrate community health for Hawke’s Bay Fish and Game. Using data from Survey 1 (Figure 2-45, Figure 2-46 and Figure 2-47), Stansfield (2013) compared the macroinvertebrate community of the upper Mohaka River to that of the upper Ngaruroro River, a river that is assessed as being in pristine condition. The analysis demonstrated that upper Mohaka River macroinvertebrate community health was as good as or better than Ngaruroro River macroinvertebrate community health.

By comparison with Fish and Game study sites on the Ngaruroro River, the upper Mohaka River had (Stansfield, 2013):

. A much higher density of EPT taxa per unit area

. Greater numbers of overall EPT taxa (greater taxa richness)

. On average 40% greater EPT biomass when compared to the upper Ngaruroro River

. Comparable MCI values

The available information shows that the effects of Taharua outflows on macroinvertebrate community health, although being significant directly downstream of the confluence, is negligible a few kilometres further downstream.

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Longitudinal survey summary

Summary of longitudinal surveys

1. DIN concentrations increase markedly downstream of the Taharua confluence and remain elevated for over 50 km downstream.

2. DRP concentrations, although showing slight elevation downstream of the Taharua confluence, return to low levels after approximately 15 km.

3. Under low flow conditions, Taharua outflows cause a dramatic drop in water clarity in the Mohaka River returning to 4 m and greater after approximately 10 km downstream.

4. Algal biomass and visual cover increases directly downstream of the Taharua confluence and then returns to background levels within 10 km.

5. Phormidium cover increases significantly downstream of the Taharua confluence but remained within the ‘green’ band of current interim guidelines.

6. Phormidium cover was highest for the river reach 10 km downstream of the Taharua confluence.

7. Macroinvertebrate indices, apart for monitoring sites directly downstream of the Taharua confluence, show the community to be in excellent condition with little evidence of adverse effects from Taharua outflows.

8. Macroinvertebrate biomass compares favourably with rivers valued for their trout fisheries elsewhere in New Zealand.

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2.3.3 Recent nitrogen and phosphorus trends in the Taharua Catchment Routine SoE monitoring of the Taharua River commenced in mid-2001. Nitrate-nitrogen concentrations increased from this date from around 1.5 mg/l when monitoring began, to a peak of around 3.5 to 4.0 mg/l by mid-2011. This trend was evident at both the Taharua River at Wairango and Twin Culverts monitoring sites (Figure 2-48 and Figure 2-49). These two sites are in the upper Taharua catchment. They record the highest nitrate-nitrogen concentrations of any of the Taharua River routine monitoring sites. The dominant land-use upstream of these sites is dairying.

In-stream nitrate-nitrogen concentrations have reduced recently, with the upward trend levelling off around mid-2011, and declining significantly since that date at both the Wairango and Twin Culverts monitoring sites (Table 2-17).

Differences in dissolved inorganic nitrogen and nitrate-nitrogen dissolved inorganic nitrogen = nitrate nitrogen + nitrite nitrogen + ammoniacal nitrogen OR DIN = NO3-N + NO2-N + NH4-N

In the Taharua catchment, nitrate-nitrogen contributes to over 99% of dissolved inorganic nitrogen with nitrite-nitrogen and ammoniacal-nitrogen concentrations being below the laboratory limits of detection (0.002 and 0.01 mg/l respectively) on most sampling occasions. For comparison, nitrate-nitrogen (NO3-N) levels are similar to dissolved inorganic nitrogen (DIN) at monitoring sites throughout the Taharua catchment.

Figure 2-48: Time series of nitrate-nitrogen concentration measured in the headwaters of the Taharua River at the Wairango monitoring site. For comparative purposes, nitrate-nitrogen are similar to dissolved inorganic nitrogen (DIN) levels at monitoring sites throughout the Taharua catchment. The dashed lines are regression ‘lines of best fit’ from 2001 to mid 2011 and mid 2011 to the end of 2013.

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Figure 2-49: Time series of nitrate-nitrogen concentration measured in the headwaters of the Taharua River at the Twin Culverts monitoring site. For comparative purposes, nitrate-nitrogen approximates dissolved inorganic nitrogen (DIN) levels at monitoring sites throughout the Taharua catchment. The dashed lines are regression ‘lines of best fit’ from 1999 to mid 2011 and mid 2011 to the end of 2013.

River water at these two sites has taken about 6 years to move from being rainfall to entering the river (Lynch et al., in press). This means that any water sampled from the river is revealing the impacts of land-use practices about 6 years before it was sampled.

Nitrate-nitrogen concentrations in groundwater bores near the Twin Culverts monitoring site show similar trends to those measured in-stream. The patterns of changes in surface water and groundwater nitrate- nitrogen concentrations are superimposed on one another in Figure 2-50.

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Figure 2-50: Time series of nitrate-nitrogen concentration measured in the headwaters of the Taharua River at the Twin Culverts monitoring site and nitrate-nitrogen concentration measured in groundwater bores in the local area. Note: the Surface Water and Groundwater Y-axes (vertical axes) are on different scales.

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The three bores included in Figure 2-50 all had peak nitrate-nitrogen concentrations around 12 to 14 mg/l. Concentrations then trend down to a current concentration of around 4 to 6 mg/l. A detailed discussion of groundwater quality in the Taharua catchment is provided in Lynch et al. (in press).

Table 2-16: Proximity to the Taharua River at Twin Culverts surface water monitoring site, mean water residence time and depth of bores included in Figure 2-50.

Bore Distance and direction from Twin Mean Residence Time Depth (m) Culverts (yrs) 5835 5.9 km north 1.5 9.0 5836 3.9 km north 3.5 14.0 5838 2.9 km north 2.5 13.0

Around 6 to 10 years ago land-use practices in the catchment changed from high levels of nitrogen fertiliser application to promote pasture establishment, to a strategy of using lower fertiliser application to sustain pasture growth (B. Powell, HBRC, pers. comm. 2014). This change in fertiliser application rates around 2004 to 2008 appears now to be reflected in the river water quality monitoring.

Several additional initiatives in the catchment are likely to continue the declining trend in in-stream nitrate- nitrogen concentrations. These initiatives include practices such as (B. Powell, HBRC, pers. comm. 2014):

. Avoiding times of year (May-end July) when N fertiliser is at high risk of being leached.

. Upgrades to farm dairy effluent systems, including low rate application, storage and deferred irrigation.

. Winter crop areas reduced, and moved back from the Taharua stream edge.

. Reduced cow numbers from a peak of 9500 to 7600.

DRP concentrations have also been declining at the Taharua River at Wairango and Twin Culverts monitoring sites but for a significantly longer period, between mid-2001 and December 2013 (Table 2-17, Figure 2-51 and Figure 2-52).

Over this period concentrations of DRP have dropped from around 0.025 mg/l to the current level of around 0.015 mg/l. This is noteworthy given the intensive land-use in the catchment upstream of these monitoring sites, since this pattern demonstrates that nutrient management strategies are capable of reducing both DRP and DIN losses from land, and improving in-stream water quality. It may also be that legacy effects of the initial conversions from sheep and beef to dairy in the early 2000s have diminished.

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There are several specific mitigation measures that probably contribute to the observed reduction in in- stream DRP. These measures include (B. Powell, HBRC, pers. comm. 2014):

. Establishing riparian fencing, stock exclusion, and buffer zones around grazed crops.

. Upgrades to farm dairy effluent systems, including low rate application, storage and deferred irrigation.

. Identification of areas with high soil P levels and action to reduce these. Such as targeted management of Olsen P levels.

. More intensive on farm soil sampling to focus fertiliser application and investment in the right areas. Associated improved monitoring of fertiliser application.

. Reducing runoff from races and from other nutrient input hot-spots (critical source areas).

Nitrate and phosphorus are transported in different ways in the environment. Nitrate travels in groundwater, so its distribution is affected by time taken for water to infiltrate into the soil and travel through the aquifer before arriving in a stream.

By contrast, phosphorus is generally transported in overland flow, which can rapidly enter a stream. This means that in-stream phosphorus concentrations are usually derived from current land-use practices, but nitrate-nitrogen concentrations are the result of historic and current land-use practices.

Figure 2-51: Time series of dissolved reactive phosphorus concentration measured in the headwaters of the Taharua River at the Wairango monitoring site. The dashed line is a regression ‘line of best fit’ and provides a indication of the general trend in the data.

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Figure 2-52: Time series of dissolved reactive phosphorus concentration measured in the headwaters of the Taharua River at the Twin Culverts monitoring site. The dashed line is a regression ‘line of best fit’ and provides a indication of the general trend in the data.

Significant trends in DRP and nitrate-nitrogen at the Taharua at Wairango and Twin Culverts monitoring sites over the period 2002-2013 include the following (p values summarised in Table 2-17):

. DRP concentrations decline while nitrate-nitrogen concentrations increase, over the full dataset.

. Analysing shorter time periods reduces the statistical significance of the DRP trends (as shown in Table 2-17).

. At the Twin Culverts and Wairango monitoring sites, there is an increasing trend in nitrate- nitrogen during 2002-2009 followed by a decreasing trend from 2010 to 2013.

A minimum of five years of monthly data observations are typically required for robust trend analysis.

Given the age of the river water being sampled and how this relates to land-use changes and current land- use practices, it is unlikely the declining trends being seen in nitrate-nitrogen in groundwater will change in the near future. Further work is planned to quantify likely future trends, taking into account land-use practices, groundwater age and on-farm mitigation measures.

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Table 2-17: Trend analysis results for DRP and Nitrate-nitrogen for the Taharua River at Twin Culverts and Wairango SoE monitoring sites. Trend results, based on a Mann-Kendall test, are included summarising the full dataset as well as sub setting the dataset into three year increments. In all tables that present trend results, the changes are represented in bold when they are significant (ie, p value is less than 0.05). Given a significant trend for a particular variable, the Percent Annual Change (PAC) is highlighted in BLUE if there was a significant improvement in the water quality variable, and highlighted in RED if there was a significant deterioration in the water quality variable Dissolved reactive phosphorus Nitrate-nitrogen Percent Percent Site and Time Period Trend Trend Median Annual Median Annual p value p value Change Change Taharua Rv at Wairango 2002-2013 0.016 0.004 -3.1 2.80 <0.001 4.0 2002-2005 0.021 0.892 -5.9 2.31 0.341 4.4 2006-2009 0.017 0.224 -6.0 2.87 0.217 3.2 2010-2013 0.015 1.000 0.0 3.30 <0.001 -10.4

Taharua Rv at Twin Culverts 2002-2013 0.015 0.013 -3.3 3.03 <0.001 5.7 2002-2005 0.017 0.568 -5.9 2.21 <0.001 14.0 2006-2009 0.015 0.018 -13.0 3.07 <0.001 6.3 2010-2013 0.013 0.498 3.8 3.60 <0.001 -5.6

The data presented in this section suggest:

. Over the last 10 years, there have been statistically significant increases in nitrate-nitrogen concentrations measured at the Wairango and Twin Culverts SoE monitoring sites (p value < 0.001; Table 2-17), which relate to land-use changes and historical farming practices.

. Over the last 6 years nitrate-nitrogen concentrations measured in-stream at the Wairango and Twin Culverts monitoring sites have improved from 2010 to 2013 (p value < 0.001; Table 2-17). This appears to be related to improved farming practices.

. In-stream DRP concentrations have improved in recent years (p value < 0.05; Table 2-17). This improvement is probably the result of implementing nutrient mitigation measures.

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2.3.4 Possible targets for nitrogen loads from the Taharua Catchment Nitrogen contributed from the Taharua River dominates the in-stream nitrogen levels of the upper Mohaka River.

The evidence for this is seen in in-stream nitrogen levels at the Mohaka River downstream of the Taharua River confluence with:

. The Mohaka River upstream of the Taharua River confluence (Figure 2-53).

. The Taharua River at Red Hut (Figure 2-54).

There is no relationship between nitrogen concentrations measured in the Mohaka upstream of the Tahaura River tributary (on a given date) and nitrogen concentrations measured downstream of the Tahaura River on the same date (Figure 2-53) (Pearson p = 0.098).

However, concentrations of total nitrogen measured in the Taharua at Red Hut are strongly correlated (Pearson p = <0.001) with the concentration of total nitrogen measured in the Mohaka River downstream of the Taharua confluence (Figure 2-54). This suggests that contributions from the Taharua River dominate total nitrogen concentrations in the Mohaka River downstream of the tributary junction. This means that observed increases in the levels of TN in the Taharua at Red Hut are likely to be mirrored by increases in the Mohaka downstream.

Figure 2-53: Relationship between total nitrogen (TN) concentration in the Mohaka River downstream of Taharua River confluence and the Mohaka River upstream of Taharua River confluence.

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Figure 2-54: Relationship between total nitrogen (TN) concentration in the Mohaka River downstream (D/S) of Taharua River confluence and the Taharua River at Red Hut monitoring site.

There is also a strong correlation (Pearson p <0.001) between total nitrogen (TN) concentrations in the Taharua River at Red Hut and dissolved inorganic nitrogen (DIN) concentrations in the Mohaka River downstream of the Taharua confluence (Figure 2-55).

These results suggest that the incidence of eutrophication in the Mohaka River may be reduced if nitrogen contributions from the Taharua River to the Mohaka River are reduced. The strong correlation between DIN concentration and TN in the respective rivers suggests a target to manage eutrophication in the Mohaka River could be set by choosing an appropriate total nitrogen target in the Taharua River at Red Hut.

For example, the relationship in Figure 2-55 can be used to give an estimate of an appropriate TN target in the Taharua River at Red Hut to meet a target concentration for DIN in the Mohaka River downstream of the Taharua River. This target could be set as 0.3 mg/l in the Mohaka River, since this value is the 20 day accrual limit for DIN suggested by Biggs (2000), and it is also typical of TN close to State Highway 5, where periphyton cover is favourable. The relationship in Figure 2-55 can be used to give an estimate of an appropriate TN target in the Taharua River at Red Hut, based on TN in the Mohaka River. In this example, the equivalent concentration in the Taharua River at Red Hut would be around 0.93 mg/l of TN (Figure 2-55), based on the line of best fit.

A more cautious target could also be established from this data by choosing a relationship between the two sites that reflects the spread of observations. In this situation Taharua at Red Hut TN values of approximately 0.7 mg/l would be equivalent to a nominal DIN target of 0.3 mg/l for the Mohaka River downstream of the Taharua River (Figure 2-55).

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Figure 2-55: Relationship between Taharua River total nitrogen (TN) concentration (measured at Red Hut) and the Mohaka River D/S Taharua River confluence dissolved inorganic nitrogen (DIN) concentration.

Figure 2-56 is a scatterplot of TN concentrations measured in the Taharua River at Red Hut from March 2008 to December 2013. Included on the plot is a line at the suggested target of 0.93 mg/l and a second line at the more conservative target of 0.70 mg/l.

Average TN concentrations over this period are around 1.4 mg/l. Using the relationship described in Figure 2-55 a reduction in TN concentrations of between 35% and 50% is required to achieve the suggested target values for TN. If it is assumed that any reduction in nitrogen leached from the land is proportional to the reduction subsequently observed in in-stream TN concentrations, then a reduction of approximately 35% to 50% is required in nitrogen applied to the catchment, to meet a 0.3 mg/l DIN concentration target downstream in the Mohaka River.

It is worth noting that the average age of river water in the Taharua River at Red Hut is around 8 to 10 years. What is being measured in-stream is therefore influenced by land-use practices about 8 to 10 years before the date that the sample is taken. Unlike the monitoring sites in the upper Taharua River (Wairango and Twin Culverts), there is no obvious downward trend in nitrogen concentrations evident at Red Hut in recent times. A possible explanation for this is that the reductions seen at the upstream site are yet to be experienced in the lower catchment, due to the groundwater lag. Further work is needed to better understand groundwater age and lag times, and changes in land-use practices and on-farm mitigation measures.

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Figure 2-56: Total nitrogen (TN) concentration measured in the Taharua River at Red Hut. The Taharua River at Red Hut monitoring site is located directly upstream of the confluence of the Taharua River and the Mohaka River. Included on the plot are two potential targets for average TN concentration (red line 0.70 mg/l; yellow line 0.93 mg/l) for the Taharua River at Red Hut to meet an average DIN concentration of ~ 0.3 mg/l in the Mohaka River D/S of the Taharua River confluence.

To meet the TN target of 0.93 mg/l at Red Hut, a reduction of 35% in in-stream TN loads is required. This would require a reduction in annual in-stream loads from the current 230 tonnes to around 150 tonnes. To meet the more conservative TN target of 0.70 mg/l, a reduction of 50% in total in-stream nitrogen loads is required. This would require a reduction in annual in-stream loads from the current 230 tonnes to around 115 tonnes (Table 2-18).

Table 2-18: Annual total nitrogen loads measured in-stream in the Taharua River. Loads relate to 'attenuated'8 in- stream loads and are based on an average of annual loads calculated for each year running 2008 to 2013. The estimates are therefore based on a longer dataset and calculated differently than those summarised in Figure 2-34. Average 2008 - 2013 Load (T/yr) Yield (kg/ha/yr) Current Taharua at Red Hut (Average 2008 – 2013) 230 17.2 Target Taharua at Red Hut ~35% reduction (TN 0.93 mg/l) 150 11.2 Target Taharua at Red Hut ~50% reduction (TN 0.70 mg/l) 115 8.6

For comparison, in-stream total nitrogen yield at Red Hut is approximately half that of Twin Culverts and Wairango, because the large part of the catchment upstream of this site in native forest and production forest, that only leaches low levels of nitrogen (Table 2-19). This is not the case for the Twin Culverts and Wairango monitoring sites, which have upstream catchments dominated by dairy. TN yields for all remaining SoE monitoring sites outside of the Taharua catchment (excluding the Mohaka D/S of Taharua) are between 2 and 8 kg N/ha/yr (Appendix G lists nutrient and sediment yields for the remaining SoE monitoring sites).

8 ‘Attenuated’ in-stream load and yield means that the nitrogen has been fully attenuated from leaving the surface of the catchment to being measured in the river. Nitrogen attenuation occurs as it travels from below the root-zone, through sub-surface flow paths to the stream. Denitrification is a significant attenuation process and involves bacterial conversion of nitrate to nitrogen gas. The in-stream loads and yields are therefore lower than the root-zone or farm gate loads and yields. The yields are the total mass of nutrient transported in a year divided by the upstream catchment area. They are loads ‘standardised’ by catchment area and can be compared across catchments of varying size.

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Table 2-19: Annual total nitrogen loads measured in-stream in the Taharua River. Loads relate to 'attenuated' in- stream loads. Average 2008 - 2013 Load (T/yr) Yield (kg/ha/yr) Taharua at Red Hut 230 17.2 Taharua at Twin Culverts 112 35.9 Taharua at Wairango 50 29.8

An alternative approach to setting nitrogen targets could be to identify specific DIN concentration targets for key sites downstream of the Taharua confluence and then estimate the required concentration of TN leaving the Taharua River to meet the targets. The results from Longitudinal Surveys provide an opportunity to demonstrate this.

DIN concentrations measured during the Longitudinal Surveys were observed generally to decline with distance downstream (Figure 2-57). The relationship between DIN concentration and distance is highly significant (Pearson p << 0.001; Table 2-20) for all surveys. The gradient (slope) of the regression equation (Table 2-20) represents the rate (mg/l DIN per km) at which DIN is attenuated and diluted travelling downstream of the Taharua confluence.

During low flows (Survey 1, Survey 3 and Survey 4) the rate at which DIN concentration declines with distance is higher (that is the regression line has a ‘steeper’ gradient) and the loss rate is approximately 0.0098 mg/l DIN per km. At times of higher flow (Survey 2) the rate at which DIN concentration declines with distance is lower at approximately 0.0062 mg/l DIN per km (Figure 2-57).

Figure 2-57: Linear regression of reductions in dissolved inorganic nitrogen (DIN) for the Mohaka River Longitudinal Surveys. Note: the DIN concentration for the Mohaka River at SH5 (Glenfalls) for Survey 1 has been taken as the average of NIWA samples taken on the 16/2/2013 and the 6/3/2013. The actual sampling date(s) for Survey 1 was the 28/2/2013 and the 1/3/2013.

Interestingly the rate of DIN decline for the 3 Longitudinal Surveys undertaken under low flow conditions are very similar, despite DIN concentrations being different in the Mohaka River downstream of the Taharua River confluence at the time of each survey. This means that the Mohaka River consumes DIN at the same rate per kilometre even when concentrations vary from 1.1 mg/l to 0.7 mg/l directly downstream of the Taharua River confluence (Figure 2-57; Table 2-20).

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Table 2-20: Regression coefficients for relationships between DIN concentration and distance downstream of the Taharua confluence. The ‘Y-Intercept’ reflects the DIN concentration (mg/l) in the Mohaka River immediately downstream of the Taharua River confluence. The ‘Gradient’ reflects the rate of DIN concentration decline with distance downstream of the Taharua (mg/l/km). Gradient Survey Y - Intercept (mg/l) r – square p - value Flow conditions (mg/l/km) Survey 1 1.08 -0.0124 0.97 < 0.001 Low Survey 2 0.73 -0.0062 0.87 < 0.001 Moderate Survey 3 0.92 -0.0110 0.94 < 0.001 Low Survey 4 0.75 -0.0094 0.96 < 0.001 Low Average -0.0098

Using the rate of DIN concentration decline with distance measured during the longitudinal surveys allows an estimate of what the DIN concentration would be at sites downstream of the Taharua confluence, given hypothetical concentrations of DIN in the Mohaka River downstream of Taharua (Table 2-21). For example, if there was a DIN concentration of 0.5 mg/l in the Mohaka River downstream of Taharua, and the rate of reduction in DIN is taken as the average rate of the four Longitudinal Surveys, then DIN concentrations at key sites including the Mangatainoka hot springs, the Pakaututu Bridge and the Mohaka at SH5 would all be below 0.3 mg/l.

In a simple form, if a representative rate of DIN concentration decline with distance could be determined for the upper Mohaka River during summer low flow conditions (as measured during Survey 1, Survey 3 and Survey 4), then it may be possible to identify Taharua TN concentration targets to meet specific DIN concentration targets at sites downstream in the Mohaka River.

Table 2-21: Estimated DIN concentration at sites downstream of the Taharua River confluence based on average DIN reduction rates measured during the four longitudinal surveys and hypothetical DIN concentrations in the Mohaka River D/S of Taharua. Near nat. = near natural background levels.

Distance from Taharua Rv. 22 km 38 km 60 km

Mohaka Rv at Mohaka Rv at Mohaka Rv at Site name Mangatainoka hot springs Pakaututu Bridge SH5 DIN (mg/l) Mohaka Rv Average All Surveys Average All Surveys Average All Surveys D/S Taharua 1.40 1.18 1.03 0.81 1.30 1.08 0.93 0.71 1.20 0.98 0.83 0.61 1.10 0.88 0.73 0.51 1.00 0.78 0.63 0.41 0.90 0.68 0.53 0.31 0.80 0.58 0.43 0.21 0.70 0.48 0.33 0.11 0.60 0.38 0.23 Near nat. 0.50 0.28 0.13 0.40 0.18 Near nat. 0.30 Near nat.

Development of a robust model linking nutrient loss from current and historic land-use to what is sampled in-stream is required to confidently identify a catchment load to meet a specific in-stream nutrient concentration. Such a model would ideally take into account groundwater and stream nutrient attenuation

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processes as well as groundwater lag times. The approaches demonstrated above are simplistic and should therefore be treated with caution.

2.4 Land intensification in the upper Rangitaiki catchment – potential impacts on the upper Waipunga River The only monitoring site with elevated nitrogen concentrations other than the Taharua River and sites directly affected by Taharua River outflows is the Waiarua Stream.

A time series of nitrate-nitrogen samples collected from neighbouring sites at Waiarua Stream at SH5 and the Waipunga River at Pohukura Road (Figure 2-1) show distinctly different trends in nitrate-nitrogen (Figure 2-59).

The Waiarua Stream has a distinct increasing trend over time, particularly evident from 2006 to the present date. Although yet to be proven, it appears this site is influenced by intensive land-use occurring on the Rangitaiki Plains, with nutrient leaching from this area leading to increased nitrate-nitrogen concentrations in this small tributary stream of the upper Waipunga River (Figure 2-58).

Contrastingly, nitrate-nitrogen concentrations were elevated at the Waipunga River sampling site in the period 2006 – 2008. From 2008 nitrate-nitrogen concentrations have trended down to approach the very low levels that were typical of this site from the mid-90s to around 2004. The catchment of this monitoring site is dominated by production forest and native vegetation (Figure 2-58) with the nitrate-nitrogen hump likely being driven by a forestry rotation occurring in the catchment during early to mid-2000. While it has been recognised that overall nitrogen leaching from planted forests is lower than other major land-uses, there are key times during the forest rotation when nitrogen leaching may occur (Davis, 2014).

Figure 2-58: Dairy farming in the headwaters of the Waiarua Stream (left) and production forestry (mid ground) in the headwaters of the Waipunga River (right).

A forest rotation can periodically increase nitrate leaching when slash increases the amount of organic matter that breaks down by mineralisation and leaches nutrients. Additionally, nitrogen uptake by the forest is disrupted, further increasing the potential for nitrate loss to surface water and groundwater. Both these effects can increase nitrate-nitrogen concentrations in surface waters for several years (Davis, 2005). The trend in nitrate-nitrogen concentration at this site is consistent with this hypothesis (Figure 2-59).

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Figure 2-59: Time series of nitrate-nitrogen concentration measured in the headwaters of the Waipunga River at two sites. For comparative purposes, nitrate-nitrogen approximates dissolved inorganic nitrogen (DIN) levels.

Although nitrate-nitrogen levels are higher in the Waiarua Stream than expected in a catchment dominated by native vegetation, they are still low when compared to the Taharua River at Twin Culverts (Figure 2-60). By contrast, the volume of water flowing from the Waiarua Stream is quite low, being 30% of the flow of the upper Waipunga River and 7% of the total flow leaving the Waipunga catchment. These figures are based on instantaneous flows measured during the concurrent gauging study. This is in contrast to the Taharua River that – at times of low flow – can contribute up to 70% of the flow of the upper Mohaka River.

The elevated nitrate-nitrogen in the Waiarua Stream therefore poses little risk to the wider Waipunga and Mohaka rivers as the nutrient is diluted by tributary inflows such as the upper Waipunga River, Okeke Stream and Mokomokonui River, travelling downstream to the confluence of the Waipunga and Mohaka rivers. Nutrient attenuation processes also remove nitrogen.

This conclusion is supported by samples collected during the Concurrent Gauging study that showed the Waipunga River upstream of the Mohaka River had very low nitrogen concentrations (discussed in Section 2.2), which indicated the Waiarua Stream had minimal influence on the lower Waipunga River and Mohaka River downstream of the Waipunga River confluence.

Although at present elevated nitrogen concentrations in the Waiarua Stream pose little risk to the wider catchment, the increasing trend is of concern and HBRC will continue to monitor this site for the foreseeable future. A collaborative project underway with Environment Bay of Plenty investigating groundwater boundaries between the Taharua, upper Ripia, upper Waipunga and the Rangitaiki Plains areas will also help HBRC understand the groundwater capture zone of the upper Waipunga River, and any potential risk that further intensification of the Rangitaiki Plains may have on the Waipunga and Mohaka rivers.

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Figure 2-60: Time series of nitrate-nitrogen concentration measured in the headwaters of the Taharua River at the Twin Culverts monitoring site compared with nitrate-nitrogen concentration in the upper Waipunga River at the Waiarua River monitoring site.

2.5 Nutrient limitation and Nutrient Diffusion Substrate studies An important step in identifying appropriate nutrient management strategies and concentration limits to limit excessive periphyton growth is to ascertain which nutrient limits algal growth (Death et al., 2007).

At least two methods exist to identify the nutrient most likely to control algal growth:

. Nutrient diffusing substrate (NDS) assays, which is the most rigorous method for assessing periphyton response to nutrients (Wilcock et al., 2007).

. Assessment of the soluble N:P ratios and concentrations, which also provides insights regarding the nutrient most likely to be growth limiting (Wilcock et al., 2007).

NDS assays involve direct measurement of N or P limitation. The method used for nutrient diffusing substrates is described in detail in Death et al. (2007). The method places jars of nutrient-impregnated agar onto the river bed and measures the algal growth response. The assays have four treatments:

1. A control treatment without any nutrient added (termed ‘Control’).

2. A treatment with nitrogen added (termed ‘+N’).

3. A treatment with phosphorus added (termed ‘+P’).

4. A treatment with both N and P added (termed ‘+N+P’).

A filter paper is placed over each jar, through which the nutrient diffuses (‘bleeds’). The in situ response of the algae to the nutrient condition created by each treatment is observed as a relative stimulation of growth.

If the river is ‘phosphorus’ limited at the time of the assay then increased algal growth would be observed in the +P and +N+P treatments relative to the control and +N treatment.

If both N and P are in short supply (thereby limiting growth), then it is likely that significant increases in algal growth would only occur on the +N+P treatment.

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For each treatment there are generally five replicates, giving a total of 20 samples per tray. These trays (1 tray of 5 replicates for each of the 4 treatments) are nominally deployed for two weeks, allowing sufficient time for algae to grow on the filter papers before being removed and sent to the laboratory for analysis. Algal growth response is then estimated by measuring the amount of chlorophyll a on each filter paper.

Wilcock et al. (2007) also identified the value of directly measuring and identifying limiting nutrients through the deployment of Nutrient Diffusing Substrate (NDS) assays, and identified this technique as being the most robust method available at the time (and arguably still today) for assessing nutrient limitation of periphyton.

Over recent years a number of nutrient diffusing substrate studies have been carried out in the upper Mohaka River (2007, 2008 and 2011) and the middle Mohaka River (2008 and 2009).

The results of the 2007 and 2008 studies were reported in Stansfield (2008) who concluded the following:

“Nutrient limitation experiments conducted in winter using nutrient diffusing agar substrates confirm that nitrogen and phosphorus limits periphyton growths upstream of the Taharua River confluence while the remaining sites downstream all show phosphorus limitation. The same experiments conducted in summer showed that the sites located upstream and downstream of the Taharua River confluence are nitrogen and phosphorus limited while the remaining sites downstream show nitrogen limitation. The differences between treatments were more pronounced in the mid to lower reaches of the catchment suggesting that light, temperature or shear stress may be playing a larger role in determining periphyton growths in the upper reaches (Taharua River confluence area).

The results of the nutrient limitation experiments indicate that both dissolved phosphorus and nitrogen are important nutrients to manage within this catchment if we are to minimise periphyton biomass and thereby improve aquatic ecosystem health.”

NDS studies of the Mohaka River upstream of the Taharua confluence in April 2011 confirmed the findings of Stansfield (2008), with algal growth being strongly limited by the availability of both nitrogen and phosphorus (Figure 2-61). Therefore the addition of one nutrient in the absence of the other may not initiate a growth response but an increase in both will.

Algal Biomass (mg/m2) Biomass Algal 20

Plus P Plus N Control

Plus P Plus N

Nutrient Treatment

Figure 2-61: Nutrient diffusing substrate (NDS) results for the Mohaka River upstream of the Taharua River April 2011.

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The Mohaka River upstream of the Taharua River confluence has very low concentrations of both nitrogen and phosphorus. This results in strong nutrient co-limitation of periphyton growth so that both nitrogen and phosphorus limit growth. This was evident in the NDS results of 2007, 2008 and 2011.

Outflows from the Taharua River increase both DIN (up to 10-fold) and DRP concentrations (typically by 2 to 3-fold) downstream of the confluence. This results in stimulation of periphyton growth and uptake of nutrients. DRP concentrations drop quickly downstream of the confluence, as demonstrated from monitoring data collected during the longitudinal surveys, as a result of this assimilation by periphyton growth resulting in phosphorus limitation of algal growth as DIN concentrations remain well above algal growth requirements for more than 50 km downstream.

Any additional increases in nitrogen from the upper Mohaka catchment have potential to cause increased periphyton growth in the lower reaches of the river. This is due to increased phosphorus availability downstream of the Waipunga River, as the surface water quality monitoring data shows. At present, nitrogen levels are high in the upper-catchment and low in the lower catchment; the opposite is seen with phosphorus. It is therefore logical that periphyton switches from being phosphorus limited in the upper catchment to nitrogen limited in the lower catchment.

2.6 25 years of monitoring data from the Mohaka River at State Highway 5 and State Highway 2. NIWA have two long-term National River Water Quality Monitoring Network (NRWQMN) sites on the Mohaka River. The most upstream site is located on the Mohaka River at State Highway 5 (Glenfalls) and the most downstream sites is located on State Highway 2 (Raupunga) (Figure 2-1). Both sites have a dataset of monthly observations taken over a period of 25 years. The frequency (monthly) and the duration (25 years) of monitoring data collected by the NIWA NRWQMN provides a powerful dataset for investigating past and present changes in water quality.

2.6.1 Trend analysis of NIWA NRWQMN data The NIWA NRWQMN site on the Mohaka River at State Highway 5 (Glenfalls) is situated downstream of the Taharua and Ripia rivers and offers an opportunity to look at long-term changes in water quality in the middle Mohaka River. With the exception of the Taharua catchment, there is little intensive land-use upstream of this sampling point (Lynch et al., in press). The NIWA NRWQMN site on the Mohaka River at State Highway 2 (Raupunga) is close to the sea and is influenced by all land-use practices throughout the catchment including water draining the Waipunga and Te Hoe River catchments. The site at Raupunga represents water quality before it is discharged to Hawke Bay.

The 25 year record provides a powerful dataset for investigating past and present changes in water quality. The trend analysis of water clarity (black disc) and nutrient data has been split across two time periods, including an ‘historic’ period running from 1989 to 2000 and a ‘present-day’ period from 2002 to 2013. The trend analysis for the State Highway 5 (Glenfalls) site is presented in Table 2-22 and State Highway 2 (Raupunga) site in Table 2-23.

Trends for the historic period are different to those of the current period. At both sites total nitrogen (TN) and dissolved inorganic nitrogen (DIN) improve during the historic period, but degrade during the current period.

For the historic period the rates of DIN reduction measured as the Percent Annual Change (PAC) is 2.4% PAC at the Mohaka at Glenfalls site, which is half that at the Raupunga site, at 4.7% PAC. Trends during the current period are opposite to the historic trends, with both sites currently showing a significant degradation in TN and DIN. It was in the early 2000s that changes to water quality in the upper Mohaka became apparent (Section 2.3) and increases in nitrogen load from the Taharua catchment became quite signficant (Section

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2.3.3). It is likely this land-use change is influencing TN and DIN trends in the middle and lower Mohaka catchment.

Black disc clarity and phosphorus also show contrasting trends for the historic and current time periods. For the historic period at Glenfalls there is no signifcant change for Black Disc (BD), Total Phosphorus (TP) or Dissolved Reactive Phosphorus (DRP), but there are signifcant improvements in these parameters at Raupunga.

For the historic period the improving PACs for BD (7.4%) and TP (6.2%) at Raupunga are high. Glenfalls has improving trends for BD and TP at present, but previously there was no significant trend. However, at Raupunga there are no signicant trends for the current period, although there were historically significant improving trends.

Table 2-22: Trend analysis results for, Black Disc, TP, DRP, TN and DIN for the Mohaka River at State Highway 5 (Glenfalls) NIWA NRWQMN monitoring site. Given a significant trend for a particular variable, the Percent Annual Change (PAC) is highlighted in BLUE if there was a significant improvement in the water quality variable, and highlighted in RED if there was a significant deterioration in the water quality variable. Historic (1989-2000) Black Disc TP DRP TN DIN Median 2.3 0.011 0.006 0.198 0.138 p value 0.154 0.917 0.848 0.005 0.001 Mohaka PAC -2.16 0 0 -1.64 -2.41 River at SH5 (Glenfalls) Current (2002-2013) Black Disc TP DRP TN DIN Median 2.6 0.011 0.005 0.302 0.225 p value 0.023 0.026 0.695 <0.001 <0.001 PAC 3.15 -2.60 0 3.74 5.03

Table 2-23: Trend analysis results for, Black Disc, TP, DRP, TN and DIN for the Mohaka River at State Highway 2 (Raupunga) NIWA NRWQMN monitoring site. Historic (1989-2000) Black Disc TP DRP TN DIN Median 0.405 0.026 0.009 0.169 0.098 p value <0.001 <0.001 0.016 0.001 < 0.001 Mohaka PAC 7.43 -6.24 -2.24 -3.59 -4.70 River at SH2 (Raupunga) Current (2002-2013) Black Disc TP DRP TN DIN Median 0.785 0.018 0.008 0.215 0.13 p value 0.701 0.198 0.406 0.017 0.014 PAC 0.51 -1.39 0 1.82 2.26

Land-use changes in the Taharua catchment are well understood, particularly as it relates to nitrogen loss, and goes some way to explain ‘current’ trends in TN and DIN at the NIWA NRWQMN sites. Rutherford and Parshotam (2011) reported nitrogen concentrations (principally as nitrate) increasing significantly in the Taharua River in the previous decade, coinciding with land use changes from forest/scrub to sheep/beef to

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dairying. This is consistent with Phillips (2009), who looked at a simplified mass balance model for nitrogen loss from the Taharua catchment and discusses:

. A catchment prior to 1982 that was largely undeveloped; land use in 1987 in the Taharua catchment that comprised only extensive pasture supporting mainly sheep and beef

. Land use in 1999 where 6% of the Taharua catchment was in dairy

. The 2009 situation that is comparable to the current day, with 35% of the catchment in dairying.

Increasing trends in TN and DIN in the middle and lower Mohaka catchment are likely to be a consequence of land use change and intensification in the Taharua catchment that is described by Rutherford and Parshotam (2011) and Phillips (2009).

In summary, nitrogen has improved at both Glenfalls and Raupunga sites, and water clarity (BD) and phosphorus have improved historically at Raupunga and currently are improving at Glenfalls. However, understanding the causes of these trends would require careful investigation of land management practices and land-use change across the Mohaka catchment over the last two to three decades. This detailed analysis is outside the scope of this report. Some analysis and discussion of broad land-use change across the catchment between 1996 and 2008 are provided in Lynch et al. (in press). Lynch et al. (in press) shows the most significant land use change to be conversion of high producing exotic grassland, low producing grassland and manuka and/or kanuka to exotic forestry. Although the area of land cover change (4300 hectares) is a relatively small percent (1.8%) of the total catchment area (244000 hectares), the conversion to forestry may influence long-term trends in water quality.

Production forestry is the most dominant ‘commercial’ land-use across the Mohaka catchment covering over 18% (44000 hectares) of land surface. As a land use, this is second only to native vegetation that covers 67% (162000 hectares) of catchment area (Lynch et al., in press). Differing stages of a production forest can influence water quality in differing ways. Some stages, such as roading and harvesting, result in episodic pulses of sediment and associated nutrient entering streams and rivers. Establishment and early growth stages of a production forest can result in shifts in nutrient loss (see Section 2.4). Whereas medium and long term growth stages would see a reduction in sediment and nutient loss as a forest matures. Forest establishment and forestry rotations that have occurred over the same time period as data collected by the NIWA NRWQMN program may have influenced trends in water clarity (BD) and phosphorus (Baillie & Neary, 2015; Eyles & Fahey, 2006).

2.6.2 Time series analysis of DIN and DRP concentrations at Glenfalls Anecdotal evidence suggests in recent years periphyton growth and detached periphyton drift have increased in the middle Mohaka River around State Highway 5. This section of river is popular for recreational activities such as fishing, kayaking, camping and rafting, and is the most publicly accessible stretch of the Mohaka River. Nuisance periphyton growth levels in this river section could affect recreational values and river users.

DIN concentration, DRP concentration and the ratio of DIN to DRP are plotted up in Figure 2-62, Figure 2-63 and Figure 2-64 for the Mohaka River at State Highway 5 (Glenfalls).

Analysis of the data reveals several interesting features:

. Strong seasonality is evident in DIN concentrations, with summer troughs and winter peaks (Figure 2-62). This is typical of other rivers in Hawke’s Bay (Uytendaal & Ausseil, 2013).

. Summer DIN concentrations prior to 2003 and (to a limited extent) prior to 2008 were very low and often fell below a concentration of 0.150 mg/l for extended periods over the summer months

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– a concentration level that would have potential to limit periphyton growth rate (circled in red in Figure 2-62) (HBRC, 2013b).

. Post 2008, in-stream concentrations increase markedly with summer troughs remaining well above 0.150 mg/l (circled in green in Figure 2-62).

. DRP concentrations are very low, averaging 0.006 mg/l and show no significant change over time (Table 2-22).

. Prior to DIN trending up from 2001/2002, DIN/DRP ratios reflect co-limiting conditions over summer periods (refer text note below). Increases in DIN concentration from 2003 and particularly from 2008 have reduced the influence of nitrogen as a periphyton growth-limiting nutrient during summer periods.

. The increased concentrations of nitrogen can largely be attributed to nitrogen loss from the Taharua catchment as this is the only area of intensive land-use upstream of the NIWA monitoring site, but forestry rotations may have a secondary effect.

Figure 2-62: Time series of Dissolved Inorganic Nitrogen (DIN) concentration measured in the Mohaka River at State Highway 5 at the NIWA NRWQMN site. The red line approximates a concentration level that would have potential to limit periphyton growth rate.

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Figure 2-63: Time series of Dissolved Reactive Phosphorus (DRP) concentration measured in the Mohaka River at State Highway 5 at the NIWA NRWQMN site. The red line approximates a concentration level that would have potential to limit periphyton growth rate.

Figure 2-64: Time series of DIN:DRP ratios measured in the Mohaka River at State Highway 5 at the NIWA NRWQMN site. See text box below for a summary of nutrient ratios. Ratios falling below the red line (<7:1) reflect likely N-limitation, ratios above the green line (>15:1) likely P-limitation.

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Nitrogen to phosphorus concentrations ratios

McDowell et al. (2009) identified how ratios of nitrogen to phosphorus may indicate limitation of periphyton growth by one or other of the nutrients, as follows:

. N-limitation was likely when N and P were present at ratios <7:1 (N:P),

. co-limitation (either nutrient may limit growth) when N and P were present at ratios between 7:1 and 15:1 (N:P)

. P-limitation was likely when N and P were present at ratios >15:1 (N:P).

The ratios represent the relative abundance of the nutrients, not their absolute availability. For example if both DIN and DRP concentrations are high, then both may be present at concentrations that exceed biological requirements and neither may be limiting. Nutrient ratios are useful for identifying the nutrient that is in excess, as opposed to absolute concentration thresholds.

2.7 The near-shore coastal environment. The Mohaka River meets the sea 48 km north of Napier, passing between large cliffs before entering the sea through a gravel and fine sediment bar. There is an area of approximately 10 hectares of slow moving, shallow water directly behind the bar that is a feeding and roosting ground for waterfowl and wading birds. Large numbers of mullet and kahawai also feed throughout this area. Gulls, terns and dotterel (Cromarty & Scott, 1995) have been observed on the gravel bar.

Since 2006, HBRC has been monitoring water quality approximately 0.75 km offshore of the Mohaka River mouth as part of the near-shore water quality SoE monitoring programme. More recently, Council has been monitoring estuarine water quality monthly to inform the Mohaka Plan Change process.

Marine saltwater enters the estuaries of most rivers in Hawke’s Bay. However, the Mohaka estuary is riverine dominated and no marine saltwater has been detected within the lower reaches of the river. Conductivity loggers were deployed around the estuary between the 12th December 2013 and the 10th January 2014. This time period covered two spring tides coinciding with low flows. No saline water was detected. There are several factors which could be contributing to the absence of saline water. It is likely that a combination of a shallow entrance at the mouth, a relatively steep channel gradient, and a strong freshwater river flow are preventing tidal movement through the estuary mouth whilst a relatively impermeable gravel barrier limits salt-water permeating through the gravel bar into the lower river. The river may also be entering the sea directly from an elevated land unit, reducing the distance that tidal water may move up-river.

This lack of marine saltwater intrusion indicates that the receiving environment for any contaminants coming from the Mohaka River is the near-shore coastal environment. The main threats to the marine environment in this area are increased levels of nutrients in the water and increased levels of land-derived sedimentation. The long term coastal water quality SoE monitoring data indicates that nutrient concentrations adjacent to the Mohaka river mouth are similar to other river-influenced sites in Hawke’s Bay and unlikely to have any impact on the nearshore environment. Sedimentation rates within the nearshore environment are not currently monitored, neither are the impacts of this sedimentation on coastal ecology. The area around the Mohaka river mouth is a naturally turbid area however it is not known how the current levels of turbidity relate to pristine state.

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3 Native fish distribution in the Mohaka River

3.1 Fish surveys in the Mohaka Catchment Over the years significant effort has been made to map distributions of native fish species in the Mohaka River catchment. In particular, in 1985, Ministry of Agriculture and Fisheries (MAF) gathered information in relation to a potential hydro scheme on the lower Mohaka (Strickland, 1985) and in 2012 HBRC commissioned work on native fish surveys in the upper and lower Mohaka River, the Taharua River and the Waipunga River catchments (Maclean, 2012a; Maclean, 2012b; Maclean, 2014). The results of the 2012 surveys were consistent with historic fish distribution records as recorded in the New Zealand Freshwater Fish Database (NIWA). The report found that native fish diversity was very low in the upstream upper catchment, with trout (brown and rainbow) and longfin eel being dominant. From all the 2012 surveys only one koaro was found in the Waipunga River off State Highway 5, and no other native fish.

Native fish surveys carried out recently in the lower Mohaka River (Maclean, 2014) found a much higher diversity of migratory species of fish, particularly in streams with good connectivity to the main river. Diadromous bullies (redfin, common and bluegill), torrentfish, inanga and smelt were all found at up to four sites below the Te Hoe/ Maungaharuru gorges in the lower river. These species can be easily deterred by fast-water barriers and/or steep falls, and hence do not often venture far inland in steeper catchments. Their presence indicates good access to the coast. Many tributary streams of the lower Mohaka River had steep falls and rapids at their junction with the main stem (e.g. Mangapuru and Mangawharangi Streams), and these sites had a low diversity of native fish. At these difficult-to-swim-to sites, only shortfin and longfin eel were found, and the native fish community resembled that found at sites upstream of the gorge. In other words, when sites were close to the coast and did not have barriers to fish migration, a wide diversity of species was found. By contrast, fish diversity was limited at sites that were a long way inland and/or above steep waterfalls.

Figure 3-1 provides a map based summary of fish species diversity across the Mohaka catchment and clearly demonstrates the increase in species diversity downstream of the gorge.

3.2 Native fish distribution and volcanism It is likely that the low diversity of native fish in the upper Mohaka catchment has a largely natural explanation. The significant volcanic eruption near Taupo approximately 1800 years ago, is likely to have destroyed all fish in the Mohaka catchment. This would have eliminated any non-migratory native species such as dwarf galaxias in the upper catchment (McDowell, 1996).

Strickland (1985) also concluded that most native fish were unable to navigate the Te Hoe/ Maungaharuru gorges in the lower river, downstream of the Te Hoe River confluence. It is likely that the Te Hoe/ Maungaharuru gorges are a natural barrier to all but the best native fish climbers. These include the longfin eel and, to a limited extent, koaro, shortfin eel and possibly banded kokopu (Strickland, 1985).

The fish community in the upper catchment is therefore comprised of introduced, non-migratory self- sustaining populations of brown and rainbow trout; and native migratory species capable of navigating the gorge below the Te Hoe River confluence.

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Figure 3-1: Fish species diversity of the Mohaka River catchment. The size of the dot reflects the number of fish species recorded at a site during electric fishing surveys. Columns in the table that are shaded indicate diadromous species, i.e. species that require access to and from the ocean.

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3.3 Pressures on native fish species It is likely that adverse impacts on native fish species throughout the Mohaka catchment are rare compared to other catchments around the region such as the Karamu.

Water quality is generally excellent throughout the catchment. The elevated nitrate concentrations in the upper Taharua River are isolated from areas of high native fish diversity that occur in the lower river catchment, such as the streams and river between the Te Hoe/ Maungaharuru gorges and the sea (Strickland, 1985).

The most significant threat to native fish are likely to be reductions in stream habitat quality, such as increased sedimentation choking the interstitial spaces in the stream bed, causing a reduction in available habitat. Large areas of the catchment are covered by native forest, which provides excellent habitat and long term protection. However, these areas are largely above natural barriers that occur in the lower Mohaka River, so the reduced level of native fish diversity is natural.

There are few constructed barriers to fish migration in the larger tributary streams. Most barriers to fish passage are natural, including gorges mentioned above and large waterfalls found on some of the deeply incised tributary streams.

3.4 Distribution of koura There is very little known about koura distribution throughout the Mohaka River, although McDowell (1996) identifies some significant effects from the Taupo eruption on Koura distribution.

4 Upper Mohaka and Taharua trout habitat assessments – comment from Glen Mclean (Technically Trout) The Mohaka River supports an outstanding trout fishery for both rainbow and brown trout as recognised in the Water Conservation Order for this river. Adult brown trout densities in the upper river are some of the highest recorded in New Zealand. The headwaters including the Oamaru and Kaipo Rivers provide important spawning habitat and support significant numbers of ‘young of the year’ trout of both species.

The Taharua River was previously a recognised brown trout fishery in its own right. This fishery is separated from the main Mohaka fishery by falls near the confluence. These also prevent rainbow trout resident downstream in the Mohaka River establishing a population in the Taharua River.

Over the last decade or more the Taharua fishery has declined significantly, with many fewer juvenile and adult fish now present. This observation is supported by records kept by Poronui Lodge. The causes of these changes are not readily apparent, although streamflow (anecdotally) appears to have reduced. Investigation of spawning habitat, stream erosion and sediment indicates the Taharua River tributary streams continue to provide suitable habitat, and that bank erosion and stream sedimentation, a process that would have reduced the quality of trout spawning habitat, is less likely now than in past decades due to the extensive riparian fencing and improved stream bank protection now in place.

Surveys of the tributary streams indicate strong juvenile trout recruitment from the tributaries downstream of Poronui Lodge, in particular from the Ohaoko Stream draining from the Kaimanawa Forest Park. However above Poronui Lodge there appears very little spawning despite the fact that several of the tributaries appear ideal, and in one case, support a resident population isolated in the headwaters by a waterfall. In the past

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this stretch of the Taharua River was an important fishing beat for Poronui Lodge and was recognised as producing the largest trout in the Taharua River.

That this stretch of the Taharua River has much less spawning than lower reaches suggests that the falls upstream of Poronui Lodge act as a barrier to trout migrating upstream. Whether this was always the case is unknown. Typically juvenile brown trout migrate downstream out of the spawning tributaries as they grow and their requirements change. It is hypothesised that the changes in flow which have emphasised a series of bedrock falls along the river may have impacted on the distances these trout now migrate downstream and/or their ability to return back upstream, causing many of these fish to be lost from the Taharua River. Additional work is required to better understand potential changes in streamflow that may have occurred over recent times.

5 Summary and conclusion Despite land-use changes in the upper catchment, the Mohaka River remains one of Hawke’s Bay’s outstanding rivers as recognised through the existing Water Conservation Order, the high level of ‘naturalness’ that remains throughout the catchment and the overall health of the river.

For most of its catchment area the Mohaka River has excellent nutrient water quality, with very low levels of nitrogen and low to moderate levels of phosphorus when compared to natural background levels. Stream ecological health is also very good, with macroinvertebrate communities dominated by pollution sensitive taxa.

Overall, the following conclusions can be drawn from the data, analysis and information presented in this report:

. Most sampling sites across the Mohaka River have excellent water quality.

. Overall, the ecological health of the Mohaka River is excellent.

. The results show periphyton biomass levels to be in excellent condition throughout the upper and middle catchment, based on measurements taken by HBRC over the course of the SoE monitoring program. Biomass levels are typically below the 50 mg/m2 Biggs (2000) ‘biodiversity’ threshold and, with the exception of one or two monthly observations in the lower Mohaka River at Willow Flat and Raupunga, all measurements are below the 120 mg/m2 threshold.

. Current water quality issues within the upper zone, upstream of the Ripia River, are largely due to intensive farming within the Taharua sub-catchment on free draining pumice soils.

. The effects of Taharua outflows on water quality downstream can be summarised as follows:

− Nitrogen contributed from the Taharua River dominates the in-stream nitrogen levels of the upper Mohaka River.

− DIN concentrations increase markedly downstream of the Taharua confluence and remain elevated for over 60 km downstream.

− DRP concentrations, although showing slight elevation downstream of the Taharua confluence, return to very low levels after approximately 15 km.

− Under low flow conditions, Taharua outflows cause a dramatic drop in water clarity in the Mohaka River returning to 4m and greater after approximately 10 km downstream.

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− Algal biomass and visual cover increases directly downstream of the Taharua confluence and then returns to background levels within 10 km.

− Phormidium cover increases significantly downstream of the Taharua confluence but remained within the ‘green’ band of current interim guidelines.

− Phormidium cover was highest for the river reach 10 km downstream of the Taharua confluence.

− Macroinvertebrate indices, apart from monitoring sites directly downstream of the Taharua confluence, show the community to be in excellent condition with little evidence of adverse effects from Taharua outflows.

− EPT (Ephemeroptera (mayfly), Plecoptera (stonefly) and Trichoptera (caddisfly)) biomass levels are very high, with little evidence of any impact from Taharua outflows.

− Macroinvertebrate indices and EPT density, diversity and biomass were higher when compared to the upper Ngaruroro River, showing the macroinvertebrate community to be in excellent health.

. Changes in water quality at surface water monitoring sites in the Taharua River can be summarised as follows:

− Over the last ten years, there have been significant increases in nitrate-nitrogen concentration measured at the Wairango and Twin Culverts SoE monitoring sites which relate to land-use changes and historical farming practices.

− Reductions in nitrate concentration in the upper Taharua River have not been repeated in the lower Taharua River – this likely being due to river water being ‘older’ in the lower catchment. That is, there is a greater land-use ‘legacy’ effect in the lower river influencing in-stream nitrate concentrations and improvements may still be a year or two away from permeating through the groundwater.

− Nutrient mitigation measures undertaken over recent years have improved in-stream DRP concentrations.

. Nitrogen levels have increased significantly through the middle Mohaka River over summer low flow conditions, and are now at levels that would not limit periphyton growth. Phosphorus concentrations remain very low.

. With increased DIN concentrations in the upper and middle Mohaka River, any increases in phosphorus concentrations would likely result in increased periphyton growth over and above what is seen today. Alongside mitigation of nitrogen loss from the upper catchment, continuing works in the upper catchment to reduce phosphorus loss from the catchment should be seen as a continuing priority to reduce eutrophication effects of the upper catchment and further reduce risk of increased periphyton growth.

. Continued mitigation of nitrogen loss from the Taharua catchment will limit nuisance algal growth in the upper and middle catchment and result in improved river health overall.

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. Land-use changes in the Rangitikei Plains and associated increases in nitrogen measured in the Waiarua Stream are having negligible effects on water quality downstream in the Waipunga River and the wider Mohaka River. The Waiarua Stream is the only monitoring site with elevated nitrogen concentrations other than the Taharua River and sites directly affected by Taharua River outflows.

. Nutrient limitation appears to switch from strong phosphorus limitation in the upper and middle catchment (due to elevated nitrogen concentrations and low phosphorus concentrations) to nitrogen limitation in the lower catchment (due to elevated phosphorus concentrations and low nitrogen concentrations). Further increases in nitrogen concentration in the lower catchment, given the increased availability of phosphorus, would in all likelihood result in increased periphyton growth.

. Reductions in water clarity are the most significant change in water quality through the lower zone. The reduction in black disc clarity and increase in turbidity at the monitoring sites in the lower Mohaka River at Willowflat and Raupunga is important. Understanding the cause of the degradation in water clarity in the lower Mohaka is a high priority. Even under natural conditions, the widespread occurrence of papa/mudstone throughout this zone would lead to naturally elevated turbidity levels compared to the upper and middle zones. Quantifying the contributions from natural background geological effects and from catchment disturbance through production forest operations is beyond the scope of this report. However, limiting sediment loss through improved management of riparian buffers and areas susceptible to landslip and erosion should be seen as a priority.

. The lack of marine saltwater entering the lower Mohaka River indicates that the receiving environment for any contaminants coming from the Mohaka River is the near-shore coastal environment. The long term SoE monitoring data indicate that nutrient concentrations are low and unlikely to have any impact on the nearshore environment.

Mohaka River Catchment 119

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Franklin P.A. (2013) "Dissolved oxygen criteria for freshwater fish in New Zealand: a revised approach" New Zealand Journal of Marine and Freshwater Research 48: 112-126. Hamilton D. (2005) "Land use impacts on nutrient export in the Cenrtal Volcanic Plateau, North Island" New Zealand Journal of Forestry 49: 27-31. Hay J., Hayes J., Young R. (2006) "Water quality guidelines to protect trout fishery values", Cawthron Institute. HBRC. (2006) "Hawke's Bay Regional Resource Management Plan (Includes Regional Policy Statement)" Operative 28 August 2006, No. ISBN 1-877405-11-6, Hawkes Bay Regional Council. HBRC. (2013) "Tukituki River Catchment - Managing Nuisance Growth Using Nutrient Limits. Technical Workshop Summary", Hawke's Bay Regional Council. Hickey C.W. (2013a) "Site-specific nitrate guidelines for Hawke's Bay" NIWA report for Hawke's Bay Regional Council, NIWA. Hickey C.W. (2013b) "Updating nitrate toxicity effects on freshwater aquatic species" NIWA report prepared for the Ministry of Building, Innovation and Employment, NIWA. Hickey C.W., Martin M.L. (2009) "A review of nitrate toxicity to freshwater aquatic species", NIWA. Landman M.J., Van Den Heuvel M.R., Ling N. (2005) "Relative sensitivities of common freshwater fish and invertebrates to acute hypoxia" New Zealand Journal of Marine and Freshwater Research 39: 1061-1067. Lynch et al., in press. "Mohaka Catchment. An Environmental Characterisation", Hawke's Bay Regional Council. Maclean G. (2012a) "A brief assessment of fishery values in the Waipunga River" Prepared for Hawke’s Bay Regional Council, Technically Trout. Maclean G. (2012b) "Summary of Upper Mohaka and Taharua Fish Surveys – March 2012" Prepared for Hawke’s Bay Regional Council, Technically Trout. Maclean G. (2014) "Field survey of the fish populations of the lower Mohaka River" Prepared for Hawke’s Bay Regional Council, Technically Trout. Mathieson F., Quinn J., Hickey C. (2012) "Review of the New Zealand in-stream plant and nutrient guidelines and development of an extended decision making framework. Phases 1 and 2 final report." Prepared for the Ministry of Science and Innovation Envirolink fund, No. HAM2012-081, NIWA. McDowell R.M. (1996) "Freshwater fishes of south-eastern Australia", Reed, Sydney. McDowell R.W., Larned S.T., Houlbrooke D.J. (2009) "Nitrogen and phosphorus in New Zealand streams and rivers: control and impact of eutrophication and the influence of land management" New Zealand Journal of Marine and Freshwater Research 43: 985-999. Menneer J.C., Ledgard S.F., Gillingham A.G. (2004) "Land use impacts on nitrogen and phosphorus loss and management options for intervention" Prepared for the Environment Bay of Plenty, AgResearch. MfE. (2007) "Lake water quality in New Zealand: status in 2006 and recent trends 1990-2006", Published by the Ministry for the Environment, Wellington, New Zealand. MfE. (2013) "Proposed amendments to the National Policy Statement for Freshwater Management 2011: A discussion document", Ministry for the Environment: Wellington. MfE/MoH. (2003) "Microbiological Water Quality Guidelines for Marine and Freshwater Reacreational Areas", Ministry for the Environment and Ministry for Health: Wellington. MfE/MoH. (2009) "New Zealand Guidelines for Cyanobacteria in Recreational Fresh Waters - Interim Guidelines" Prepared for the Ministry for the Environment and the Ministry of Health by SA Wood, DP

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Hamilton, WJ Paul, KA Safi and WM Williamson., Ministry for the Environment and Ministry of Health: Wellington. Norton E. (2012) "Proposed Hurunui and Waiau River Regional Plan and Proposed Plan Change 3 to the Canterbury Natural Resources Regional Plan. Implications for Water Quality. Section 42A Report", NIWA, Christchurch. Phillips J. (2009) "Taharua Catchment Nutrients from land use: Preliminary report", No. ISBN 1-877174-49- 1., Hawkes Bay Regional Council. Quinn J., Hickey C.W. (1990) "Characterisation and classification of benthic invertebrate communities in 88 New Zealand rivers in relation to environmental factors" New Zealand Journal of Marine and Freshwater Research 24: 387-409. Rutherford K., Parshotam A. (2011) "Effects of land use on Nitrogen and Periphyton in the Mohaka River, Hawke's Bay" Prepared for Hawkes Bay Regional Council No. NIWA Client Report No: HAM2012-077, NIWA. Scarsbrook M.R., McBride G.B. (2007) "Effects of Sampling frequency on water quality trend analyses in Hawke’s Bay rivers (1996-2005)" Prepared for Hawke's Bay Regional Council, NIWA. Shearer K. (2015) "Mohaka Longitudinal Study - Macroinvertebrate Denisity and Biomass." Letter Communication to Hawke's Bay Regional Council, 30th March, 2015. Cawthron Institute. Shearer K.A., Hays J.A. (2010) "Invertebrate Drift and Trout Growth Potential in the Taharua and Upper Mohaka Rivers: An Investigation of Effects of Dairy Farming Across Three Seasons" Prepared for Hawkes Bay Regional Council and Fish and Game Council, Cawthron Institute. Snelder T., Biggs B.J., Weatherhead M. (2010) "New Zealand River Environment Classification User Guide" Publication number: ME 1026 ISBN: 978-0-478-33295-7, Ministry for the Environment. Stansfield B. (2008) "Upper Mohaka River catchment water quality and benthic ecology" Environmental Management Group Technical Report, Hawkes Bay Regional Council. Stansfield B. (2013) "Aquatic macroinvertebrate communities of the Ngaruroro River catchment", Environmental Impact Assessments Ltd. Stark J.D. (1985) "A macroinvertebrate community index of water quality for stony streams", Ministry of Works and Development. Stark J.D., Maxted J.R. (2007) "A user guide for the Macroinvertebrate Community Index", No. Cawthron Report No. 1166. Prepared for the Ministry for the Environment Strahler A.N. (1952) "Hypsometric (area-altitude) analysis of erosional topology" Geological Society of America Bulletin 63: 1117–1142. doi:10.1130/0016-7606(1952)63[1117:HAAOET]2.0.CO;2. Strickland R.R. (1985) "Distribution and habitats of fishes in the Mohaka River", Fisheries Research Division. NZ Ministry of Agriculture and Fisheries. Urbina M.A., Forster M.E., Glover C.N. (2011) "Leap of faith: Voluntary emersion behaviour and physiological adaptations to aerial exposure in a non-aestivating freshwater fish in response to aquatic hypoxia" Physiology and Behaviour 103: 240-247. Uytendaal A., Ausseil O. (2013) "Tukituki Catchment: Recommended Water Quality Limits and Targets for the Tukituki Plan Change 6", Hawke’s Bay Regional Council. Wanowski J.W.J. (1979) "Morphological limitations, prey size selectivity, and growth response of juvenile Atlantic salmon, Salmo salar" Journal of fish biology 14: 89-100. Wilcock B., Biggs B., Death R., Hickey C.W., Larned S.T., Quinn J. (2007) "Limiting nutrients for controlling undesireable periphyton growth" Report Prepared for Horizons Regional Council, No. HAM2007-006, NIWA, Hamilton NZ.

122 Mohaka River Catchment

Appendix A Site metadata and flow statistics for water quality monitoring sites Site metadata for water quality monitoring sites across the Mohaka catchment.

HBRC Easting Northing Catchment Distance from Concurrent Longtitudinal Monitoring Site Name SOE Site ID (NZTM) (NZTM) Area (ha) the sea (km) Gauging Survey 2446 Taharua Rv at Wairango 1883989 5687530 1667 180 Yes 2445 Taharua Rv at Twin Culv 1884707 5683875 3122 176 Yes 3278 Taharua Rv at Henry's Br 1884117 5678035 8150 166 Yes Yes 2442 Taharua Rv at Poronui Stn 1884696 5676634 9663 163 Yes 3418 Kaipo Str U/S Oamaru Rv 1881778 5670305 5173 157 Yes 3410 Oamaru Rv U/S Kaipo Str 1882792 5669722 6550 157 Yes 3479 Mohaka (-) 2.3km U/S Taharua Confl 1883935 5669395 12007 156 Yes 2961 Mohaka Rv U/S Taharua Rv or Mohaka Rv (-) 1.9km U/S Taharua Confl 1884096 5669340 12008 155 Yes Yes Yes 3151 Taharua Rv at Red Hut 1885681 5669805 13349 153 Yes Yes 3408 Ripia Rv at Lchnvr Stn 1892122 5676116 1854 152 Yes 3152 Mohaka Rv D/S Taharua Rv or Mohaka 0.5km D/S Taharua Confl 1886102 5668901 28088 152 Yes Yes Yes 3487 Mohaka 1km D/S Taharua Confl 1886143 5668528 28088 152 Yes 3488 Mohaka 3.7km D/S Taharua Confl 1887743 5667434 29348 149 Yes 3489 Mohaka 5.43km D/S Taharua Confl 1888921 5667110 32844 147 Yes 3490 Mohaka 6.8km D/S Taharua Confl 1889532 5666531 33102 147 Yes 3491 Mohaka 9.8km D/S Taharua Confl 1890980 5664832 34227 143 Yes 3492 Mohaka 14.4km D/S Taharua Confl 1892415 5662780 36152 138 Yes 599 Mohaka 21.9km D/S Taharua Confl 1893270 5659664 43553 134 Yes 3494 Mohaka 24.2km D/S Taharua Confl 1894171 5658390 44153 132 Yes 3495 Mohaka 30.3km D/S Taharua Confl 1897738 5657383 51358 125 Yes 3496 Mohaka 35.7km D/S Taharua Confl 1901129 5656047 52616 122 Yes 325 Waiarua Strm 1904051 5683542 2675 121 Yes 322 Waipunga Rv at Pohokura Rd 1905421 5682817 8775 119 Yes Yes 604 Ripia Rv U/S Mohaka Rv 1904295 5656775 18261 119 Yes Yes 3412 Mohaka Rv U/S Ripia Rv or Mohaka 38.3km D/S Taharua Confl 1902738 5655026 62558 118 Yes Yes 3186 Mohaka Rv D/S Ripia Rv 1903691 5654324 81904 116 Yes 3416 Okoeke Strm at SH5 1906073 5679451 4099 115 Yes 321 Mokomokonui Rv 1910613 5671662 14684 101 Yes 601 Mohaka Rv at SH5 (NIWA) Mohaka 56.9km D/S Taharua Confl 1913978 5657171 103421 93 Yes Yes Yes 3417 Waipunga Rv U/S Mohaka Rv 1918845 5665215 47372 84 Yes 3182 Mohaka Rv D/S Waipunga Rv 1920171 5665593 160211 80 Yes 3404 Mohaka Rv U/S Te Hoe Rv 1930048 5673973 174409 61 Yes 606 Te Hoe Rv U/S Mohaka Rv 1930918 5673913 36871 60 Yes 595 Mohaka Rv at Willowflat 1941849 5675440 221077 40 Yes 3 Mohaka Rv at Raupunga (NIWA) 1958185 5666140 237180 13 Yes Yes

Mohaka River Catchment

Flow statistics for long-term SoE monitoring sites for the Mohaka River catchment.

Lower Upper Minimum Maximum Mean Std. Dev. Median 3X Median Flow record Flow record Reporting name Quartile Quartile Flow record type (l/s) (l/s) (l/s) (l/s) (l/s) (l/s) from to (l/s) (l/s) Mohaka Rv U/S Taharua Rv 1322 200423 6508 6445 3068 4718 7587 14155 4/06/1963 1/01/2014 Correlative Taharua Rv at Wairango 112 4417 470 335 263 391 566 1174 26/01/2008 1/01/2014 Correlative Taharua Rv at Twin Culv 495 6024 954 430 690 854 1078 2563 26/01/2008 1/01/2014 Correlative Taharua Rv at Henry's Br 1728 31898 2514 977 1993 2243 2678 6729 26/01/2008 1/01/2014 Measured Taharua Rv at Poronui Stn 1496 26652 3584 1957 2379 3127 4145 9380 4/06/1963 1/01/2014 Correlative Taharua Rv at Red Hut 1545 44397 5102 3333 3051 4325 6058 12976 26/01/2008 1/01/2014 Correlative Mohaka Rv D/S Taharua Rv 3755 354975 12904 11369 6834 9747 14807 29240 4/06/1963 1/01/2014 Correlative Ripia Rv U/S Mohaka Rv 958 225092 6796 7255 2923 4781 8011 14344 4/06/1963 1/01/2014 Correlative Mohaka Rv D/S Ripia Rv 7867 1159372 37863 37276 17963 27511 44101 82533 4/06/1963 1/01/2014 Correlative Waiarua Strm 338 26140 1010 835 564 778 1150 2335 4/06/1963 1/01/2014 Correlative Waipunga Rv at Pohokura Rd 1096 57835 2574 1837 1593 2064 2881 6191 4/06/1963 1/01/2014 Correlative Mokomokonui Rv 1090 123305 4640 4443 2313 3434 5450 10301 1/03/1957 1/01/2014 Correlative Mohaka Rv at SH5 (NIWA) 7867 1159372 37863 37276 17963 27511 44101 82533 4/06/1963 1/01/2014 Measured Mohaka Rv D/S Waipunga Rv No Flow No Flow No Flow No Flow No Flow No Flow No Flow No Flow N/A N/A No Flow Mohaka Rv at Willowflat 16034 2018040 74182 72778 36071 54424 87456 163271 1/03/1957 1/01/2014 Correlative Mohaka Rv at Raupunga 15153 2201464 78653 79478 37031 57071 93144 171214 1/03/1957 1/01/2014 Measured Mohaka Rv at Raupunga (NIWA) 15153 2201464 78653 79478 37031 57071 93144 171214 1/03/1957 1/01/2014 Measured

124 Mohaka River Catchment

Appendix B Summary statistics by flow

All flows E. coli Elec. Site Turbidity Black DRP DIN DIN / NO3-N NH4-N DO TOC Hardness Temp Chla MCI % EPT Statistic SS (mg/l) (CFU/ TP (mg/l) TN (mg/l) DO (%) Cond. pH name (NTU) Disc (m) (mg/l) (mg/l) DRP (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (oC) (mg/m2) (Unit) taxa 100ml) (uS/cm) Minimum 0.2 1.5 1 0.2 0.002 0.002 0.055 0.012 2 0.001 0.005 8.2 79 28 6.4 0.5 7.9 4.1 0.0 118.5 57.7 5%'ile 0.3 1.5 1 0.6 0.002 0.002 0.055 0.014 5 0.001 0.005 9.1 89 31 6.8 0.5 8.3 5.6 0.1 no data no data 25%'ile 0.4 1.5 1 3.2 0.004 0.002 0.055 0.024 8 0.009 0.005 10.2 95 39 7.2 0.8 10.5 7.6 0.3 122.9 60.0 Median 0.7 1.5 2 4.3 0.006 0.002 0.109 0.040 12 0.028 0.005 10.9 97 47 7.3 1.0 12.0 9.8 1.0 127.6 66.7 75%'ile 1.1 1.5 11 6.0 0.008 0.005 0.136 0.054 22 0.040 0.005 11.4 100 54 7.4 1.3 13.0 12.7 2.8 132.5 69.5 95%'ile 4.9 23.3 56 7.9 0.027 0.008 0.253 0.106 52 0.084 0.019 12.7 104 64 7.8 2.7 15.3 15.3 11.9 no data no data Maximum 11.9 25.0 140 8.4 0.050 0.009 0.365 0.290 105 0.280 0.038 13.6 107 68 8.1 4.6 15.8 16.5 24.0 148.2 70.4 Mean 1.3 3.6 11 4.4 0.008 0.003 0.116 0.048 17 0.034 0.007 10.8 97 47 7.3 1.2 11.8 10.1 2.5 129.5 64.9 Std. Dev. 1.9 5.7 22 2.0 0.009 0.002 0.062 0.044 17 0.044 0.006 1.0 5 10 0.3 0.8 2.0 3.0 4.4 10.4 6.5

Mohaka Rv U/S Taharua Rv Count 60 64 59 57 65 66 61 65 65 65 66 59 55 58 59 34 41 59 46 6 3 Minimum 0.1 1.5 1 0.3 0.009 0.002 2.200 2.212 44 2.200 0.005 7.3 67 89 5.9 0.5 20.0 8.9 no data 84.8 42.3 5%'ile 0.2 1.5 1 1.4 0.012 0.008 2.540 2.512 93 2.500 0.005 7.6 69 95 6.4 0.5 22.0 9.5 no data no data no data 25%'ile 0.4 1.5 3 3.2 0.015 0.012 2.900 2.812 154 2.800 0.005 8.1 74 100 6.7 0.8 23.0 10.5 no data 88.7 43.2 Median 0.7 1.5 7 4.7 0.018 0.015 3.403 3.311 207 3.300 0.005 8.5 79 104 6.8 1.0 25.0 11.0 no data 95.4 45.8 75%'ile 1.1 1.5 19 6.6 0.022 0.019 3.770 3.611 280 3.600 0.013 8.8 83 108 7.1 1.7 26.0 11.5 no data 101.7 50.8 95%'ile 2.2 9.0 144 9.9 0.053 0.035 4.269 4.099 361 4.080 0.046 9.6 91 117 7.3 3.5 28.5 12.0 no data no data no data Maximum 10.0 13.0 1200 10.0 0.149 0.073 4.790 4.410 1455 4.400 0.077 10.1 93 174 8.1 5.9 30.0 12.9 no data 106.7 52.4 Mean 1.0 2.4 42 4.9 0.025 0.017 3.363 3.249 254 3.229 0.012 8.5 79 105 6.9 1.4 24.8 11.0 no data 95.4 46.8 Std. Dev. 1.4 2.4 166 2.4 0.024 0.010 0.547 0.492 236 0.490 0.015 0.6 7 11 0.3 1.1 2.1 0.7 no data 8.5 5.1

Taharua Rv at Wairango Count 57 58 58 55 58 59 58 58 58 58 59 58 58 58 58 36 40 59 no data 5 3 Minimum 0.2 1.5 1 0.3 0.006 0.002 3.100 3.005 28 3.000 0.005 7.8 71 11 6.3 0.5 15.0 8.9 no data 93.3 42.9 5%'ile 0.2 1.5 1 1.1 0.009 0.002 3.150 3.032 127 3.000 0.005 8.6 80 96 6.7 0.5 21.6 9.2 no data no data no data 25%'ile 0.5 1.5 3 2.1 0.014 0.009 3.501 3.413 220 3.400 0.005 9.5 87 102 6.9 0.6 24.0 10.6 no data 96.7 43.2 Median 0.9 1.5 9 3.5 0.019 0.013 3.700 3.614 278 3.600 0.005 9.8 92 106 7.0 0.9 25.0 11.3 no data 103.8 44.0 75%'ile 1.4 6.0 27 4.9 0.023 0.016 3.900 3.766 396 3.750 0.013 10.1 97 109 7.2 1.3 26.0 11.9 no data 107.2 46.7 95%'ile 3.7 10.6 414 6.9 0.054 0.028 4.326 4.111 1656 4.100 0.027 10.8 101 119 7.5 3.0 27.0 13.0 no data no data no data Maximum 12.5 37.0 1500 9.1 0.141 0.122 4.903 4.813 1805 4.800 0.054 10.9 104 168 8.0 5.5 28.0 13.4 no data 109.6 47.6 Mean 1.3 4.5 63 3.6 0.024 0.015 3.725 3.615 397 3.598 0.010 9.8 91 105 7.1 1.2 24.9 11.2 no data 102.2 44.8 Std. Dev. 1.7 5.3 214 1.9 0.024 0.016 0.353 0.334 387 0.335 0.010 0.6 7 16 0.3 1.0 2.2 1.1 no data 6.6 2.5

Taharua Rv at Twin Culv Count 59 59 59 54 59 60 60 60 59 60 60 60 59 60 60 36 41 61 no data 5 3 Minimum 0.5 1.5 1 1.2 0.005 0.002 1.960 1.521 138 1.480 0.005 7.9 70 64 6.8 0.6 14.9 9.7 24.0 129.2 57.7 5%'ile 0.6 1.5 1 no data 0.007 0.004 1.967 1.692 151 1.664 0.005 8.1 72 67 6.8 no data no data 9.7 no data no data no data 25%'ile 1.0 1.5 3 2.9 0.011 0.008 2.083 1.970 200 1.960 0.005 10.0 93 90 7.1 no data 14.9 10.3 no data no data no data Median 1.3 1.5 7 4.3 0.012 0.010 2.302 2.212 221 2.200 0.005 10.2 96 95 7.4 0.6 19.0 11.2 24.0 129.2 57.7 75%'ile 1.8 1.9 17 4.5 0.019 0.011 2.442 2.479 310 2.475 0.005 10.5 99 99 7.6 no data 23.0 12.0 no data no data no data 95%'ile 11.7 68.6 84 no data 0.042 0.012 2.600 2.512 797 2.500 0.025 11.1 103 107 8.1 no data no data 13.0 no data no data no data Maximum 13.1 99.0 86 5.6 0.053 0.012 2.600 2.512 1156 2.500 0.041 11.2 104 109 8.2 0.6 23.0 13.1 24.0 129.2 57.7 Mean 2.4 8.1 19 3.7 0.016 0.009 2.288 2.201 288 2.188 0.007 10.1 94 93 7.4 0.6 19.0 11.2 24.0 129.2 57.7 Std. Dev. 3.3 23.6 28 1.3 0.010 0.002 0.215 0.274 220 0.279 0.008 0.9 9 11 0.4 0.0 5.7 1.1 0.0 0.0 0.0 Taharua Rv at Henry's Br Count 13 17 12 9 17 19 17 19 19 19 19 13 12 14 14 1 2 13 1 1 1

Mohaka River Catchment

All Flows E. coli Elec. Site Turbidity Black DRP DIN DIN / NO3-N NH4-N DO TOC Hardness Temp Chla MCI % EPT Statistic SS (mg/l) (CFU/ TP (mg/l) TN (mg/l) DO (%) Cond. pH name (NTU) Disc (m) (mg/l) (mg/l) DRP (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (oC) (mg/m2) (Unit) taxa 100ml) (uS/cm) Minimum 0.7 1.5 1 0.2 0.011 0.002 1.020 0.832 32 0.800 0.005 7.9 72 49 6.7 0.5 11.0 6.9 0.4 111.3 52.2 5%'ile 0.8 1.5 1 0.3 0.013 0.002 1.236 0.981 56 0.971 0.005 9.3 82 60 6.9 0.5 13.2 7.6 0.8 no data no data 25%'ile 1.2 5.0 2 0.7 0.016 0.008 1.542 1.494 126 1.452 0.005 10.4 93 71 7.0 0.7 17.1 9.1 2.8 113.0 no data Median 1.8 9.0 10 1.4 0.021 0.011 1.852 1.710 163 1.700 0.005 10.6 98 80 7.1 1.0 18.8 10.5 6.4 118.2 52.2 75%'ile 3.5 22.0 22 2.3 0.030 0.012 2.000 1.903 224 1.893 0.011 10.9 101 86 7.2 1.5 19.7 12.0 32.2 119.6 no data 95%'ile 9.1 63.6 414 3.1 0.095 0.022 2.325 2.225 904 2.215 0.029 11.8 105 93 7.4 2.4 21.0 13.3 76.8 no data no data Maximum 23.6 125.0 1300 3.4 0.240 0.032 2.552 2.310 980 2.300 0.050 12.2 109 122 8.6 5.5 22.0 14.2 93.0 120.0 52.2 Mean 3.1 18.3 70 1.5 0.031 0.011 1.782 1.674 223 1.660 0.009 10.6 97 78 7.2 1.2 18.2 10.5 19.7 116.5 52.2 Std. Dev. 3.8 23.5 223 0.9 0.037 0.005 0.336 0.344 217 0.346 0.009 0.7 7 12 0.3 0.9 2.3 1.8 24.5 4.6 0.0

Taharua Rv at Poronui Stn Count 45 46 46 46 46 46 42 47 46 47 46 46 44 46 46 36 40 47 18 3 1 Minimum 0.7 1.3 1 0.2 0.006 0.002 0.710 0.592 39 0.580 0.005 9.3 83 44 6.5 0.5 10.1 5.4 0.1 83.8 21.9 5%'ile 0.8 1.5 2 0.4 0.008 0.002 0.825 0.701 71 0.650 0.005 9.6 85 57 6.6 0.5 10.8 7.5 no data no data no data 25%'ile 1.3 1.5 5 1.1 0.011 0.004 1.260 1.146 139 1.135 0.005 10.4 94 69 7.1 0.9 16.6 9.1 0.1 88.2 26.2 Median 1.9 4.0 13 1.8 0.014 0.007 1.450 1.317 204 1.300 0.005 10.8 99 78 7.2 1.2 18.0 10.5 13.6 95.2 39.1 75%'ile 3.0 7.6 43 2.8 0.020 0.008 1.642 1.531 387 1.520 0.005 11.4 103 88 7.4 1.5 19.5 12.4 27.2 105.4 40.8 95%'ile 11.7 31.1 316 3.9 0.038 0.013 1.892 1.802 876 1.790 0.024 11.9 109 99 7.8 2.4 22.0 14.3 no data no data no data Maximum 16.9 62.0 470 5.4 0.072 0.015 1.912 1.863 932 1.850 0.068 12.2 113 105 8.1 4.9 22.0 14.5 27.2 107.6 41.4 Mean 3.0 7.3 53 1.9 0.018 0.007 1.429 1.317 308 1.301 0.008 10.8 98 78 7.3 1.3 17.7 10.7 13.6 96.2 34.1

Taharua Rv at Red Hut Std. Dev. 3.1 10.5 101 1.1 0.011 0.003 0.295 0.301 253 0.304 0.009 0.7 7 13 0.3 0.8 2.9 2.2 19.2 10.0 10.7 Count 60 63 59 52 64 64 62 64 64 64 64 57 56 57 58 35 41 58 2 5 3 Minimum 0.5 1.2 1 0.3 0.002 0.002 0.310 0.260 25 0.250 0.005 8.7 84 37 6.6 0.5 9.2 4.8 0.1 109.6 44.0 5%'ile 0.6 1.5 2 0.4 0.006 0.002 0.387 0.289 37 0.279 0.005 9.9 92 41 6.9 0.5 10.1 6.6 0.1 no data no data 25%'ile 1.0 1.5 4 1.4 0.008 0.002 0.585 0.484 83 0.465 0.005 10.6 97 50 7.2 0.9 13.2 8.4 1.1 113.5 46.7 Median 1.3 1.5 8 2.3 0.010 0.004 0.721 0.635 154 0.620 0.005 11.1 100 63 7.4 1.1 15.0 10.3 5.0 119.8 54.8 75%'ile 2.1 5.0 24 3.4 0.014 0.007 0.896 0.807 348 0.795 0.005 11.5 103 71 7.6 1.5 17.0 12.6 12.5 123.2 57.3 95%'ile 7.9 30.0 132 4.5 0.043 0.010 1.147 1.055 499 1.042 0.018 12.3 108 81 8.0 2.9 19.2 15.2 54.7 no data no data Maximum 15.9 59.0 320 5.8 0.125 0.015 1.300 1.217 557 1.200 0.056 12.6 118 89 8.1 3.1 20.0 16.1 68.0 129.3 58.1 Mean 2.1 6.0 28 2.4 0.015 0.005 0.745 0.651 210 0.636 0.007 11.1 100 62 7.4 1.3 15.1 10.4 11.3 119.2 52.3 Std. Dev. 2.7 10.5 52 1.3 0.017 0.003 0.235 0.242 156 0.242 0.007 0.8 5 13 0.3 0.7 2.7 2.8 16.2 7.2 7.4

Mohaka Rv D/S Taharua Rv Count 63 66 62 59 68 68 64 68 68 68 68 61 61 62 62 37 43 63 45 6 3 Minimum 0.2 1.5 1 0.5 0.002 0.002 0.055 0.013 3 0.001 0.005 8.4 81 50 6.8 0.9 15.0 5.1 2.5 116.4 50.0 5%'ile 0.4 1.5 1 0.8 0.004 0.002 0.055 0.014 4 0.004 0.005 8.6 85 51 7.0 0.9 15.0 5.6 no data no data no data 25%'ile 1.0 1.5 4 1.7 0.008 0.002 0.120 0.038 9 0.022 0.005 10.1 95 56 7.4 1.4 16.0 8.1 3.5 122.1 52.5 Median 1.6 1.5 10 2.5 0.010 0.006 0.134 0.079 15 0.067 0.005 11.1 99 65 7.6 1.6 17.2 11.0 3.9 127.3 55.9 75%'ile 2.5 4.5 19 3.5 0.014 0.008 0.196 0.126 19 0.117 0.006 11.8 104 71 7.8 2.2 18.6 14.5 28.0 133.0 57.7 95%'ile 8.1 14.1 47 6.6 0.025 0.012 0.271 0.207 52 0.169 0.020 13.2 140 77 8.3 3.7 21.4 19.0 no data no data no data Maximum 93.0 29.0 4900 7.1 0.036 0.013 0.400 0.251 91 0.210 0.082 15.9 168 83 9.4 3.8 22.0 20.8 42.7 139.0 58.6 Mean 5.0 4.2 170 2.8 0.012 0.006 0.154 0.089 18 0.073 0.009 11.1 103 64 7.7 1.9 17.3 11.2 14.1 127.5 55.1 Std. Dev. 16.7 5.5 878 1.6 0.006 0.003 0.071 0.061 16 0.057 0.013 1.5 16 9 0.5 0.8 1.9 4.1 17.1 8.4 3.7

Ripia Rv U/S Mohaka Rv Count 30 36 31 29 36 37 36 37 37 37 37 28 27 31 31 13 14 31 6 5 4

126 Mohaka River Catchment

All Flows E. coli Elec. Site Turbidity Black DRP DIN DIN / NO3-N NH4-N DO TOC Hardness Temp Chla MCI % EPT Statistic SS (mg/l) (CFU/ TP (mg/l) TN (mg/l) DO (%) Cond. pH name (NTU) Disc (m) (mg/l) (mg/l) DRP (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (oC) (mg/m2) (Unit) taxa 100ml) (uS/cm) Minimum 0.2 1.5 1 0.1 0.002 0.002 0.210 0.170 19 0.160 0.005 8.4 72 39 6.7 0.5 10.6 5.1 0.0 127.0 60.9 5%'ile 0.4 1.5 1 0.4 0.004 0.002 0.260 0.177 24 0.165 0.005 8.5 83 53 7.1 0.7 15.1 5.8 0.1 no data no data 25%'ile 0.9 1.5 3 1.4 0.006 0.002 0.299 0.232 39 0.220 0.005 10.4 99 60 7.4 1.0 18.3 8.0 0.6 127.6 60.9 Median 1.2 1.5 8 2.3 0.008 0.005 0.372 0.282 52 0.270 0.005 11.1 102 67 7.7 1.4 19.4 11.7 1.7 129.5 65.8 75%'ile 2.4 3.3 15 2.9 0.012 0.007 0.438 0.350 135 0.338 0.005 11.9 104 75 7.8 2.0 20.0 13.3 5.0 133.9 70.6 95%'ile 9.4 17.2 122 4.4 0.020 0.010 0.516 0.505 211 0.493 0.046 12.6 114 86 8.2 6.5 22.0 17.4 99.4 no data no data Maximum 24.0 114.0 620 7.5 0.154 0.011 0.530 0.550 251 0.540 0.070 13.5 129 93 8.8 15.1 24.0 18.4 200.0 135.3 70.6 Mean 2.7 5.7 33 2.3 0.012 0.005 0.375 0.302 88 0.287 0.009 11.0 101 67 7.6 2.1 19.0 11.2 13.6 130.6 65.8 Std. Dev. 4.0 16.5 105 1.4 0.021 0.003 0.088 0.095 64 0.095 0.013 1.2 9 11 0.4 2.8 2.5 3.7 38.0 4.3 6.9

Mohaka Rv D/S Ripia Rv Count 46 48 48 45 48 48 43 47 47 47 48 47 47 48 47 28 31 48 40 3 2 Minimum 1.3 1.5 1 0.5 0.007 0.002 0.530 0.440 57 0.420 0.005 8.9 76 70 6.7 0.9 14.0 7.3 0.2 114.7 46.9 5%'ile 1.5 1.5 2 0.8 0.008 0.002 0.532 0.454 59 0.440 0.005 8.9 78 71 6.9 0.9 14.1 7.8 no data no data no data 25%'ile 1.9 3.0 5 1.4 0.010 0.005 0.600 0.516 79 0.500 0.005 10.2 91 75 7.0 1.3 15.0 8.6 0.2 116.8 47.6 Median 2.4 5.0 12 1.6 0.014 0.006 0.670 0.598 97 0.585 0.005 10.6 94 83 7.2 1.4 16.0 9.3 25.0 119.1 52.6 75%'ile 3.2 9.0 14 2.7 0.018 0.007 0.722 0.632 122 0.620 0.005 11.0 98 91 7.4 1.9 16.3 10.2 49.7 121.6 54.7 95%'ile 4.3 39.6 45 4.3 0.022 0.009 0.814 0.720 326 0.708 0.016 13.5 122 99 7.7 3.0 19.3 11.3 no data no data no data Maximum 6.9 46.0 51 5.1 0.035 0.009 0.880 0.750 335 0.720 0.046 16.5 136 100 8.1 3.0 19.9 11.3 49.7 126.2 55.2 Waiarua Strm Mean 2.7 8.3 13 2.0 0.015 0.006 0.667 0.582 128 0.568 0.007 10.8 96 84 7.2 1.6 15.9 9.3 25.0 119.5 51.4 Std. Dev. 1.1 10.3 13 1.1 0.005 0.002 0.087 0.076 87 0.077 0.007 1.4 11 9 0.3 0.6 1.4 1.1 35.0 4.3 3.8 Count 30 34 29 28 34 35 34 34 34 34 35 27 26 29 27 12 14 29 2 5 5 Minimum 0.8 1.5 1 0.4 0.006 0.002 0.055 0.049 16 0.027 0.005 9.5 85 52 7.0 0.5 10.5 7.0 27.5 118.5 52.2 5%'ile 1.0 1.5 1 0.5 0.007 0.002 0.107 0.073 16 0.057 0.005 9.7 87 52 7.0 0.5 10.6 7.0 no data no data no data 25%'ile 1.5 2.6 1 0.8 0.010 0.005 0.215 0.139 21 0.127 0.005 10.7 93 55 7.3 1.0 12.0 8.4 no data 118.7 52.6 Median 2.4 7.4 3 1.1 0.014 0.007 0.293 0.206 27 0.194 0.005 10.9 95 60 7.4 1.1 13.0 9.0 27.5 119.3 53.8 75%'ile 3.3 14.3 7 1.6 0.020 0.008 0.326 0.242 41 0.223 0.005 11.2 102 64 7.7 1.5 13.2 11.4 no data 120.5 54.9 Rd 95%'ile 5.4 31.3 20 4.2 0.025 0.010 0.428 0.338 76 0.315 0.024 12.3 112 73 8.0 2.0 15.0 13.1 no data no data no data Maximum 6.0 32.0 26 4.8 0.027 0.010 0.470 0.345 120 0.330 0.035 12.5 114 74 8.2 2.0 15.2 13.2 27.5 120.9 55.2 Mean 2.6 10.7 5 1.5 0.016 0.007 0.277 0.199 34 0.185 0.007 11.0 98 60 7.5 1.2 12.7 9.8 27.5 119.6 53.7 Std. Dev. 1.4 9.8 6 1.1 0.006 0.002 0.094 0.076 22 0.074 0.007 0.7 7 7 0.3 0.5 1.3 2.1 0.0 1.2 1.5

Waipunga Rv at Pohokura Count 20 25 19 18 24 25 24 25 25 25 25 18 17 18 19 12 14 18 1 3 3 Minimum 0.3 1.5 1 0.4 0.010 0.006 0.055 0.007 0 0.001 0.005 8.3 83 53 7.2 0.5 15.0 5.6 0.0 130.0 57.7 5%'ile 0.4 1.5 1 0.4 0.014 0.009 0.055 0.010 1 0.001 0.005 9.4 88 56 7.2 0.5 15.2 6.2 no data no data no data 25%'ile 1.0 1.5 3 1.1 0.016 0.012 0.076 0.017 1 0.007 0.005 10.4 98 65 7.5 1.2 18.4 7.7 1.1 130.0 57.9 Median 1.4 2.3 7 2.3 0.018 0.014 0.136 0.050 4 0.037 0.005 11.1 101 72 7.6 1.5 21.5 10.0 2.7 132.6 60.0 75%'ile 3.9 7.0 19 3.5 0.023 0.014 0.183 0.089 7 0.078 0.005 11.9 103 80 7.7 1.9 23.0 13.4 12.7 136.9 60.8 95%'ile 11.2 20.0 32 5.3 0.036 0.017 0.320 0.230 14 0.220 0.010 12.4 107 84 8.2 2.9 23.8 16.4 no data no data no data Maximum 13.2 22.0 35 7.1 0.054 0.020 0.322 0.232 19 0.220 0.033 13.2 108 84 8.3 2.9 24.0 17.0 42.7 145.6 61.1 Mean 3.3 5.9 11 2.6 0.021 0.013 0.139 0.063 5 0.051 0.006 11.1 100 72 7.6 1.6 20.4 10.5 9.9 134.4 59.5

Mokomokonui Rv Std. Dev. 3.5 6.5 10 1.7 0.008 0.002 0.075 0.057 4 0.057 0.005 1.1 5 9 0.3 0.7 2.8 3.3 18.4 6.5 1.6 Count 30 30 30 29 30 30 28 30 30 30 30 29 28 30 28 12 14 30 5 5 5

Mohaka River Catchment 127

All Flows E. coli Elec. Site Turbidity Black DRP DIN DIN / NO3-N NH4-N DO TOC Hardness Temp Chla MCI % EPT Statistic SS (mg/l) (CFU/ TP (mg/l) TN (mg/l) DO (%) Cond. pH name (NTU) Disc (m) (mg/l) (mg/l) DRP (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (oC) (mg/m2) (Unit) taxa 100ml) (uS/cm) Minimum 0.3 no data 2 0.1 0.004 0.001 0.224 0.135 15 no data 0.001 8.9 98 65 7.7 no data no data 4.9 no data 111.2 48.0 5%'ile 0.5 no data 5 0.2 0.005 0.001 0.277 0.204 22 no data 0.002 9.5 98 70 7.7 no data no data 5.8 no data no data no data 25%'ile 0.7 no data 11 1.0 0.007 0.004 0.306 0.234 36 no data 0.003 10.0 99 81 7.8 no data no data 8.7 no data 111.9 49.5 Median 1.3 no data 17 2.8 0.010 0.005 0.342 0.265 50 no data 0.004 10.8 101 88 7.9 no data no data 11.6 no data 117.3 50.0 75%'ile 4.1 no data 42 4.1 0.018 0.008 0.412 0.323 80 no data 0.006 11.4 104 95 8.1 no data no data 14.9 no data 120.9 54.3 95%'ile 24.5 no data 242 6.2 0.056 0.011 0.571 0.408 274 no data 0.009 12.1 108 113 8.4 no data no data 17.5 no data no data no data Maximum 173.0 no data 3076 8.4 0.379 0.014 0.951 0.467 384 no data 0.015 12.5 111 218 8.8 no data no data 20.9 no data 122.5 57.1 Mean 7.6 no data 99 2.8 0.023 0.006 0.374 0.281 76 no data 0.005 10.8 102 90 8.0 no data no data 11.6 no data 116.7 51.7 Std. Dev. 25.5 no data 411 2.0 0.054 0.003 0.118 0.066 75 no data 0.003 0.9 3 20 0.2 no data no data 3.9 no data 5.0 3.6

Mohaka Rv at SH5 (NIWA) Count 60 no data 60 60 60 60 60 60 60 no data 60 60 60 60 60 no data no data 60 no data 5 5 Minimum 0.2 1.5 1 0.1 0.002 0.002 0.150 0.038 13 0.026 0.005 7.8 77 58 7.0 0.5 17.7 5.1 0.0 102.7 50.0 5%'ile 0.7 1.5 1 0.1 0.005 0.002 0.231 0.135 17 0.123 0.005 8.6 93 66 7.3 0.9 21.0 6.4 0.0 no data no data 25%'ile 1.3 1.5 3 0.5 0.009 0.002 0.282 0.207 28 0.181 0.005 10.5 100 77 7.6 1.3 26.0 8.6 1.1 106.1 50.0 Median 3.4 5.0 8 1.2 0.015 0.006 0.332 0.233 42 0.220 0.005 11.2 102 87 7.8 2.2 28.5 12.1 5.3 116.3 52.8 75%'ile 9.1 15.3 19 2.0 0.029 0.009 0.387 0.274 107 0.260 0.006 11.8 107 100 8.2 2.8 32.0 14.6 15.5 128.8 55.6 Rv 95%'ile 53.7 92.4 277 5.2 0.060 0.013 0.557 0.431 135 0.379 0.058 12.4 116 116 8.6 3.5 36.8 18.5 81.1 no data no data Maximum 910.0 1400.0 460 6.9 1.060 0.014 0.937 0.592 257 0.580 0.087 12.7 122 121 10.1 3.5 37.0 19.9 290.0 133.0 55.6 Mean 25.3 41.7 32 1.7 0.040 0.006 0.354 0.250 64 0.232 0.012 11.0 103 89 7.9 2.1 28.5 12.0 21.2 117.3 52.8 Std. Dev. 124.5 191.7 90 1.6 0.144 0.004 0.126 0.091 49 0.089 0.017 1.1 8 15 0.5 0.8 4.7 3.9 54.4 15.2 4.0

Mohaka Rv D/S Waipunga Count 53 53 53 48 53 53 52 53 53 53 53 50 50 52 53 31 34 51 29 3 2 Minimum 1.4 1.5 1 0.1 0.002 0.002 0.109 0.019 8 0.008 0.005 7.0 75 62 7.1 0.5 27.0 6.1 0.4 93.3 28.6 5%'ile 1.5 4.5 2 0.1 0.007 0.002 0.169 0.087 9 0.076 0.005 8.9 92 78 7.3 0.7 28.4 6.4 0.5 no data no data 25%'ile 5.0 12.5 8 0.2 0.016 0.002 0.232 0.142 16 0.131 0.005 10.8 102 89 7.8 2.0 31.0 9.0 2.6 101.2 28.6 Median 17.5 29.5 14 0.3 0.032 0.009 0.295 0.190 22 0.172 0.005 11.9 105 100 7.9 2.5 35.0 11.7 9.6 125.0 47.7 75%'ile 53.4 84.0 31 0.6 0.071 0.013 0.368 0.237 42 0.217 0.005 12.5 109 113 8.0 2.8 37.3 14.3 50.4 127.5 66.7 95%'ile 820.8 360.0 201 1.7 0.274 0.017 0.766 0.347 93 0.320 0.068 13.3 118 126 8.1 4.3 41.0 18.2 94.3 no data no data Maximum 1490.0 3000.0 400 2.3 1.740 0.024 1.178 0.418 115 0.350 0.132 13.3 119 131 8.4 4.5 45.0 19.2 96.5 128.3 66.7 Mean 107.7 138.0 39 0.5 0.096 0.009 0.340 0.196 33 0.177 0.013 11.5 105 100 7.8 2.5 34.6 11.8 30.0 115.5 47.7 Std. Dev. 293.8 472.6 75 0.5 0.275 0.006 0.196 0.079 26 0.070 0.024 1.4 9 16 0.2 0.9 4.3 3.8 33.1 19.3 26.9 Mohaka Rv at Willowflat Count 37 40 39 37 40 40 35 39 39 39 40 38 36 40 40 34 37 39 13 3 2 Minimum 0.7 1.5 1 0.0 0.004 0.002 0.055 0.013 3 0.005 0.005 8.1 87 70 7.2 0.5 32.0 6.2 0.0 96.8 32.0 5%'ile 0.9 1.5 1 0.1 0.005 0.002 0.087 0.027 9 0.015 0.005 8.9 87 86 7.6 0.9 33.0 6.6 0.1 no data no data 25%'ile 3.6 5.2 6 0.2 0.010 0.004 0.192 0.112 16 0.099 0.005 10.4 100 97 7.8 1.9 35.8 9.7 0.7 96.8 33.4 Median 16.3 17.0 16 0.3 0.024 0.009 0.298 0.188 20 0.174 0.005 11.4 104 111 8.0 2.4 39.0 12.6 21.9 102.0 37.5 75%'ile 64.5 68.0 29 0.7 0.059 0.015 0.362 0.253 29 0.220 0.005 12.2 111 128 8.2 3.2 42.3 16.8 51.0 109.8 54.4 95%'ile 804.7 280.8 117 2.0 0.208 0.019 0.666 0.348 49 0.330 0.044 13.5 130 139 8.7 4.8 49.7 19.8 158.6 no data no data Maximum 1660.0 2500.0 410 2.9 1.980 0.028 1.180 0.430 57 0.410 0.056 14.6 146 146 8.9 7.2 51.0 21.0 290.0 112.7 60.0 Mean 112.0 107.4 33 0.6 0.090 0.010 0.314 0.183 23 0.167 0.010 11.3 106 112 8.0 2.6 39.7 12.9 39.0 103.4 43.2 Std. Dev. 311.4 376.5 67 0.7 0.296 0.006 0.192 0.097 11 0.092 0.013 1.5 12 17 0.3 1.3 5.0 4.3 61.9 7.2 14.8

Mohaka Rv at Raupunga Count 39 45 39 36 45 46 42 46 46 46 46 37 34 39 40 34 37 38 26 5 3

128 Mohaka River Catchment

All Flows E. coli Elec. Site Turbidity Black DRP DIN DIN / NO3-N NH4-N DO TOC Hardness Temp Chla MCI % EPT Statistic SS (mg/l) (CFU/ TP (mg/l) TN (mg/l) DO (%) Cond. pH name (NTU) Disc (m) (mg/l) (mg/l) DRP (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (oC) (mg/m2) (Unit) taxa 100ml) (uS/cm) Minimum 0.7 no data 1 0.1 0.005 0.001 0.081 0.003 1 no data 0.001 8.6 95 99 7.1 no data no data 7.1 no data 96.8 41.7 5%'ile 0.8 no data 3 0.1 0.007 0.001 0.103 0.007 3 no data 0.001 9.3 97 105 7.8 no data no data 7.6 no data no data no data 25%'ile 2.3 no data 6 0.2 0.010 0.003 0.161 0.056 12 no data 0.003 10.2 100 114 8.0 no data no data 11.0 no data 97.9 43.3 Median 4.6 no data 15 1.0 0.018 0.008 0.244 0.161 19 no data 0.004 11.0 105 118 8.3 no data no data 15.1 no data 105.9 45.2 75%'ile 27.5 no data 42 1.7 0.055 0.013 0.324 0.226 28 no data 0.005 12.0 118 129 8.7 no data no data 18.9 no data 113.9 46.4 95%'ile 72.7 no data 413 3.2 0.171 0.016 0.621 0.426 47 no data 0.009 13.2 131 141 9.0 no data no data 22.5 no data no data no data (NIWA) Maximum 240.0 no data 738 4.8 0.453 0.019 0.748 0.675 71 no data 0.018 15.8 144 200 9.2 no data no data 25.4 no data 115.0 47.4 Mean 21.8 no data 67 1.2 0.047 0.008 0.275 0.168 22 no data 0.004 11.2 110 122 8.4 no data no data 14.9 no data 105.9 44.9 Std. Dev. 40.3 no data 139 1.1 0.077 0.005 0.154 0.133 13 no data 0.003 1.3 12 15 0.4 no data no data 4.9 no data 9.3 2.4

Mohaka Rv at Raupunga Count 60 no data 60 59 60 60 60 60 60 no data 60 60 60 60 60 no data no data 60 no data 4 4

Mohaka River Catchment 129

Less than three times median flow E. coli Elec. Site Turbidity Black DRP DIN DIN / NO3-N NH4-N DO TOC Hardness Temp Chla MCI % EPT Statistic SS (mg/l) (CFU/ TP (mg/l) TN (mg/l) DO (%) Cond. pH name (NTU) Disc (m) (mg/l) (mg/l) DRP (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (oC) (mg/m2) (Unit) taxa 100ml) (uS/cm) Minimum 0.2 1.5 1 0.5 0.002 0.002 0.055 0.012 2 0.001 0.005 8.2 79 28 6.4 0.5 8.0 4.1 0.0 118.5 57.7 5%'ile 0.3 1.5 1 2.2 0.002 0.002 0.055 0.014 4 0.001 0.005 9.0 90 33 7.0 0.5 8.6 5.5 0.1 no data no data 25%'ile 0.4 1.5 1 3.3 0.004 0.002 0.055 0.021 9 0.007 0.005 10.1 95 42 7.2 0.8 10.9 7.7 0.3 122.9 60.0 Median 0.6 1.5 3 4.5 0.005 0.002 0.109 0.039 13 0.022 0.005 10.9 97 48 7.3 1.0 12.0 10.0 1.0 127.6 66.7 75%'ile 0.9 1.5 12 6.1 0.008 0.004 0.136 0.053 22 0.039 0.005 11.5 100 54 7.4 1.3 13.1 12.7 2.9 132.5 69.5 95%'ile 3.7 18.5 57 7.9 0.024 0.006 0.270 0.112 54 0.093 0.021 12.8 105 65 7.8 2.7 15.3 15.3 12.2 no data no data Maximum 6.7 25.0 140 8.4 0.050 0.008 0.365 0.290 105 0.280 0.038 13.6 107 68 8.1 4.6 15.8 16.5 24.0 148.2 70.4 Mean 1.0 3.1 12 4.7 0.008 0.003 0.116 0.047 18 0.034 0.007 10.8 97 48 7.3 1.2 12.0 10.2 2.6 129.5 64.9 Std. Dev. 1.2 5.2 23 1.9 0.009 0.002 0.064 0.046 17 0.045 0.006 1.1 5 9 0.3 0.8 1.9 3.1 4.4 10.4 6.5

Mohaka Rv U/S Taharua Rv Count 55 59 54 52 60 61 56 60 60 60 61 54 50 53 55 32 39 54 45 6 3 Minimum 0.1 1.5 1 1.4 0.009 0.002 2.200 2.212 86 2.200 0.005 7.3 67 89 5.9 0.5 20.0 9.1 no data 84.8 42.3 5%'ile 0.2 1.5 1 1.6 0.012 0.007 2.500 2.507 113 2.495 0.005 7.6 69 95 6.6 0.5 22.0 9.8 no data no data no data 25%'ile 0.3 1.5 3 3.4 0.015 0.012 2.826 2.782 165 2.775 0.005 8.1 74 100 6.7 0.7 23.0 10.6 no data 88.7 43.2 Median 0.5 1.5 6 4.9 0.018 0.014 3.300 3.305 207 3.300 0.005 8.5 79 103 6.9 1.0 25.0 11.0 no data 95.4 45.8 75%'ile 0.9 1.5 18 6.6 0.021 0.018 3.720 3.540 282 3.525 0.011 8.9 83 107 7.1 1.4 26.0 11.4 no data 101.7 50.8 95%'ile 1.5 6.3 67 10.0 0.045 0.023 4.062 3.934 419 3.915 0.031 9.5 91 113 7.3 3.0 27.7 11.9 no data no data no data Maximum 1.9 13.0 410 10.0 0.130 0.040 4.640 4.410 1455 4.400 0.067 10.1 93 118 8.1 3.6 29.0 12.9 no data 106.7 52.4 Mean 0.7 2.1 23 5.2 0.022 0.015 3.302 3.202 268 3.184 0.010 8.5 79 103 6.9 1.2 24.6 11.0 no data 95.4 46.8 Std. Dev. 0.4 2.0 64 2.3 0.018 0.006 0.542 0.501 253 0.499 0.012 0.6 7 6 0.3 0.8 2.0 0.7 no data 8.5 5.1

Taharua Rv at Wairango Count 48 49 49 47 49 50 49 49 49 49 50 49 49 49 50 33 37 50 no data 5 3 Minimum 0.2 1.5 1 0.8 0.006 0.002 3.100 3.005 28 3.000 0.005 7.8 71 11 6.3 0.5 15.0 9.0 no data 93.3 42.9 5%'ile 0.2 1.5 1 1.1 0.009 0.002 3.115 3.027 138 3.015 0.005 8.8 81 96 6.7 0.5 22.0 9.2 no data no data no data 25%'ile 0.4 1.5 3 2.3 0.013 0.009 3.500 3.420 226 3.400 0.005 9.6 89 103 7.0 0.6 24.0 10.6 no data 96.7 43.2 Median 0.7 1.5 10 3.6 0.018 0.012 3.704 3.615 301 3.600 0.005 9.8 92 106 7.0 0.8 25.0 11.4 no data 103.8 44.0 75%'ile 1.2 5.2 24 5.4 0.022 0.016 3.901 3.813 407 3.800 0.014 10.1 97 109 7.2 1.3 26.0 11.9 no data 107.2 46.7 95%'ile 2.7 10.0 350 7.1 0.032 0.026 4.379 4.112 1656 4.100 0.026 10.9 101 117 7.5 2.4 27.0 13.0 no data no data no data Maximum 4.5 12.0 1500 9.1 0.139 0.122 4.903 4.813 1805 4.800 0.054 10.9 104 122 8.0 3.3 28.0 13.4 no data 109.6 47.6 Mean 1.0 3.6 61 3.8 0.021 0.014 3.737 3.627 422 3.611 0.010 9.8 92 105 7.1 1.1 25.0 11.3 no data 102.2 44.8 Std. Dev. 0.9 3.0 221 2.0 0.019 0.016 0.368 0.342 405 0.342 0.009 0.6 7 14 0.3 0.7 2.2 1.0 no data 6.6 2.5

Taharua Rv at Twin Culv Count 52 52 52 47 52 53 53 53 52 53 53 53 52 53 54 35 40 54 no data 5 3 Minimum 0.5 1.5 1 1.2 0.005 0.002 1.960 1.521 138 1.480 0.005 7.9 70 64 6.8 0.6 14.9 9.7 24.0 129.2 57.7 5%'ile 0.6 1.5 1 no data 0.007 0.004 1.967 1.692 151 1.664 0.005 8.1 72 67 6.8 no data no data 9.7 no data no data no data 25%'ile 1.0 1.5 3 2.9 0.011 0.008 2.083 1.970 200 1.960 0.005 10.0 93 90 7.1 no data 14.9 10.3 no data no data no data Median 1.3 1.5 7 4.3 0.012 0.010 2.302 2.212 221 2.200 0.005 10.2 96 95 7.4 0.6 19.0 11.2 24.0 129.2 57.7 75%'ile 1.8 1.9 17 4.5 0.019 0.011 2.442 2.479 310 2.475 0.005 10.5 99 99 7.6 no data 23.0 12.0 no data no data no data 95%'ile 11.7 68.6 84 no data 0.042 0.012 2.600 2.512 797 2.500 0.025 11.1 103 107 8.1 no data no data 13.0 no data no data no data Maximum 13.1 99.0 86 5.6 0.053 0.012 2.600 2.512 1156 2.500 0.041 11.2 104 109 8.2 0.6 23.0 13.1 24.0 129.2 57.7 Mean 2.4 8.1 19 3.7 0.016 0.009 2.288 2.201 288 2.188 0.007 10.1 94 93 7.4 0.6 19.0 11.2 24.0 129.2 57.7 Std. Dev. 3.3 23.6 28 1.3 0.010 0.002 0.215 0.274 220 0.279 0.008 0.9 9 11 0.4 0.0 5.7 1.1 0.0 0.0 0.0

Taharua Rv at Henry's Br Count 13 17 12 9 17 19 17 19 19 19 19 13 12 14 14 1 2 13 1 1 1

130 Mohaka River Catchment

< 3 X Median Flow E. coli Elec. Site Turbidity Black DRP DIN DIN / NO3-N NH4-N DO TOC Hardness Temp Chla MCI % EPT Statistic SS (mg/l) (CFU/ TP (mg/l) TN (mg/l) DO (%) Cond. pH name (NTU) Disc (m) (mg/l) (mg/l) DRP (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (oC) (mg/m2) (Unit) taxa 100ml) (uS/cm) Minimum 0.7 1.5 1 0.2 0.011 0.002 1.020 0.930 49 0.920 0.005 7.9 72 57 6.7 0.5 13.0 6.9 0.4 111.3 52.2 5%'ile 0.8 1.5 1 0.4 0.013 0.002 1.171 1.122 65 1.112 0.005 9.5 86 63 6.9 0.5 14.1 7.6 0.8 no data no data 25%'ile 1.2 4.7 2 0.9 0.016 0.008 1.600 1.510 129 1.500 0.005 10.3 94 73 7.1 0.7 17.3 9.1 2.8 113.0 no data Median 1.6 8.0 9 1.5 0.020 0.011 1.875 1.752 171 1.735 0.005 10.6 99 80 7.1 1.0 18.8 10.9 6.4 118.2 52.2 75%'ile 2.5 15.0 20 2.4 0.027 0.012 2.035 1.910 230 1.900 0.011 10.9 101 86 7.2 1.4 19.7 12.0 32.2 119.6 no data 95%'ile 7.3 62.8 308 3.1 0.070 0.018 2.340 2.250 920 2.240 0.028 11.7 105 92 7.3 2.3 21.0 13.6 76.8 no data no data Maximum 10.4 125.0 1300 3.4 0.240 0.032 2.552 2.310 980 2.300 0.050 12.2 109 95 8.6 2.4 22.0 14.2 93.0 120.0 52.2 Mean 2.4 16.3 59 1.6 0.028 0.011 1.814 1.712 237 1.699 0.009 10.6 97 79 7.2 1.1 18.4 10.7 19.7 116.5 52.2 Std. Dev. 2.1 23.5 210 0.9 0.036 0.005 0.338 0.326 226 0.327 0.009 0.7 7 9 0.3 0.5 2.1 1.8 24.5 4.6 0.0

Taharua Rv at Poronui Stn Count 40 41 41 41 41 41 37 42 41 42 41 41 39 41 42 35 39 42 18 3 1 Minimum 0.7 1.3 1 0.4 0.007 0.002 0.750 0.662 66 0.650 0.005 9.3 83 56 6.5 0.5 10.2 5.4 27.2 83.8 21.9 5%'ile 0.7 1.5 1 0.5 0.008 0.002 0.952 0.847 101 0.835 0.005 9.6 86 63 6.6 0.5 12.9 7.2 no data no data no data 25%'ile 1.2 1.5 5 1.2 0.011 0.003 1.323 1.205 154 1.200 0.005 10.4 95 73 7.1 0.8 17.0 9.2 no data 88.2 26.2 Median 1.6 3.7 13 2.0 0.014 0.006 1.480 1.340 223 1.330 0.005 10.8 99 79 7.2 1.1 18.5 10.6 27.2 95.2 39.1 75%'ile 2.6 7.0 43 3.0 0.019 0.008 1.666 1.550 449 1.530 0.009 11.4 104 88 7.4 1.5 19.6 12.4 no data 105.4 40.8 95%'ile 5.6 18.8 320 4.0 0.032 0.012 1.892 1.802 882 1.790 0.026 11.8 109 99 7.8 2.4 22.0 14.5 no data no data no data Maximum 12.1 30.0 470 5.4 0.057 0.014 1.912 1.863 932 1.850 0.068 12.0 113 105 8.1 2.4 22.0 14.5 27.2 107.6 41.4 Mean 2.2 5.4 55 2.1 0.016 0.006 1.469 1.358 327 1.341 0.009 10.8 99 80 7.2 1.2 18.0 10.8 27.2 96.2 34.1

Taharua Rv at Red Hut Std. Dev. 1.9 6.0 107 1.1 0.008 0.003 0.267 0.269 249 0.273 0.010 0.7 7 11 0.3 0.5 2.5 2.2 0.0 10.0 10.7 Count 52 54 51 45 55 55 53 55 55 55 55 49 48 49 51 33 39 50 1 5 3 Minimum 0.5 1.2 1 0.3 0.002 0.002 0.310 0.260 37 0.250 0.005 8.7 84 41 6.6 0.5 10.2 4.8 0.1 109.6 44.0 5%'ile 0.5 1.5 1 0.7 0.006 0.002 0.407 0.286 47 0.277 0.005 9.9 92 44 6.9 0.5 11.2 6.6 0.4 no data no data 25%'ile 1.0 1.5 4 1.7 0.008 0.002 0.625 0.520 91 0.510 0.005 10.6 98 54 7.3 0.8 13.9 8.5 1.8 113.5 46.7 Median 1.2 1.5 7 2.5 0.010 0.004 0.740 0.660 175 0.650 0.005 11.1 101 63 7.4 1.0 15.5 10.7 5.0 119.8 54.8 75%'ile 2.0 4.1 20 3.5 0.014 0.006 0.945 0.855 370 0.845 0.005 11.5 104 71 7.6 1.4 17.0 12.8 12.6 123.2 57.3 95%'ile 3.6 16.7 140 4.7 0.021 0.009 1.152 1.060 505 1.047 0.017 12.3 109 82 8.0 2.6 19.3 15.4 55.6 no data no data Maximum 9.6 29.0 320 5.8 0.059 0.015 1.300 1.217 557 1.200 0.025 12.6 118 89 8.1 3.1 20.0 16.1 68.0 129.3 58.1 Mean 1.6 3.9 27 2.6 0.012 0.004 0.769 0.674 224 0.660 0.007 11.1 101 63 7.4 1.2 15.4 10.6 11.8 119.2 52.3 Std. Dev. 1.4 5.6 54 1.2 0.008 0.003 0.229 0.235 155 0.235 0.004 0.8 5 12 0.3 0.6 2.4 2.8 16.4 7.2 7.4

Mohaka Rv D/S Taharua Rv Count 58 61 57 55 63 63 59 63 63 63 63 56 56 57 58 34 40 58 43 6 3 Minimum 0.2 1.5 1 0.8 0.002 0.002 0.055 0.013 3 0.001 0.005 8.4 81 50 6.8 0.9 15.0 5.1 2.5 116.4 50.0 5%'ile 0.3 1.5 1 0.9 0.004 0.002 0.055 0.014 4 0.004 0.005 8.6 85 51 7.0 0.9 15.1 5.6 no data no data no data 25%'ile 0.9 1.5 4 1.8 0.008 0.002 0.120 0.038 9 0.022 0.005 10.0 95 57 7.4 1.3 16.1 8.1 3.5 122.1 52.5 Median 1.5 1.5 10 2.5 0.010 0.006 0.134 0.072 14 0.058 0.005 11.2 99 65 7.6 1.7 17.3 10.9 3.9 127.3 55.9 75%'ile 2.3 3.8 17 3.5 0.014 0.008 0.196 0.127 19 0.118 0.007 11.8 105 71 7.8 2.3 18.7 14.6 28.0 133.0 57.7 95%'ile 9.2 11.5 34 6.6 0.024 0.012 0.271 0.209 53 0.169 0.020 13.4 141 78 8.4 3.7 21.6 19.2 no data no data no data Maximum 93.0 15.0 4900 7.1 0.036 0.013 0.400 0.251 91 0.210 0.082 15.9 168 83 9.4 3.8 22.0 20.8 42.7 139.0 58.6 Mean 4.9 3.4 174 2.9 0.011 0.006 0.154 0.088 18 0.072 0.009 11.1 103 64 7.7 1.9 17.5 11.2 14.1 127.5 55.1 Std. Dev. 17.0 3.6 893 1.6 0.006 0.003 0.071 0.061 16 0.058 0.013 1.5 17 8 0.5 0.9 1.8 4.2 17.1 8.4 3.7

Ripia Rv U/S Mohaka Rv Count 29 35 30 28 35 36 36 36 36 36 36 27 26 30 30 12 13 30 6 5 4

Mohaka River Catchment 131

< 3 X Median Flow E. coli Elec. Site Turbidity Black DRP DIN DIN / NO3-N NH4-N DO TOC Hardness Temp Chla MCI % EPT Statistic SS (mg/l) (CFU/ TP (mg/l) TN (mg/l) DO (%) Cond. pH name (NTU) Disc (m) (mg/l) (mg/l) DRP (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (oC) (mg/m2) (Unit) taxa 100ml) (uS/cm) Minimum 0.2 1.5 1 0.5 0.002 0.002 0.210 0.170 24 0.160 0.005 8.4 72 51 7.0 0.5 16.6 5.1 0.0 127.0 60.9 5%'ile 0.4 1.5 1 0.8 0.003 0.002 0.260 0.176 28 0.164 0.005 8.5 82 54 7.1 0.6 16.8 6.1 0.2 no data no data 25%'ile 0.9 1.5 3 1.6 0.006 0.002 0.311 0.237 42 0.225 0.005 10.4 99 61 7.4 1.0 18.8 8.1 0.9 127.6 60.9 Median 1.2 1.5 8 2.4 0.008 0.005 0.372 0.290 74 0.280 0.005 11.1 102 69 7.7 1.2 19.7 11.8 1.8 129.5 65.8 75%'ile 2.3 2.3 15 3.0 0.011 0.006 0.438 0.365 139 0.347 0.005 11.8 105 76 7.8 2.0 21.0 13.3 4.7 133.9 70.6 95%'ile 5.0 8.0 51 4.6 0.013 0.010 0.510 0.508 216 0.497 0.027 12.7 115 87 8.2 8.6 22.4 17.6 108.2 no data no data Maximum 8.7 17.0 410 7.5 0.015 0.011 0.530 0.550 251 0.540 0.070 13.5 129 93 8.8 15.1 24.0 18.4 200.0 135.3 70.6 Mean 1.7 2.5 20 2.5 0.008 0.005 0.375 0.308 93 0.294 0.009 11.0 102 69 7.7 2.1 19.8 11.3 14.5 130.6 65.8 Std. Dev. 1.6 2.7 63 1.3 0.003 0.003 0.086 0.096 64 0.095 0.012 1.2 9 10 0.3 3.0 1.7 3.6 39.4 4.3 6.9

Mohaka Rv D/S Ripia Rv Count 42 43 43 41 43 43 39 43 43 43 43 42 42 43 42 23 26 43 37 3 2 Minimum 1.3 1.5 1 0.5 0.007 0.002 0.530 0.440 59 0.420 0.005 8.9 76 70 6.7 0.9 14.0 7.3 0.2 114.7 46.9 5%'ile 1.5 1.5 2 0.8 0.008 0.002 0.533 0.461 62 0.443 0.005 8.9 78 72 6.9 0.9 14.1 7.8 no data no data no data 25%'ile 1.9 3.0 5 1.4 0.010 0.005 0.601 0.525 80 0.508 0.005 10.2 90 76 7.0 1.3 15.0 8.6 0.2 116.8 47.6 Median 2.3 5.0 11 1.6 0.014 0.006 0.670 0.602 97 0.590 0.005 10.6 94 84 7.2 1.4 16.0 9.3 25.0 119.1 52.6 75%'ile 3.1 8.3 15 2.7 0.018 0.007 0.724 0.632 122 0.620 0.005 11.0 98 91 7.4 1.9 16.2 10.2 49.7 121.6 54.7 95%'ile 4.4 41.0 46 4.4 0.022 0.009 0.816 0.723 326 0.711 0.017 13.7 123 99 7.7 3.0 19.4 11.3 no data no data no data Maximum 6.9 46.0 51 5.1 0.035 0.009 0.880 0.750 335 0.720 0.046 16.5 136 100 8.1 3.0 19.9 11.3 49.7 126.2 55.2 Waiarua Strm Mean 2.6 8.2 13 2.0 0.015 0.006 0.670 0.586 130 0.572 0.007 10.8 96 85 7.2 1.6 15.9 9.3 25.0 119.5 51.4 Std. Dev. 1.1 10.5 13 1.1 0.005 0.002 0.085 0.073 87 0.074 0.007 1.4 12 9 0.3 0.6 1.4 1.1 35.0 4.3 3.8 Count 29 33 28 27 33 34 33 33 33 33 34 26 25 28 26 12 13 28 2 5 5 Minimum 0.8 1.5 1 0.4 0.006 0.002 0.055 0.049 16 0.027 0.005 9.5 85 52 7.0 0.5 10.5 7.0 27.5 118.5 52.2 5%'ile 1.0 1.5 1 0.5 0.007 0.002 0.107 0.073 16 0.057 0.005 9.7 87 52 7.0 0.5 10.6 7.0 no data no data no data 25%'ile 1.5 2.6 1 0.8 0.010 0.005 0.215 0.139 21 0.127 0.005 10.7 93 55 7.3 1.0 12.0 8.4 no data 118.7 52.6 Median 2.4 7.4 3 1.1 0.014 0.007 0.293 0.206 27 0.194 0.005 10.9 95 60 7.4 1.1 13.0 9.0 27.5 119.3 53.8 75%'ile 3.3 14.3 7 1.6 0.020 0.008 0.326 0.242 41 0.223 0.005 11.2 102 64 7.7 1.5 13.2 11.4 no data 120.5 54.9 Rd 95%'ile 5.4 31.3 20 4.2 0.025 0.010 0.428 0.338 76 0.315 0.024 12.3 112 73 8.0 2.0 15.0 13.1 no data no data no data Maximum 6.0 32.0 26 4.8 0.027 0.010 0.470 0.345 120 0.330 0.035 12.5 114 74 8.2 2.0 15.2 13.2 27.5 120.9 55.2 Mean 2.6 10.7 5 1.5 0.016 0.007 0.277 0.199 34 0.185 0.007 11.0 98 60 7.5 1.2 12.7 9.8 27.5 119.6 53.7 Std. Dev. 1.4 9.8 6 1.1 0.006 0.002 0.094 0.076 22 0.074 0.007 0.7 7 7 0.3 0.5 1.3 2.1 0.0 1.2 1.5

Mokomokonui Rv Std. Dev. 3.5 6.5 10 1.7 0.008 0.002 0.075 0.057 4 0.057 0.005 1.1 5 9 0.3 0.7 2.8 3.3 18.4 6.5 1.6 Count 30 30 30 29 30 30 28 30 30 30 30 29 28 30 28 12 14 30 5 5 5

132 Mohaka River Catchment

< 3 X Median Flow E. coli Elec. Site Turbidity Black DRP DIN DIN / NO3-N NH4-N DO TOC Hardness Temp Chla MCI % EPT Statistic SS (mg/l) (CFU/ TP (mg/l) TN (mg/l) DO (%) Cond. pH name (NTU) Disc (m) (mg/l) (mg/l) DRP (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (oC) (mg/m2) (Unit) taxa 100ml) (uS/cm) Minimum 0.3 no data 2 0.1 0.004 0.001 0.224 0.135 15 no data 0.001 8.9 98 65 7.7 no data no data 4.9 no data 112.1 no data 5%'ile 0.5 no data 5 0.3 0.005 0.001 0.276 0.203 22 no data 0.001 9.4 98 70 7.7 no data no data 5.8 no data no data no data 25%'ile 0.7 no data 11 1.2 0.007 0.004 0.306 0.235 37 no data 0.003 10.0 99 82 7.8 no data no data 8.7 no data 114.7 no data Median 1.2 no data 16 2.9 0.009 0.005 0.342 0.265 50 no data 0.004 10.7 101 88 7.9 no data no data 11.7 no data 118.8 no data 75%'ile 3.1 no data 41 4.1 0.016 0.008 0.409 0.321 84 no data 0.006 11.4 104 95 8.1 no data no data 15.0 no data 121.4 no data 95%'ile 17.0 no data 126 6.3 0.041 0.010 0.530 0.413 276 no data 0.010 12.1 108 113 8.4 no data no data 17.5 no data no data no data Maximum 99.8 no data 3076 8.4 0.198 0.014 0.708 0.467 384 no data 0.015 12.5 111 218 8.8 no data no data 20.9 no data 122.5 no data Mean 4.8 no data 96 2.9 0.016 0.006 0.366 0.281 77 no data 0.005 10.7 102 91 8.0 no data no data 11.7 no data 118.1 no data Std. Dev. 13.6 no data 416 2.0 0.027 0.003 0.092 0.066 76 no data 0.003 0.9 3 20 0.2 no data no data 3.9 no data 4.5 no data

Mohaka Rv at SH5 (NIWA) Count 58 no data 58 58 58 58 58 58 58 no data 58 58 58 58 58 no data no data 58 no data 4 no data Minimum no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data 5%'ile no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data 25%'ile no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data Median no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data 75%'ile no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data Rv 95%'ile no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data Maximum no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data Mean no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data Std. Dev. no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data

Mohaka Rv D/S Waipunga Count no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data Minimum 1.4 1.5 1 0.1 0.002 0.002 0.109 0.019 10 0.008 0.005 7.0 75 73 7.3 0.5 27.0 6.1 0.4 93.3 28.6 5%'ile 1.4 4.4 2 0.1 0.006 0.002 0.162 0.081 13 0.070 0.005 8.8 92 82 7.4 0.7 28.3 6.4 0.5 no data no data 25%'ile 4.9 10.6 8 0.2 0.016 0.002 0.231 0.141 17 0.130 0.005 10.6 102 89 7.8 1.9 31.0 9.0 2.6 101.2 28.6 Median 14.5 29.0 14 0.3 0.030 0.008 0.283 0.189 24 0.172 0.005 11.5 105 101 7.9 2.5 35.0 11.8 9.6 125.0 47.7 75%'ile 35.2 52.0 25 0.6 0.050 0.012 0.357 0.235 46 0.220 0.005 12.4 109 113 8.0 2.8 37.8 14.5 50.4 127.5 66.7 95%'ile 136.4 210.8 88 1.7 0.144 0.016 0.488 0.348 94 0.320 0.057 13.3 118 126 8.1 4.4 41.0 18.2 94.3 no data no data Maximum 1000.0 270.0 140 2.3 0.167 0.017 0.520 0.418 115 0.350 0.132 13.3 119 131 8.1 4.5 45.0 19.2 96.5 128.3 66.7 Mean 56.4 51.8 23 0.5 0.044 0.008 0.299 0.196 35 0.178 0.012 11.4 105 102 7.9 2.4 34.8 12.0 30.0 115.5 47.7 Std. Dev. 170.7 64.3 28 0.5 0.042 0.005 0.097 0.082 26 0.072 0.024 1.4 9 15 0.2 0.9 4.3 3.9 33.1 19.3 26.9 Mohaka Rv at Willowflat Count 34 37 37 35 37 37 32 36 36 36 37 35 33 37 37 32 35 36 13 3 2 Minimum 0.7 1.5 1 0.1 0.004 0.002 0.055 0.013 3 0.005 0.005 8.1 87 83 7.2 0.5 32.0 6.2 0.0 96.8 32.0 5%'ile 0.9 1.5 1 0.1 0.005 0.002 0.079 0.025 10 0.013 0.005 8.8 87 90 7.6 0.9 33.3 6.5 0.1 no data no data 25%'ile 3.2 5.1 6 0.2 0.010 0.004 0.191 0.104 16 0.092 0.005 10.2 99 99 7.8 1.9 36.3 9.8 0.7 96.8 33.4 Median 15.0 16.5 15 0.4 0.022 0.008 0.282 0.184 21 0.172 0.005 11.2 104 111 8.0 2.4 39.0 12.7 21.9 102.0 37.5 75%'ile 38.9 50.0 27 0.7 0.042 0.014 0.358 0.249 29 0.228 0.005 12.2 111 129 8.2 3.2 42.8 16.8 51.0 109.8 54.4 95%'ile 150.7 175.6 59 2.0 0.124 0.018 0.481 0.360 50 0.338 0.041 13.6 132 139 8.7 4.3 49.8 19.9 158.6 no data no data Maximum 1000.0 185.0 100 2.9 0.134 0.020 0.600 0.430 57 0.410 0.056 14.6 146 146 8.9 7.2 51.0 21.0 290.0 112.7 60.0 Mean 56.3 37.9 20 0.6 0.036 0.009 0.280 0.181 23 0.166 0.009 11.2 105 114 8.0 2.5 39.9 13.1 39.0 103.4 43.2 Std. Dev. 166.5 50.9 20 0.7 0.037 0.006 0.116 0.099 11 0.095 0.012 1.5 12 16 0.3 1.2 5.0 4.4 61.9 7.2 14.8

Mohaka Rv at Raupunga Count 36 42 36 34 42 43 39 43 43 43 43 34 31 36 37 32 35 35 26 5 3

Mohaka River Catchment 133

< 3 X Median Flow E. coli Elec. Site Turbidity Black DRP DIN DIN / NO3-N NH4-N DO TOC Hardness Temp Chla MCI % EPT Statistic SS (mg/l) (CFU/ TP (mg/l) TN (mg/l) DO (%) Cond. pH name (NTU) Disc (m) (mg/l) (mg/l) DRP (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (oC) (mg/m2) (Unit) taxa 100ml) (uS/cm) Minimum 0.7 no data 1 0.1 0.005 0.001 0.081 0.003 1 no data 0.001 8.6 95 99 7.1 no data no data 7.1 no data 96.8 no data 5%'ile 0.8 no data 3 0.1 0.007 0.001 0.102 0.007 3 no data 0.001 9.3 97 105 7.8 no data no data 7.6 no data no data no data 25%'ile 2.2 no data 6 0.3 0.010 0.003 0.160 0.049 12 no data 0.003 10.2 100 114 8.0 no data no data 11.1 no data 97.9 no data Median 4.4 no data 15 1.0 0.016 0.008 0.240 0.158 19 no data 0.004 11.0 106 119 8.3 no data no data 15.3 no data 105.9 no data 75%'ile 23.5 no data 41 1.8 0.054 0.012 0.310 0.223 28 no data 0.005 12.0 118 129 8.7 no data no data 19.3 no data 113.9 no data 95%'ile 63.2 no data 427 3.2 0.122 0.016 0.532 0.411 47 no data 0.008 13.2 132 141 9.0 no data no data 22.5 no data no data no data (NIWA) Maximum 179.0 no data 738 4.8 0.453 0.019 0.748 0.675 71 no data 0.018 15.8 144 200 9.2 no data no data 25.4 no data 115.0 no data Mean 17.7 no data 67 1.2 0.041 0.008 0.266 0.161 22 no data 0.004 11.2 110 122 8.4 no data no data 15.1 no data 105.9 no data Std. Dev. 28.7 no data 141 1.1 0.066 0.005 0.145 0.129 13 no data 0.003 1.3 12 15 0.4 no data no data 4.9 no data 9.3 no data

Mohaka Rv at Raupunga Count 58 no data 58 57 58 58 58 58 58 no data 58 58 58 58 58 no data no data 58 no data 4 no data

134 Mohaka River Catchment

Less than median flow E. coli Elec. Site Turbidity Black DRP DIN DIN / NO3-N NH4-N DO TOC Hardness Temp Chla MCI % EPT Statistic SS (mg/l) (CFU/ TP (mg/l) TN (mg/l) DO (%) Cond. pH name (NTU) Disc (m) (mg/l) (mg/l) DRP (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (oC) (mg/m2) (Unit) taxa 100ml) (uS/cm) Minimum 0.2 1.5 1 3.2 0.002 0.002 0.055 0.014 3 0.001 0.005 8.2 79 33 6.4 0.5 8.5 4.1 0.1 118.5 57.7 5%'ile 0.2 1.5 1 3.5 0.002 0.002 0.055 0.014 5 0.001 0.005 9.0 88 38 6.7 0.5 9.0 5.6 0.1 no data no data 25%'ile 0.3 1.5 1 4.5 0.004 0.002 0.055 0.019 9 0.005 0.005 9.7 96 47 7.2 0.6 12.0 9.0 0.5 122.9 60.0 Median 0.6 1.5 4 6.0 0.005 0.002 0.104 0.029 13 0.015 0.005 10.3 97 53 7.4 0.9 13.0 11.8 1.4 127.6 66.7 75%'ile 0.8 1.5 14 6.6 0.007 0.002 0.132 0.051 22 0.038 0.005 11.3 100 57 7.4 1.3 13.8 13.7 4.3 132.5 69.5 95%'ile 3.4 10.0 51 8.1 0.024 0.006 0.296 0.097 44 0.074 0.018 12.7 103 65 7.9 3.7 15.7 15.9 17.9 no data no data Maximum 3.8 24.0 58 8.4 0.048 0.007 0.365 0.210 105 0.200 0.025 13.6 107 68 8.1 4.6 15.8 16.5 24.0 148.2 70.4 Mean 0.8 2.5 11 5.7 0.008 0.003 0.113 0.041 18 0.027 0.007 10.6 97 52 7.3 1.2 12.8 11.2 3.5 129.5 64.9 Std. Dev. 0.9 4.2 14 1.5 0.009 0.001 0.072 0.035 17 0.035 0.005 1.2 5 8 0.3 1.0 1.8 3.1 5.4 10.4 6.5

Mohaka Rv U/S Taharua Rv Count 33 36 32 30 37 38 37 38 38 38 38 33 30 32 33 16 21 32 25 6 3 Minimum 0.1 1.5 1 1.6 0.009 0.002 2.200 2.212 114 2.200 0.005 7.3 67 94 5.9 0.5 20.0 9.8 no data 84.8 42.3 5%'ile 0.1 1.5 1 2.4 0.012 0.002 2.485 2.402 118 2.390 0.005 7.5 69 95 6.3 0.5 20.9 10.0 no data no data no data 25%'ile 0.3 1.5 4 4.8 0.015 0.011 2.700 2.686 150 2.675 0.005 8.0 72 97 6.8 0.5 23.0 10.8 no data 87.4 43.2 Median 0.4 1.5 7 6.1 0.018 0.015 3.020 2.915 201 2.900 0.005 8.2 76 101 6.9 1.0 23.0 11.0 no data 92.7 45.8 75%'ile 1.0 1.5 18 7.8 0.021 0.018 3.330 3.312 293 3.300 0.013 8.6 80 105 7.1 1.4 25.8 11.4 no data 101.1 50.8 95%'ile 1.5 4.0 51 10.0 0.053 0.022 3.706 3.613 1405 3.600 0.031 8.9 89 111 7.4 2.8 27.0 11.9 no data no data no data Maximum 1.9 13.0 60 10.0 0.130 0.023 3.770 3.613 1455 3.600 0.044 9.0 92 111 8.1 3.1 27.0 12.5 no data 106.7 52.4 Mean 0.6 2.0 13 6.1 0.023 0.015 3.041 2.969 292 2.952 0.010 8.2 77 102 6.9 1.1 23.9 11.0 no data 94.2 46.8 Std. Dev. 0.5 2.2 15 2.3 0.022 0.005 0.412 0.386 322 0.385 0.009 0.5 6 5 0.4 0.7 2.0 0.6 no data 9.4 5.1

Taharua Rv at Wairango Count 27 28 28 27 28 29 29 29 29 29 29 28 28 28 29 15 19 29 no data 4 3 Minimum 0.2 1.5 1 1.9 0.006 0.002 3.100 3.012 146 3.000 0.005 7.8 71 11 6.3 0.5 15.0 9.2 no data 93.3 42.9 5%'ile 0.2 1.5 1 2.0 0.008 0.002 3.290 3.200 184 3.190 0.005 8.3 78 92 6.6 0.5 17.8 9.4 no data no data no data 25%'ile 0.3 1.5 3 3.6 0.010 0.008 3.476 3.389 233 3.375 0.005 9.4 88 104 7.0 0.6 24.0 10.7 no data 95.6 43.2 Median 0.5 1.5 9 4.1 0.019 0.012 3.700 3.612 297 3.600 0.005 9.8 92 107 7.1 0.7 25.0 11.4 no data 100.8 44.0 75%'ile 0.8 1.5 19 5.7 0.023 0.015 3.800 3.712 465 3.700 0.013 10.1 96 110 7.2 1.3 26.0 11.8 no data 105.1 46.7 95%'ile 1.3 9.5 86 7.7 0.030 0.018 3.927 3.846 1762 3.825 0.026 10.5 102 120 8.0 3.0 27.0 13.0 no data no data no data Maximum 1.9 12.0 370 9.1 0.032 0.022 4.402 4.300 1805 4.300 0.028 10.6 104 122 8.0 3.3 27.0 13.4 no data 106.4 47.6 Mean 0.6 2.5 25 4.5 0.018 0.011 3.638 3.555 525 3.538 0.009 9.7 91 104 7.1 1.0 24.4 11.3 no data 100.3 44.8 Std. Dev. 0.4 2.7 70 1.7 0.007 0.006 0.264 0.258 519 0.258 0.007 0.6 7 19 0.3 0.8 2.8 1.0 no data 5.9 2.5

Taharua Rv at Twin Culv Count 27 27 27 24 27 28 29 29 28 29 28 28 28 29 29 14 18 29 no data 4 3 Minimum 0.5 1.5 1 2.5 0.005 0.002 1.960 1.902 167 1.890 0.005 7.9 70 89 6.8 no data 23.0 9.7 24.0 129.2 57.7 5%'ile 0.6 1.5 1 no data 0.006 0.004 1.965 1.914 170 1.902 0.005 8.0 71 89 6.8 no data no data 9.7 no data no data no data 25%'ile 1.0 1.5 3 3.3 0.011 0.008 2.125 2.057 211 2.045 0.005 10.0 94 93 7.1 no data no data 10.4 no data no data no data Median 1.3 1.5 6 4.4 0.012 0.009 2.400 2.312 226 2.300 0.005 10.1 97 95 7.5 no data 23.0 11.4 24.0 129.2 57.7 75%'ile 1.7 1.5 19 4.5 0.016 0.010 2.481 2.503 313 2.500 0.005 10.5 99 99 7.6 no data no data 12.2 no data no data no data 95%'ile 1.8 3.8 85 no data 0.021 0.012 2.600 2.512 917 2.500 0.005 11.1 104 108 8.1 no data no data 13.1 no data no data no data Maximum 1.9 4.0 86 5.6 0.021 0.012 2.600 2.512 1156 2.500 0.005 11.2 104 109 8.2 no data 23.0 13.1 24.0 129.2 57.7 Mean 1.3 1.8 20 4.0 0.013 0.009 2.304 2.259 307 2.248 0.005 10.1 94 97 7.4 no data 23.0 11.3 24.0 129.2 57.7 Std. Dev. 0.4 0.8 30 1.0 0.004 0.002 0.219 0.227 235 0.228 0.000 0.9 9 5 0.4 no data 0.0 1.1 0.0 0.0 0.0

Taharua Rv at Henry's Br Count 11 14 11 8 14 16 15 16 16 16 16 12 11 12 12 no data 1 12 1 1 1

Mohaka River Catchment 135

< Median Flow E. coli Elec. Site Turbidity Black DRP DIN DIN / NO3-N NH4-N DO TOC Hardness Temp Chla MCI % EPT Statistic SS (mg/l) (CFU/ TP (mg/l) TN (mg/l) DO (%) Cond. pH name (NTU) Disc (m) (mg/l) (mg/l) DRP (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (oC) (mg/m2) (Unit) taxa 100ml) (uS/cm) Minimum 0.7 1.5 1 0.8 0.011 0.002 1.400 1.310 109 1.300 0.005 7.9 72 73 7.0 0.5 17.0 6.9 0.4 111.3 52.2 5%'ile 0.7 1.5 1 1.0 0.012 0.002 1.440 1.355 111 1.345 0.005 8.5 75 73 7.0 0.5 17.0 7.2 0.4 no data no data 25%'ile 1.1 1.5 1 1.9 0.014 0.008 1.600 1.536 137 1.525 0.005 10.0 94 79 7.1 0.5 18.0 9.3 3.2 111.3 no data Median 1.2 4.5 9 2.3 0.016 0.010 1.891 1.792 172 1.780 0.005 10.5 99 82 7.1 0.8 19.0 11.4 5.4 114.8 52.2 75%'ile 1.5 7.0 17 2.9 0.020 0.012 2.050 1.948 245 1.938 0.013 10.8 102 89 7.3 1.2 20.0 12.2 40.9 118.2 no data 95%'ile 2.5 16.0 64 3.3 0.030 0.014 2.221 2.123 970 2.110 0.025 11.8 108 94 8.0 1.9 21.0 13.7 93.0 no data no data Maximum 2.6 18.0 85 3.4 0.032 0.014 2.302 2.200 980 2.200 0.029 12.2 109 95 8.6 1.9 21.0 14.2 93.0 118.2 52.2 Mean 1.3 5.4 14 2.3 0.018 0.009 1.846 1.745 288 1.733 0.009 10.4 97 83 7.2 0.9 19.1 10.9 24.0 114.8 52.2 Std. Dev. 0.5 4.4 20 0.7 0.005 0.004 0.248 0.244 281 0.244 0.007 0.9 9 6 0.3 0.5 1.3 2.0 30.7 4.9 0.0

Taharua Rv at Poronui Stn Count 19 18 18 18 18 18 18 19 18 19 18 18 16 19 19 14 17 19 10 2 1 Minimum 0.7 1.3 3 1.0 0.007 0.002 1.020 0.930 93 0.910 0.005 9.3 83 68 6.5 0.5 17.0 5.4 no data 83.8 21.9 5%'ile 0.7 1.5 3 1.0 0.008 0.002 1.200 1.110 102 1.005 0.005 9.5 85 69 6.5 0.5 17.0 6.4 no data no data no data 25%'ile 1.0 1.5 5 2.3 0.010 0.002 1.350 1.272 167 1.260 0.005 10.1 95 79 7.1 0.8 18.0 10.2 no data 86.7 26.2 Median 1.3 1.5 11 2.8 0.012 0.006 1.522 1.413 270 1.400 0.005 10.7 99 88 7.3 1.0 19.3 11.4 no data 92.4 39.1 75%'ile 1.8 3.4 31 3.2 0.014 0.008 1.680 1.597 665 1.578 0.012 11.4 103 93 7.5 1.2 20.0 13.1 no data 99.9 40.8 95%'ile 2.6 5.0 62 4.4 0.022 0.012 1.892 1.800 900 1.788 0.022 11.8 109 103 7.9 1.8 22.0 14.5 no data no data no data Maximum 2.8 5.0 110 5.4 0.036 0.014 1.900 1.863 932 1.850 0.031 12.0 109 105 7.9 1.9 22.0 14.5 no data 104.6 41.4 Mean 1.4 2.3 21 2.7 0.013 0.006 1.528 1.429 386 1.412 0.009 10.7 99 86 7.3 1.0 19.3 11.1 no data 93.3 34.1

Taharua Rv at Red Hut Std. Dev. 0.6 1.3 25 1.0 0.006 0.003 0.218 0.225 280 0.230 0.006 0.8 6 10 0.4 0.4 1.5 2.4 no data 8.9 10.7 Count 28 30 27 25 31 31 30 31 31 31 31 26 25 27 27 13 18 27 no data 4 3 Minimum 0.5 1.2 1 0.3 0.002 0.002 0.450 0.260 46 0.250 0.005 8.7 84 43 6.6 0.5 12.0 4.8 0.3 109.6 44.0 5%'ile 0.5 1.5 1 0.7 0.005 0.002 0.590 0.507 53 0.483 0.005 9.6 95 51 6.9 0.5 13.3 5.9 0.6 no data no data 25%'ile 0.7 1.5 4 2.1 0.007 0.002 0.688 0.602 103 0.590 0.005 10.3 99 62 7.3 0.8 15.0 9.3 2.9 113.5 46.7 Median 1.1 1.5 6 3.2 0.009 0.004 0.820 0.732 224 0.720 0.005 11.0 101 70 7.4 0.9 16.4 11.4 8.2 119.8 54.8 75%'ile 1.3 1.5 21 3.8 0.014 0.006 1.032 0.934 412 0.923 0.009 11.2 103 75 7.8 1.2 18.0 14.0 15.8 123.2 57.3 95%'ile 2.0 10.3 87 5.0 0.021 0.009 1.159 1.087 510 1.073 0.020 12.3 109 82 8.1 2.9 19.2 15.6 62.4 no data no data Maximum 3.1 14.0 160 5.8 0.041 0.015 1.300 1.217 557 1.200 0.025 12.4 118 89 8.1 3.1 19.4 16.1 68.0 129.3 58.1 Mean 1.1 2.5 20 3.0 0.011 0.004 0.854 0.764 263 0.750 0.008 10.9 101 68 7.5 1.2 16.4 11.5 14.6 119.2 52.3 Std. Dev. 0.5 2.9 32 1.3 0.007 0.003 0.201 0.209 162 0.209 0.005 0.8 5 9 0.4 0.7 1.8 2.9 18.2 7.2 7.4

Mohaka Rv D/S Taharua Rv Count 35 37 34 34 39 39 37 39 39 39 39 34 34 35 35 18 22 35 26 6 3 Minimum 0.4 1.5 1 1.6 0.002 0.002 0.055 0.013 3 0.001 0.005 8.4 81 57 7.0 0.9 16.4 5.1 2.5 116.4 50.0 5%'ile 0.4 1.5 1 1.6 0.003 0.002 0.055 0.014 3 0.002 0.005 8.5 83 58 7.1 no data no data 5.7 no data no data no data 25%'ile 0.7 1.5 4 2.4 0.007 0.002 0.106 0.032 7 0.015 0.005 9.7 94 65 7.6 1.2 17.3 10.7 3.5 122.1 52.5 Median 1.1 1.5 8 3.3 0.009 0.005 0.130 0.046 12 0.029 0.005 11.0 102 68 7.7 1.6 17.7 13.8 3.9 127.3 55.9 75%'ile 1.9 1.5 18 4.0 0.011 0.007 0.142 0.083 17 0.071 0.005 11.3 106 73 7.9 1.7 19.0 15.3 28.0 133.0 57.7 95%'ile 56.8 5.1 2710 6.9 0.022 0.010 0.211 0.133 38 0.125 0.016 14.9 130 80 8.9 no data no data 20.1 no data no data no data Maximum 93.0 9.0 4900 7.1 0.036 0.013 0.214 0.142 62 0.126 0.022 15.9 135 83 9.4 3.8 22.0 20.8 42.7 139.0 58.6 Mean 6.3 1.9 268 3.6 0.010 0.005 0.124 0.058 14 0.044 0.007 10.8 102 69 7.8 1.8 18.4 13.0 14.1 127.5 55.1 Std. Dev. 21.6 1.6 1122 1.7 0.006 0.003 0.047 0.039 12 0.040 0.004 1.8 13 7 0.5 1.0 1.8 4.0 17.1 8.4 3.7

Ripia Rv U/S Mohaka Rv Count 18 23 19 17 23 24 24 24 24 24 24 17 16 19 19 6 7 19 6 5 4

136 Mohaka River Catchment

< Median Flow E. coli Elec. Site Turbidity Black DRP DIN DIN / NO3-N NH4-N DO TOC Hardness Temp Chla MCI % EPT Statistic SS (mg/l) (CFU/ TP (mg/l) TN (mg/l) DO (%) Cond. pH name (NTU) Disc (m) (mg/l) (mg/l) DRP (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (oC) (mg/m2) (Unit) taxa 100ml) (uS/cm) Minimum 0.3 1.5 1 1.0 0.002 0.002 0.210 0.170 33 0.160 0.005 8.4 80 59 7.1 0.7 18.3 5.1 0.2 127.0 60.9 5%'ile 0.4 1.5 1 1.2 0.004 0.002 0.255 0.172 38 0.166 0.005 8.5 84 60 7.2 0.7 18.4 6.2 0.2 no data no data 25%'ile 0.8 1.5 3 2.1 0.005 0.002 0.311 0.245 48 0.235 0.005 10.1 100 67 7.6 0.9 19.0 10.5 1.2 127.6 60.9 Median 1.1 1.5 6 2.8 0.008 0.004 0.381 0.290 82 0.280 0.005 10.9 102 73 7.8 1.2 19.8 12.9 2.3 129.5 65.8 75%'ile 1.4 1.5 11 3.4 0.009 0.005 0.450 0.378 142 0.357 0.005 11.4 106 78 8.0 1.9 21.3 15.1 8.5 133.9 70.6 95%'ile 3.4 4.0 106 5.5 0.012 0.007 0.512 0.504 232 0.492 0.016 12.6 118 90 8.4 11.9 23.3 18.3 142.9 no data no data Maximum 3.9 4.2 410 7.5 0.013 0.007 0.530 0.550 251 0.540 0.045 13.5 129 93 8.8 15.1 24.0 18.4 200.0 135.3 70.6 Mean 1.3 1.8 24 2.9 0.007 0.004 0.380 0.311 102 0.298 0.007 10.8 102 73 7.8 2.2 20.2 12.6 19.8 130.6 65.8 Std. Dev. 0.8 0.8 76 1.3 0.003 0.002 0.088 0.098 64 0.097 0.008 1.2 10 9 0.4 3.6 1.5 3.5 46.2 4.3 6.9

Mohaka Rv D/S Ripia Rv Count 28 29 29 27 29 29 28 29 29 29 29 28 28 29 28 15 17 29 26 3 2 Minimum 1.3 1.5 4 0.8 0.007 0.002 0.570 0.490 80 0.470 0.005 8.9 76 72 6.7 0.9 14.5 8.1 0.2 114.7 46.9 5%'ile 1.5 1.5 4 0.9 0.008 0.002 0.577 0.503 82 0.489 0.005 9.1 79 73 6.8 no data no data 8.3 no data no data no data 25%'ile 1.9 3.0 8 1.3 0.010 0.003 0.653 0.582 91 0.570 0.005 10.2 91 80 7.1 1.3 15.5 8.6 0.2 116.8 47.6 Median 2.1 4.9 12 1.9 0.013 0.006 0.692 0.612 103 0.600 0.005 10.5 94 87 7.3 1.4 16.2 9.6 25.0 119.1 52.6 75%'ile 3.4 8.0 21 3.1 0.017 0.006 0.755 0.648 223 0.630 0.005 10.9 98 91 7.5 1.6 16.6 10.7 49.7 121.6 54.7 95%'ile 4.1 45.4 49 4.8 0.025 0.007 0.842 0.738 329 0.720 0.005 12.6 114 99 7.9 no data no data 11.3 no data no data no data Maximum 4.3 46.0 51 5.1 0.035 0.008 0.880 0.750 335 0.720 0.005 13.0 119 100 8.1 3.0 19.9 11.3 49.7 126.2 55.2 Waiarua Strm Mean 2.5 9.1 17 2.3 0.014 0.005 0.699 0.612 154 0.599 0.005 10.6 95 86 7.3 1.6 16.4 9.7 25.0 119.5 51.4 Std. Dev. 0.9 12.5 14 1.2 0.006 0.002 0.078 0.061 95 0.060 0.000 0.9 9 8 0.3 0.7 1.6 1.1 35.0 4.3 3.8 Count 19 22 18 18 22 23 23 23 23 23 23 16 15 18 16 7 8 18 2 5 5 Minimum 0.8 1.5 1 0.4 0.006 0.002 0.055 0.049 17 0.027 0.005 9.9 93 53 7.0 0.7 10.9 8.4 27.5 118.5 52.2 5%'ile 0.9 1.5 1 0.4 0.007 0.002 0.079 0.059 17 0.039 0.005 9.9 no data 53 7.0 no data no data 8.4 no data no data no data 25%'ile 1.3 1.5 2 0.7 0.010 0.005 0.185 0.121 22 0.110 0.005 10.9 94 55 7.3 1.0 12.8 8.6 no data 118.7 52.6 Median 1.6 4.9 4 1.1 0.014 0.006 0.289 0.195 27 0.182 0.005 11.0 101 63 7.5 1.1 13.2 11.0 27.5 119.3 53.8 75%'ile 3.2 13.5 8 2.6 0.016 0.008 0.307 0.226 41 0.215 0.005 11.2 107 68 7.8 1.3 13.9 12.9 no data 120.5 54.9 Rd 95%'ile 5.8 31.7 12 4.7 0.022 0.010 0.338 0.261 102 0.244 0.015 12.1 no data 74 8.1 no data no data 13.2 no data no data no data Maximum 6.0 32.0 12 4.8 0.023 0.010 0.340 0.265 120 0.250 0.020 12.1 114 74 8.2 1.9 15.2 13.2 27.5 120.9 55.2 Mean 2.3 9.8 5 1.8 0.013 0.006 0.253 0.178 36 0.164 0.006 11.1 101 62 7.5 1.2 13.2 10.9 27.5 119.6 53.7 Std. Dev. 1.5 11.2 4 1.4 0.004 0.003 0.082 0.066 25 0.066 0.004 0.6 7 7 0.3 0.4 1.2 2.0 0.0 1.2 1.5

Waipunga Rv at Pohokura Count 12 16 11 11 15 16 15 16 16 16 16 10 9 11 11 7 8 10 1 3 3 Minimum 0.3 1.5 2 0.5 0.010 0.009 0.055 0.007 0 0.001 0.005 8.3 83 53 7.2 0.9 16.0 7.0 0.0 130.0 57.7 5%'ile 0.3 1.5 3 0.7 0.011 0.010 0.055 0.008 1 0.001 0.005 8.7 85 58 7.3 no data no data 7.0 no data no data no data 25%'ile 0.5 1.5 7 2.8 0.016 0.012 0.055 0.013 1 0.002 0.005 9.9 98 72 7.6 1.2 22.0 10.8 1.1 130.0 57.9 Median 1.2 1.5 15 3.3 0.017 0.014 0.107 0.021 2 0.008 0.005 10.5 102 78 7.6 1.6 22.5 13.0 2.7 132.6 60.0 75%'ile 1.4 3.7 20 4.6 0.018 0.014 0.151 0.072 5 0.060 0.005 11.1 103 82 7.8 1.9 23.0 14.5 12.7 136.9 60.8 95%'ile 8.4 19.6 34 6.5 0.043 0.015 0.281 0.183 15 0.173 0.008 12.2 108 84 8.3 no data no data 16.8 no data no data no data Maximum 11.0 22.0 35 7.1 0.054 0.015 0.320 0.230 19 0.220 0.010 12.3 108 84 8.3 2.8 24.0 17.0 42.7 145.6 61.1 Mean 1.7 4.1 15 3.6 0.019 0.013 0.123 0.050 4 0.037 0.005 10.5 100 76 7.7 1.6 21.9 12.4 9.9 134.4 59.5

Mokomokonui Rv Std. Dev. 2.5 5.7 10 1.6 0.010 0.002 0.070 0.056 5 0.056 0.001 1.0 6 8 0.3 0.6 2.5 3.2 18.4 6.5 1.6 Count 17 17 17 16 17 17 16 17 17 17 17 16 15 17 16 7 8 17 5 5 5

Mohaka River Catchment 137

< Median Flow E. coli Elec. Site Turbidity Black DRP DIN DIN / NO3-N NH4-N DO TOC Hardness Temp Chla MCI % EPT Statistic SS (mg/l) (CFU/ TP (mg/l) TN (mg/l) DO (%) Cond. pH name (NTU) Disc (m) (mg/l) (mg/l) DRP (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (oC) (mg/m2) (Unit) taxa 100ml) (uS/cm) Minimum 0.3 no data 2 0.6 0.004 0.001 0.224 0.135 30 no data 0.001 8.9 98 81 7.7 no data no data 5.4 no data 112.1 no data 5%'ile 0.4 no data 4 1.5 0.004 0.001 0.245 0.178 35 no data 0.002 9.5 99 82 7.8 no data no data 6.5 no data no data no data 25%'ile 0.6 no data 9 3.0 0.006 0.002 0.301 0.238 49 no data 0.003 10.0 101 86 7.9 no data no data 9.6 no data 114.7 no data Median 0.9 no data 12 3.6 0.008 0.004 0.331 0.271 64 no data 0.004 10.3 103 93 8.1 no data no data 13.2 no data 118.8 no data 75%'ile 1.2 no data 22 4.8 0.009 0.006 0.414 0.334 117 no data 0.006 11.2 105 100 8.2 no data no data 16.1 no data 121.4 no data 95%'ile 3.3 no data 72 7.4 0.012 0.008 0.516 0.415 324 no data 0.010 12.1 108 121 8.5 no data no data 18.2 no data no data no data Maximum 5.4 no data 921 8.4 0.039 0.008 0.534 0.467 384 no data 0.015 12.5 111 218 8.8 no data no data 20.9 no data 122.5 no data Mean 1.1 no data 43 4.0 0.009 0.004 0.356 0.282 100 no data 0.005 10.6 103 97 8.1 no data no data 12.8 no data 118.1 no data Std. Dev. 1.0 no data 149 1.6 0.006 0.002 0.081 0.070 87 no data 0.003 0.9 3 23 0.2 no data no data 3.8 no data 4.5 no data

Mohaka Rv at SH5 (NIWA) Count 37 no data 37 37 37 37 37 37 37 no data 37 37 37 37 37 no data no data 37 no data 4 no data Minimum no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data 5%'ile no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data 25%'ile no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data Median no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data 75%'ile no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data Rv 95%'ile no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data Maximum no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data Mean no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data Std. Dev. no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data

Mohaka Rv D/S Waipunga Count no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data Minimum 1.4 1.5 1 0.2 0.002 0.002 0.109 0.019 10 0.008 0.005 7.0 75 85 7.3 1.1 30.0 7.1 0.4 93.3 28.6 5%'ile 1.4 2.6 2 0.2 0.003 0.002 0.126 0.039 12 0.028 0.005 7.5 79 86 7.4 1.2 30.0 8.1 0.5 no data no data 25%'ile 2.0 9.0 5 0.4 0.010 0.002 0.206 0.118 19 0.106 0.005 9.9 96 98 7.8 2.3 33.0 11.5 3.7 93.3 28.6 Median 4.1 10.3 11 0.7 0.015 0.005 0.234 0.142 34 0.131 0.005 10.8 103 105 7.9 2.4 35.5 13.1 35.1 110.8 47.7 75%'ile 7.3 21.0 26 1.1 0.021 0.007 0.261 0.187 55 0.152 0.005 12.0 108 122 8.0 2.6 39.0 16.4 51.9 128.3 66.7 95%'ile 16.3 35.6 65 2.2 0.041 0.011 0.307 0.232 86 0.219 0.028 12.4 119 129 8.1 3.1 43.4 18.2 95.7 no data no data Maximum 17.9 36.0 85 2.3 0.049 0.011 0.307 0.250 95 0.240 0.036 12.5 119 131 8.1 3.1 45.0 18.3 96.5 128.3 66.7 Mean 5.4 14.9 18 0.8 0.017 0.005 0.233 0.145 40 0.131 0.007 10.7 102 108 7.8 2.3 35.8 13.5 34.9 110.8 47.7 Std. Dev. 4.6 10.4 20 0.6 0.011 0.003 0.051 0.053 24 0.051 0.008 1.5 11 14 0.2 0.5 3.9 3.1 33.7 24.7 26.9 Mohaka Rv at Willowflat Count 16 18 18 16 18 18 17 18 18 18 18 16 15 18 18 17 18 17 11 2 2 Minimum 0.7 1.5 1 0.2 0.004 0.002 0.055 0.013 3 0.005 0.005 8.1 87 88 7.6 1.1 33.0 10.5 0.8 96.8 32.0 5%'ile 0.7 1.5 1 0.2 0.005 0.002 0.055 0.016 7 0.006 0.005 8.3 87 92 7.6 1.2 33.5 10.8 1.2 no data no data 25%'ile 1.6 1.9 5 0.4 0.007 0.002 0.164 0.071 16 0.060 0.005 9.4 97 107 8.0 2.0 37.5 12.4 15.6 96.8 33.4 Median 3.2 5.2 12 0.7 0.010 0.004 0.198 0.113 21 0.100 0.005 10.6 109 116 8.0 2.4 41.0 15.9 28.6 102.0 37.5 75%'ile 7.2 13.0 24 1.4 0.019 0.008 0.277 0.158 32 0.150 0.005 11.9 117 135 8.4 3.1 43.5 19.0 81.8 109.8 54.4 95%'ile 20.7 18.1 52 2.6 0.027 0.013 0.343 0.219 53 0.203 0.019 14.2 142 143 8.9 5.6 49.0 19.8 248.9 no data no data Maximum 21.2 20.0 63 2.9 0.032 0.014 0.362 0.220 57 0.210 0.036 14.6 146 146 8.9 7.2 51.0 20.0 290.0 112.7 60.0 Mean 6.0 7.8 16 1.0 0.013 0.005 0.205 0.115 25 0.102 0.007 10.9 108 119 8.1 2.6 40.7 15.6 58.9 103.4 43.2 Std. Dev. 6.3 6.1 16 0.8 0.008 0.004 0.079 0.062 14 0.060 0.006 1.9 17 17 0.3 1.3 4.5 3.3 74.5 7.2 14.8

Mohaka Rv at Raupunga Count 18 23 20 17 23 24 22 24 24 24 24 17 15 19 20 19 20 18 15 5 3

138 Mohaka River Catchment

< Median Flow E. coli Elec. Site Turbidity Black DRP DIN DIN / NO3-N NH4-N DO TOC Hardness Temp Chla MCI % EPT Statistic SS (mg/l) (CFU/ TP (mg/l) TN (mg/l) DO (%) Cond. pH name (NTU) Disc (m) (mg/l) (mg/l) DRP (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (oC) (mg/m2) (Unit) taxa 100ml) (uS/cm) Minimum 0.7 no data 1 0.1 0.005 0.001 0.081 0.003 1 no data 0.001 9.4 95 106 7.8 no data no data 7.1 no data 96.8 no data 5%'ile 0.7 no data 2 0.8 0.006 0.001 0.086 0.005 1 no data 0.001 9.4 99 108 7.9 no data no data 10.3 no data no data no data 25%'ile 1.5 no data 5 1.2 0.009 0.002 0.127 0.026 9 no data 0.003 10.3 109 116 8.4 no data no data 13.3 no data 97.9 no data Median 2.4 no data 10 1.7 0.011 0.004 0.162 0.065 20 no data 0.004 11.3 116 121 8.7 no data no data 17.3 no data 105.9 no data 75%'ile 3.2 no data 23 2.5 0.013 0.008 0.222 0.146 29 no data 0.005 12.3 125 130 8.9 no data no data 20.5 no data 113.9 no data 95%'ile 6.1 no data 110 4.2 0.022 0.011 0.276 0.224 56 no data 0.006 13.4 138 150 9.1 no data no data 23.2 no data no data no data (NIWA) Maximum 56.0 no data 738 4.8 0.089 0.012 0.703 0.441 71 no data 0.007 15.8 144 200 9.2 no data no data 25.4 no data 115.0 no data Mean 4.2 no data 41 1.9 0.014 0.005 0.189 0.092 22 no data 0.004 11.4 117 126 8.6 no data no data 17.0 no data 105.9 no data Std. Dev. 9.6 no data 129 1.0 0.014 0.003 0.109 0.092 16 no data 0.002 1.4 11 17 0.3 no data no data 4.6 no data 9.3 no data

Mohaka Rv at Raupunga Count 32 no data 32 32 32 32 32 32 32 no data 32 32 32 32 32 no data no data 32 no data 4 no data

Mohaka River Catchment 139

Less than lower quartile flow E. coli Elec. Site Turbidity Black DRP DIN DIN / NO3-N NH4-N DO TOC Hardness Temp Chla MCI % EPT Statistic SS (mg/l) (CFU/ TP (mg/l) TN (mg/l) DO (%) Cond. pH name (NTU) Disc (m) (mg/l) (mg/l) DRP (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (oC) (mg/m2) (Unit) taxa 100ml) (uS/cm) Minimum 0.2 1.5 1 3.2 0.002 0.002 0.055 0.014 3 0.001 0.005 8.2 79 46 6.4 0.5 8.5 4.1 0.3 118.5 57.7 5%'ile 0.2 1.5 1 3.4 0.002 0.002 0.055 0.014 6 0.001 0.005 8.7 83 47 6.9 no data 8.9 6.5 0.3 no data no data 25%'ile 0.3 1.5 1 4.5 0.003 0.002 0.055 0.018 8 0.004 0.005 9.5 93 50 7.2 0.5 12.5 10.6 1.0 120.7 60.0 Median 0.5 1.5 6 6.0 0.005 0.002 0.100 0.026 13 0.015 0.005 10.0 97 56 7.4 0.9 13.6 12.7 2.2 124.2 66.7 75%'ile 0.8 1.5 14 6.6 0.007 0.002 0.118 0.051 21 0.035 0.005 11.0 100 58 7.5 1.1 14.5 14.6 4.8 129.0 69.5 95%'ile 2.5 7.0 39 8.2 0.017 0.006 0.205 0.127 56 0.112 0.016 12.4 105 66 8.0 no data 15.8 16.2 22.0 no data no data Maximum 3.8 13.0 53 8.4 0.025 0.007 0.300 0.210 105 0.200 0.018 12.8 107 68 8.1 1.6 15.8 16.5 24.0 132.5 70.4 Mean 0.7 2.1 10 5.7 0.006 0.003 0.096 0.041 18 0.027 0.007 10.2 96 55 7.4 0.9 13.3 12.4 4.6 124.8 64.9 Std. Dev. 0.8 2.5 13 1.4 0.005 0.002 0.056 0.041 20 0.042 0.004 1.1 6 6 0.3 0.4 2.0 2.9 6.6 5.9 6.5

Mohaka Rv U/S Taharua Rv Count 20 22 20 19 23 24 23 24 24 24 24 21 19 21 21 8 12 21 15 4 3 Minimum 0.1 1.5 3 3.2 0.013 0.009 2.200 2.212 114 2.200 0.005 7.3 67 96 5.9 0.5 20.0 9.8 no data 84.8 52.4 5%'ile 0.1 1.5 3 3.2 0.014 0.009 2.300 2.287 118 2.275 0.005 7.4 68 96 6.0 no data no data 9.9 no data no data no data 25%'ile 0.2 1.5 3 5.2 0.015 0.014 2.700 2.637 143 2.625 0.005 7.7 73 98 6.8 0.5 22.0 10.8 no data 84.8 no data Median 0.3 1.5 9 6.0 0.017 0.015 2.910 2.824 193 2.800 0.005 8.1 75 101 6.9 0.9 23.0 11.0 no data 95.8 52.4 75%'ile 1.0 1.5 23 7.3 0.019 0.018 3.200 3.110 225 3.100 0.014 8.4 80 104 7.1 1.4 23.3 11.4 no data 106.7 no data 95%'ile 1.1 10.7 56 9.1 0.042 0.022 3.399 3.311 321 3.300 0.039 9.0 88 111 7.9 no data no data 11.7 no data no data no data Maximum 1.1 13.0 60 9.4 0.045 0.022 3.430 3.313 331 3.300 0.044 9.0 89 111 8.1 1.5 25.0 11.7 no data 106.7 52.4 Mean 0.5 2.3 17 6.1 0.020 0.016 2.921 2.855 195 2.840 0.012 8.1 76 102 6.9 0.9 22.7 11.0 no data 95.8 52.4 Std. Dev. 0.4 3.1 18 1.7 0.008 0.004 0.331 0.313 60 0.311 0.011 0.5 6 5 0.5 0.5 1.4 0.5 no data 15.5 0.0

Taharua Rv at Wairango Count 14 14 14 14 14 15 15 15 15 15 15 15 15 15 15 6 9 15 no data 2 1 Minimum 0.2 1.5 1 2.1 0.008 0.002 3.100 3.012 146 3.000 0.005 7.8 71 11 6.3 0.5 22.0 9.4 no data 93.3 42.9 5%'ile 0.2 1.5 1 2.2 0.008 0.003 3.150 3.062 157 3.050 0.005 8.1 74 35 6.4 no data no data 9.6 no data no data no data 25%'ile 0.2 1.5 2 3.7 0.010 0.009 3.426 3.337 209 3.325 0.005 9.4 86 106 6.9 0.5 24.0 10.9 no data 93.3 no data Median 0.4 1.5 10 4.0 0.016 0.012 3.600 3.612 321 3.500 0.005 9.6 92 109 7.1 1.1 25.0 11.3 no data 95.6 42.9 75%'ile 0.5 1.5 21 4.8 0.022 0.016 3.800 3.712 410 3.700 0.016 9.9 93 110 7.3 1.3 25.5 11.7 no data 97.8 no data 95%'ile 1.0 7.1 303 8.8 0.032 0.021 3.901 3.821 1367 3.800 0.028 10.2 98 122 7.9 no data no data 12.8 no data no data no data Maximum 1.0 8.0 370 9.1 0.032 0.022 3.902 3.822 1656 3.800 0.028 10.2 98 122 8.0 3.3 27.0 13.0 no data 97.8 42.9 Mean 0.4 2.1 37 4.4 0.017 0.012 3.596 3.522 397 3.500 0.011 9.5 90 103 7.1 1.3 24.8 11.3 no data 95.6 42.9 Std. Dev. 0.3 1.8 97 1.7 0.008 0.005 0.250 0.250 364 0.248 0.008 0.6 7 26 0.4 1.1 1.6 0.8 no data 3.2 0.0

Taharua Rv at Twin Culv Count 13 14 14 12 14 15 15 15 15 15 15 15 15 15 15 6 9 15 no data 2 1 Minimum 0.5 1.5 1 2.5 0.005 0.002 1.960 1.902 211 1.890 0.005 8.9 85 90 6.8 no data 23.0 10.4 24.0 129.2 57.7 5%'ile no data no data no data no data no data 0.002 1.960 1.912 211 1.900 0.005 no data no data no data no data no data no data no data no data no data no data 25%'ile 0.9 1.5 3 3.2 0.012 0.007 2.300 2.237 224 2.225 0.005 10.0 95 94 7.1 no data no data 11.2 no data no data no data Median 1.3 1.5 6 4.4 0.012 0.008 2.411 2.415 302 2.400 0.005 10.1 97 96 7.3 no data 23.0 11.9 24.0 129.2 57.7 75%'ile 1.7 1.9 17 4.5 0.020 0.010 2.500 2.511 347 2.500 0.005 10.5 100 99 7.6 no data no data 12.5 no data no data no data 95%'ile no data no data no data no data no data 0.010 2.600 2.512 1116 2.500 0.005 no data no data no data no data no data no data no data no data no data no data Maximum 1.9 4.0 86 4.5 0.021 0.010 2.600 2.512 1156 2.500 0.005 11.2 104 109 7.6 no data 23.0 13.1 24.0 129.2 57.7 Mean 1.3 1.9 17 3.9 0.014 0.008 2.388 2.346 360 2.335 0.005 10.2 96 97 7.3 no data 23.0 11.8 24.0 129.2 57.7 Std. Dev. 0.5 0.9 29 0.9 0.005 0.002 0.195 0.202 270 0.204 0.000 0.6 5 5 0.3 no data 0.0 0.8 0.0 0.0 0.0

Taharua Rv at Henry's Br Count 7 9 8 5 9 11 10 11 11 11 11 9 9 9 9 no data 1 9 1 1 1

140 Mohaka River Catchment

< Lower Quartile Flow E. coli Elec. Site Turbidity Black DRP DIN DIN / NO3-N NH4-N DO TOC Hardness Temp Chla MCI % EPT Statistic SS (mg/l) (CFU/ TP (mg/l) TN (mg/l) DO (%) Cond. pH name (NTU) Disc (m) (mg/l) (mg/l) DRP (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (oC) (mg/m2) (Unit) taxa 100ml) (uS/cm) Minimum 0.7 1.5 1 1.6 0.013 0.002 1.500 1.415 109 1.400 0.005 7.9 72 81 7.0 0.5 18.0 6.9 0.4 118.2 no data 5%'ile no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data 25%'ile 0.9 1.5 1 2.0 0.014 0.009 1.750 1.665 133 1.650 0.005 10.2 96 84 7.1 0.5 18.5 10.8 1.8 no data no data Median 1.1 2.3 6 2.8 0.015 0.011 1.915 1.812 172 1.800 0.009 10.6 101 89 7.2 0.9 19.0 11.4 3.5 118.2 no data 75%'ile 1.3 5.1 27 3.1 0.023 0.013 2.051 1.961 213 1.950 0.018 11.0 104 92 7.3 1.1 20.5 11.8 28.2 no data no data 95%'ile no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data Maximum 2.4 18.0 85 3.4 0.032 0.014 2.100 2.029 980 2.000 0.029 12.2 109 95 7.3 1.9 21.0 13.0 52.6 118.2 no data Mean 1.2 4.6 19 2.6 0.019 0.010 1.879 1.790 266 1.775 0.012 10.5 98 88 7.2 1.0 19.4 11.0 15.0 118.2 no data Std. Dev. 0.5 5.6 29 0.7 0.007 0.004 0.205 0.205 292 0.204 0.009 1.2 11 5 0.1 0.5 1.2 1.8 25.1 0.0 no data

Taharua Rv at Poronui Stn Count 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 6 8 8 4 1 no data Minimum 0.7 1.3 3 1.0 0.007 0.002 1.220 1.117 93 1.100 0.005 9.3 86 77 6.5 0.5 18.0 5.4 no data 89.6 39.1 5%'ile 0.7 1.4 3 1.1 0.007 0.002 1.258 1.150 96 1.135 0.005 9.4 88 78 6.5 no data 18.0 6.6 no data no data no data 25%'ile 0.8 1.5 4 2.5 0.009 0.002 1.472 1.389 152 1.375 0.005 10.1 94 84 7.0 0.8 18.0 10.4 no data 89.6 no data Median 1.2 1.5 8 2.9 0.010 0.006 1.535 1.447 270 1.430 0.005 10.7 97 89 7.2 0.9 20.0 11.0 no data 97.1 39.1 75%'ile 1.3 1.5 43 3.2 0.014 0.008 1.696 1.614 710 1.595 0.012 11.4 103 93 7.6 1.2 21.0 13.2 no data 104.6 no data 95%'ile 2.6 4.7 96 5.1 0.020 0.013 1.883 1.821 911 1.808 0.028 11.7 109 102 7.9 no data 22.0 14.4 no data no data no data Maximum 2.8 5.0 110 5.4 0.022 0.014 1.900 1.863 932 1.850 0.031 11.8 109 103 7.9 1.9 22.0 14.5 no data 104.6 39.1 Mean 1.2 2.0 25 2.9 0.012 0.006 1.576 1.482 389 1.468 0.010 10.6 99 89 7.3 1.0 19.8 11.4 no data 97.1 39.1

Taharua Rv at Red Hut Std. Dev. 0.6 1.1 30 1.1 0.004 0.004 0.180 0.193 294 0.193 0.007 0.8 6 7 0.4 0.5 1.5 2.2 no data 10.6 0.0 Count 15 17 15 14 17 17 17 17 17 17 17 15 15 15 15 6 10 15 no data 2 1 Minimum 0.5 1.5 1 0.3 0.002 0.002 0.650 0.520 47 0.510 0.005 8.7 84 62 6.6 0.5 15.0 5.2 1.1 109.6 44.0 5%'ile 0.5 1.5 2 0.8 0.004 0.002 0.667 0.567 82 0.555 0.005 9.2 90 62 6.8 no data 15.1 7.5 1.3 no data no data 25%'ile 0.6 1.5 4 2.8 0.006 0.002 0.792 0.704 176 0.692 0.005 10.1 98 68 7.3 0.7 16.0 10.8 4.9 112.5 46.7 Median 1.0 1.5 10 3.4 0.008 0.002 0.862 0.772 371 0.760 0.005 10.9 100 71 7.5 0.9 17.0 12.8 12.8 116.7 54.8 75%'ile 1.3 1.5 23 3.9 0.013 0.004 1.045 0.948 456 0.938 0.009 11.2 104 76 7.8 1.0 18.5 14.6 30.0 123.0 57.3 95%'ile 1.9 5.8 52 5.5 0.018 0.010 1.137 1.074 534 1.061 0.019 12.3 114 85 8.1 no data 19.4 15.8 65.9 no data no data Maximum 2.1 11.0 52 5.8 0.022 0.015 1.170 1.114 557 1.100 0.022 12.4 118 89 8.1 1.2 19.4 16.1 68.0 123.2 58.1 Mean 1.0 2.0 17 3.3 0.009 0.004 0.907 0.817 321 0.805 0.008 10.7 101 72 7.5 0.9 17.2 12.6 20.6 117.2 52.3 Std. Dev. 0.4 2.1 18 1.3 0.004 0.003 0.156 0.161 158 0.162 0.005 0.9 7 7 0.4 0.3 1.4 2.6 21.0 5.9 7.4

Mohaka Rv D/S Taharua Rv Count 20 21 20 20 23 23 21 23 23 23 23 20 20 21 21 8 11 21 16 5 3 Minimum 0.4 1.5 4 1.8 0.002 0.002 0.055 0.014 4 0.001 0.005 8.4 81 57 7.0 1.2 17.7 8.6 3.5 116.4 50.0 5%'ile no data 1.5 no data no data 0.002 0.002 0.055 0.015 4 0.002 0.005 no data no data no data no data no data no data no data no data no data no data 25%'ile 0.5 1.5 8 2.8 0.007 0.002 0.055 0.030 8 0.012 0.005 8.9 86 68 7.5 1.2 18.0 12.9 9.6 118.3 51.3 Median 0.9 1.5 10 3.6 0.009 0.002 0.122 0.039 13 0.022 0.005 10.0 96 73 7.7 1.5 19.0 14.6 28.0 124.0 55.0 75%'ile 1.4 1.5 23 6.3 0.011 0.005 0.137 0.053 18 0.035 0.005 10.3 102 76 7.9 1.7 21.3 15.1 39.0 129.3 57.7 95%'ile no data 1.5 no data no data 0.014 0.012 0.213 0.128 57 0.122 0.020 no data no data no data no data no data no data no data no data no data no data Maximum 1.9 1.5 4900 7.1 0.014 0.013 0.214 0.129 62 0.124 0.022 11.3 105 83 8.4 1.7 22.0 20.8 42.7 131.0 58.6 Mean 1.0 1.5 556 4.3 0.009 0.004 0.113 0.050 17 0.035 0.007 9.8 94 72 7.7 1.5 19.6 14.2 24.7 123.8 54.5 Std. Dev. 0.6 0.0 1629 2.0 0.003 0.003 0.057 0.036 15 0.038 0.005 1.0 9 7 0.4 0.4 2.2 3.4 19.8 7.3 4.3

Ripia Rv U/S Mohaka Rv Count 8 12 9 8 12 13 13 13 13 13 13 7 6 9 9 2 3 9 3 3 3

Mohaka River Catchment 141

< Lower Quartile Flow E. coli Elec. Site Turbidity Black DRP DIN DIN / NO3-N NH4-N DO TOC Hardness Temp Chla MCI % EPT Statistic SS (mg/l) (CFU/ TP (mg/l) TN (mg/l) DO (%) Cond. pH name (NTU) Disc (m) (mg/l) (mg/l) DRP (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (oC) (mg/m2) (Unit) taxa 100ml) (uS/cm) Minimum 0.3 1.5 1 1.4 0.002 0.002 0.260 0.170 82 0.160 0.005 8.4 80 61 7.6 1.4 18.8 11.0 1.4 127.0 60.9 5%'ile no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data 25%'ile 0.7 1.5 4 2.2 0.005 0.002 0.378 0.288 127 0.278 0.005 9.1 87 76 7.9 1.5 19.3 12.6 1.9 127.0 60.9 Median 0.9 1.5 8 3.0 0.008 0.002 0.480 0.402 172 0.380 0.005 10.1 100 80 8.0 1.7 20.9 14.4 15.2 131.2 65.8 75%'ile 1.2 1.8 45 4.5 0.008 0.002 0.506 0.434 214 0.413 0.006 10.5 106 87 8.2 2.0 23.0 16.8 99.4 135.3 70.6 95%'ile no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data Maximum 1.2 3.1 410 7.5 0.013 0.005 0.530 0.502 251 0.490 0.045 12.5 129 93 8.8 2.1 24.0 18.4 200.0 135.3 70.6 Mean 0.9 1.8 62 3.5 0.007 0.002 0.437 0.366 168 0.350 0.010 9.9 100 80 8.0 1.7 21.2 14.5 54.3 131.2 65.8 Std. Dev. 0.3 0.6 133 2.0 0.003 0.001 0.089 0.104 60 0.101 0.013 1.3 16 10 0.3 0.3 2.3 2.5 74.3 5.9 6.9

Mohaka Rv D/S Ripia Rv Count 8 9 9 8 9 9 9 9 9 9 9 9 9 9 9 3 4 9 8 2 2 Minimum 1.3 1.5 5 1.3 0.008 0.002 0.570 0.510 83 0.500 0.005 8.9 76 80 6.7 0.9 16.0 8.1 49.7 117.5 46.9 5%'ile 1.3 1.5 5 1.3 0.008 0.002 0.574 0.520 84 0.510 0.005 no data no data 80 no data no data no data 8.1 no data no data no data 25%'ile 1.7 1.5 8 2.0 0.009 0.002 0.663 0.591 96 0.577 0.005 10.2 91 83 7.2 1.0 16.1 8.6 no data 118.1 47.1 Median 2.1 3.0 12 2.7 0.011 0.006 0.700 0.612 122 0.600 0.005 10.2 96 90 7.3 1.3 16.2 10.2 49.7 120.0 47.8 75%'ile 2.9 6.5 15 3.3 0.017 0.006 0.765 0.657 270 0.645 0.005 10.6 98 93 7.5 1.4 16.3 10.7 no data 124.7 53.4 95%'ile 3.8 45.9 35 4.3 0.033 0.007 0.871 0.747 334 0.720 0.005 no data no data 100 no data no data no data 11.3 no data no data no data Maximum 3.8 46.0 35 4.3 0.035 0.007 0.880 0.750 335 0.720 0.005 11.7 101 100 8.1 1.4 16.3 11.3 49.7 126.2 55.2 Waiarua Strm Mean 2.3 10.3 14 2.7 0.014 0.005 0.710 0.629 168 0.615 0.005 10.3 93 90 7.4 1.2 16.2 9.8 49.7 121.2 50.0 Std. Dev. 0.8 16.5 9 0.9 0.008 0.002 0.087 0.064 100 0.061 0.000 0.7 8 6 0.4 0.3 0.1 1.1 0.0 4.5 4.6 Count 10 12 10 10 12 13 13 13 13 13 13 9 8 10 9 3 4 10 1 3 3 Minimum 0.8 1.5 1 0.6 0.008 0.002 0.055 0.049 17 0.027 0.005 10.8 95 53 7.3 0.7 13.1 8.4 27.5 118.5 53.8 5%'ile no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data 25%'ile 1.2 1.5 3 1.1 0.009 0.004 0.163 0.085 20 0.073 0.005 10.8 98 63 7.5 0.8 13.4 8.6 no data 118.5 53.8 Median 1.6 1.5 4 2.6 0.011 0.005 0.244 0.199 27 0.187 0.005 11.1 104 66 7.7 1.0 13.9 11.4 27.5 118.9 54.5 75%'ile 2.2 12.8 6 3.3 0.014 0.007 0.298 0.220 41 0.207 0.005 11.3 108 72 7.9 1.1 14.6 13.0 no data 119.3 55.2 Rd 95%'ile no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data Maximum 3.4 31.0 9 4.8 0.019 0.010 0.340 0.265 61 0.250 0.020 11.8 108 74 8.2 1.1 15.2 13.2 27.5 119.3 55.2 Mean 1.8 7.9 5 2.5 0.012 0.005 0.226 0.162 32 0.147 0.007 11.1 103 66 7.7 0.9 14.0 10.9 27.5 118.9 54.5 Std. Dev. 0.9 10.1 3 1.5 0.004 0.003 0.097 0.080 15 0.081 0.005 0.4 6 8 0.3 0.2 0.9 2.3 0.0 0.6 1.0

Waipunga Rv at Pohokura Count 6 9 6 6 8 9 8 9 9 9 9 5 4 6 6 3 4 5 1 2 2 Minimum 0.3 1.5 4 2.8 0.015 0.009 0.055 0.014 1 0.001 0.005 9.4 83 70 7.2 1.6 23.0 7.0 2.7 130.0 57.9 5%'ile no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data 25%'ile 0.4 1.5 8 3.7 0.016 0.013 0.080 0.015 1 0.004 0.005 10.1 97 73 7.6 1.6 23.0 7.8 2.7 130.0 57.9 Median 0.5 1.5 13 4.6 0.018 0.014 0.126 0.036 3 0.009 0.005 10.2 99 82 7.6 1.8 23.5 14.0 22.7 131.3 59.3 75%'ile 1.3 1.5 20 5.2 0.020 0.014 0.150 0.068 5 0.057 0.005 11.0 102 84 7.8 1.9 24.0 15.1 42.7 132.6 60.7 95%'ile no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data Maximum 1.4 5.9 35 7.1 0.054 0.015 0.190 0.091 7 0.079 0.010 11.9 106 84 8.2 1.9 24.0 17.0 42.7 132.6 60.7 Mean 0.8 2.1 15 4.6 0.022 0.013 0.119 0.043 3 0.027 0.006 10.5 98 79 7.7 1.8 23.5 12.2 22.7 131.3 59.3

Mokomokonui Rv Std. Dev. 0.5 1.6 10 1.4 0.013 0.002 0.048 0.032 2 0.033 0.002 0.8 8 6 0.3 0.2 0.7 4.0 28.3 1.8 2.0 Count 8 8 8 8 8 8 8 8 8 8 8 7 6 8 7 2 2 8 2 2 2

142 Mohaka River Catchment

< Lower Quartile Flow E. coli Elec. Site Turbidity Black DRP DIN DIN / NO3-N NH4-N DO TOC Hardness Temp Chla MCI % EPT Statistic SS (mg/l) (CFU/ TP (mg/l) TN (mg/l) DO (%) Cond. pH name (NTU) Disc (m) (mg/l) (mg/l) DRP (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (oC) (mg/m2) (Unit) taxa 100ml) (uS/cm) Minimum 0.3 no data 4 0.6 0.004 0.001 0.224 0.135 34 no data 0.001 8.9 98 82 7.8 no data no data 5.9 no data 112.1 no data 5%'ile 0.3 no data 4 1.9 0.004 0.001 0.253 0.177 38 no data 0.002 9.3 99 83 7.8 no data no data 6.9 no data no data no data 25%'ile 0.6 no data 10 3.6 0.005 0.002 0.306 0.242 56 no data 0.003 9.9 103 93 8.0 no data no data 11.5 no data 114.7 no data Median 0.6 no data 13 4.8 0.006 0.003 0.337 0.279 90 no data 0.005 10.2 104 98 8.1 no data no data 14.5 no data 118.8 no data 75%'ile 0.9 no data 25 5.7 0.008 0.005 0.448 0.334 170 no data 0.007 11.1 107 106 8.3 no data no data 16.7 no data 121.4 no data 95%'ile 4.3 no data 419 8.1 0.023 0.007 0.511 0.403 359 no data 0.013 12.0 109 162 8.6 no data no data 19.5 no data no data no data Maximum 5.4 no data 921 8.4 0.039 0.008 0.524 0.432 384 no data 0.015 12.1 111 218 8.8 no data no data 20.9 no data 122.5 no data Mean 1.0 no data 61 4.7 0.008 0.003 0.366 0.285 130 no data 0.005 10.4 104 104 8.2 no data no data 13.9 no data 118.1 no data Std. Dev. 1.2 no data 193 1.7 0.007 0.002 0.086 0.067 102 no data 0.003 0.9 3 27 0.2 no data no data 3.9 no data 4.5 no data

Mohaka Rv at SH5 (NIWA) Count 22 no data 22 22 22 22 22 22 22 no data 22 22 22 22 22 no data no data 22 no data 4 no data Minimum no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data 5%'ile no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data 25%'ile no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data Median no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data 75%'ile no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data Rv 95%'ile no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data Maximum no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data Mean no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data Std. Dev. no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data

Mohaka Rv D/S Waipunga Count no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data Minimum 1.4 1.5 1 0.6 0.009 0.002 0.109 0.019 10 0.008 0.005 9.8 94 98 7.3 1.5 36.0 9.9 2.7 no data no data 5%'ile no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data 25%'ile 1.4 4.2 6 1.0 0.009 0.002 0.200 0.110 19 0.099 0.005 10.2 97 113 7.8 2.1 36.0 11.1 4.7 no data no data Median 2.2 9.1 14 1.1 0.013 0.003 0.241 0.151 36 0.140 0.005 10.5 101 122 7.9 2.6 37.5 13.1 26.7 no data no data 75%'ile 5.1 10.9 34 1.6 0.016 0.005 0.307 0.187 55 0.149 0.015 11.2 110 127 8.0 2.7 41.0 14.4 48.2 no data no data 95%'ile no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data Maximum 6.8 14.0 85 1.8 0.019 0.011 0.307 0.205 72 0.187 0.036 12.3 119 131 8.1 3.1 45.0 16.6 49.7 no data no data Mean 3.2 8.1 26 1.2 0.013 0.004 0.234 0.137 38 0.120 0.012 10.7 104 119 7.8 2.4 38.8 13.0 26.5 no data no data Std. Dev. 2.3 4.5 31 0.4 0.004 0.004 0.074 0.067 23 0.062 0.013 1.0 11 12 0.3 0.6 3.7 2.5 25.2 no data no data Mohaka Rv at Willowflat Count 6 6 6 6 6 6 6 6 6 6 6 5 4 6 6 6 6 5 4 no data no data Minimum 0.7 1.5 1 0.6 0.005 0.002 0.055 0.013 3 0.005 0.005 8.8 88 111 7.6 2.1 41.0 10.5 0.8 96.8 no data 5%'ile no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data 25%'ile 0.7 1.5 6 1.1 0.006 0.002 0.081 0.026 13 0.014 0.005 9.2 92 126 7.8 2.1 42.0 11.6 11.8 no data no data Median 1.9 2.3 12 1.5 0.008 0.002 0.156 0.068 23 0.062 0.005 10.2 97 136 8.0 2.4 43.0 13.6 25.7 96.8 no data 75%'ile 3.2 7.0 17 2.0 0.014 0.004 0.198 0.117 38 0.105 0.005 11.4 110 139 8.1 3.1 47.0 15.5 66.9 no data no data 95%'ile no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data no data Maximum 5.5 17.0 63 2.9 0.019 0.014 0.282 0.218 57 0.177 0.036 13.6 121 146 8.2 3.4 51.0 16.8 105.2 96.8 no data Mean 2.3 5.0 19 1.6 0.010 0.004 0.151 0.083 26 0.069 0.008 10.5 101 132 8.0 2.6 44.5 13.6 39.4 96.8 no data Std. Dev. 1.9 5.5 23 0.8 0.005 0.004 0.078 0.065 18 0.058 0.010 1.9 14 12 0.2 0.6 3.8 2.5 45.5 0.0 no data

Mohaka Rv at Raupunga Count 6 8 6 6 8 9 8 9 9 9 9 5 4 6 6 6 6 5 4 1 no data

Mohaka River Catchment 143

< Lower Quartile Flow E. coli Elec. Site Turbidity Black DRP DIN DIN / NO3-N NH4-N DO TOC Hardness Temp Chla MCI % EPT Statistic SS (mg/l) (CFU/ TP (mg/l) TN (mg/l) DO (%) Cond. pH name (NTU) Disc (m) (mg/l) (mg/l) DRP (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (oC) (mg/m2) (Unit) taxa 100ml) (uS/cm) Minimum 0.7 no data 3 1.0 0.005 0.001 0.081 0.003 1 no data 0.001 9.4 103 107 7.9 no data no data 10.3 no data 96.8 no data 5%'ile 0.7 no data 3 1.1 0.005 0.001 0.082 0.004 1 no data 0.001 9.7 104 109 7.9 no data no data 10.5 no data no data no data 25%'ile 1.4 no data 6 1.4 0.008 0.001 0.121 0.011 5 no data 0.002 10.5 111 116 8.5 no data no data 13.8 no data 97.9 no data Median 2.2 no data 13 2.1 0.010 0.003 0.160 0.031 20 no data 0.004 11.0 118 122 8.7 no data no data 18.4 no data 105.9 no data 75%'ile 2.6 no data 33 2.9 0.012 0.007 0.207 0.118 28 no data 0.005 11.8 125 130 8.9 no data no data 21.5 no data 113.9 no data 95%'ile 4.6 no data 95 4.6 0.016 0.008 0.259 0.184 53 no data 0.006 13.2 128 147 9.0 no data no data 24.5 no data no data no data (NIWA) Maximum 4.8 no data 114 4.8 0.017 0.008 0.259 0.192 57 no data 0.006 13.4 128 151 9.0 no data no data 25.4 no data 115.0 no data Mean 2.2 no data 24 2.3 0.010 0.004 0.163 0.067 19 no data 0.004 11.3 118 124 8.6 no data no data 17.8 no data 105.9 no data Std. Dev. 1.2 no data 28 1.1 0.003 0.003 0.056 0.067 16 no data 0.002 1.1 8 11 0.3 no data no data 4.5 no data 9.3 no data

Mohaka Rv at Raupunga Count 19 no data 19 19 19 19 19 19 19 no data 19 19 19 19 19 no data no data 19 no data 4 no data

144 Mohaka River Catchment

Appendix C Trend analysis results for water quality variables Sample Trend Trend Site Variable Period n Min Median Max p PAC

TN (mg⁄L) 28⁄1⁄04-15⁄2⁄13 37 0.055 0.256 0.600 0.395 2.2

TP (mg⁄L) 28⁄1⁄04-15⁄2⁄13 36 0.002 0.022 0.117 0.501 3.4

DIN (mg⁄L) 28⁄1⁄04-15⁄2⁄13 37 0.016 0.170 0.430 0.618 0.6

DRP (mg⁄L) 28⁄1⁄04-15⁄2⁄13 36 0.002 0.009 0.018 0.958 0.0

NO3 (mg⁄L) 28⁄1⁄04-15⁄2⁄13 37 0.005 0.145 0.410 0.842 0.7

BD 28⁄1⁄04-16⁄8⁄12 35 0.1 0.5 3.0 0.143 -4.3 Turbidity final Mohaka Rv (NTU) 28⁄1⁄04-16⁄8⁄12 34 0.9 7.9 143.0 0.038 18.9 at Raupunga ECOLI (cfu⁄100mL) 24⁄8⁄04-16⁄8⁄12 31 1 14 40 0.083 8.3 (quarterly) DIN⁄DRP 28⁄1⁄04-15⁄2⁄13 36 7.6 20.9 141.0 1.000 -0.3

NH3 (mg⁄L) 28⁄1⁄04-15⁄2⁄13 37 0.005 0.005 0.070 0.161 0.0

SS (mg⁄L) 28⁄1⁄04-26⁄2⁄13 37 1.5 11.1 185.0 0.190 14.8

TOC (mg⁄L) 28⁄1⁄04-30⁄5⁄12 33 0.5 2.0 4.3 0.032 10.0

TON (mg⁄L) 28⁄1⁄04-15⁄2⁄13 36 0.050 0.070 0.290 0.380 0.0 ECFINAL (uS⁄cm) 28⁄1⁄04-16⁄8⁄12 35 83 111 140 0.626 -0.4

HDT (mg⁄L) 28⁄1⁄04-16⁄5⁄12 34 29 38 46 0.208 1.3

TN (mg⁄L) 13⁄1⁄04-4⁄12⁄13 119 0.078 0.228 1.011 0.240 1.1

TP (mg⁄L) 13⁄1⁄04-4⁄12⁄13 119 0.005 0.018 0.453 0.813 0.0

DIN (mg⁄L) 13⁄1⁄04-4⁄12⁄13 120 0.002 0.142 0.675 0.140 1.6

DRP (mg⁄L) 13⁄1⁄04-4⁄12⁄13 119 0.001 0.008 0.026 0.542 0.0

NO3 (mg⁄L)

BD 13⁄1⁄04-4⁄12⁄13 118 0.0 0.9 4.8 0.979 0.0 Turbidity final Mohaka Rv (NTU) 13⁄1⁄04-4⁄12⁄13 120 0.5 4.5 274.0 0.187 2.4 at Raupunga ECOLI (NIWA) (cfu⁄100mL) 8⁄2⁄05-4⁄12⁄13 107 1 16 14136 0.951 0.0

DIN⁄DRP 13⁄1⁄04-4⁄12⁄13 119 0.7 17.1 71.0 0.015 3.8

NH3 (mg⁄L) 13⁄1⁄04-4⁄12⁄13 120 0.001 0.004 0.018 0.161 0.0

SS (mg⁄L)

TOC (mg⁄L)

TON (mg⁄L) ECFINAL (uS⁄cm) 13⁄1⁄04-4⁄12⁄13 120 89 117 413 0.000 1.7

Mohaka River Catchment

HDT (mg⁄L) Trend Trend Site Variable Sample Period n Min Median Max p PAC

TN (mg⁄L) 13⁄1⁄04-4⁄12⁄13 120 0.196 0.314 0.951 0.000 3.3

TP (mg⁄L) 13⁄1⁄04-4⁄12⁄13 120 0.004 0.011 0.379 0.191 -1.8

DIN (mg⁄L) 13⁄1⁄04-4⁄12⁄13 120 0.099 0.240 0.467 0.000 4.2

DRP (mg⁄L) 13⁄1⁄04-4⁄12⁄13 119 0.001 0.005 0.014 0.935 0.0

NO3 (mg⁄L) No Data

BD 13⁄1⁄04-4⁄12⁄13 120 0.1 2.8 8.4 0.380 1.3 Turbidity final Mohaka Rv (NTU) 13⁄1⁄04-4⁄12⁄13 120 0.3 1.1 173.0 0.043 3.8 ECOLI at SH5 (cfu⁄100mL) 8⁄2⁄05-4⁄12⁄13 107 1 20 3076 0.715 -2.1 (NIWA) DIN⁄DRP 13⁄1⁄04-4⁄12⁄13 119 11.2 46.0 414.0 0.042 3.9

NH3 (mg⁄L) 13⁄1⁄04-4⁄12⁄13 120 0.001 0.004 0.015 0.958 0.0

SS (mg⁄L) No Data

TOC (mg⁄L) No Data

TON (mg⁄L) No Data ECFINAL (uS⁄cm) 13⁄1⁄04-4⁄12⁄13 120 59 87 218 0.008 1.2

HDT (mg⁄L) No Data

TN (mg⁄L) 28⁄1⁄04-16⁄8⁄12 35 0.119 0.300 1.178 0.357 1.3

TP (mg⁄L) 28⁄1⁄04-16⁄8⁄12 35 0.012 0.032 0.892 0.586 2.6

DIN (mg⁄L) 28⁄1⁄04-16⁄8⁄12 35 0.035 0.182 0.340 0.233 1.6

DRP (mg⁄L) 28⁄1⁄04-16⁄8⁄12 35 0.002 0.008 0.027 1.000 0.0

NO3 (mg⁄L) 28⁄1⁄04-16⁄8⁄12 35 0.017 0.166 0.320 0.302 1.4

BD 28⁄1⁄04-16⁄8⁄12 35 0.1 0.4 3.2 0.176 -7.4 Turbidity final Mohaka Rv (NTU) 28⁄1⁄04-16⁄8⁄12 34 0.9 8.6 753.8 0.034 16.0 at Willowflat ECOLI (cfu⁄100mL) 24⁄8⁄04-16⁄8⁄12 31 1 8 211 0.014 18.2 (quarterly) DIN⁄DRP 28⁄1⁄04-16⁄8⁄12 35 5.4 24.0 131.5 0.552 1.9

NH3 (mg⁄L) 28⁄1⁄04-16⁄8⁄12 35 0.005 0.005 0.068 0.504 0.0

SS (mg⁄L) 28⁄1⁄04-16⁄8⁄12 35 1.5 24.0 1514.5 0.104 7.4

TOC (mg⁄L) 28⁄1⁄04-30⁄5⁄12 34 0.5 1.8 4.3 0.000 14.9

TON (mg⁄L) 28⁄1⁄04-16⁄8⁄12 35 0.050 0.079 0.690 1.000 0.0 ECFINAL (uS⁄cm) 28⁄1⁄04-16⁄8⁄12 35 73 101 134 0.213 -1.2

HDT (mg⁄L) 28⁄1⁄04-16⁄5⁄12 34 25 34 48 0.690 0.5

146 Mohaka River Catchment

Trend Trend Site Variable Sample Period n Min Median Max p PAC

TN (mg⁄L) 17⁄8⁄09-13⁄12⁄13 42 0.210 0.366 0.530 0.525 -2.7

TP (mg⁄L) 17⁄8⁄09-13⁄12⁄13 47 0.002 0.008 0.154 0.178 -4.2

DIN (mg⁄L) 17⁄8⁄09-13⁄12⁄13 46 0.170 0.282 0.550 0.924 -2.5

DRP (mg⁄L) 17⁄8⁄09-13⁄12⁄13 47 0.002 0.005 0.011 0.920 0.0

NO3 (mg⁄L) 17⁄8⁄09-13⁄12⁄13 46 0.160 0.270 0.540 0.631 -3.7

BD 17⁄8⁄09-13⁄12⁄13 45 0.1 2.3 7.5 0.002 19.5 Turbidity final Mohaka Rv (NTU) 17⁄8⁄09-13⁄12⁄13 45 0.2 1.2 24.0 0.851 -1.3 ECOLI D⁄S Ripia (cfu⁄100mL) 17⁄8⁄09-13⁄12⁄13 47 1 8 620 0.635 3.1 Rv DIN⁄DRP 17⁄8⁄09-13⁄12⁄13 46 18.5 62.7 251.0 0.924 -1.5

NH3 (mg⁄L) 17⁄8⁄09-13⁄12⁄13 47 0.005 0.005 0.070 0.233 0.0

SS (mg⁄L) 17⁄8⁄09-13⁄12⁄13 47 1.5 1.5 114.0 0.046 0.0

TOC (mg⁄L) 17⁄8⁄09-17⁄5⁄12 25 0.5 1.4 15.1 0.397 -4.6

TON (mg⁄L) 17⁄8⁄09-6⁄11⁄13 42 0.050 0.050 0.340 0.782 0.0 ECFINAL (uS⁄cm) 17⁄8⁄09-13⁄12⁄13 47 39 68 93 0.457 2.9

HDT (mg⁄L) 17⁄8⁄09-21⁄6⁄12 29 11 19 24 0.575 -1.6

TN (mg⁄L) 31⁄3⁄08-19⁄12⁄13 60 0.310 0.692 1.162 0.412 3.9

TP (mg⁄L) 31⁄3⁄08-19⁄12⁄13 64 0.004 0.011 0.125 0.449 -3.7

DIN (mg⁄L) 31⁄3⁄08-19⁄12⁄13 64 0.249 0.620 1.072 0.233 3.9

DRP (mg⁄L) 31⁄3⁄08-19⁄12⁄13 64 0.002 0.004 0.015 0.948 0.0

NO3 (mg⁄L) 31⁄3⁄08-19⁄12⁄13 64 0.220 0.595 1.060 0.188 5.1

BD 31⁄3⁄08-19⁄12⁄13 61 0.3 2.1 5.3 0.466 6.0 Turbidity final Mohaka Rv (NTU) 31⁄3⁄08-19⁄12⁄13 62 0.4 1.3 15.9 0.080 9.2 ECOLI D⁄S Taharua (cfu⁄100mL) 31⁄3⁄08-19⁄12⁄13 63 1 9 320 0.519 2.2 Rv DIN⁄DRP 31⁄3⁄08-19⁄12⁄13 64 25.0 150.1 536.0 0.415 7.9

NH3 (mg⁄L) 31⁄3⁄08-19⁄12⁄13 64 0.005 0.005 0.031 0.047 0.0

SS (mg⁄L) 31⁄3⁄08-19⁄12⁄13 63 1.2 1.5 59.0 0.213 0.0

TOC (mg⁄L) 31⁄3⁄08-2⁄2⁄12 42 0.5 1.1 3.4 0.364 12.4

TON (mg⁄L) 31⁄3⁄08-19⁄12⁄13 59 0.050 0.050 0.200 0.126 0.0 ECFINAL (uS⁄cm) 31⁄3⁄08-19⁄12⁄13 61 37 62 89 0.231 2.7

HDT (mg⁄L) 31⁄3⁄08-2⁄5⁄13 48 9 15 20 0.411 3.2

Mohaka River Catchment 147

Trend Trend Site Variable Sample Period n Min Median Max p PAC

TN (mg⁄L) 17⁄8⁄09-13⁄12⁄13 50 0.150 0.332 0.937 0.113 -6.9

TP (mg⁄L) 17⁄8⁄09-13⁄12⁄13 51 0.002 0.015 1.060 0.000 -28.9

DIN (mg⁄L) 17⁄8⁄09-13⁄12⁄13 51 0.038 0.233 0.592 0.488 -1.7

DRP (mg⁄L) 17⁄8⁄09-13⁄12⁄13 51 0.002 0.006 0.014 0.641 0.0

NO3 (mg⁄L) 17⁄8⁄09-13⁄12⁄13 51 0.026 0.220 0.580 0.254 -3.6

BD 17⁄8⁄09-13⁄12⁄13 46 0.1 1.2 6.9 0.007 25.7 Turbidity final Mohaka Rv (NTU) 17⁄8⁄09-13⁄12⁄13 51 0.2 3.4 910.0 0.261 -8.3 D⁄S ECOLI Waipunga (cfu⁄100mL) 17⁄8⁄09-13⁄12⁄13 51 1 8 460 0.539 12.4 Rv DIN⁄DRP 17⁄8⁄09-13⁄12⁄13 51 13.4 41.9 181.3 0.437 -5.6

NH3 (mg⁄L) 17⁄8⁄09-13⁄12⁄13 51 0.005 0.005 0.087 0.208 0.0

SS (mg⁄L) 17⁄8⁄09-13⁄12⁄13 51 1.5 5.0 1400.0 0.000 -31.0

TOC (mg⁄L) 17⁄8⁄09-17⁄5⁄12 29 0.5 2.3 3.5 0.463 -9.0

TON (mg⁄L) 17⁄8⁄09-6⁄11⁄13 49 0.050 0.060 0.750 0.164 0.0 ECFINAL (uS⁄cm) 17⁄8⁄09-13⁄12⁄13 50 58 87 121 0.423 2.7

HDT (mg⁄L) 17⁄8⁄09-21⁄6⁄12 33 18 29 37 0.868 -4.3

TN (mg⁄L) 17⁄1⁄08-19⁄12⁄13 61 0.055 0.119 0.365 0.001 -9.8

TP (mg⁄L) 17⁄1⁄08-19⁄12⁄13 65 0.002 0.006 0.048 0.282 5.9

DIN (mg⁄L) 17⁄1⁄08-19⁄12⁄13 65 0.012 0.043 0.290 0.662 -1.5

DRP (mg⁄L) 17⁄1⁄08-19⁄12⁄13 65 0.002 0.002 0.009 0.766 0.0

NO3 (mg⁄L) 17⁄1⁄08-19⁄12⁄13 65 0.001 0.028 0.280 1.000 0.0

BD 21⁄2⁄08-19⁄12⁄13 62 0.2 4.2 8.1 0.191 5.7 Turbidity final Mohaka Rv (NTU) 17⁄1⁄08-19⁄12⁄13 63 0.2 0.7 11.9 0.302 8.6 U⁄S ECOLI Taharua (cfu⁄100mL) 17⁄1⁄08-19⁄12⁄13 64 1 2 140 0.020 24.9 Rv DIN⁄DRP 17⁄1⁄08-19⁄12⁄13 65 2.4 12.3 105.0 0.534 -3.8

NH3 (mg⁄L) 17⁄1⁄08-19⁄12⁄13 65 0.005 0.005 0.062 0.039 0.0

SS (mg⁄L) 17⁄1⁄08-19⁄12⁄13 64 1.5 1.5 24.0 0.550 0.0

TOC (mg⁄L) 17⁄1⁄08-2⁄2⁄12 43 0.5 0.9 4.6 0.118 9.2

TON (mg⁄L) 17⁄1⁄08-19⁄12⁄13 60 0.050 0.050 0.270 0.088 0.0 ECFINAL (uS⁄cm) 17⁄1⁄08-19⁄12⁄13 62 28 46 67 0.947 0.6

HDT (mg⁄L) 17⁄1⁄08-2⁄5⁄13 49 8 12 18 0.726 -0.9

148 Mohaka River Catchment

Trend Trend Site Variable Sample Period n Min Median Max p PAC

TN (mg⁄L) 10⁄5⁄04-16⁄11⁄13 36 0.055 0.138 0.322 0.878 0.1

TP (mg⁄L) 10⁄5⁄04-16⁄11⁄13 39 0.010 0.019 0.035 0.012 -2.7

DIN (mg⁄L) 10⁄5⁄04-16⁄11⁄13 39 0.007 0.048 0.232 0.580 0.8

DRP (mg⁄L) 10⁄5⁄04-16⁄11⁄13 39 0.005 0.014 0.021 0.032 -3.2

NO3 (mg⁄L) 10⁄5⁄04-16⁄11⁄13 39 0.001 0.036 0.220 1.000 0.0

BD 10⁄5⁄04-16⁄11⁄13 38 0.3 2.6 5.2 0.507 2.0 Turbidity final Mokomokonui (NTU) 10⁄5⁄04-16⁄11⁄13 39 0.1 1.4 13.3 0.434 2.9 Rv ECOLI (cfu⁄100mL) 24⁄8⁄04-16⁄11⁄13 38 1 5 32 0.018 10.1 (quarterly) DIN⁄DRP 10⁄5⁄04-16⁄11⁄13 39 0.5 3.6 19.2 0.072 5.2

NH3 (mg⁄L) 10⁄5⁄04-16⁄11⁄13 39 0.005 0.005 0.033 1.000 0.0

SS (mg⁄L) 10⁄5⁄04-16⁄11⁄13 39 1.5 1.5 32.0 0.481 0.0

TOC (mg⁄L) 10⁄5⁄04-8⁄11⁄11 31 0.5 1.4 8.1 0.475 3.1

TON (mg⁄L) 10⁄5⁄04-16⁄8⁄13 35 0.050 0.050 0.140 0.098 0.0 ECFINAL (uS⁄cm) 10⁄5⁄04-16⁄11⁄13 39 53 72 89 1.000 0.0

HDT (mg⁄L) 10⁄5⁄04-15⁄5⁄12 33 13 21 30 0.671 0.0

TN (mg⁄L) 28⁄1⁄04-16⁄11⁄13 39 0.055 0.165 0.528 0.003 -5.0

TP (mg⁄L) 28⁄1⁄04-16⁄11⁄13 40 0.004 0.013 0.067 0.014 -6.0

DIN (mg⁄L) 28⁄1⁄04-16⁄11⁄13 40 0.013 0.103 0.268 0.324 -3.6

DRP (mg⁄L) 28⁄1⁄04-16⁄11⁄13 39 0.002 0.007 0.015 0.136 -4.1

NO3 (mg⁄L) 28⁄1⁄04-16⁄11⁄13 40 0.003 0.079 0.227 0.179 -4.9

BD 28⁄1⁄04-16⁄11⁄13 39 0.3 2.3 6.0 0.355 4.2 Turbidity final Ripia Rv U⁄S (NTU) 28⁄1⁄04-16⁄11⁄13 39 0.4 1.2 14.0 0.459 3.3 Mohaka Rv ECOLI (cfu⁄100mL) 25⁄8⁄04-16⁄11⁄13 38 1 7 3100 0.408 5.2 (quarterly) DIN⁄DRP 28⁄1⁄04-16⁄11⁄13 39 2.8 15.2 115.0 0.853 0.6

NH3 (mg⁄L) 28⁄1⁄04-16⁄11⁄13 40 0.005 0.005 0.110 0.382 0.0

SS (mg⁄L) 28⁄1⁄04-16⁄11⁄13 40 1.5 3.0 64.0 0.179 0.0

TOC (mg⁄L) 28⁄1⁄04-17⁄5⁄12 33 0.6 1.5 14.2 0.038 6.1

TON (mg⁄L) 28⁄1⁄04-16⁄11⁄13 38 0.050 0.050 0.390 0.114 0.0 ECFINAL (uS⁄cm) 28⁄1⁄04-16⁄11⁄13 40 50 65 78 0.501 -0.5

HDT (mg⁄L) 28⁄1⁄04-17⁄5⁄12 34 12 18 24 0.457 -1.1

Mohaka River Catchment 149

Trend Trend Site Variable Sample Period n Min Median Max p PAC

TN (mg⁄L) 29⁄3⁄12-19⁄12⁄13 8 1.960 2.300 2.600 0.548 2.4

TP (mg⁄L) 6⁄9⁄10-9⁄9⁄13 8 0.010 0.012 0.053 0.452 28.7

DIN (mg⁄L) 6⁄9⁄10-19⁄12⁄13 10 1.521 2.212 2.512 0.371 9.5

DRP (mg⁄L) 6⁄9⁄10-19⁄12⁄13 10 0.007 0.010 0.012 1.000 0.0

NO3 (mg⁄L) 6⁄9⁄10-19⁄12⁄13 10 1.480 2.200 2.500 0.371 9.5

BD Turbidity final Taharua (NTU) 6⁄9⁄10-19⁄12⁄13 6 0.7 1.3 13.1 0.500 -40.4 ECOLI Rv at (cfu⁄100mL) Henry's Br DIN⁄DRP 6⁄9⁄10-19⁄12⁄13 10 138.3 216.3 358.9 0.371 11.1

NH3 (mg⁄L) 6⁄9⁄10-19⁄12⁄13 10 0.005 0.005 0.041 1.000 0.0

SS (mg⁄L) 6⁄9⁄10-19⁄12⁄13 10 1.5 1.5 99.0 0.480 0.0

TOC (mg⁄L)

TON (mg⁄L) 19⁄4⁄12-19⁄12⁄13 6 0.050 0.050 0.100 0.500 0.0 ECFINAL (uS⁄cm)

HDT (mg⁄L)

TN (mg⁄L) 28⁄1⁄04-17⁄10⁄13 88 0.933 1.559 2.552 0.000 3.9

TP (mg⁄L) 28⁄1⁄04-17⁄10⁄13 93 0.010 0.022 0.240 0.409 -0.8

DIN (mg⁄L) 28⁄1⁄04-17⁄10⁄13 93 0.783 1.460 2.310 0.000 4.8

DRP (mg⁄L) 28⁄1⁄04-17⁄10⁄13 93 0.002 0.011 0.033 0.065 -3.1

NO3 (mg⁄L) 28⁄1⁄04-17⁄10⁄13 93 0.771 1.440 2.300 0.000 4.9

BD 28⁄1⁄04-17⁄10⁄13 90 0.2 1.5 4.0 0.040 -4.9 Turbidity final Taharua (NTU) 28⁄1⁄04-17⁄10⁄13 91 0.3 1.7 31.4 0.039 5.6 Rv at ECOLI Poronui (cfu⁄100mL) 24⁄8⁄04-17⁄10⁄13 90 1 8 1300 0.145 8.9 Stn DIN⁄DRP 28⁄1⁄04-17⁄10⁄13 93 32.0 131.8 980.0 0.005 9.2

NH3 (mg⁄L) 28⁄1⁄04-17⁄10⁄13 93 0.005 0.005 0.100 0.848 0.0

SS (mg⁄L) 28⁄1⁄04-17⁄10⁄13 92 1.5 8.4 84.5 0.148 5.9

TOC (mg⁄L) 28⁄1⁄04-2⁄2⁄12 84 0.5 1.0 12.0 0.636 1.2

TON (mg⁄L) 28⁄1⁄04-17⁄10⁄13 88 0.050 0.090 1.060 0.771 0.0 ECFINAL (uS⁄cm) 28⁄1⁄04-17⁄10⁄13 92 49 78 122 0.197 0.7

HDT (mg⁄L) 28⁄1⁄04-9⁄5⁄12 88 11 18 24 0.053 1.3

150 Mohaka River Catchment

Trend Trend Site Variable Sample Period n Min Median Max p PAC

TN (mg⁄L) 31⁄3⁄08-19⁄12⁄13 61 0.710 1.432 1.912 0.094 3.0

TP (mg⁄L) 31⁄3⁄08-19⁄12⁄13 63 0.008 0.017 0.072 0.266 -3.0

DIN (mg⁄L) 31⁄3⁄08-19⁄12⁄13 63 0.592 1.305 1.822 0.003 4.8

DRP (mg⁄L) 31⁄3⁄08-19⁄12⁄13 63 0.002 0.007 0.015 1.000 0.0

NO3 (mg⁄L) 31⁄3⁄08-19⁄12⁄13 63 0.580 1.300 1.810 0.002 4.8

BD 31⁄3⁄08-28⁄11⁄13 57 0.2 1.8 4.5 0.190 3.8 Turbidity final Taharua (NTU) 31⁄3⁄08-19⁄12⁄13 62 0.1 1.9 16.9 0.135 11.1 ECOLI Rv at Red (cfu⁄100mL) 31⁄3⁄08-19⁄12⁄13 62 1 13 470 0.433 7.0 Hut DIN⁄DRP 31⁄3⁄08-19⁄12⁄13 63 39.5 200.2 901.0 0.304 7.8

NH3 (mg⁄L) 31⁄3⁄08-19⁄12⁄13 63 0.005 0.005 0.068 0.786 0.0

SS (mg⁄L) 31⁄3⁄08-19⁄12⁄13 62 1.3 4.1 62.0 0.228 0.0

TOC (mg⁄L) 31⁄3⁄08-2⁄2⁄12 41 0.5 1.1 4.9 0.197 11.5

TON (mg⁄L) 31⁄3⁄08-19⁄12⁄13 60 0.050 0.100 0.270 0.404 -4.5 ECFINAL (uS⁄cm) 31⁄3⁄08-19⁄12⁄13 60 44 78 105 0.152 1.3

HDT (mg⁄L) 31⁄3⁄08-2⁄5⁄13 47 10 18 22 0.263 1.7

TN (mg⁄L) 28⁄1⁄04-19⁄12⁄13 103 2.490 3.330 4.903 0.000 3.4

TP (mg⁄L) 28⁄1⁄04-19⁄12⁄13 104 0.006 0.021 0.141 0.039 -2.8

DIN (mg⁄L) 28⁄1⁄04-19⁄12⁄13 103 2.400 3.223 4.813 0.000 3.9

DRP (mg⁄L) 28⁄1⁄04-19⁄12⁄13 104 0.002 0.014 0.122 0.102 -2.6

NO3 (mg⁄L) 28⁄1⁄04-19⁄12⁄13 103 2.390 3.200 4.800 0.000 3.9

BD 28⁄1⁄04-19⁄12⁄13 96 0.3 3.0 9.1 0.231 2.0 Turbidity final Taharua (NTU) 28⁄1⁄04-19⁄12⁄13 104 0.1 0.8 12.5 0.049 4.9 ECOLI Rv at Twin (cfu⁄100mL) 24⁄8⁄04-19⁄12⁄13 101 1 11 1500 0.144 3.8 Culv DIN⁄DRP 28⁄1⁄04-19⁄12⁄13 103 28.0 230.0 1805.0 0.000 7.4

NH3 (mg⁄L) 28⁄1⁄04-19⁄12⁄13 104 0.005 0.005 0.088 0.161 0.0

SS (mg⁄L) 28⁄1⁄04-19⁄12⁄13 104 1.5 2.6 48.0 0.228 0.0

TOC (mg⁄L) 28⁄1⁄04-2⁄2⁄12 83 0.5 0.8 5.5 0.143 3.4

TON (mg⁄L) 28⁄1⁄04-19⁄12⁄13 100 0.050 0.090 0.481 0.020 -2.3 ECFINAL (uS⁄cm) 28⁄1⁄04-19⁄12⁄13 103 11 101 168 0.000 1.9

HDT (mg⁄L) 28⁄1⁄04-11⁄4⁄13 88 15 23 28 0.000 2.9

Mohaka River Catchment 151

Trend Trend Site Variable Sample Period n Min Median Max p PAC

TN (mg⁄L) 28⁄1⁄04-19⁄12⁄13 100 2.200 3.100 4.640 0.004 2.3

TP (mg⁄L) 28⁄1⁄04-19⁄12⁄13 102 0.009 0.020 0.149 0.026 -2.5

DIN (mg⁄L) 28⁄1⁄04-19⁄12⁄13 101 2.212 2.940 4.410 0.000 2.5

DRP (mg⁄L) 28⁄1⁄04-19⁄12⁄13 102 0.002 0.016 0.110 0.025 -2.5

NO3 (mg⁄L) 28⁄1⁄04-19⁄12⁄13 101 2.200 2.900 4.400 0.000 2.6

BD 28⁄1⁄04-19⁄12⁄13 97 0.3 4.1 10.0 0.002 5.2 Turbidity final Taharua (NTU) 28⁄1⁄04-19⁄12⁄13 102 0.1 0.6 10.0 0.010 7.9 ECOLI Rv at (cfu⁄100mL) 24⁄8⁄04-19⁄12⁄13 100 1 8 1200 0.865 0.0 Wairango DIN⁄DRP 28⁄1⁄04-19⁄12⁄13 100 31.3 180.3 1455.0 0.002 5.4

NH3 (mg⁄L) 28⁄1⁄04-19⁄12⁄13 103 0.005 0.005 0.140 0.011 0.0

SS (mg⁄L) 28⁄1⁄04-19⁄12⁄13 103 1.5 1.5 13.0 0.364 0.0

TOC (mg⁄L) 28⁄1⁄04-2⁄2⁄12 83 0.5 0.9 20.3 0.008 11.0

TON (mg⁄L) 28⁄1⁄04-19⁄12⁄13 96 0.050 0.087 0.633 0.176 0.0 ECFINAL (uS⁄cm) 28⁄1⁄04-19⁄12⁄13 103 89 100 174 0.000 1.0

HDT (mg⁄L) 28⁄1⁄04-11⁄4⁄13 87 18 23 29 0.000 2.2

TN (mg⁄L) 28⁄1⁄04-16⁄11⁄13 39 0.450 0.610 0.816 0.115 1.9

TP (mg⁄L) 28⁄1⁄04-16⁄11⁄13 40 0.007 0.017 0.035 0.002 -4.0

DIN (mg⁄L) 28⁄1⁄04-16⁄11⁄13 39 0.360 0.492 0.670 0.001 3.7

DRP (mg⁄L) 28⁄1⁄04-16⁄11⁄13 40 0.002 0.007 0.016 0.155 -3.0

NO3 (mg⁄L) 28⁄1⁄04-16⁄11⁄13 39 0.350 0.470 0.660 0.001 4.3

BD 28⁄1⁄04-16⁄11⁄13 39 0.5 1.5 3.5 0.331 2.0 Turbidity final Waiarua (NTU) 28⁄1⁄04-16⁄11⁄13 40 1.0 2.1 4.3 0.003 6.2 Strm ECOLI (cfu⁄100mL) 24⁄8⁄04-16⁄11⁄13 38 1 8 65 0.595 2.0 (quarterly) DIN⁄DRP 28⁄1⁄04-16⁄11⁄13 39 26.1 84.2 325.0 0.002 7.3

NH3 (mg⁄L) 28⁄1⁄04-16⁄11⁄13 40 0.005 0.005 0.046 0.070 0.0

SS (mg⁄L) 28⁄1⁄04-16⁄11⁄13 39 1.5 6.0 46.0 1.000 0.0

TOC (mg⁄L) 28⁄1⁄04-8⁄11⁄11 32 0.5 1.3 3.0 0.039 6.9

TON (mg⁄L) 28⁄1⁄04-16⁄8⁄13 38 0.050 0.050 0.390 0.137 0.0 ECFINAL (uS⁄cm) 28⁄1⁄04-16⁄11⁄13 40 63 81 98 0.053 0.8

HDT (mg⁄L) 28⁄1⁄04-15⁄5⁄12 34 11 16 20 0.055 0.8

152 Mohaka River Catchment

Trend Trend Site Variable Sample Period n Min Median Max p PAC

TN (mg⁄L) 28⁄1⁄04-15⁄2⁄13 35 0.102 0.333 0.551 0.004 -5.3

TP (mg⁄L) 28⁄1⁄04-15⁄2⁄13 36 0.005 0.019 0.041 0.124 -2.4

DIN (mg⁄L) 28⁄1⁄04-15⁄2⁄13 37 0.065 0.245 0.461 0.011 -8.0

DRP (mg⁄L) 28⁄1⁄04-15⁄2⁄13 37 0.002 0.007 0.018 0.424 -4.8

NO3 (mg⁄L) 28⁄1⁄04-15⁄2⁄13 37 0.047 0.220 0.450 0.029 -8.1

BD 28⁄1⁄04-9⁄1⁄13 34 0.4 1.3 4.8 0.487 -3.4 Waipunga Turbidity final Rv at (NTU) 28⁄1⁄04-9⁄1⁄13 35 0.5 1.9 6.0 0.031 6.5 Pohokura ECOLI Rd (cfu⁄100mL) 24⁄8⁄04-9⁄1⁄13 33 1 4 26 0.511 0.0

(quarterly) DIN⁄DRP 28⁄1⁄04-15⁄2⁄13 37 7.6 33.8 195.0 0.182 -7.6 NH3 (mg⁄L) 28⁄1⁄04-15⁄2⁄13 37 0.005 0.005 0.160 0.194 0.0

SS (mg⁄L) 28⁄1⁄04-15⁄2⁄13 37 1.5 7.7 32.0 0.425 5.5

TOC (mg⁄L) 28⁄1⁄04-8⁄11⁄11 30 0.5 1.0 12.6 0.456 4.1

TON (mg⁄L) 28⁄1⁄04-15⁄2⁄13 34 0.050 0.050 0.180 0.922 0.0 ECFINAL (uS⁄cm) 28⁄1⁄04-9⁄1⁄13 34 49 62 74 0.836 -0.2

HDT (mg⁄L) 28⁄1⁄04-15⁄5⁄12 31 8 13 18 0.943 0.0

The tables presented in Appendix C present the state and trend of water quality variables from sites within the Mohaka catchment. The minima, medians and maxima are given for each variable at each site for the sample period indicated. Sample periods in amber indicate the time period covered less than 8 out of the 10 years from Jan 2004 to Dec 2013, and caution should be exercised when comparing these results to other sites with longer records. We explored whether any trends over time were evident by using Seasonal Kendall tests with a significance level (α) of 0.05. Sen slope was used to estimate the Percent Annual Change (PAC) and gives an indication of the magnitude of change over time. A statistically significant (p < 0.05, in bold) change of 1% or more was considered “meaningful”. Cells are coloured blue when a meaningfully significant improvement in water quality was observed (“sig better”), and are coloured red when a meaningfully significant deterioration in water quality was observed (“sig worse”). Cells are shaded grey when the direction of change in the variable of interest is neither intuitively good nor bad (e.g. conductivity, DIN/DRP).

Mohaka River Catchment 153

Appendix D Regional ranking tables for select water quality variables Tables in the following pages are coloured and coded in line with the major regional water management zones identified below. Letters relate to:

154 Mohaka River Catchment

Median Sample Reporting Median Sample Reporting Site Rank Catchment Site Rank Catchment TN size (n) Zone TN size (n) Zone Regional SoE sites Ngaruroro Rv at Kuripapango (NIWA) 0.046 60 1 Ngaruroro C Mangatewai Strm at SH50 0.440 14 53 Tukituki B Taruarau Rv 0.055 14 2 Ngaruroro C Mangatutu Strm 0.460 18 54 Tutaekuri C ranked by median Mokau Strm 0.055 12 2 Wairoa F Mangaone Rv at Rissington 0.470 37 55 Tutaekuri C total nitrogen 2009- Makaroro Rv (NIWA) 0.086 60 4 Tukituki B Mangamahaki Strm 0.524 12 56 Tukituki B Tutaekuri Rv at Lawrence Hut 0.102 34 5 Tutaekuri C Mangarau Strm at Keirunga Rd 0.534 17 57 Karamu/Clive C 2013 Mohaka Rv U⁄S Taharua Rv 0.109 61 6 Mohaka E Opoutama Strm 0.559 18 58 Northern Coastal F Ngaruroro Rv at Whanawhana 0.110 33 7 Ngaruroro C Maraetotara Rv at Te Awanga 0.586 31 59 Maraetotara / Waimarama A Waikaretaheke Rv 0.116 13 8 Wairoa F Taurekaitai Strm 0.620 31 60 Porangahau A Aniwaniwa Strm 0.117 29 9 Wairoa F Maraekakaho Strm 0.646 14 61 Ngaruroro C Waiau Rv 0.120 25 10 Wairoa F Herehere Strm 0.660 32 62 Karamu/Clive C TN (mg/l), 2009-2013, Ripia Rv U⁄S Mohaka Rv 0.134 36 11 Mohaka E Mahiaruhe Strm 0.670 11 63 Aropoanui D with colours signifying Mokomokonui Rv 0.136 28 12 Mohaka E Waiarua Strm 0.670 34 63 Mohaka E Ngaruroro Rv U⁄S HB Dairies 0.141 16 13 Ngaruroro C Poporangi Strm 0.688 14 65 Ngaruroro C reporting zone. Lower Ngaruroro Rv at Chesterhope (NIWA) 0.173 60 14 Ngaruroro C Waipawa Rv 50m U⁄S oxi pond 0.695 44 66 Tukituki B ranks are ‘better’. Tukituki Rv at SH50 0.175 64 15 Tukituki B Sandy Ck 0.700 35 67 Aropoanui D Ngaruroro Rv D⁄S HB Dairies 0.180 33 16 Ngaruroro C Waipawa Rv U⁄S Tukituki Rv 0.705 44 68 Tukituki B Medians generated Tutaekuri Rv at Puketapu 0.180 13 16 Tutaekuri C Mohaka Rv D⁄S Taharua Rv 0.721 64 69 Mohaka E from sample sizes of at Anaura Strm 0.189 15 18 Waikari D Waipawa Rv at SH2 0.740 58 70 Tukituki B least 30 are considered Te Kumi Strm 0.193 17 19 Wairoa F Waipawa Rv 400m D⁄S oxi pond 0.750 44 71 Tukituki B Ngaruroro Rv at Fernhill 0.212 32 20 Ngaruroro C Tukituki Rv at Black Br 0.783 58 72 Tukituki B robust (Snelder pers. Ngaruroro Rv at Ohiti 0.213 16 21 Ngaruroro C Tukituki Rv at Red Br 0.783 64 72 Tukituki B comm. 2014). Medians Tukituki Rv at Waipukurau Ongaonga Rd 0.219 14 22 Tukituki B Ohiwa Strm 0.785 13 74 Ngaruroro C Waipawa Rv at SH50 0.220 58 23 Tukituki B Ruahapia Strm 0.850 17 75 Karamu/Clive C generated from sample Mangaone Rv at Dartmoor 0.240 13 24 Tutaekuri C Tukituki Rv at Red Br (NIWA) 0.874 60 76 Tukituki B sizes less than 30 Ngaruroro Rv at Motorway 0.240 17 24 Ngaruroro C Pouhokio Strm 0.937 32 77 Maraetotara / Waimarama A Mohaka Rv at Raupunga (NIWA) 0.244 60 26 Mohaka E Mangatarata Strm 0.978 58 78 Tukituki B should be treated with Tutaekuri Rv at Brookfields Br 0.250 31 27 Tutaekuri C Taipo Strm 0.980 31 79 Karamu/Clive C caution. Tutaekuri Rv U⁄S Mangaone Rv 0.251 32 28 Tutaekuri C Tukipo Rv at SH50 1.008 62 80 Tukituki B Kopuawhara Strm 0.261 31 29 Northern Coastal F Clive Rv 1.034 31 81 Karamu/Clive C Wairoa Rv U⁄S Wairoa 0.265 27 30 Wairoa F Maraetotara Rv at Waimarama Rd 1.039 31 82 Maraetotara / Waimarama A Ruakituri Rv 0.269 30 31 Wairoa F Tukituki Rv at Tamumu Br 1.100 57 83 Tukituki B Makaretu Rv at SH50 0.278 59 32 Tukituki B Tukituki Rv at SH2 1.220 78 84 Tukituki B Arawapanui Rv 0.290 31 33 Aropoanui D Mangarau Strm at Te Aute Rd 1.260 23 85 Karamu/Clive C Waipunga Rv at Pohokura Rd 0.293 24 34 Mohaka E Papanui Strm 1.345 35 86 Tukituki B Mohaka Rv at Willowflat 0.295 35 35 Mohaka E Tukipo Rv U⁄S Makaretu Rv 1.370 13 87 Tukituki B Te Iringaowhare Strm 0.295 5 35 Wairoa F Taharua Rv at Red Hut 1.450 62 88 Mohaka E Mohaka Rv at Raupunga 0.298 42 37 Mohaka E Tukituki Rv at Tapairu Rd 1.460 49 89 Tukituki B Mangaorapa Strm 0.300 31 38 Porangahau A Poukawa Strm 1.460 39 89 Karamu/Clive C Mangakuri Rv 0.310 31 39 Southern Coastal A Tukituki Rv 50m U⁄S oxi pond 1.540 44 91 Tukituki B Makaretu Rv U⁄S Maharakeke Strm 0.327 14 40 Tukituki B Porangahau Strm 1.780 63 92 Tukituki B Porangahau Rv 0.332 29 41 Porangahau A Taharua Rv at Poronui Stn 1.852 42 93 Mohaka E Mohaka Rv D⁄S Waipunga Rv 0.332 52 41 Mohaka E Maharakeke Strm U⁄S Makaretu Rv 1.864 14 94 Tukituki B Waitio Strm 0.337 32 43 Ngaruroro C Tukituki Rv 400m D⁄S oxi pond 1.950 44 95 Tukituki B Mohaka Rv at SH5 (NIWA) 0.342 60 44 Mohaka E Mangaonuku Strm 2.072 57 96 Tukituki B Waikari Rv 0.353 31 45 Waikari D Maharakeke Strm at Limeworks Station Rd 2.087 14 97 Tukituki B Hangaroa Rv 0.355 28 46 Wairoa F Awanui Strm 2.100 39 98 Karamu/Clive C Tutaekuri-Waimate Strm 0.368 29 47 Ngaruroro C Waingongoro Strm 2.117 32 99 Southern Coastal A Esk Rv at Waipunga Br 0.370 30 48 Esk D Taharua Rv at Henry's Br 2.302 17 100 Mohaka E Mohaka Rv D⁄S Ripia Rv 0.372 43 49 Mohaka E Karewarewa Strm 2.800 33 101 Karamu/Clive C Mangapoike Rv 0.379 25 50 Wairoa F Kahahakuri Strm 2.988 27 102 Tukituki B Esk Rv at Berry Rd 0.406 26 51 Esk D Taharua Rv at Wairango 3.403 58 103 Mohaka E Makara Strm 0.414 13 52 Tukituki B Taharua Rv at Twin Culv 3.700 60 104 Mohaka E

Mohaka River Catchment

Median Sample Reporting Median Sample Reporting Site Rank Catchment Site Rank Catchment TP size (n) Zone TP size (n) Zone Regional SoE sites Taruarau Rv 0.002 14 1 Ngaruroro C Tutaekuri Rv at Puketapu 0.021 13 53 Tutaekuri C Ngaruroro Rv at Whanawhana 0.003 34 2 Ngaruroro C Taharua Rv at Poronui Stn 0.021 46 53 Mohaka E ranked by median Ngaruroro Rv at Kuripapango (NIWA) 0.004 60 3 Ngaruroro C Tukituki Rv at Red Br (NIWA) 0.022 60 55 Tukituki B total phosphorus Tutaekuri Rv at Lawrence Hut 0.005 34 4 Tutaekuri C Waipawa Rv U⁄S Tukituki Rv 0.023 43 56 Tukituki B Ngaruroro Rv U⁄S HB Dairies 0.006 17 5 Ngaruroro C Tutaekuri Rv at Brookfields Br 0.023 31 56 Tutaekuri C 2009-2013 Mohaka Rv U⁄S Taharua Rv 0.006 65 5 Mohaka E Tukipo Rv U⁄S Makaretu Rv 0.024 13 58 Tukituki B Waipawa Rv at SH50 0.007 59 7 Tukituki B Tukituki Rv 50m U⁄S oxi pond 0.024 43 58 Tukituki B Aniwaniwa Strm 0.007 30 7 Wairoa F Mangatutu Strm 0.024 18 58 Tutaekuri C TP (mg/l), 2009-2013, Mokau Strm 0.007 11 7 Wairoa F Mohaka Rv at Raupunga 0.024 45 58 Mohaka E with colours signifying Waikaretaheke Rv 0.007 14 7 Wairoa F Hangaroa Rv 0.024 29 58 Wairoa F Makaroro Rv (NIWA) 0.008 60 11 Tukituki B Tukituki Rv at Tamumu Br 0.025 58 63 Tukituki B reporting zone. Lower Tukituki Rv at SH50 0.008 67 11 Tukituki B Esk Rv at Berry Rd 0.026 27 64 Esk D ranks are ‘better’. Ngaruroro Rv at Ohiti 0.008 17 11 Ngaruroro C Waikari Rv 0.026 32 64 Waikari D Ngaruroro Rv D⁄S HB Dairies 0.008 34 11 Ngaruroro C Mangaone Rv at Rissington 0.027 38 66 Tutaekuri C Medians generated Mohaka Rv D⁄S Ripia Rv 0.008 48 11 Mohaka E Tukipo Rv at SH50 0.028 63 67 Tukituki B from sample sizes of Tukituki Rv at Waipukurau Ongaonga Rd 0.009 14 16 Tukituki B Wairoa Rv U⁄S Wairoa 0.028 29 67 Wairoa F Anaura Strm 0.009 17 16 Waikari D Maraekakaho Strm 0.029 14 69 Ngaruroro C at least 30 are Kopuawhara Strm 0.009 31 16 Northern Coastal F Arawapanui Rv 0.029 31 69 Aropoanui D considered robust Te Kumi Strm 0.009 17 16 Wairoa F Waitio Strm 0.031 31 71 Ngaruroro C Ngaruroro Rv at Fernhill 0.010 33 20 Ngaruroro C Mangamahaki Strm 0.032 12 72 Tukituki B (Snelder pers. comm. Mohaka Rv at SH5 (NIWA) 0.010 60 20 Mohaka E Poporangi Strm 0.032 14 72 Ngaruroro C 2014). Medians Mohaka Rv D⁄S Taharua Rv 0.010 68 20 Mohaka E Esk Rv at Waipunga Br 0.032 30 72 Esk D Ripia Rv U⁄S Mohaka Rv 0.010 36 20 Mohaka E Mohaka Rv at Willowflat 0.032 40 72 Mohaka E generated from Mangaorapa Strm 0.012 31 24 Porangahau A Waingongoro Strm 0.033 32 76 Southern Coastal A sample sizes less than Taharua Rv at Henry's Br 0.012 17 24 Mohaka E Tukituki Rv at Tapairu Rd 0.033 48 76 Tukituki B Pouhokio Strm 0.013 32 26 Maraetotara / Waimarama A Maharakeke Strm U⁄S Makaretu Rv 0.035 14 78 Tukituki B 30 should be treated Ngaruroro Rv at Motorway 0.013 17 26 Ngaruroro C Opoutama Strm 0.035 18 78 Northern Coastal F with caution. Taharua Rv at Red Hut 0.014 64 28 Mohaka E Kahahakuri Strm 0.036 27 80 Tukituki B Waiarua Strm 0.014 34 28 Mohaka E Mangaone Rv at Dartmoor 0.038 13 81 Tutaekuri C Waipunga Rv at Pohokura Rd 0.014 24 28 Mohaka E Waipawa Rv 400m D⁄S oxi pond 0.040 42 82 Tukituki B Mohaka Rv D⁄S Waipunga Rv 0.015 53 31 Mohaka E Porangahau Strm 0.043 63 83 Tukituki B Waipawa Rv 50m U⁄S oxi pond 0.016 43 32 Tukituki B Maharakeke Strm at Limeworks Station Rd 0.046 14 84 Tukituki B Waipawa Rv at SH2 0.016 58 32 Tukituki B Tutaekuri-Waimate Strm 0.046 28 84 Ngaruroro C Tutaekuri Rv U⁄S Mangaone Rv 0.016 32 32 Tutaekuri C Taurekaitai Strm 0.049 31 86 Porangahau A Mangakuri Rv 0.017 31 35 Southern Coastal A Makara Strm 0.050 13 87 Tukituki B Maraetotara Rv at Te Awanga 0.017 32 35 Maraetotara / Waimarama A Mangatewai Strm at SH50 0.051 14 88 Tukituki B Porangahau Rv 0.017 31 35 Porangahau A Te Iringaowhare Strm 0.053 5 89 Wairoa F Makaretu Rv U⁄S Maharakeke Strm 0.017 14 35 Tukituki B Mahiaruhe Strm 0.058 12 90 Aropoanui D Tukituki Rv at Black Br 0.017 58 35 Tukituki B Mangarau Strm at Keirunga Rd 0.060 17 91 Karamu/Clive C Ruakituri Rv 0.017 30 35 Wairoa F Ruahapia Strm 0.069 17 92 Karamu/Clive C Maraetotara Rv at Waimarama Rd 0.018 31 41 Maraetotara / Waimarama A Tukituki Rv 400m D⁄S oxi pond 0.070 43 93 Tukituki B Makaretu Rv at SH50 0.018 62 41 Tukituki B Sandy Ck 0.072 35 94 Aropoanui D Mangaonuku Strm 0.018 59 41 Tukituki B Herehere Strm 0.074 32 95 Karamu/Clive C Tukituki Rv at Red Br 0.018 64 41 Tukituki B Mangarau Strm at Te Aute Rd 0.084 23 96 Karamu/Clive C Ngaruroro Rv at Chesterhope (NIWA) 0.018 60 41 Ngaruroro C Ohiwa Strm 0.114 13 97 Ngaruroro C Mohaka Rv at Raupunga (NIWA) 0.018 60 41 Mohaka E Clive Rv 0.142 32 98 Karamu/Clive C Mokomokonui Rv 0.018 30 41 Mohaka E Karewarewa Strm 0.171 33 99 Karamu/Clive C Taharua Rv at Wairango 0.018 58 41 Mohaka E Poukawa Strm 0.188 37 100 Karamu/Clive C Taharua Rv at Twin Culv 0.019 59 49 Mohaka E Papanui Strm 0.192 35 101 Tukituki B Waiau Rv 0.019 25 49 Wairoa F Awanui Strm 0.215 38 102 Karamu/Clive C Tukituki Rv at SH2 0.020 77 51 Tukituki B Mangatarata Strm 0.260 59 103 Tukituki B Mangapoike Rv 0.020 25 51 Wairoa F Taipo Strm 0.410 31 104 Karamu/Clive C 156 Mohaka River Catchment

Median Sample Reporting Median Sample Reporting Site Rank Catchment Site Rank Catchment DIN size (n) Zone DIN size (n) Zone Regional SoE sites Ngaruroro Rv at Kuripapango (NIWA) 0.009 60 1 Ngaruroro C Tutaekuri-Waimate Strm 0.253 29 53 Ngaruroro C Mangamahaki Strm 0.018 12 2 Tukituki B Mohaka Rv at SH5 (NIWA) 0.265 60 54 Mohaka E ranked by median Taruarau Rv 0.026 14 3 Ngaruroro C Esk Rv at Waipunga Br 0.271 30 55 Esk D dissolved inorganic Waikaretaheke Rv 0.026 13 3 Wairoa F Mohaka Rv D⁄S Ripia Rv 0.282 47 56 Mohaka E Tutaekuri Rv at Lawrence Hut 0.027 32 5 Tutaekuri C Mangatewai Strm at SH50 0.286 14 57 Tukituki B nitrogen 2009-2013 Aniwaniwa Strm 0.027 29 5 Wairoa F Herehere Strm 0.300 32 58 Karamu/Clive C Mokau Strm 0.032 11 7 Wairoa F Esk Rv at Berry Rd 0.305 27 59 Esk D Anaura Strm 0.036 16 8 Waikari D Opoutama Strm 0.309 18 60 Northern Coastal F Waiau Rv 0.037 25 9 Wairoa F Mangatutu Strm 0.334 18 61 Tutaekuri C DIN (mg/l), 2009-2013, Mohaka Rv U⁄S Taharua Rv 0.040 65 10 Mohaka E Mangaone Rv at Rissington 0.335 37 62 Tutaekuri C with colours signifying Taurekaitai Strm 0.041 31 11 Porangahau A Mahiaruhe Strm 0.365 11 63 Aropoanui D Porangahau Rv 0.042 30 12 Porangahau A Papanui Strm 0.393 35 64 Tukituki B reporting zone. Lower Ngaruroro Rv at Whanawhana 0.044 32 13 Ngaruroro C Maraetotara Rv at Te Awanga 0.418 31 65 Maraetotara / Waimarama A ranks are ‘better’. Mokomokonui Rv 0.050 30 14 Mohaka E Maraekakaho Strm 0.419 14 66 Ngaruroro C Ngaruroro Rv U⁄S HB Dairies 0.052 16 15 Ngaruroro C Sandy Ck 0.438 35 67 Aropoanui D Medians generated Mangakuri Rv 0.053 31 16 Southern Coastal A Taipo Strm 0.471 32 68 Karamu/Clive C from sample sizes of at Makara Strm 0.055 13 17 Tukituki B Ohiwa Strm 0.499 13 69 Ngaruroro C Makaroro Rv (NIWA) 0.056 60 18 Tukituki B Poporangi Strm 0.538 14 70 Ngaruroro C least 30 are considered Wairoa Rv U⁄S Wairoa 0.060 27 19 Wairoa F Waipawa Rv 50m U⁄S oxi pond 0.582 44 71 Tukituki B robust (Snelder pers. Hangaroa Rv 0.064 28 20 Wairoa F Waipawa Rv U⁄S Tukituki Rv 0.583 44 72 Tukituki B Mangatarata Strm 0.070 58 21 Tukituki B Ruahapia Strm 0.588 17 73 Karamu/Clive C comm. 2014). Medians Ripia Rv U⁄S Mohaka Rv 0.079 37 22 Mohaka E Waiarua Strm 0.598 34 74 Mohaka E generated from sample Tukituki Rv at SH50 0.084 64 23 Tukituki B Tukituki Rv at Black Br 0.601 58 75 Tukituki B Tutaekuri Rv at Puketapu 0.091 13 24 Tutaekuri C Tukituki Rv at Red Br 0.604 64 76 Tukituki B sizes less than 30 Ngaruroro Rv at Chesterhope (NIWA) 0.106 60 25 Ngaruroro C Tukituki Rv at Red Br (NIWA) 0.607 60 77 Tukituki B should be treated with Te Kumi Strm 0.106 17 25 Wairoa F Waipawa Rv 400m D⁄S oxi pond 0.620 44 78 Tukituki B Ngaruroro Rv D⁄S HB Dairies 0.107 33 27 Ngaruroro C Mohaka Rv D⁄S Taharua Rv 0.635 68 79 Mohaka E caution. Aropaoanui Rv 0.110 31 28 Aropoanui D Waipawa Rv at SH2 0.652 58 80 Tukituki B Te Iringaowhare Strm 0.110 5 28 Wairoa F Clive Rv 0.673 31 81 Karamu/Clive C Ruakituri Rv 0.111 30 30 Wairoa F Pouhokio Strm 0.734 32 82 Maraetotara / Waimarama A Mangaorapa Strm 0.120 31 31 Porangahau A Tukipo Rv at SH50 0.737 62 83 Tukituki B Ngaruroro Rv at Ohiti 0.130 17 32 Ngaruroro C Mangarau Strm at Te Aute Rd 0.817 23 84 Karamu/Clive C Tukituki Rv at Waipukurau Ongaonga Rd 0.132 14 33 Tukituki B Maraetotara Rv at Waimarama Rd 0.830 31 85 Maraetotara / Waimarama A Ngaruroro Rv at Fernhill 0.134 34 34 Ngaruroro C Tukituki Rv at Tamumu Br 0.867 57 86 Tukituki B Waipawa Rv at SH50 0.135 59 35 Tukituki B Awanui Strm 0.887 39 87 Karamu/Clive C Mangaone Rv at Dartmoor 0.139 13 36 Tutaekuri C Tukituki Rv at SH2 1.014 78 88 Tukituki B Ngaruroro Rv at Motorway 0.140 17 37 Ngaruroro C Tukipo Rv U⁄S Makaretu Rv 1.180 13 89 Tukituki B Tutaekuri Rv at Brookfields Br 0.155 31 38 Tutaekuri C Porangahau Strm 1.210 63 90 Tukituki B Mohaka Rv at Raupunga (NIWA) 0.161 60 39 Mohaka E Tukituki Rv at Tapairu Rd 1.277 49 91 Tukituki B Makaretu Rv at SH50 0.163 60 40 Tukituki B Tukituki Rv 50m U⁄S oxi pond 1.307 44 92 Tukituki B Tutaekuri Rv U⁄S Mangaone Rv 0.165 32 41 Tutaekuri C Taharua Rv at Red Hut 1.317 64 93 Mohaka E Kopuawhara Strm 0.171 31 42 Northern Coastal F Maharakeke Strm U⁄S Makaretu Rv 1.560 14 94 Tukituki B Poukawa Strm 0.173 39 43 Karamu/Clive C Tukituki Rv 400m D⁄S oxi pond 1.608 44 95 Tukituki B Mangapoike Rv 0.173 25 43 Wairoa F Karewarewa Strm 1.706 33 96 Karamu/Clive C Waikari Rv 0.180 32 45 Waikari D Taharua Rv at Poronui Stn 1.710 47 97 Mohaka E Mohaka Rv at Raupunga 0.188 46 46 Mohaka E Maharakeke Strm at Limeworks Station Rd 1.761 14 98 Tukituki B Mohaka Rv at Willowflat 0.190 39 47 Mohaka E Mangaonuku Strm 1.873 57 99 Tukituki B Mangarau Strm at Keirunga Rd 0.191 17 48 Karamu/Clive C Waingongoro Strm 1.925 32 100 Southern Coastal A Waipunga Rv at Pohokura Rd 0.206 25 49 Mohaka E Taharua Rv at Henry's Br 2.212 19 101 Mohaka E Makaretu Rv U⁄S Maharakeke Strm 0.212 14 50 Tukituki B Kahahakuri Strm 2.700 27 102 Tukituki B Mohaka Rv D⁄S Waipunga Rv 0.233 53 51 Mohaka E Taharua Rv at Wairango 3.311 58 103 Mohaka E Waitio Strm 0.247 32 52 Ngaruroro C Taharua Rv at Twin Culv 3.614 60 104 Mohaka E Mohaka River Catchment 157

Median Sample Reporting Median Sample Reporting Site Rank Catchment Site Rank Catchment DRP size (n) Zone DRP size (n) Zone Mangakuri Rv 0.002 31 1 Southern Coastal A Waiau Rv 0.012 25 50 Wairoa F Mangaorapa Strm 0.002 31 1 Porangahau A Tukituki Rv at SH2 0.013 76 54 Tukituki B Tukituki Rv at Waipukurau Ongaonga Rd 0.002 14 1 Tukituki B Waipawa Rv at SH2 0.013 59 54 Tukituki B Regional SoE sites Waipawa Rv at SH50 0.002 60 1 Tukituki B Tutaekuri Rv U⁄S Mangaone Rv 0.013 32 54 Tutaekuri C ranked by median Ngaruroro Rv at Kuripapango (NIWA) 0.002 60 1 Ngaruroro C Taharua Rv at Twin Culv 0.013 60 54 Mohaka E Ngaruroro Rv at Whanawhana 0.002 34 1 Ngaruroro C Mangaonuku Strm 0.014 59 58 Tukituki B dissolved reactive Ngaruroro Rv U⁄S HB Dairies 0.002 17 1 Ngaruroro C Tukipo Rv U⁄S Makaretu Rv 0.014 13 58 Tukituki B phosphorus 2009- Taruarau Rv 0.002 14 1 Ngaruroro C Mokomokonui Rv 0.014 30 58 Mohaka E Mohaka Rv U⁄S Taharua Rv 0.002 66 1 Mohaka E Tutaekuri Rv at Puketapu 0.015 13 61 Tutaekuri C 2013 Aniwaniwa Strm 0.002 30 1 Wairoa F Taharua Rv at Wairango 0.015 59 61 Mohaka E Kopuawhara Strm 0.002 31 1 Northern Coastal F Tutaekuri Rv at Brookfields Br 0.016 31 63 Tutaekuri C Mokau Strm 0.002 11 1 Wairoa F Te Iringaowhare Strm 0.016 5 63 Wairoa F DRP (mg/l), 2009- Waikaretaheke Rv 0.002 14 1 Wairoa F Tukituki Rv 50m U⁄S oxi pond 0.017 43 65 Tukituki B Porangahau Rv 0.004 31 14 Porangahau A Tukituki Rv at Tamumu Br 0.017 58 65 Tukituki B 2013, with colours Tukituki Rv at SH50 0.004 66 14 Tukituki B Waikari Rv 0.017 32 65 Waikari D signifying reporting Tutaekuri Rv at Lawrence Hut 0.004 34 14 Tutaekuri C Mangatutu Strm 0.018 18 68 Tutaekuri C Mohaka Rv D⁄S Taharua Rv 0.004 68 14 Mohaka E Tukipo Rv at SH50 0.019 63 69 Tukituki B zone. Lower ranks are Pouhokio Strm 0.005 32 18 Maraetotara / Waimarama A Mangaone Rv at Rissington 0.019 38 69 Tutaekuri C ‘better’. Medians Makaroro Rv (NIWA) 0.005 60 18 Tukituki B Aropaoanui Rv 0.019 31 69 Aropoanui D Ngaruroro Rv at Ohiti 0.005 17 18 Ngaruroro C Makara Strm 0.020 13 72 Tukituki B generated from Ngaruroro Rv D⁄S HB Dairies 0.005 34 18 Ngaruroro C Waipawa Rv U⁄S Tukituki Rv 0.020 44 72 Tukituki B sample sizes of at least Mohaka Rv at SH5 (NIWA) 0.005 60 18 Mohaka E Waingongoro Strm 0.021 32 74 Southern Coastal A 30 are considered Mohaka Rv D⁄S Ripia Rv 0.005 48 18 Mohaka E Tukituki Rv at Tapairu Rd 0.022 49 75 Tukituki B Hangaroa Rv 0.005 29 18 Wairoa F Esk Rv at Berry Rd 0.022 27 75 Esk D robust (Snelder pers. Ruakituri Rv 0.005 30 18 Wairoa F Kahahakuri Strm 0.023 27 77 Tukituki B comm. 2014). Medians Anaura Strm 0.006 17 26 Waikari D Taurekaitai Strm 0.024 31 78 Porangahau A Mohaka Rv D⁄S Waipunga Rv 0.006 53 26 Mohaka E Esk Rv at Waipunga Br 0.024 30 78 Esk D generated from Ripia Rv U⁄S Mohaka Rv 0.006 37 26 Mohaka E Maraekakaho Strm 0.025 14 80 Ngaruroro C sample sizes less than Waiarua Strm 0.006 35 26 Mohaka E Poporangi Strm 0.025 14 80 Ngaruroro C Mangapoike Rv 0.006 25 26 Wairoa F Waitio Strm 0.025 31 80 Ngaruroro C 30 should be treated Ngaruroro Rv at Fernhill 0.007 33 31 Ngaruroro C Maharakeke Strm U⁄S Makaretu Rv 0.026 14 83 Tukituki B with caution. Taharua Rv at Red Hut 0.007 64 31 Mohaka E Mahiaruhe Strm 0.026 12 83 Aropoanui D Waipunga Rv at Pohokura Rd 0.007 25 31 Mohaka E Porangahau Strm 0.028 63 85 Tukituki B Opoutama Strm 0.007 18 31 Northern Coastal F Waipawa Rv 400m D⁄S oxi pond 0.028 44 85 Tukituki B Ngaruroro Rv at Chesterhope (NIWA) 0.008 60 35 Ngaruroro C Mangaone Rv at Dartmoor 0.028 13 85 Tutaekuri C Ngaruroro Rv at Motorway 0.008 17 35 Ngaruroro C Maharakeke Strm at Limeworks Station Rd 0.029 14 88 Tukituki B Mohaka Rv at Raupunga (NIWA) 0.008 60 35 Mohaka E Tutaekuri-Waimate Strm 0.031 29 89 Ngaruroro C Te Kumi Strm 0.008 17 35 Wairoa F Ruahapia Strm 0.034 17 90 Karamu/Clive C Wairoa Rv U⁄S Wairoa 0.008 29 35 Wairoa F Mangatewai Strm at SH50 0.040 14 91 Tukituki B Tukituki Rv at Red Br 0.009 64 40 Tukituki B Sandy Ck 0.044 34 92 Aropoanui D Mohaka Rv at Raupunga 0.009 46 40 Mohaka E Mangarau Strm at Keirunga Rd 0.048 17 93 Karamu/Clive C Mohaka Rv at Willowflat 0.009 40 40 Mohaka E Tukituki Rv 400m D⁄S oxi pond 0.051 44 94 Tukituki B Maraetotara Rv at Te Awanga 0.010 32 43 Maraetotara / Waimarama A Herehere Strm 0.057 32 95 Karamu/Clive C Maraetotara Rv at Waimarama Rd 0.010 31 43 Maraetotara / Waimarama A Mangarau Strm at Te Aute Rd 0.070 23 96 Karamu/Clive C Makaretu Rv U⁄S Maharakeke Strm 0.010 14 43 Tukituki B Clive Rv 0.101 32 97 Karamu/Clive C Tukituki Rv at Black Br 0.010 58 43 Tukituki B Ohiwa Strm 0.111 13 98 Ngaruroro C Taharua Rv at Henry's Br 0.010 19 43 Mohaka E Poukawa Strm 0.134 37 99 Karamu/Clive C Mangamahaki Strm 0.011 12 48 Tukituki B Karewarewa Strm 0.140 33 100 Karamu/Clive C Taharua Rv at Poronui Stn 0.011 46 48 Mohaka E Papanui Strm 0.154 35 101 Tukituki B Makaretu Rv at SH50 0.012 62 50 Tukituki B Mangatarata Strm 0.167 59 102 Tukituki B Tukituki Rv at Red Br (NIWA) 0.012 60 50 Tukituki B Awanui Strm 0.182 38 103 Karamu/Clive C Waipawa Rv 50m U⁄S oxi pond 0.012 44 50 Tukituki B Taipo Strm 0.270 31 104 Karamu/Clive C 158 Mohaka River Catchment

Median Sample Reporting Median Sample Reporting Site Rank Catchment Site Rank Catchment NO3-N size (n) Zone NO3-N size (n) Zone Mangamahaki Strm 0.001 12 1 Tukituki B Opoutama Strm 0.245 18 50 Northern Coastal F Regional SoE sites Taruarau Rv 0.010 14 2 Ngaruroro C Esk Rv at Waipunga Br 0.260 29 51 Esk D ranked by median Tutaekuri Rv at Lawrence Hut 0.014 32 3 Tutaekuri C Mohaka Rv D⁄S Ripia Rv 0.270 47 52 Mohaka E Waikaretaheke Rv 0.014 13 3 Wairoa F Herehere Strm 0.275 32 53 Karamu/Clive C nitrate 2009-2013 Aniwaniwa Strm 0.015 28 5 Wairoa F Mangatewai Strm at SH50 0.280 14 54 Tukituki B Ngaruroro Rv at Whanawhana 0.018 32 6 Ngaruroro C Papanui Strm 0.280 35 54 Tukituki B Taurekaitai Strm 0.020 31 7 Porangahau A Esk Rv at Berry Rd 0.290 24 56 Esk D Mokau Strm 0.021 12 8 Wairoa F Mangaone Rv at Rissington 0.310 37 57 Tutaekuri C NO3-N (mg/l), 2009- Anaura Strm 0.025 16 9 Waikari D Mangatutu Strm 0.320 18 58 Tutaekuri C 2013, with colours Waiau Rv 0.025 25 9 Wairoa F Taipo Strm 0.320 32 58 Karamu/Clive C signifying reporting Makara Strm 0.027 13 11 Tukituki B Mahiaruhe Strm 0.320 11 58 Aropoanui D Mohaka Rv U⁄S Taharua Rv 0.028 65 12 Mohaka E Sandy Ck 0.390 35 61 Aropoanui D zone. Lower ranks Mangakuri Rv 0.031 31 13 Southern Coastal A Maraetotara Rv at Te Awanga 0.400 31 62 Maraetotara / Waimarama A are ‘better’. Medians Porangahau Rv 0.036 30 14 Porangahau A Maraekakaho Strm 0.405 14 63 Ngaruroro C generated from Mokomokonui Rv 0.037 30 15 Mohaka E Ruahapia Strm 0.420 17 64 Karamu/Clive C Ngaruroro Rv U⁄S HB Dairies 0.040 16 16 Ngaruroro C Ohiwa Strm 0.480 13 65 Ngaruroro C sample sizes of at Wairoa Rv U⁄S Wairoa 0.040 27 16 Wairoa F Poporangi Strm 0.525 14 66 Ngaruroro C least 30 are Hangaroa Rv 0.050 28 18 Wairoa F Waipawa Rv 50m U⁄S oxi pond 0.575 44 67 Tukituki B Mangatarata Strm 0.056 58 19 Tukituki B Waipawa Rv U⁄S Tukituki Rv 0.575 44 67 Tukituki B considered robust Tukituki Rv at SH50 0.066 64 20 Tukituki B Tukituki Rv at Black Br 0.580 58 69 Tukituki B (Snelder pers. comm. Ripia Rv U⁄S Mohaka Rv 0.067 37 21 Mohaka E Waiarua Strm 0.585 34 70 Mohaka E Tutaekuri Rv at Puketapu 0.078 13 22 Tutaekuri C Tukituki Rv at Red Br 0.590 64 71 Tukituki B 2014). Medians Te Kumi Strm 0.093 16 23 Wairoa F Waipawa Rv 400m D⁄S oxi pond 0.611 44 72 Tukituki B generated from Ruakituri Rv 0.094 30 24 Wairoa F Clive Rv 0.620 31 73 Karamu/Clive C Ngaruroro Rv D⁄S HB Dairies 0.095 33 25 Ngaruroro C Mohaka Rv D⁄S Taharua Rv 0.620 68 73 Mohaka E sample sizes less Arawapanui Rv 0.097 31 26 Aropoanui D Waipawa Rv at SH2 0.640 58 75 Tukituki B than 30 should be Te Iringaowhare Strm 0.098 5 27 Wairoa F Pouhokio Strm 0.710 31 76 Maraetotara / Waimarama A treated with caution. Mangaorapa Strm 0.113 31 28 Porangahau A Tukipo Rv at SH50 0.715 62 77 Tukituki B Ngaruroro Rv at Motorway 0.120 17 29 Ngaruroro C Mangarau Strm at Te Aute Rd 0.790 23 78 Karamu/Clive C Ngaruroro Rv at Ohiti 0.120 17 29 Ngaruroro C Maraetotara Rv at Waimarama Rd 0.800 31 79 Maraetotara / Waimarama A Ngaruroro Rv at Fernhill 0.121 34 31 Ngaruroro C Awanui Strm 0.840 39 80 Karamu/Clive C Tukituki Rv at Waipukurau Ongaonga Rd 0.125 14 32 Tukituki B Tukituki Rv at Tamumu Br 0.850 57 81 Tukituki B Waipawa Rv at SH50 0.126 59 33 Tukituki B Tukituki Rv at SH2 0.955 78 82 Tukituki B Poukawa Strm 0.130 39 34 Karamu/Clive C Tukipo Rv U⁄S Makaretu Rv 1.170 13 83 Tukituki B Mangaone Rv at Dartmoor 0.132 13 35 Tutaekuri C Porangahau Strm 1.200 63 84 Tukituki B Waikari Rv 0.141 32 36 Waikari D Tukituki Rv at Tapairu Rd 1.230 49 85 Tukituki B Tutaekuri Rv at Brookfields Br 0.143 31 37 Tutaekuri C Tukituki Rv 400m D⁄S oxi pond 1.235 44 86 Tukituki B Mangapoike Rv 0.146 25 38 Wairoa F Tukituki Rv 50m U⁄S oxi pond 1.260 44 87 Tukituki B Makaretu Rv at SH50 0.152 60 39 Tukituki B Taharua Rv at Red Hut 1.300 64 88 Mohaka E Tutaekuri Rv U⁄S Mangaone Rv 0.154 32 40 Tutaekuri C Karewarewa Strm 1.520 33 89 Karamu/Clive C Kopuawhara Strm 0.159 31 41 Northern Coastal F Maharakeke Strm U⁄S Makaretu Rv 1.540 14 90 Tukituki B Mohaka Rv at Willowflat 0.172 39 42 Mohaka E Taharua Rv at Poronui Stn 1.700 47 91 Mohaka E Mohaka Rv at Raupunga 0.174 46 43 Mohaka E Maharakeke Strm at Limeworks Station Rd 1.740 14 92 Tukituki B Waipunga Rv at Pohokura Rd 0.194 25 44 Mohaka E Mangaonuku Strm 1.860 57 93 Tukituki B Mangarau Strm at Keirunga Rd 0.199 17 45 Karamu/Clive C Waingongoro Strm 1.910 31 94 Southern Coastal A Makaretu Rv U⁄S Maharakeke Strm 0.200 14 46 Tukituki B Taharua Rv at Henry's Br 2.200 19 95 Mohaka E Mohaka Rv D⁄S Waipunga Rv 0.220 53 47 Mohaka E Kahahakuri Strm 2.600 27 96 Tukituki B Tutaekuri-Waimate Strm 0.230 29 48 Ngaruroro C Taharua Rv at Wairango 3.300 58 97 Mohaka E Waitio Strm 0.235 32 49 Ngaruroro C Taharua Rv at Twin Culv 3.600 60 98 Mohaka E

Mohaka River Catchment 159

Median Sample Reporting Median Sample Reporting Regional SoE Site Rank Catchment Site Rank Catchment Black Disk Size (n) Zone Black Disk Size (n) Zone sites ranked by Tutaekuri Rv at Lawrence Hut 5.9 33 1 Tutaekuri C Waipawa Rv at SH50 1.5 56 50 Tukituki B median black Ngaruroro Rv at Kuripapango (NIWA) 5.3 59 2 Ngaruroro C Esk Rv at Waipunga Br 1.5 26 51 Esk D Taharua Rv at Wairango 4.7 55 3 Mohaka E Tutaekuri Rv U⁄S Mangaone Rv 1.5 31 52 Tutaekuri C disc clarity Taruarau Rv 4.7 13 4 Ngaruroro C Porangahau Rv 1.4 28 53 Porangahau A 2009-2013 Mohaka Rv U⁄S Taharua Rv 4.3 57 5 Mohaka E Makaretu Rv U⁄S Maharakeke Strm 1.4 14 54 Tukituki B Taharua Rv at Henry's Br 4.3 9 6 Mohaka E Pouhokio Strm 1.4 31 55 Maraetotara / Waimarama A Taharua Rv at Twin Culv 3.5 54 7 Mohaka E Tukituki Rv at Waipukurau Ongaonga Rd 1.4 13 55 Tukituki B Maraekakaho Strm 3.4 12 8 Ngaruroro C Taharua Rv at Poronui Stn 1.4 46 57 Mohaka E Black Disc (m), Ngaruroro Rv at Whanawhana 3.4 31 9 Ngaruroro C Mangatutu Strm 1.4 18 58 Tutaekuri C 2009-2013, with Ohiwa Strm 3.4 12 9 Ngaruroro C Esk Rv at Berry Rd 1.4 26 59 Esk D Waitio Strm 3.4 30 9 Ngaruroro C Poukawa Strm 1.3 35 60 Karamu/Clive C colours signifying Mangaonuku Strm 3.2 53 12 Tukituki B Ngaruroro Rv at Chesterhope (NIWA) 1.3 60 61 Ngaruroro C reporting zone. Aniwaniwa Strm 3.1 29 13 Wairoa F Te Iringaowhare Strm 1.3 3 62 Wairoa F Lower ranks are Mokau Strm 3.0 12 14 Wairoa F Mangarau Strm at Te Aute Rd 1.3 15 63 Karamu/Clive C Mohaka Rv at SH5 (NIWA) 2.8 60 15 Mohaka E Clive Rv 1.2 19 64 Karamu/Clive C ‘better’. Medians Tutaekuri Rv at Puketapu 2.8 14 16 Tutaekuri C Karewarewa Strm 1.2 28 65 Karamu/Clive C generated from Ngaruroro Rv U⁄S HB Dairies 2.8 16 17 Ngaruroro C Mohaka Rv D⁄S Waipunga Rv 1.2 48 65 Mohaka E Ripia Rv U⁄S Mohaka Rv 2.5 29 18 Mohaka E Tukituki Rv at SH50 1.2 58 67 Tukituki B sample sizes of at Te Kumi Strm 2.5 18 19 Wairoa F Ngaruroro Rv D⁄S HB Dairies 1.2 30 68 Ngaruroro C least 30 are Makaroro Rv (NIWA) 2.3 60 20 Tukituki B Ngaruroro Rv at Fernhill 1.2 28 69 Ngaruroro C Mohaka Rv D⁄S Ripia Rv 2.3 45 20 Mohaka E Sandy Ck 1.2 28 70 Aropoanui D considered robust Mokomokonui Rv 2.3 29 20 Mohaka E Mahiaruhe Strm 1.2 12 71 Aropoanui D (Snelder pers. Mohaka Rv D⁄S Taharua Rv 2.3 59 23 Mohaka E Awanui Strm 1.1 29 72 Karamu/Clive C comm. 2014). Tukituki Rv at Red Br (NIWA) 2.3 60 24 Tukituki B Waipunga Rv at Pohokura Rd 1.1 18 73 Mohaka E Maraetotara Rv at Waimarama Rd 2.2 29 25 Maraetotara / Waimarama A Mangaorapa Strm 1.1 31 74 Porangahau A Medians Maraetotara Rv at Te Awanga 2.2 31 26 Maraetotara / Waimarama A Mangakuri Rv 1.1 30 75 Southern Coastal A generated from Waikaretaheke Rv 2.1 13 27 Wairoa F Ruahapia Strm 1.1 10 76 Karamu/Clive C Maharakeke Strm U⁄S Makaretu Rv 2.1 13 28 Tukituki B Tutaekuri-Waimate Strm 1.1 24 77 Ngaruroro C sample sizes less Porangahau Strm 2.1 59 29 Tukituki B Mangarau Strm at Keirunga Rd 1.1 11 78 Karamu/Clive C than 30 should be Mangaone Rv at Dartmoor 2.0 12 30 Tutaekuri C Hangaroa Rv 1.1 29 78 Wairoa F Tukipo Rv U⁄S Makaretu Rv 2.0 12 31 Tukituki B Ngaruroro Rv at Motorway 1.0 15 80 Ngaruroro C treated with Mangaone Rv at Rissington 2.0 35 32 Tutaekuri C Mangatewai Strm at SH50 1.0 14 81 Tukituki B caution. Maharakeke Strm at Limeworks Station Rd 1.9 13 33 Tukituki B Mangamahaki Strm 1.0 11 82 Tukituki B Waikari Rv 1.9 31 34 Waikari D Mohaka Rv at Raupunga (NIWA) 1.0 59 82 Mohaka E Tutaekuri Rv at Brookfields Br 1.9 32 35 Tutaekuri C Papanui Strm 0.9 23 84 Tukituki B Tukipo Rv at SH50 1.8 57 36 Tukituki B Waipawa Rv at SH2 0.9 12 84 Tukituki B Taharua Rv at Red Hut 1.8 52 37 Mohaka E Opoutama Strm 0.9 18 84 Northern Coastal F Tukituki Rv at Red Br 1.8 53 38 Tukituki B Waingongoro Strm 0.9 31 87 Southern Coastal A Kopuawhara Strm 1.8 30 39 Northern Coastal F Ngaruroro Rv at Ohiti 0.8 15 88 Ngaruroro C Aropaoanui Rv 1.7 30 40 Aropoanui D Makara Strm 0.8 12 89 Tukituki B Kahahakuri Strm 1.7 24 41 Tukituki B Mangatarata Strm 0.7 50 90 Tukituki B Poporangi Strm 1.7 13 42 Ngaruroro C Taurekaitai Strm 0.7 21 91 Porangahau A Tukituki Rv at Tamumu Br 1.6 54 43 Tukituki B Ruakituri Rv 0.7 29 92 Wairoa F Makaretu Rv at SH50 1.6 58 44 Tukituki B Waiau Rv 0.6 25 93 Wairoa F Herehere Strm 1.6 22 45 Karamu/Clive C Taipo Strm 0.5 19 94 Karamu/Clive C Tukituki Rv at Black Br 1.6 50 46 Tukituki B Wairoa Rv U⁄S Wairoa 0.4 27 95 Wairoa F Waiarua Strm 1.6 28 47 Mohaka E Mangapoike Rv 0.4 24 96 Wairoa F Tukituki Rv at SH2 1.5 13 48 Tukituki B Mohaka Rv at Raupunga 0.3 36 97 Mohaka E Anaura Strm 1.5 15 49 Waikari D Mohaka Rv at Willowflat 0.3 37 98 Mohaka E

160 Mohaka River Catchment

Median Sample Reporting Median Sample Reporting Site Rank Catchment Site Rank Catchment Turbidity size (n) Zone Turbidity size (n) Zone Te Kumi Strm 0.6 17 1 Wairoa F Kahahakuri Strm 2.3 25 53 Tukituki B Regional SoE sites Taharua Rv at Wairango 0.7 57 2 Mohaka E Mangaone Rv at Dartmoor 2.3 11 53 Tutaekuri C Mohaka Rv U⁄S Taharua Rv 0.7 60 3 Mohaka E Tukipo Rv U⁄S Makaretu Rv 2.4 13 55 Tukituki B ranked by median Maraekakaho Strm 0.7 13 4 Ngaruroro C Waipunga Rv at Pohokura Rd 2.4 20 55 Mohaka E turbidity 2009-2013 Ngaruroro Rv at Kuripapango (NIWA) 0.8 60 5 Ngaruroro C Waiarua Strm 2.4 30 57 Mohaka E Tutaekuri Rv at Lawrence Hut 0.8 32 6 Tutaekuri C Tukituki Rv at Black Br 2.5 52 58 Tukituki B Taharua Rv at Twin Culv 0.9 59 7 Mohaka E Makaretu Rv at SH50 2.5 61 59 Tukituki B Mangaonuku Strm 1.0 58 8 Tukituki B Mangarau Strm at Te Aute Rd 2.5 23 59 Karamu/Clive C Turbidity (NTU), 2009- Waipawa Rv 50m U⁄S oxi pond 1.0 44 9 Tukituki B Esk Rv at Berry Rd 2.7 26 61 Esk D 2013, with colours Waipawa Rv U⁄S Tukituki Rv 1.1 44 10 Tukituki B Tutaekuri Rv U⁄S Mangaone Rv 2.7 31 62 Tutaekuri C Waipawa Rv 400m D⁄S oxi pond 1.1 44 11 Tukituki B Anaura Strm 2.7 17 63 Waikari D signifying reporting Waipawa Rv at SH2 1.2 57 12 Tukituki B Tukituki Rv at Tamumu Br 2.8 57 64 Tukituki B zone. Lower ranks are Maraetotara Rv at Te Awanga 1.2 30 13 Maraetotara / Waimarama A Awanui Strm 2.8 35 65 Karamu/Clive C Waitio Strm 1.2 30 14 Ngaruroro C Mangatutu Strm 2.8 17 66 Tutaekuri C ‘better’. Medians Mohaka Rv D⁄S Ripia Rv 1.2 46 14 Mohaka E Mangamahaki Strm 2.9 10 67 Tukituki B generated from Aniwaniwa Strm 1.2 27 14 Wairoa F Porangahau Rv 2.9 29 68 Porangahau A Mohaka Rv at SH5 (NIWA) 1.3 60 17 Mohaka E Waikari Rv 2.9 30 69 Waikari D sample sizes of at least Mohaka Rv D⁄S Taharua Rv 1.3 63 18 Mohaka E Ruahapia Strm 3.0 16 70 Karamu/Clive C 30 are considered Taharua Rv at Henry's Br 1.3 13 19 Mohaka E Mangatewai Strm at SH50 3.2 14 71 Tukituki B Porangahau Strm 1.3 62 20 Tukituki B Mangarau Strm at Keirunga Rd 3.3 16 72 Karamu/Clive C robust (Snelder pers. Taruarau Rv 1.4 14 21 Ngaruroro C Te Iringaowhare Strm 3.3 5 73 Wairoa F comm. 2014). Medians Mokomokonui Rv 1.4 30 22 Mohaka E Makaretu Rv U⁄S Maharakeke Strm 3.3 13 74 Tukituki B Maraetotara Rv at Waimarama Rd 1.5 30 23 Maraetotara / Waimarama A Ngaruroro Rv at Chesterhope (NIWA) 3.4 60 75 Ngaruroro C generated from Tukituki Rv 50m U⁄S oxi pond 1.5 44 24 Tukituki B Mohaka Rv D⁄S Waipunga Rv 3.4 53 76 Mohaka E Poukawa Strm 1.5 35 24 Karamu/Clive C Pouhokio Strm 3.5 31 77 Maraetotara / Waimarama A sample sizes less than Maharakeke Strm U⁄S Makaretu Rv 1.6 14 26 Tukituki B Mahiaruhe Strm 3.8 12 78 Aropoanui D 30 should be treated Ripia Rv U⁄S Mohaka Rv 1.6 30 27 Mohaka E Clive Rv 3.8 26 79 Karamu/Clive C Mokau Strm 1.7 10 28 Wairoa F Sandy Ck 4.0 29 80 Aropoanui D with caution. Tukituki Rv at Tapairu Rd 1.7 49 29 Tukituki B Karewarewa Strm 4.0 29 81 Karamu/Clive C Tutaekuri Rv at Puketapu 1.8 13 30 Tutaekuri C Papanui Strm 4.1 25 82 Tukituki B Taharua Rv at Poronui Stn 1.8 45 31 Mohaka E Tukituki Rv at SH50 4.2 61 83 Tukituki B Tukituki Rv at Red Br (NIWA) 1.8 60 32 Tukituki B Ngaruroro Rv D⁄S HB Dairies 4.5 32 84 Ngaruroro C Esk Rv at Waipunga Br 1.8 27 33 Esk D Mohaka Rv at Raupunga (NIWA) 4.6 60 85 Mohaka E Taharua Rv at Red Hut 1.9 60 34 Mohaka E Hangaroa Rv 4.8 28 86 Wairoa F Waikaretaheke Rv 1.9 14 35 Wairoa F Ngaruroro Rv at Motorway 4.9 17 87 Ngaruroro C Ohiwa Strm 1.9 12 36 Ngaruroro C Mangatarata Strm 5.0 58 88 Tukituki B Tukituki Rv at Red Br 2.0 59 37 Tukituki B Waingongoro Strm 5.0 31 89 Southern Coastal A Mangaone Rv at Rissington 2.0 33 38 Tutaekuri C Tutaekuri-Waimate Strm 5.1 28 90 Ngaruroro C Aropaoanui Rv 2.0 29 39 Aropoanui D Ngaruroro Rv at Fernhill 5.2 30 91 Ngaruroro C Poporangi Strm 2.1 14 40 Ngaruroro C Makara Strm 5.4 12 92 Tukituki B Ngaruroro Rv at Whanawhana 2.1 32 41 Ngaruroro C Mangaorapa Strm 5.7 29 93 Porangahau A Tukituki Rv 400m D⁄S oxi pond 2.1 44 42 Tukituki B Taipo Strm 5.8 30 94 Karamu/Clive C Tukituki Rv at SH2 2.1 56 43 Tukituki B Taurekaitai Strm 6.3 29 95 Porangahau A Maharakeke Strm at Limeworks Station Rd 2.1 13 44 Tukituki B Ngaruroro Rv at Ohiti 6.4 17 96 Ngaruroro C Kopuawhara Strm 2.1 29 44 Northern Coastal F Ruakituri Rv 7.3 27 97 Wairoa F Herehere Strm 2.1 28 46 Karamu/Clive C Opoutama Strm 7.6 17 98 Northern Coastal F Tukipo Rv at SH50 2.2 55 47 Tukituki B Mangakuri Rv 7.8 27 99 Southern Coastal A Ngaruroro Rv U⁄S HB Dairies 2.2 17 48 Ngaruroro C Waiau Rv 9.1 24 100 Wairoa F Makaroro Rv (NIWA) 2.2 60 49 Tukituki B Mohaka Rv at Raupunga 16.3 39 101 Mohaka E Tutaekuri Rv at Brookfields Br 2.2 29 50 Tutaekuri C Mohaka Rv at Willowflat 17.5 37 102 Mohaka E Tukituki Rv at Waipukurau Ongaonga Rd 2.2 14 51 Tukituki B Mangapoike Rv 18.3 24 103 Wairoa F Waipawa Rv at SH50 2.3 57 52 Tukituki B Wairoa Rv U⁄S Wairoa 18.9 26 104 Wairoa F

Mohaka River Catchment 161

Median Sample Reporting Median Sample Reporting Site Rank Catchment Site Rank Catchment E. coli size (n) Zone E. coli size (n) Zone Te Kumi Strm 1.0 17 1 Wairoa F Waikari Rv 39.5 28 49 Waikari D Mohaka Rv U⁄S Taharua Rv 2.0 59 2 Mohaka E Esk Rv at Waipunga Br 40.0 30 50 Esk D Ngaruroro Rv at Whanawhana 3.0 30 3 Ngaruroro C Waipawa Rv at SH2 40.5 58 51 Tukituki B Regional SoE sites Waipunga Rv at Pohokura Rd 3.0 19 3 Mohaka E Maraetotara Rv at Waimarama Rd 41.0 31 52 Maraetotara / Waimarama A ranked by median Ngaruroro Rv at Kuripapango (NIWA) 3.1 60 5 Ngaruroro C Mangaonuku Strm 41.0 59 52 Tukituki B Mokau Strm 4.0 11 6 Wairoa F Mangatutu Strm 41.5 18 54 Tutaekuri C E. coli 2009-2013 Aniwaniwa Strm 6.0 29 7 Wairoa F Waipawa Rv U⁄S Tukituki Rv 42.0 43 55 Tukituki B Ngaruroro Rv D⁄S HB Dairies 6.5 30 8 Ngaruroro C Arawapanui Rv 43.0 29 56 Aropoanui D Ngaruroro Rv at Motorway 7.0 17 9 Ngaruroro C Makaretu Rv at SH50 45.0 57 57 Tukituki B E. coli (CFU/100ml), Ngaruroro Rv U⁄S HB Dairies 7.0 17 9 Ngaruroro C Maraetotara Rv at Te Awanga 46.5 32 58 Maraetotara / Waimarama A 2009-2013, with Mokomokonui Rv 7.0 30 9 Mohaka E Tukituki Rv at SH2 53.0 57 59 Tukituki B Taharua Rv at Henry's Br 7.0 12 9 Mohaka E Mangaone Rv at Dartmoor 56.0 13 60 Tutaekuri C colours signifying Taharua Rv at Wairango 7.0 58 9 Mohaka E Tukituki Rv 50m U⁄S oxi pond 57.0 44 61 Tukituki B reporting zone. Mohaka Rv D⁄S Taharua Rv 7.5 62 14 Mohaka E Poporangi Strm 57.5 12 62 Ngaruroro C Lower ranks are Mohaka Rv D⁄S Ripia Rv 8.0 48 15 Mohaka E Maraekakaho Strm 61.0 12 63 Ngaruroro C Mohaka Rv D⁄S Waipunga Rv 8.0 53 15 Mohaka E Hangaroa Rv 64.0 28 64 Wairoa F ‘better’. Medians Taharua Rv at Twin Culv 9.0 59 17 Mohaka E Tukituki Rv 400m D⁄S oxi pond 72.0 44 65 Tukituki B generated from Te Iringaowhare Strm 9.0 5 17 Wairoa F Waipawa Rv 400m D⁄S oxi pond 77.5 44 66 Tukituki B sample sizes of at Taharua Rv at Poronui Stn 9.5 46 19 Mohaka E Tukituki Rv at Tapairu Rd 78.5 44 67 Tukituki B Tukituki Rv at SH50 10.0 57 20 Tukituki B Ruakituri Rv 79.0 29 68 Wairoa F least 30 are Anaura Strm 10.0 17 20 Waikari D Mangapoike Rv 85.0 24 69 Wairoa F considered robust Ripia Rv U⁄S Mohaka Rv 10.0 31 20 Mohaka E Wairoa Rv U⁄S Wairoa 85.0 28 69 Wairoa F (Snelder pers. Tutaekuri Rv at Lawrence Hut 11.0 33 23 Tutaekuri C Tutaekuri-Waimate Strm 87.0 27 71 Ngaruroro C Tutaekuri Rv at Puketapu 11.0 13 23 Tutaekuri C Kahahakuri Strm 90.0 14 72 Tukituki B comm. 2014). Taruarau Rv 11.5 12 25 Ngaruroro C Kopuawhara Strm 91.5 30 73 Northern Coastal F Medians generated Waiarua Strm 12.0 29 26 Mohaka E Waingongoro Strm 105.0 32 74 Southern Coastal A from sample sizes Makaroro Rv (NIWA) 12.1 60 27 Tukituki B Porangahau Rv 110.0 31 75 Porangahau A Taharua Rv at Red Hut 13.0 59 28 Mohaka E Porangahau Strm 110.0 57 75 Tukituki B less than 30 should Mohaka Rv at Willowflat 14.0 39 29 Mohaka E Tukipo Rv at SH50 110.0 59 75 Tukituki B be treated with Tutaekuri Rv U⁄S Mangaone Rv 14.5 32 30 Tutaekuri C Pouhokio Strm 120.0 32 78 Maraetotara / Waimarama A caution. Ngaruroro Rv at Ohiti 15.0 17 31 Ngaruroro C Poukawa Strm 130.0 38 79 Karamu/Clive C Tutaekuri Rv at Brookfields Br 15.0 31 31 Tutaekuri C Mangakuri Rv 140.0 31 80 Southern Coastal A Waikaretaheke Rv 15.0 14 31 Wairoa F Mahiaruhe Strm 149.0 10 81 Aropoanui D Mohaka Rv at Raupunga (NIWA) 15.2 60 34 Mohaka E Mangaorapa Strm 160.0 31 82 Porangahau A Mohaka Rv at Raupunga 16.0 39 35 Mohaka E Ohiwa Strm 180.0 11 83 Ngaruroro C Mohaka Rv at SH5 (NIWA) 16.6 60 36 Mohaka E Clive Rv 190.0 31 84 Karamu/Clive C Tukituki Rv at Tamumu Br 20.0 57 37 Tukituki B Sandy Ck 220.0 27 85 Aropoanui D Esk Rv at Berry Rd 21.0 27 38 Esk D Opoutama Strm 220.0 18 85 Northern Coastal F Waipawa Rv at SH50 22.0 57 39 Tukituki B Mangatarata Strm 235.0 54 87 Tukituki B Ngaruroro Rv at Fernhill 25.5 30 40 Ngaruroro C Mangarau Strm at Keirunga Rd 240.0 17 88 Karamu/Clive C Ngaruroro Rv at Chesterhope (NIWA) 27.5 60 41 Ngaruroro C Awanui Strm 250.0 38 89 Karamu/Clive C Tukituki Rv at Black Br 29.0 55 42 Tukituki B Taurekaitai Strm 260.0 31 90 Porangahau A Tukituki Rv at Red Br 32.0 59 43 Tukituki B Mangarau Strm at Te Aute Rd 270.0 23 91 Karamu/Clive C Waiau Rv 33.0 24 44 Wairoa F Ruahapia Strm 280.0 17 92 Karamu/Clive C Tukituki Rv at Red Br (NIWA) 34.3 60 45 Tukituki B Papanui Strm 295.0 20 93 Tukituki B Waitio Strm 35.0 30 46 Ngaruroro C Karewarewa Strm 330.0 32 94 Karamu/Clive C Waipawa Rv 50m U⁄S oxi pond 37.0 44 47 Tukituki B Taipo Strm 330.0 31 94 Karamu/Clive C Mangaone Rv at Rissington 37.5 36 48 Tutaekuri C Herehere Strm 540.0 31 96 Karamu/Clive C

162 Mohaka River Catchment

Median Sample Reporting Median Sample Reporting Regional SoE sites Site Rank Catchment Site Rank Catchment ranked by median MCI size (n) Zone MCI size (n) Zone Te Kumi Strm 136.1 4 1 Wairoa F Maraetotara Rv at Waimarama Rd 101.0 5 46 Maraetotara / Waimarama A MCI 2009-2013 Mokomokonui Rv 132.6 5 2 Mohaka E Tukituki Rv at SH2 101.0 1 46 Tukituki B Mokau Strm 131.3 1 3 Wairoa F Te Iringaowhare Strm 100.1 2 48 Wairoa F Ngaruroro Rv at Kuripapango (NIWA) 130.0 5 4 Ngaruroro C Waitio Strm 99.1 5 49 Ngaruroro C MCI, 2009-2013, with Mohaka Rv D⁄S Ripia Rv 129.5 3 5 Mohaka E Porangahau Strm 98.2 5 50 Tukituki B colours signifying Taharua Rv at Henry's Br 129.2 1 6 Mohaka E Sandy Ck 98.1 4 51 Aropoanui D Tutaekuri Rv at Lawrence Hut 127.8 5 7 Tutaekuri C Kopuawhara Strm 98.0 5 52 Northern Coastal F reporting zone. Mohaka Rv U⁄S Taharua Rv 127.6 6 8 Mohaka E Tukituki Rv at Tamumu Br 97.9 5 53 Tukituki B Lower ranks are Ripia Rv U⁄S Mohaka Rv 127.3 5 9 Mohaka E Hangaroa Rv 97.3 5 54 Wairoa F ‘better’. Medians Aniwaniwa Strm 126.5 5 10 Wairoa F Pouhokio Strm 96.7 5 55 Maraetotara / Waimarama A Mohaka Rv at Willowflat 125.0 3 11 Mohaka E Mangaonuku Strm 96.7 4 55 Tukituki B generated from Taruarau Rv 120.7 1 12 Ngaruroro C Ngaruroro Rv at Motorway 96.6 4 57 Ngaruroro C sample sizes of at Mohaka Rv D⁄S Taharua Rv 119.8 6 13 Mohaka E Ngaruroro Rv at Fernhill 96.5 4 58 Ngaruroro C Waipunga Rv at Pohokura Rd 119.3 3 14 Mohaka E Kahahakuri Strm 96.3 1 59 Tukituki B least 30 are Waiarua Strm 119.1 5 15 Mohaka E Waikari Rv 95.8 5 60 Waikari D considered robust Makaretu Rv at SH50 118.4 5 16 Tukituki B Taharua Rv at Wairango 95.4 5 61 Mohaka E (Snelder pers. comm. Taharua Rv at Poronui Stn 118.2 3 17 Mohaka E Taharua Rv at Red Hut 95.2 5 62 Mohaka E Mohaka Rv at SH5 (NIWA) 117.3 5 18 Mohaka E Waingongoro Strm 94.1 5 63 Southern Coastal A 2014). Medians Makaroro Rv (NIWA) 116.6 5 19 Tukituki B Mangapoike Rv 92.8 2 64 Wairoa F generated from Waiau Rv 116.4 3 20 Wairoa F Tukituki Rv at Red Br (NIWA) 92.3 5 65 Tukituki B Mohaka Rv D⁄S Waipunga Rv 116.3 3 21 Mohaka E Opoutama Strm 91.3 4 66 Northern Coastal F sample sizes less Mangaone Rv at Rissington 116.0 5 22 Tutaekuri C Tutaekuri Rv at Puketapu 88.0 1 67 Tutaekuri C than 30 should be Ngaruroro Rv at Whanawhana 115.8 5 23 Ngaruroro C Maraetotara Rv at Te Awanga 86.7 5 68 Maraetotara / Waimarama A Ruakituri Rv 115.7 4 24 Wairoa F Tutaekuri Rv at Brookfields Br 86.0 4 69 Tutaekuri C treated with caution. Ngaruroro Rv U⁄S HB Dairies 113.2 4 25 Ngaruroro C Mahiaruhe Strm 85.2 2 70 Aropoanui D Waipawa Rv at SH50 112.9 5 26 Tukituki B Tukituki Rv at Red Br 84.2 5 71 Tukituki B Mangatutu Strm 111.8 1 27 Tutaekuri C Ohiwa Strm 84.2 1 71 Ngaruroro C Anaura Strm 111.7 4 28 Waikari D Mangarau Strm at Keirunga Rd 82.7 4 73 Karamu/Clive C Tukipo Rv at SH50 110.9 4 29 Tukituki B Tutaekuri-Waimate Strm 81.1 3 74 Ngaruroro C Waipawa Rv at SH2 110.7 1 30 Tukituki B Mangakuri Rv 80.0 5 75 Southern Coastal A Esk Rv at Berry Rd 110.5 4 31 Esk D Mangaorapa Strm 79.2 5 76 Porangahau A Ngaruroro Rv D⁄S HB Dairies 110.0 5 32 Ngaruroro C Clive Rv 76.8 1 77 Karamu/Clive C Tukituki Rv at SH50 108.9 5 33 Tukituki B Wairoa Rv U⁄S Wairoa 76.7 1 78 Wairoa F Poporangi Strm 108.9 1 33 Ngaruroro C Porangahau Rv 76.0 5 79 Porangahau A Ngaruroro Rv at Ohiti 107.5 4 35 Ngaruroro C Mangatarata Strm 75.9 4 80 Tukituki B Maraekakaho Strm 107.4 1 36 Ngaruroro C Taurekaitai Strm 75.6 5 81 Porangahau A Tutaekuri Rv U⁄S Mangaone Rv 107.2 3 37 Tutaekuri C Tukituki Rv at Black Br 75.6 5 81 Tukituki B Aropaoanui Rv 107.2 5 37 Aropoanui D Mangarau Strm at Te Aute Rd 75.2 4 83 Karamu/Clive C Waikaretaheke Rv 106.7 3 39 Wairoa F Papanui Strm 72.5 1 84 Tukituki B Mohaka Rv at Raupunga (NIWA) 105.9 4 40 Mohaka E Herehere Strm 68.9 5 85 Karamu/Clive C Esk Rv at Waipunga Br 104.6 5 41 Esk D Karewarewa Strm 68.7 2 86 Karamu/Clive C Taharua Rv at Twin Culv 103.8 5 42 Mohaka E Poukawa Strm 68.0 2 87 Karamu/Clive C Mangaone Rv at Dartmoor 103.3 1 43 Tutaekuri C Awanui Strm 67.7 2 88 Karamu/Clive C Ngaruroro Rv at Chesterhope (NIWA) 103.2 5 44 Ngaruroro C Taipo Strm 66.7 5 89 Karamu/Clive C Mohaka Rv at Raupunga 102.0 5 45 Mohaka E Ruahapia Strm 62.7 4 90 Karamu/Clive C

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Median Sample Reporting Median Sample Reporting Regional SoE sites Site Rank Catchment Site Rank Catchment TSS size (n) Zone TSS size (n) Zone ranked by median Mangaonuku Strm 1.5 59 1 Tukituki B Tukituki Rv 50m U⁄S oxi pond 8.4 44 50 Tukituki B Total Phosphorus Tukituki Rv at Waipukurau Ongaonga Rd 1.5 14 1 Tukituki B Mangamahaki Strm 8.5 12 51 Tukituki B Maraekakaho Strm 1.5 14 1 Ngaruroro C Karewarewa Strm 8.5 33 51 Karamu/Clive C 2009-2013 Ohiwa Strm 1.5 12 1 Ngaruroro C Mangatewai Strm at SH50 8.8 13 53 Tukituki B Taruarau Rv 1.5 14 1 Ngaruroro C Awanui Strm 8.8 39 53 Karamu/Clive C Tutaekuri Rv at Lawrence Hut 1.5 33 1 Tutaekuri C Clive Rv 8.8 32 55 Karamu/Clive C Sites ranked by median Waitio Strm 1.5 32 1 Ngaruroro C Waipawa Rv at SH2 9.0 58 56 Tukituki B Mohaka Rv U⁄S Taharua Rv 1.5 64 1 Mohaka E Waiarua Strm 9.0 34 56 Mohaka E Total Suspended Solids Taharua Rv at Wairango 1.5 58 1 Mohaka E Tukituki Rv at Tamumu Br 9.2 58 58 Tukituki B (TSS, mg/L), 2009-2013, Te Kumi Strm 1.5 17 1 Wairoa F Tukituki Rv 400m D⁄S oxi pond 9.5 44 59 Tukituki B with colours signifying Taharua Rv at Henry's Br 1.9 17 11 Mohaka E Tukituki Rv at Red Br 10.5 60 60 Tukituki B Maharakeke Strm U⁄S Makaretu Rv 3.0 14 12 Tukituki B Waikaretaheke Rv 11.0 14 61 Wairoa F reporting zone. Lower Aniwaniwa Strm 3.0 30 12 Wairoa F Ngaruroro Rv at Motorway 11.3 17 62 Ngaruroro C ranks are ‘better’. Mohaka Rv D⁄S Ripia Rv 3.3 48 14 Mohaka E Ngaruroro Rv at Ohiti 11.8 17 63 Ngaruroro C Waipawa Rv 400m D⁄S oxi pond 3.3 44 15 Tukituki B Tukituki Rv at Black Br 12.0 58 64 Tukituki B Medians generated Tutaekuri Rv at Puketapu 3.5 13 16 Tutaekuri C Waipawa Rv at SH50 12.0 58 64 Tukituki B from sample sizes of at Porangahau Strm 3.7 63 17 Tukituki B Ngaruroro Rv D⁄S HB Dairies 12.5 32 66 Ngaruroro C Waikari Rv 4.0 32 18 Waikari D Sandy Ck 12.5 35 66 Aropoanui D least 30 are considered Maharakeke Strm at Limeworks Station Rd 4.3 13 19 Tukituki B Tukituki Rv at SH50 13.0 62 68 Tukituki B robust (Snelder pers. Tukipo Rv U⁄S Makaretu Rv 4.3 13 19 Tukituki B Ruahapia Strm 13.0 17 68 Karamu/Clive C comm. 2014). Medians Mangaone Rv at Dartmoor 4.3 13 19 Tutaekuri C Mahiaruhe Strm 13.0 12 68 Aropoanui D Herehere Strm 4.5 31 22 Karamu/Clive C Mangarau Strm at Keirunga Rd 13.5 17 71 Karamu/Clive C generated from sample Ngaruroro Rv at Whanawhana 4.5 32 22 Ngaruroro C Mangatarata Strm 13.8 59 72 Tukituki B sizes less than 30 Ripia Rv U⁄S Mohaka Rv 4.5 36 22 Mohaka E Papanui Strm 13.8 33 72 Tukituki B Waipawa Rv 50m U⁄S oxi pond 4.8 44 25 Tukituki B Tukituki Rv at SH2 13.8 57 72 Tukituki B should be treated with Mangaone Rv at Rissington 4.8 35 25 Tutaekuri C Waipunga Rv at Pohokura Rd 14.3 25 75 Mohaka E caution. Maraetotara Rv at Te Awanga 5.0 32 27 Maraetotara / Waimarama A Waingongoro Strm 15.0 32 76 Southern Coastal A Makaretu Rv U⁄S Maharakeke Strm 5.0 14 27 Tukituki B Mohaka Rv D⁄S Waipunga Rv 15.3 53 77 Mohaka E Poukawa Strm 5.0 39 27 Karamu/Clive C Tutaekuri-Waimate Strm 16.0 29 78 Ngaruroro C Tutaekuri Rv U⁄S Mangaone Rv 5.0 32 27 Tutaekuri C Ngaruroro Rv at Fernhill 16.5 32 79 Ngaruroro C Mohaka Rv D⁄S Taharua Rv 5.0 66 27 Mohaka E Taurekaitai Strm 18.5 31 80 Porangahau A Anaura Strm 5.1 17 32 Waikari D Te Iringaowhare Strm 20.3 5 81 Wairoa F Ngaruroro Rv U⁄S HB Dairies 5.3 17 33 Ngaruroro C Taharua Rv at Poronui Stn 22.0 46 82 Mohaka E Mangarau Strm at Te Aute Rd 5.5 23 34 Karamu/Clive C Poporangi Strm 24.0 14 83 Ngaruroro C Kahahakuri Strm 5.8 27 35 Tukituki B Taipo Strm 27.5 32 84 Karamu/Clive C Mangatutu Strm 6.0 18 36 Tutaekuri C Kopuawhara Strm 28.0 31 85 Northern Coastal F Arawapanui Rv 6.0 31 36 Aropoanui D Mangaorapa Strm 31.5 31 86 Porangahau A Taharua Rv at Twin Culv 6.0 59 36 Mohaka E Makara Strm 33.5 13 87 Tukituki B Maraetotara Rv at Waimarama Rd 6.3 31 39 Maraetotara / Waimarama A Pouhokio Strm 40.0 32 88 Maraetotara / Waimarama A Tutaekuri Rv at Brookfields Br 6.8 31 40 Tutaekuri C Porangahau Rv 40.3 31 89 Porangahau A Mokau Strm 6.8 11 40 Wairoa F Mangakuri Rv 42.5 31 90 Southern Coastal A Waipawa Rv U⁄S Tukituki Rv 7.0 44 42 Tukituki B Waiau Rv 65.8 25 91 Wairoa F Mokomokonui Rv 7.0 30 42 Mohaka E Mohaka Rv at Raupunga 68.0 45 92 Mohaka E Tukituki Rv at Tapairu Rd 7.5 44 44 Tukituki B Wairoa Rv U⁄S Wairoa 70.3 29 93 Wairoa F Tukipo Rv at SH50 7.6 63 45 Tukituki B Mohaka Rv at Willowflat 84.0 40 94 Mohaka E Taharua Rv at Red Hut 7.6 63 45 Mohaka E Hangaroa Rv 91.5 29 95 Wairoa F Makaretu Rv at SH50 8.0 62 47 Tukituki B Mangapoike Rv 96.5 25 96 Wairoa F Esk Rv at Berry Rd 8.0 27 47 Esk D Ruakituri Rv 97.0 30 97 Wairoa F Esk Rv at Waipunga Br 8.0 30 47 Esk D Opoutama Strm 131.0 18 98 Northern Coastal F

164 Mohaka River Catchment

Appendix E NPS-FW (2014) NOF attribute tables

Periphyton NOF attribute table

Mohaka River Catchment

Nitrate NOF attribute table

166 Mohaka River Catchment

Ammonia NOF attribute table

Mohaka River Catchment 167

Dissolved Oxygen NOF attribute table

168 Mohaka River Catchment

Escherichia coli NOF attribute table

Mohaka River Catchment 169

Appendix F Mohaka catchment NOF periphyton compliance table

A band B band C band D band NOF band: exceeded no more than 8% of samples ≤50 mg/m2 >50 and ≤120 mg/m2 >120 and ≤200 mg/m2 > 200 mg/m2

Total A band B band C band D band A band B band C band D band Overall NOF Site name Data from No. obs. No. obs. No. obs. No. obs. No. obs. % obs. % obs. % obs. % obs. band Mohaka Rv U/S Taharua Rv 2009 - 2013 46 46 0 0 0 100.0% 0.0% 0.0% 0.0% A Taharua Rv at Wairango No Data NA NA NA NA NA NA NA NA NA NA Taharua Rv at Twin Culv No Data NA NA NA NA NA NA NA NA NA NA Taharua Rv at Henry's Br 2013 1 1 0 0 0 NA NA NA NA NA Taharua Rv at Poronui Stn 2009 - 2013 18 16 2 0 0 88.9% 11.1% 0.0% 0.0% B Taharua Rv at Red Hut 2009 - 2012 2 2 0 0 0 NA NA NA NA NA Mohaka Rv D/S Taharua Rv 2009 - 2013 40 42 3 0 0 93.3% 6.7% 0.0% 0.0% A Ripia Rv U/S Mohaka Rv 2009 - 2013 6 6 0 0 0 100.0% 0.0% 0.0% 0.0% A Mohaka Rv D/S Ripia Rv 2009 - 2013 40 37 1 2 0 92.5% 2.5% 5.0% 0.0% A Mohaka Rv at SH5 (NIWA) No Data NA NA NA NA NA NA NA NA NA NA Waiarua Strm 2009 - 2011 2 2 0 0 0 NA NA NA NA NA Waipunga Rv at Pohokura Rd 2009 1 1 0 0 0 NA NA NA NA NA Mokomokonui Rv 2009 - 2013 5 5 0 0 0 100.0% 0.0% 0.0% 0.0% A Mohaka Rv D/S Waipunga Rv 2009 - 2013 29 26 2 1 0 89.7% 6.9% 3.4% 0.0% A Mohaka Rv at Willowflat 2009 - 2011 13 10 3 0 0 76.9% 23.1% 0.0% 0.0% B Mohaka Rv at Raupunga 2009 - 2012 26 19 5 2 0 73.1% 19.2% 7.7% 0.0% B Mohaka Rv at Raupunga (NIWA) No Data NA NA NA NA NA NA NA NA NA NA

Mohaka River Catchment

Appendix G Nutrient and sediment loads and yields for long-term SoE monitoring sites

Catchment Flow Yield SS Load TP Load TN Load DRP Load DIN Load SS Yield TP Yield TN Yield DRP Yield DIN Yield Reporting name area (ha) (l/s/ha) (T/yr) (T/yr) (T/yr) (T/yr) (T/yr) (kg/ha/yr) (kg/ha/yr)) (kg/ha/yr) (kg/ha/yr) (kg/ha/yr)

Mohaka Rv U/S Taharua Rv 12071 0.539 725 1.64 23.6 0.62 9.7 60 0.14 1.96 0.051 0.80 Taharua Rv at Wairango 1953 0.240 35 0.36 49.7 0.25 48.1 18 0.18 25.44 0.129 24.61 Taharua Rv at Twin Culv 3562 0.268 134 0.69 112.0 0.45 108.7 38 0.19 31.44 0.127 30.51 Taharua Rv at Henry's Br 8150 0.308 613 1.27 181.6 0.71 174.6 75 0.16 22.28 0.088 21.43 Taharua Rv at Poronui Stn 8438 0.425 2065 3.51 201.5 1.24 189.3 245 0.42 23.89 0.147 22.44 Taharua Rv at Red Hut 13581 0.376 1170 2.90 230.4 1.13 212.4 86 0.21 16.97 0.083 15.64 Mohaka Rv D/S Taharua Rv 28432 0.454 2454 5.70 303.8 2.04 265.1 86 0.20 10.68 0.072 9.32 Ripia Rv U/S Mohaka Rv 18432 0.369 875 2.36 32.4 1.29 18.7 47 0.13 1.76 0.070 1.01 Mohaka Rv D/S Ripia Rv 82408 0.459 6698 14.34 445.7 5.97 358.5 81 0.17 5.41 0.072 4.35 Waiarua Strm 2779 0.364 258 0.48 21.2 0.19 18.6 93 0.17 7.62 0.069 6.68 Waipunga Rv at Pohokura Rd 8870 0.290 871 1.30 22.5 0.57 16.2 98 0.15 2.54 0.064 1.82 Mokomokonui Rv 14634 0.317 839 2.93 19.9 2.05 9.1 57 0.20 1.36 0.140 0.62 Mohaka Rv at SH5 (NIWA) 111170 0.341 No Data 27.48 454.0 7.17 334.6 No Data 0.25 4.08 0.064 3.01 Mohaka Rv D/S Waipunga Rv 161160 No Flow No Flow No Flow No Flow No Flow No Flow No Flow No Flow No Flow No Flow No Flow Mohaka Rv at Willowflat 222345 0.334 323153 224.74 795.9 21.07 458.8 1453 1.01 3.58 0.095 2.06 Mohaka Rv at Raupunga 239172 0.329 266497 223.39 779.4 24.82 454.2 1114 0.93 3.26 0.104 1.90 Mohaka Rv at Raupunga (NIWA) 239172 0.329 No Data 117.65 683.8 20.85 416.5 No Data 0.49 2.86 0.087 1.74

Yields have been calculated for Total Phosphorus (TP), Dissolved Reactive Phosphorus (DRP), Total Nitrogen (TN), Dissolved Inorganic Nitrogen (DIN) and Suspended Solids (SS) according to: Average method. The mean concentration (based on monthly Where: observations) is multiplied by the mean flow (based on daily L Average annual export coefficient (kg yr-1 ha-1 )

observations). Ac Catchment Area (ha) K Units conversion factor (31.6) (kg s mg-1 yr-1 ) 푛 푁 퐶푀 Monthly measured instantaneous concentration (mg m-3 ) 퐾 퐶푀 푄퐷 퐿 = (∑ 푖 ) (∑ 푗 ) 푄퐷 Daily measured instantaneous flow (m3s-1 ) 퐴푐 푛 푁 푖=1 푗=1 n Number of monthly samples N Number of daily samples

(Verhoff, F. H., Yakish, S. M., and Melfi, D. A. (1980). River nutrient and chemical transport estimates. Journal of the Environmental Engineering Division 10, 591–608.)

Mohaka River Catchment

Appendix H MfE benthic cyanobacteria alert-level framework Taken from page 17 of the “Ministry for the Environment and Ministry of Health. 2009. New Zealand Guidelines for Cyanobacteria in Recreational Fresh Waters – Interim Guidelines. Prepared for the Ministry for the Environment and the Ministry of Health by SA Wood, DP Hamilton, WJ Paul, KA Safi and WM Williamson. Wellington: Ministry for the Environment.”

Mohaka River Catchment