Ashley River/Rakahuri: Ecological Minimum Flow Assessment for Ashley Gorge

WATER WAYS CONSULTING LTD

ASHLEY RIVER/RAKAHURI: ECOLOGICAL MINIMUM FLOW ASSESSMENT FOR ASHLEY GORGE

PREPARED FOR: ENVIRONMENT CANTERBURY

DATE: MAY 2017

REPORT NUMBER: 37-2017A

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Table of Contents 1 Introduction ...... 1 1.1 Background ...... 1 1.2 Scope of Report ...... 1 1.3 Ecological Considerations for Minimum Flow Setting ...... 1 2 Aquatic Habitat assessment ...... 4 2.1 Introduction ...... 4 2.2 Field Survey ...... 4 3 Habitat Assessment Results ...... 6 3.1 General Habitat Observations...... 6 3.2 Habitat Availability Variation with Changing Flow ...... 8 3.3 Fish Passage ...... 11 3.4 Algal growth ...... 14 3.5 Summary of Habitat Availability ...... 14 4 Recommendations for Minimum flow Settting ...... 16 4.1 SEFA Model ...... 16 4.1.1 Taxa to consider for minimum flow recommendations ...... 16 4.1.2 Bluegill bully and torrentfish ...... 16 4.1.3 Brown trout ...... 16 4.1.4 Chinook salmon ...... 17 4.1.5 Macroinvertebrates ...... 17 4.1.6 Fish passage ...... 17 4.1.7 Algal growth ...... 17 4.1.8 Downstream flow and freshes ...... 17 4.1.9 Water Quality and Duration of Low Flow ...... 17 5 Conclusions ...... 18 6 References ...... 19

Appendix A. New Zealand Freshwater Fish Database Summary data for Ashley River/Rakahuri ...... 20

Appendix B. Photographs of cross sections ...... 21

Appendix C Habitat preference curves ...... 30

Appendix D SEFA Area Weighted Suitability model data...... 40

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

LIST OF TABLES

Table 1: Summary information for cross sections (data collected 11 January 2017)...... 6 Table 2: Summary habitat model data showing flows that provides maximum habitat and the percentage of that habitat present at 7dMALF...... 14

LIST OF FIGURES

Figure 1: From the top upland bully, torrentfish, Canterbury galaxias and brown trout...... 3 Figure 2: Black fronted tern feeding in shallow riffle water...... 4 Figure 3: Survey reach of the Ashley River...... 5 Figure 4: Modelled habitat availability for Canterbury galaxias, upland bully, bluegill bully and torrentfish...... 8 Figure 5: Modelled habitat availability for longfin and shortfin eels...... 9 Figure 6: Modelled habitat availability for brown trout life history stages...... 9 Figure 7: Modelled habitat availability for Chinook salmon life history stages...... 10 Figure 8: Modelled habitat availability for macroinvertebrates, including general invertebrate prey and selected common invertebrates...... 10 Figure 9: Modelled habitat availability for wrybill and black fronted terns...... 11 Figure 10: Modelled fish passage with varying depth requirements for fish (from the top) 10 cm deep water, 20 cm deep water, 25 cm deep water, 30 cm deep water (bottom) all with passage pathways with water velocities less than 1.25 m/s...... 13 Figure 11: Modelled habitat availability for short and long filamentous algae...... 14

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

1 INTRODUCTION

1.1 Background The Ashley River/Rakahuri rises in the Puketeraki and Pancake ranges of north western Canterbury. These ranges are foothill areas of the Southern Alps and do not form part of the main divide of the South Island. From its headwaters, the Ashley River/Rakahuri flows through Lees Valley and then downstream through the 12 km long Ashley Gorge. Downstream of the Ashley Gorge the river flows across the Canterbury Plains and receives inflows from several tributaries including the Glentui, Garry, Okuku and Makerikeri Rivers. It flows just to the north of Rangiora before flowing out to sea via the Ashley River/Rakahuri estuary. The lower reaches of the river have a number of spring-fed tributaries including Saltwater Creek on the northern bank and Waikuku Stream and Taranaki Creek on the southern bank. Mosely (2001) and Megaughin & Hayward (draft 2016) show that the Ashley River/Rakahuri loses surface water to ground water as it crosses the Canterbury Plains. This loss of water can lead to a variable length of drying reach between the Okuku River confluence and State Highway 1 (SH1) when the flow at the Ashley Gorge drops below 2.5 m3/s. Downstream of SH1 the river gains flow from spring-fed tributary and ground water inflows.

The river lies within the Waimakariri Canterbury Water Management Strategy (CWMS) zone and currently the Zone Committee is assessing water management options for the Ashley River/Rakahuri catchment. This work includes the setting of minimum flows for the streams in the catchment including the Ashley River/Rakahuri.

1.2 Scope of Report The report provides the results of an assessment of the physical habitat provided at different river flows and assesses the minimum flow requirements to provide for the ecology of the Ashley River downstream of Ashley Gorge flow recorder. It also provides an assessment of the flow requirements to provide for fish passage between the Gorge and the river mouth. Not within scope of this report are assessments of the flow requirements for other factors such as recreational use, and landscape. It does not address issues associated with water quality.

1.3 Ecological Considerations for Minimum Flow Setting When considering flow options for rivers a number of issues and options can be considered, these include:

◼ Providing habitat for desired fish and invertebrates; ◼ Maintaining fish passage; ◼ Providing spawning habitat; ◼ Providing breeding and feeding habitat for wading birds; and ◼ Reducing the potential for undesirable algal blooms and drying reaches.

Physical habitat assessments measure and model habitat in the river. The model constructed from data collected is used to predict changes in the habitat available to aquatic organisms. As such the assessment is limited to predicting the habitat available and river features such as water depth and velocity at different flows. The assessment does not take into account factors such as the interactions between species and how these may limit the occurrence of one or more species, nor

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment does it assess the effects of water quality on organisms. If habitat is not a limiting factor then the abundance of particular species then the setting of a minimum flow will only ensure habitat is available and will not ensure the expected species will occupy the habitat

In the Ashley River/Rakahuri there are recreational fisheries for trout (Figure 1) and Chinook salmon, customary fisheries for tuna (eels) and whitebait, and the river supports six species of At Risk Declining (Goodman et al 2014) fish species including, Canterbury galaxias, bluegill bully, torrentfish, and longfin eel in or near to the study area at Ashley Gorge. In total 16 fish species have been recorded in the Ashley River (see Appendix A for list). Additional native fish such common, giant and upland bullys are also present in the river. A key consideration, aside from habitat availability, for bluegill, common and giant bully, torrentfish, short and longfin eels and Chinook salmon is fish passage to and from the sea for these species. If fish passage is unavailable these fish species cannot complete their life cycle that includes movements to and from the sea to freshwater habitats along the river.

The Ashley River is also breeding habitat for a range of threatened braided river birds including wrybill and banded dotterel (Hughey 1998) and black fronted terns (Figure 2) and black-billed gulls. These bird species are present nesting along the river generally from August to late December each year.

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Figure 1: From the top upland bully, torrentfish, Canterbury galaxias and brown trout.

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Figure 2: Black fronted tern feeding in shallow riffle water.

2 AQUATIC HABITAT ASSESSMENT

2.1 Introduction The minimum flow assessment was conducted using the standard survey method for physical habitat model System for Environmental Flow Analysis (SEFA version 1.3 Payne & Jowett 2012). This assessment requires an initial reach survey to assess the relative proportions of habitat units – e.g., riffles, runs, pools. Following the initial survey 15 cross sections are selected along the river reach that are used to represent the river habitat in the habitat model. At each cross-section the flow is gauged, a water level marker installed and during the flow gauging the stream bed composition is recorded, along with water depth and water velocity. Two subsequent site visits are undertaken during which flow is gauged at one or two cross-sections and the water level is measured at all cross sections. The, water depth, water velocity and substrate data is used in the SEFA programme to model instream habitat for fish, invertebrates and algal. The river model can also be used to assess fish passage.

2.2 Field Survey An initial field survey of the Ashley River/Rakahuri was undertaken on the 5 January 2017 along a 1.8 km reach of the river upstream and downstream of the Ashley Gorge Road bridge (Figure 3). The survey assessed the distribution and abundance of habitat units, riffle, run and pools and the braided nature of the river along this reach.

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Figure 3: Survey reach of the Ashley River.

On the 11 January 2017 fifteen cross sections were gauged, two upstream of the Ashley Gorge road bridge and thirteen downstream of the bridge. Cross sections were selected according to the abundance of habitat types, with eleven of the cross sections placed in run habitat and four in riffle habitat. This distribution corresponded with the prevalence of the different habitats types determined by an initial site survey. Pool habitat in this reach was very rare making up less than 2% of the reach and as such was not included in the habitat modelling. Cross sections were selected so that wide shallow and narrow deep cross section of each habitat type were included in the survey. Including shallow reaches was considered important as these cross-sections represent potential fish passage restrictions. At each cross section the water depth and velocity was measured at a minimum of 20 locations across the cross section and the percentage composition of river bed substrate particles was estimated in eight categories, mud/silt, sand, fine gravel, coarse gravel, cobble, boulder, bedrock and vegetation. All survey cross sections avoided areas where recreational activity altered the stream habitat. No cross-sections where placed in a short braided section of river reach due to difficulties locating a cross-section the water level gauges would be safe from 4WD activities and to avoid 4WD track modifications to the stream bed.

The Ashley Gorge flow recorder at mid-day on the 11th of January 2017 recorded a flow of 3.37 m3/s and the flow was declining through the rest of the day.

Two follow up visits were made to the cross sections to measure water levels and gauge the river to provide calibration flow data for the physical habitat model. Revisit one was undertaken on the 13 February 2017 with the flow at the Ashely Gorge recorder at mid-day being 2.66 m3/s and rising. The second revisit was on the 3 March 2017 when the mid-day flow was 2.028 m3/s and declining.

Habitat availability analyses were undertaken using the SEFA software. Habitat preferences for fish, invertebrates, algae and birds where sourced from existing habitat preference curves provided with SEFA and earlier RHYHABSIM software (Jowett 1999) (see Appendix C). The habitat models were calibrated for low flows around the 7day Mean Annual Low Flow of 2.040 m3/s (7dMALF) and habitat

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment availability was modelled flows between 0 m3/s and 4 m3/s as a reasonable low flow range. All cross-section rating curves were checked and the default rating calculations used.

3 HABITAT ASSESSMENT RESULTS

3.1 General Habitat Observations The initial habitat survey was undertaken when the flow at the Ashley Gorge recorded was 3.37 m3/s. This survey of the 1.8 km reach found that 71% of the habitat present was run habitat, 27% riffle habitat and 2% pool habitat. One section approximately 200 m long consisted of two approximately equal sized braids. Other parts of the reach downstream of the road bridge had two braids, but consisted of one major braid and one very minor braid. Often the minor braid was drying or close to drying up and these braids would not provide habitat during low flow periods and where not included in the modelling. The channel was also noted to vary considerably in width and depth characteristics providing a range of habitat types. The river also moves from one with a channel constrained by bedrock banks in the gorge to a more unconstrained river downstream of the road bridge. The river banks in the downstream reach are alluvial gravels and cobbles and are presently stabilised by vegetation. However, the river bed widens and while the wetted width is similar to the gorge reach the river has the ability to meander and braid within the wider channel downstream of the road bridge. This creates gravel bars, small islands and wide shallows and provides different habitat to the upstream gorge reach.

It was also noted that instream recreational activities around the Ashley River upstream of the road bridge modified the habitat available. This included one ‘weir’ constructed across the whole river raising the upstream water level 0.3 m and creating un-natural pool habitat. These were considered temporary habitat alterations and the area was avoided when cross sections where selected for the habitat model

Table 1: Summary information for cross sections (data collected 11 January 2017). Cross Habitat Width Max Mean Mean Flow Common Section type (m) Depth (m) Depth (m) velocity m3/s substrate1 (m/s)

1 Riffle2 14.45 0.65 0.25 1.02 3.633 Cobble (Coarse gravel, boulder

2 Run 25.35 0.34 0.22 0.53 3.005 Coarse gravel (fine gravel)

3 Run 33.6 0.54 0.30 0.32 3.145 Coarse gravel

4 Riffle 19.35 0.40 0.19 0.74 2.758 Cobble (boulder, Coarse gravel)

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

5 Run 11.65 0.86 0.53 0.44 2.705 Cobble (coarse gravel, boulder)

6 Riffle 14.3 0.56 0.29 0.69 2.825 Cobble (coarse gravel, boulder)

7 Run 16.95 0.82 0.59 0.27 2.738 Coarse gravel (fine gravel, cobble)

8 Run 21.6 0.70 0.42 0.32 2.935 Coarse gravel (fine gravel)

9 Run 30.35 0.54 0.28 0.35 2.958 Coarse gravel (fine gravel, cobble)

10 Riffle 7.8 0.67 0.38 0.96 2.884 Cobble (coarse gravel)

11 Run 9.4 0.50 0.39 0.76 2.780 Cobble (coarse gravel, boulder)

12 Run 14.2 0.88 0.61 0.32 2.813 Coarse gravel (cobble)

13 Run 18.8 1.10 0.55 0.26 2.671 Coarse gravel (sand, fine gravel)

14 Run 22.5 0.64 0.483 0.25 2.720 Coarse gravel (sand, fine gravel)

15 Run 29.3 0.69 0.29 0.31 2.657 Coarse gravel (fine gravel, cobble)

1 Most abundant substrate particle size followed by other common substrate sizes in brackets. 2 Gauging less accurate in riffles due to turbulent flow.

On the first site revisit, cross sections 2 and 14 were gauged and the flow at these sites was 2.505 m3/s and 2.183 m3/s respectively. The second revisit gauged cross sections 3 and 14 and the flows were 1.787 m3/s and 1.470 m3/s respectively. All three gauging visits show a surface flow loss from sites 2 or 3 to site 14 of 0.285 m3/s, 0.322 m3/s and 0.317 m3/s. This consistent flow loss of approximately 0.300 m3/s is thought to be loss of surface flow to ground water or to sub-surface flow in the gravel bed of the river. It is notable that flow at the Ashley Gorge flow recorder was also greater than the flows at cross sections 2 and 3:

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

◼ on the 11 January, the flow was 3.37 m3/s at the gorge and 3.005 m3/s at cross section 2; ◼ on the 17 February, the flow 2.66 m3/s at the gorge and 2.505 m3/s at cross section 2; and ◼ on the 3 March, the flow at the gorge was 2.08 m3/s and 1.787 m3/s at cross section 3.

It is unknown whether the difference between the Ashley Gorge flow recorder and cross-section 2 and 3 is due to flow losses to sub-surface flow or a ratings discrepancy at the recorder.

The survey data show several related features of the river channel. The riffle cross sections and narrow run cross sections have high mean water velocities and large stream bed particles. Wider run cross sections have lower water velocities and have a bed dominated by smaller particles sizes. Maximum depth on each cross section is generally over 0.5 m and even the wide cross sections have a deep channel within the cross section. Habitat observations made during the initial stream walk identified riffle zones as the areas where shallow water was most common and may lead to upstream fish passage difficulties. Although deeper water areas across the river channel were present (Table 1) when the initial gaugings where conducted. However, as the flow drops in the river the riffles will become shallower more rapidly than other habitats.

3.2 Habitat Availability Variation with Changing Flow Habitat availability differed amongst the four small native fish, Canterbury galaxias, upland bully, bluegill bully and torrentfish. Upland bully is a low water velocity inhabitant, often found along the river margins. Peak habitat availability for upland bully occurs at approximately 0.5 m3/s and declines above this as water velocity increases as the river increases in size. Canterbury galaxias habitat peaks at 1.5 m3/s. Bluegill bully and torrentfish habitat increases throughout the flow range modelled (Figure 4).

/m) 2 6

Bluegill bully Upland bully 4 Torrentfish Canterbury galaxias

2 Area Weighted Suitability Weighted Area (m

0 0 1 2 3 4 Flow (m3/s)

Figure 4: Modelled habitat availability for Canterbury galaxias, upland bully, bluegill bully and torrentfish.

For the two eel species the available habitat rises rapidly as flow increases from zero to 0.5 m3/s. Above this flow habitat availability continues to increase but very slowly and once flows exceed 3 m3/s the habitat predictions indicate a slow decline in available habitat (Figure 5). Therefore, any minimum flow setting process will have little effect on eel habitat availability if the minimum flow is greater than 1 m3/s.

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

10 /m)

2 8

6 Shortfin eel < 300mm Shortfin eel > 300mm Longfin eel < 300mm 4 Longfin eel > 300mm

2 Area Weighted Suitability Weighted Area (m

0 0 1 2 3 4 Flow (m3/s)

Figure 5: Modelled habitat availability for longfin and shortfin eels.

For brown trout habitat availability drops rapidly once the flow recedes below 1 m3/s, although for adult brown trout the decline rate does depend on the habitat preferences used in the model. With the preferences of Raleigh et al (1986) (blue curve, Figure 6) showing the most pronounced decline in habitat once flows drop below 0.1m3/s. For fry and yearling brown trout habitat availability peaks at 2 m3/s and 2.5 m3/s but the decline in habitat availability around these points is slow. Brown trout spawning habitat increases from 0 m3/s to 2.5 m3/s but is close to that maximum in a range from 2 m3/s to 4 m3/s (Figure 6). Brown trout spawning occurs in May and June with eggs and the alevins remaining in the redds until September or October; the majority of this period is outside the irrigation season or during the higher flow spring period.

/m) 2 5 Brown trout adult 4 Brown trout adult Brown trout yearling 3 Brown trout fry to 15cm Brown trout spawning 2

Area Weighted Suitability Weighted Area (m 1

0 0 1 2 3 4 Flow (m3/s)

Figure 6: Modelled habitat availability for brown trout life history stages. For Chinook salmon, the Ashley River/Rakahuri provides abundant fry habitat especially between 1 m3/s and 2.5 m3/s (Figure 7). Similarly, spawning habitat is relatively abundant above 2 m3/s. However, holding water for adult salmon is very limited. The model does under-estimate this habitat as the rare pool habitat has not been included in the model. Even so, as this habitat is very rare holding areas are limited in this reach of the river. However, it should be noted the Chinook salmon run is small in the Ashley River/Rakahuri and downstream fish passage issues are a possible limiting factor rather than holding habitat near Ashley Gorge.

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

/m) 2 5

4 Chinook salmon adult spawning Chinook salmon migration holding 3 Chinook salmon fry < 55 mm

Area Weighted Suitability Weighted Area (m 1

0 0 1 2 3 4 Flow (m3/s)

Figure 7: Modelled habitat availability for Chinook salmon life history stages.

For the majority of invertebrate species assessed habitat availability increases with increasing flow. The rate of decline for habitat does increase below 2 m3/s and this decline is rapid below 1 m3/s (Figure 8). As these species are important food items for fish and birds abundant invertebrate communities can help ensure the predators have sufficient food supply. A number of these invertebrates are also algal grazers and retaining them in high abundance can help reduce algal growth rates and algal biomass.

10 /m)

2 8

Food producing 6 Deleatidium (mayfly) Nesameletus (mayfly) Aoteapsyche (net-spinning caddis) 4 Pycnocentrodes (stony-cased caddis) Hydrobiosidae (free-living caddis)

2 Area Weighted Suitability Weighted Area (m

0 0 1 2 3 4 Flow (m3/s)

Figure 8: Modelled habitat availability for macroinvertebrates, including general invertebrate prey and selected common invertebrates.

Few habitat preference curves are available for bird feeding in rivers. The wrybill preferences indicate a peak feeding flow between 0.1 m3/s and 1.8 m3/s (Figure 9). Given this bird prefers shallow side braid habitat and this was relatively rare in this reach of the Ashley River/Rakahuri this is not unexpected. Downstream in the more braided reaches higher flows are likely to provide more feeding habitat. The two habitat preference curves developed for black fronted terns on other larger rivers show contrasting responses to the flow change. For the Ashley River/Rakahuri it is not possible to determine whether either of these black fronted tern models are appropriate.

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

/m) 2 3

Wrybill plover feeding 2 Black-fronted tern (Rangitata) Black-fronted tern (Waimakariri)

1 Area Weighted Suitability Weighted Area (m

0 0 1 2 3 4 Flow (m3/s)

Figure 9: Modelled habitat availability for wrybill and black fronted terns.

3.3 Fish Passage Fish passage in the Ashley River/Rakahuri must consider a number of fish species, the timing of their migrations, whether these are upstream or downstream migrations and the water depths and water velocities that can limit upstream fish passage. Another key consideration for the Ashley River/Rakahuri is the presence of a natural drying reach of the river that is present between the Okuku River confluence and SH 1 bridge. Mosley (2001) reports that this reach of the river can dry when the flow at Ashley Gorge is approximately 2.5 m3/s. More recent analyses reported in Megaughin & Hayward (draft 2016) show the same drying pattern but indicate a net loss between the Gorge recorder and SH1 is approximately 2.0 m3/s. Given the 7dMALF for the Ashley Gorge site is 2.04 m3/s this natural drying will occur most if not all years. However, the duration of dry periods, the distance of the dry riverbed and number of separate drying events can be influenced by water abstraction. Mosley (2001) also notes the Ashley River/Rakahuri’s summer flow is characterised by small freshes that can be in the range of 3 to 10 m3/s. These fresh events can reconnect the river, and during the declining flow periods following the fresh, provide opportunities for fish migrations to occur.

The native fish requiring fish passage to the mid and upper reaches of the river across the Canterbury Plains are: longfin eel, torrentfish, bluegill bully and possibly shortfin eel and common bully. Three whitebait species, giant kokopu, koaro and inanga have been recorded in the Ashley River/Rakahuri catchment, but the first two are very rare and the inanga is restricted to the lower river and tributaries. Therefore, this assessment has concentrated on the other species listed. Whitebait are also considered least vulnerable to passage issues as the upstream migrating whitebait use shallow water and migrate in late spring when water levels are sufficient to provide for migration. Kokopu and koaro move downstream as very small larval fish and do so during fresh events. Inanga reside in the lower reaches of the river, spawning in the tidal areas, and downstream passage is only hindered if the river mouth is closed.

Upstream passage for eels starts when glass eels enter freshwater in late winter and spring. The glass eels become pigmented and as the water temperature rises begin to migrate upstream. The major migration periods for both species of eel are essentially the summer period between mid- December and mid-March. Elvers (juvenile eels) do not require deep water to migrate upstream and the shallow margins of any river or stream will provide suitable habitat for migration. Therefore, to maintain fish passage the most important factor to consider is to avoid the creation of or increasing the extent and duration of drying reaches that will prevent upstream migration.

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

The downstream passage for eels will require the continuous pathway to the sea and dry reaches will prevent downstream movement. Adult eels migrate downstream in autumn and most individuals migrate during freshes. The movement during freshes should provide eels with a pathway through the potentially dry lower reaches of the Ashley River/Rakahuri.

Torrentfish migrations are not well understood but the upstream migration is conducted by small fish 20-40 mm long. These fish can move upstream in relatively small flows as long as there is a continuous wetted pathway. Adult fish are expected to migrate downstream to the lower reaches to spawn and then return upstream to adult habitat throughout the river. The fish survey information available indicates that torrentfish in the upper reaches of many rivers are predominately female whereas as those closer to the sea are male. Both sexes have to migrate downstream and this is expected to occur from late March to May. Almost nothing is known about this migration. However, in the Ashley River/Rakahuri the drying reach upstream of SH 1 will need to be flowing to allow both the downstream and return upstream migration of adult torrentfish. Like the torrentfish the spawning biology and movements of bluegill bully are not well understood. Adult bluegill bullies are smaller than torrentfish and spawning is expected to occur at a similar time in the lower reaches. Therefore, flows that provide for torrentfish movement should also accommodate bluegill bully.

Chinook salmon migrate upstream in the period from December to April each year with the peak migration periods in February and March. The large adult salmon require deeper water than upstream migrating native fish with estimates of the required water varying but 25 cm is an accepted minimum depth (Special Tribunal 2002). The cross-section data has been used to provide estimates of the flow in the Ashley River/Rakahuri in the study reach that will provide continuous water depths of 10, 20, 25 and 30 cm with water velocities less than 1.25 m/s (Figure 10). The 25 cm deep analysis indicates that a flow of 2.0 m3/s is required to provide passage. It should be noted this is only required if Chinook salmon spawn at or upstream of the entry to Ashley Gorge. With respect to Chinook salmon the lack of holding water may present some obstacles to migration.

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Ashley 7

4 Contiguous (m)

3 Total (m) Passage width 2

0 0 1 2 3 4 Flow (m3/s)

Ashley 5

3 Contiguous (m) Total (m)

2 Passage width

0 0 1 2 3 4 Flow (m3/s)

2 Contiguous (m)

Total (m) Passage width

0 0 1 2 3 4 Flow (m3/s)

Ashley 3.5

3.0

2.5

2.0 Contiguous (m)

1.5 Total (m) Passage width 1.0

0.5

0.0 0 1 2 3 4 Flow (m3/s)

Figure 10: Modelled fish passage with varying depth requirements for fish (from the top) 10 cm deep water, 20 cm deep water, 25 cm deep water, 30 cm deep water (bottom) all with passage pathways with water velocities less than 1.25 m/s.

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

3.4 Algal growth Filamentous algae is often considered undesirable when the biomass and stream bed coverage becomes extensive. Water velocity can limit the growth of these algal taxa as the algal filaments break off in higher water velocities. For the Ashley River/Rakahuri flows above 2.0 m3/s reduce habitat suitable for long filamentous algae (Figure 11). However, habitat for short filamentous algae increased throughout the flow range modelled (0 – 4.0 m3/s).

However, there are other significant nuisance growth forms of algae, and the Ashley River has been noted in recent years as supporting extensive growths of potentially toxic cyanobacteria mats (McAllister 2015). These growths are also flow dependant and have higher flow optima than filamentous algae.

10 /m)

2 8

6 Short filamentous Long filamentous 4

2 Area Weighted Suitability Weighted Area (m

0 0 1 2 3 4 Flow (m3/s)

Figure 11: Modelled habitat availability for short and long filamentous algae.

3.5 Summary of Habitat Availability Table 2 provides a summary of the habitat availability for the taxa modelled and compares maximum habitat availability to that present at the 7dMALF.

Table 2: Summary habitat model data showing flows that provides maximum habitat and the percentage of that habitat present at 7dMALF. Taxa Flow for % of Habitat Flow below maximum maximum availability which habitat habitat (m3/s) habitat trend with loss appears present at increasing flow rapid (m3/s) 7dMALF above 7dMALF

Birds

Wrybill 0.10 43 decreasing 0.1

Black-fronted tern 0.70 31 decreasing 0.4

Black-fronted tern 3.80 79 increasing N/A#

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Invertebrates

Food producing habitat 4.0+ N/A* increasing N/A

Deleatidium 4.0+ N/A increasing 0.5

Nesameletus 3.10 97 increasing 0.5

Aoteapsyche 4.0+ N/A increasing N/A

Pycnocentrodes 4.0+ N/A increasing N/A

Hydrobiosdae 4.0+ N/A increasing 0.3

Fish

Chinook salmon fry 2.20 100 decreasing 0.7

Chinook salmon 3.20 83 increasing N/A spawning

Chinook salmon holding 4.0+ N/A increasing N/A water

Brown trout adult 4.0+ N/A increasing N/A

Brown trout adults 2.80 97 increasing 0.1

Brown trout yearling 2.80 97 increasing 0.6

Brown trout fry to 15 2.05 1.00 at max 0.8 cm

Brown trout spawning 3.10 87 increasing N/A

Shortfin eel <300 mm 2.30 100 stable 0.4

Shortfin eel >300 mm 2.00 100 stable 0.2

Longfin eel <300 mm 2.80 95 increasing 0.4

Longfin eel >300 mm 2.80 95 increasing 0.2

Canterbury galaxias 1.50-1.70 99 decreasing 0.2

Upland bully 0.60 83 decreasing 0.3

Torrentfish 4.0+ N/A increasing N/A

Bluegill bully 4.0+ N/A increasing N/A

* percentage not calculated as flow for maximum habitat exceeds model flow range.

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

# no rapid changes in habitat availability with changing flow.

4 RECOMMENDATIONS FOR MINIMUM FLOW SETTTING

4.1 SEFA Model 4.1.1 Taxa to consider for minimum flow recommendations The SEFA model indicates some taxa, the eels and Canterbury galaxias, are relatively insensitive to change in flow in the Ashley River/Rakahuri, at least in the low flow range modelled. Other taxa (wrybill) and life history stages (e. trout spawning) modelled are only present or only occur in the river at times outside the expected low flow period of summer and autumn. The braided river birds that nest on the river bed do so in spring and generally depart by mid or late December. Similarly, trout and salmon spawning and egg development occurs in late autumn, winter and early spring, again outside the expected low flow period. Therefore, the flow recommendations concentrate on the effects of low flows on the following taxa and/or life history stages:

◼ Bluegill bully ◼ Torrentfish ◼ Brown trout ◼ Chinook salmon migration ◼ Macroinvertebrate species

An assessment of the effects of a change flow has been conducted for flows between 1.5 m3/s and 2.0 m3/s. The lower limit of 1.5 m3/s represents a 25% reduction in the river flow below the natural 7dMALF of 2.05m3/s. Beca (2008) consider that for low base flow rivers such as the Ashley River/Rakahuri a reduction of greater than 20% of the 7dMALF creates a high risk of the significant hydrological alteration particularly the duration of low flow conditions. 4.1.2 Bluegill bully and torrentfish These two fish are considered to be in decline (Goodman et al 2014) and utilise riffle habitat, a habitat that is often rapidly lost as flow declines. Habitat for both species increases with increasing flow and there is no obvious flow to set as a minimum flow. Therefore, the minimum flow can be set at a level that retains a desired percentage of the habitat. This is usually set at a flow below the 7dMALF (Beca 2008) to allow some abstraction but to retain a desire level of habitat. For threatened species, the retention of between 80-90 % of the available habitat at 7dMALF is often recommended. A minimum flow of 1.5 m3/s would retain 87% and 89% of the torrentfish and bluegill bully habitat present at the 7dMALF and be sufficient to maintain habitat for these species. 4.1.3 Brown trout The reduction in available habitat for brown trout yearlings and fry between flows of 1.5 m3/s and 2.0 m3/s is less than 10%. A similar trend is present for one of the two adult brown trout curves. However, for the adult habitat based on the Jowett and Hayes (1994) preferences the habitat loss between 2.0 m3/s and 1.5 m3/s is 25%. It is worth noting the habitat model does not include the occasionally deep water pool habitat and actual adult trout habitat will be slightly higher than modelled. It is also expected that the deep-water habitat will remain suitable for brown trout as flow declines to flows under the 1.5 m3/s assessed here. Spawning habitat declines by nearly 30% across this same flow range, although as noted above the spawning period is expected to be outside

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment the low flow period. Minimum flows in the range of 1.5 m3/s to 2.0 m3/s are expected to retain the majority of the brown trout habitat. 4.1.4 Chinook salmon Change in flow has varying effects on the Chinook salmon. For holding water for migrating adults the change in flow leads to a 45% reduction in holding water. This will be an over estimate as the model does not include the rare pools. However, these pools are very rare and any adjustment upwards of the available habitat will be small. Conversely, Chinook fry lose only 1% of their habitat with the change from 2.0 m3/s to 1.5 m3/s. Spawning habitat declines by 20% across this flow range, but as noted above spawning is expected to occur outside the low flow period and will not be subject to the potential habitat loss. 4.1.5 Macroinvertebrates The macroinvertebrates modelled all show a decline in habitat has flow declines. The greatest declines are present for Aoteapsyche and general food producing habitat with a loss of 25% each. However, habitat for key food species for bullies, torrentfish, Canterbury galaxias and small trout (e.g., Cadwallader 1975a, b, Glova et al 1987) the mayflies, Deleatidium and Nesametelus declines by less than 10%. Deleatidium, in particular, is abundant in braided rivers and is a key food item for native fish such as torrentfish and Canterbury galaxias and also for salmonids. Therefore, the retention of habitat for this species is an important consideration for maintaining food for fish. Habitat for the other macroinvertebrates modelled, Pycnocentrodes and hydrobiosid caddisflies declines by 10%. 4.1.6 Fish passage Fish passage can be provided through the model reach for small native fish at a flow of approximately 0.5 m3/s. However, to provide passage for large salmonids a flow of 2.0 m3/s is required. 4.1.7 Algal growth As noted above flows over 2.5 m3/s are required to begin to supress the abundance of long filamentous algae. However, no flow will exclude filamentous algae from the river as the margins and other low water velocity areas will still provide habitat for the algae. To reduce algal biomass, including both filamentous algal and algal mats it is generally accepted that flushing flows are required to dislodge the algae and clean the river bed. This requires flood flows and in the Ashley River/Rakahuri catchment the occurrence of floods is dependent on rainfall. 4.1.8 Downstream flow and freshes The flow measurements for the SEFA model found that there is approximately 0.3 m3/s of water lost from the surface flow within the study reach. Mosely (2001) and Megaughin & Hayward (draft 2016) also report a large flow loss between Ashley Gorge and SH1 and note this flow loss can result in a drying reach even when the flow is greater than the 7dMALF at Ashley Gorge. Therefore, providing aquatic habitat throughout the Ashley River/Rakahuri year round is unlikely to be possible even with no water abstraction. However, if fresh events are protected and allowed to pass downstream during the summer and autumn, this will provide periods where the river channel is wetted for the full length and provide fish passage opportunities through the year. It will also restrict the duration of dry periods and extent of river bed drying. 4.1.9 Water Quality and Duration of Low Flow The habitat modelling has not assessed the effects of low flows on water quality and the effect of low flow on algal biomass accumulation. Low flow periods that are interspersed with high flow

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment events that flush the river bed maintain are generally accepted to maintain good habitat conditions. Setting minimum flow and water allocation rules that extend the low flow periods and reduce high flow events can be expected to allow algal biomasses to proliferate that will lead to reduced habitat quality.

5 CONCLUSIONS

The SEFA habitat model indicates that as flow drops from the 7dMALF (2.05 m3/s) to 1.5 m3/s the majority of taxa modelled lose 10% or less of their predicted available habitat available. Key native fish, longfin eel, torrentfish retain a large proportion of their habitat and macroinvertebrate food resources are also maintained. Adult brown trout have relatively little habitat in the reach but the loss in the 2.0 to 1.5 m3/s flow range is is estimated to be between 10 and 25% whereas habitat for salmonid spawning and juvenile rearing will be abundant even at flows below the 7dMALF of 2.05 m3/s and the loss of habitat as flow drops to 1.5 m3/s is less than 10%.

Fish passage for small native fish and larger eels in the study reach will be provided both in upstream and downstream directions with a flow in the order of 0.5 m3/s or greater. A flow in the order of 2.5m3/s is required to provide passage for large salmonids, especially Chinook salmon.

Control or reduction of filamentous algae or algal mats, is unlikely during the low flow period and flushing flows would be required to clean the river bed.

If the minimum flow is to be set to maintain aquatic values in the vicinity of the Ashley Gorge a minimum flow of 1.5 m3/s would be a lowest suitable minimum flow to provide for the aquatic ecosystem. If the intent of the minimum flow is to provide protection for aquatic habitat downstream of the Ashley Gorge Road bridge to reaches in the vicinity of SH1 a much higher minimum flow should be set to account for flow losses to ground water. Mosley (2001) and Megaughin & Hayward (draft 2016) note that a flow of between 2.0 m3/s and 2.5 m3/s at the Gorge is the approximate flow at which the drying reach upstream of SH 1 is present.

If the minimum flow is to provide for fish passage through the study reach 0.5 m3/s will provide passage for native fish including eels. However, a flow up to 2.5 m3/s would be appropriate for passage for large salmonids.

To provide fish passage from Ashley Gorge to the sea a flow greater than the 7dMALF at the Gorge (2.05m3/s) is required. Megaughin & Hayward (draft 2016) indicate a flow of 2.0 m3/s will prevent complete drying of the reach between Okuku River confluence and SH1. If this drying reach has similar morphological characteristics to the study reach a surface flow of 0.5 m3/s will be required to provide passage for native fish and 2.5 m3/s for salmonids. Therefore, for fish passage in the worst drying reach a flow of 2.5 m3/s is required at Ashley Gorge to provide 0.5 m3/s for native fish and 4.5 m3/s to provide 2.0 m3/s for salmonids. If the drying reach has wider and shallower areas than the study reach even higher flows may be required to provide passage. Therefore, to provide fish passage it is recommended that the first water allocation band is restricted to a flow band that is between 0.4 m3/s and 0.5 m3/s wide (e.g., 2.0 m3/s to 2.4 m3/s) and no further water is abstracted until the flow at the gorge exceeds 5.0 m3/s. The 5.0 m3/s will provide an out of river allocation of water and a flow of 4.5 m3/s or 4.6 m3/s that will wet the full length of the Ashley River/Rakahuri. These small freshet events are expected to provide fish passage for native fish because water is present throughout the river but these will not be high turbid flows and there will be no bed

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment movement that are likely to discourage upstream fish movement by small native fish. However, unless the freshets exceed 5.0 m3/s at the Gorge fish passage for salmonids will remain restricted.

Flushing flows that restrict algal growth will rely on natural high rainfall events and the resultant flood events. Such flows are well outside the range of flows that are common in summer and cannot be managed or provided via setting the of a minimum flow.

6 REFERENCES

Beca (2008). Draft guideline for the selection of methods to determine ecological flows and water levels. Report prepared for the Ministry for the Environment. Cadwallader, P. L. (1975a). Feeding habits of two fish species in relation to invertebrate drift in a New Zealand river. New Zealand Journal of Marine and Freshwater Research 9(1): 11-26. Cadwallader, P. L. (1975b). Feeding relationships of galaxiids, bullies, eels and trout in a New Zealand river. Australian Journal of Marine and Freshwater Research 26: 299-316. Glova, G. J., & Duncan, M. J. (1985). Potential effects of reduced flows on fish habitats in a large braided river, New Zealand. Transactions of the American Fisheries Society, 114(2): 165-181.

Glova, G. J., Sagar, P. M., & Docherty, C. R. (1987). Diel feeding periodicity of torrentfish (Cheimarrichthys fosteri) in two braided rivers of Canterbury, New Zealand. New Zealand Journal of Marine and Freshwater Research 21(4): 555-562. Goodman, J. M., Dunn, N., Ravenscroft, P., Allibone, R. M., Boubee, J.A.T., David, B. O., Griffiths, M., Ling, N., Hitchmough, R., Rolfe, J. R. (2014). Conservation status of New Zealand freshwater fish, 2013. New Zealand Threat Classification Series 7. Department of Conservation, Wellington. Hayes, J. W., & Jowett, I. G. (1994). Microhabitat models of large drift-feeding brown trout in three New Zealand rivers. North American Journal of Fisheries Management 14: 710-725. Hughey, K.F.D. (1998). Nesting home range sizes of wrybill (Anarhynchus frontalis) and banded dotterel (Charadrius bocinctus) in relation to braided riverbed characteristics. Notornis 45: 103-111. Jowett, I. G. (2002). In-stream habitat suitability criteria for feeding inanga (Galaxias maculatus). New Zealand Journal of Marine and Freshwater Research 36: 399-407. Jowett, I.G. (1999). RHYHASBSIM – River Hydraulics and Habitat Simulation software. Jowett, I.G., & Richardson, J. (2008). Habitat use by New Zealand fish and habitat suitability models. NIWA Science and Technology Series No. 55. Jowett, I. G., Richardson, J., Biggs, B. J. F., Hickey, C. W., & Quinn, J. (1991). Microhabitat preferences of benthic invertebrates and the development of generalised Deleatidium spp. habitat suitability curves applied to four New Zealand rivers. New Zealand Journal of Marine and Freshwater Research 25: 187-199. McAllister, T. (2015). Identifying environmental parameters that promote Phormidium blooms in Canterbury rivers. Waterways Centre for Freshwater Management report No WCFM Report 2015-001.

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Megaughin, M & Hayward, S. (Draft 2016). Waimakariri land and water solutions program: hydrology current state report. Environment Canterbury Report. Mosely, P.M. 2001 Ashley River; flow management regime. Report U01/4 Technical Report Investigations and Monitoring Group. Environment Canterbury. Payne T.R., & Jowett, I.G. (2012. ) SEFA – Computer software system for Environmental Flow Analysis based on the Instream Flow Incremental Methodology. Raleigh, R.F., Zuckerman, L.D., & Nelson, P.C. (1986). Habitat suitability index models and instream flow suitability curves: brown trout revised. US Fish and Wildlife Service Biological report 82: (10-124). Shirvell, C. S., & Dungey, R. G. (1983). Microhabitats chosen by brown trout for feeding and spawning in rivers. Transactions of the American Fisheries Society 112, 355-367. Special Tribunal (2002). The Rangitata River Conservation Order Application. A report by the Special Tribunal.

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Appendix A Fish Species records for the Ashley River/Rakahuri

Scientific Name Common Name Number of records

Anguilla australis Shortfin eel 8

Anguilla dieffenbachii Longfin eel 15

Cheimarrichthys fosteri Torrentfish 14

Galaxias argenteus Giant kokopu 1

Galaxias brevipinnis Koaro 2

Galaxias maculatus Inanga 9

Galaxias vulgaris Canterbury galaxias 13

Gobiomorphus breviceps Upland bully 19

Gobiomorphus cotidianus Common bully 15

Gobiomorphus gobioides Giant bully 1

Gobiomorphus hubbsi Bluegill bully 12

Neochanna burrowsius Canterbury mudfish 5

Oncorhynchus tshawytscha Chinook salmon 3

Retropinna retropinna Common smelt 2

Rhombosolea retiaria Black flounder 3

Salmo trutta Brown trout 12

- No species recorded 3

Note – Data sourced from the New Zealand Freshwater Fish Database, search selected records with the catchment number 662.000 for the Ashley River/Rakahuri main-stem, but does include some records for tributary sites.

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Appendix B: Study Cross sections

Cross section views (all from true right bank).

Ashley 1 Deep fast riffle.

Ashley 2 Run.

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Ashley 3 Run.

Ashley 4 -Wide fast riffle.

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Ashley 5 Deep fast run.

Ashley 6 Gentle riffle.

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Ashley 7 Deep run.

Ashley 8 Medium width run.

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Ashley 9 Wide, slow run.

Ashley 10 Narrow, fast riffle.

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Ashley 11 Deep fast run.

Ashley 12 Deep slow run.

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Ashley 13 Slow run

Ashley 14 Wide shallow run.

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Ashley 15 Wide shallow run.

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Appendix C Habitat preference curves

Canterbury galaxias (Jowett & Richardson 2008) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability 0.2 Suitability 0.2 0.0 0.0 0.0 0.3 0.6 0.9 1.2 1.5 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Upland bully (Jowett & Richardson 2008) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability 0.2 Suitability 0.2 0.0 0.0 0.0 0.3 0.6 0.9 1.2 1.5 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Bluegill bully (Jowett & Richardson 2008) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability Suitability 0.2 0.2 0.0 0.0 0.0 0.3 0.6 0.9 1.2 1.5 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Torrentfish (Jowett & Richardson 2008) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability Suitability 0.2 0.2 0.0 0.0 0.0 0.3 0.6 0.9 1.2 1.5 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Inanga feeding (Jowett 2002) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability 0.2 Suitability 0.2 0.0 0.0 0.0 0.3 0.6 0.9 1.2 1.5 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Shortfin eel < 300mm (Jowett & Richardson 2008) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability Suitability 0.2 0.2 0.0 0.0 0.0 0.3 0.6 0.9 1.2 1.5 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Shortfin eel > 300mm (Jowett & Richardson 2008) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability 0.2 Suitability 0.2 0.0 0.0 0.0 0.3 0.6 0.9 1.2 1.5 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Longfin eel < 300mm (Jowett & Richardson 2008) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability Suitability 0.2 0.2 0.0 0.0 0.0 0.3 0.6 0.9 1.2 1.5 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Longfin eel > 300mm (Jowett & Richardson 2008) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability 0.2 Suitability 0.2 0.0 0.0 0.0 0.3 0.6 0.9 1.2 1.5 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Brown trout adult (Raleigh et al. 1986) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability 0.2 Suitability 0.2 0.0 0.0 0.0 0.3 0.6 0.9 1.2 1.5 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Brown trout adult (Hayes and Jowett 1994) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability Suitability 0.2 0.2 0.0 0.0 0.0 0.3 0.6 0.9 1.2 1.5 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Brown trout fry to 15cm (Raleigh et al 1986) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability 0.2 Suitability 0.2 0.0 0.0 0.0 0.3 0.6 0.9 1.2 1.5 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Brown trout yearling (Raleigh et al 1986) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability 0.2 Suitability 0.2 0.0 0.0 0.0 0.5 1.0 1.5 2.0 2.4 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Brown trout spawning (Shirvell and Dungey 1983) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability Suitability 0.2 0.2 0.0 0.0 0.0 0.3 0.6 0.9 1.2 1.5 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Chinook salmon migration holding (Raleigh et al. 1986) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability 0.2 Suitability 0.2 0.0 0.0 0.0 0.7 1.5 2.2 2.9 3.7 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Chinook salmon adult spawning (Bovee 1978) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability 0.2 Suitability 0.2 0.0 0.0 0.0 0.3 0.6 0.9 1.2 1.5 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Chinook salmon fry < 55 mm (Glova and Duncan 1985) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability Suitability 0.2 0.2 0.0 0.0 0.0 0.3 0.6 0.9 1.2 1.5 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Nesameletus (mayfly) (Jowett et al. 1991) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability 0.2 Suitability 0.2 0.0 0.0 0.0 0.4 0.8 1.2 1.6 2.0 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Hydrobiosidae (free-living caddis) (Jowett et al. 1991) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability 0.2 Suitability 0.2 0.0 0.0 0.0 0.4 0.7 1.1 1.4 1.8 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Aoteapsyche (net-spinning caddis) (Jowett et al. 1991) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability Suitability 0.2 0.2 0.0 0.0 0.0 0.4 0.8 1.2 1.6 2.0 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Pycnocentrodes (stony-cased caddis) (Jowett et al. 1991) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability 0.2 Suitability 0.2 0.0 0.0 0.0 0.4 0.7 1.1 1.4 1.8 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Deleatidium (mayfly) (Jowett et al. 1991) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability 0.2 Suitability 0.2 0.0 0.0 0.0 0.4 0.8 1.2 1.6 2.0 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Food producing (Waters 1976) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability Suitability 0.2 0.2 0.0 0.0 0.0 0.4 0.8 1.2 1.6 2.0 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Wrybill plover feeding (Hughey) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability 0.2 Suitability 0.2 0.0 0.0 0.0 0.3 0.6 0.9 1.2 1.5 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Black-fronted tern (Waimakariri) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability 0.2 Suitability 0.2 0.0 0.0 0.0 0.3 0.6 0.9 1.2 1.5 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Black-fronted tern (Rangitata) 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability Suitability 0.2 0.2 0.0 0.0 0.0 0.3 0.6 0.9 1.2 1.5 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Long filamentous 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability 0.2 Suitability 0.2 0.0 0.0 0.0 0.4 0.8 1.2 1.6 2.0 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Short filamentous 1.0 1.0 0.8 0.8 0.6 0.6

0.4 0.4 Suitability 0.2 Suitability 0.2 0.0 0.0 0.0 0.4 0.8 1.2 1.6 2.0 0.0 0.4 0.8 1.2 1.6 2.0 Depth (m) Velocity (m/s) 1.0 0.8 0.6 0.4

Suitability 0.2 0.0 1 2 3 4 5 6 7 8 Substrate category

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

Appendix D SEFA habitat model outputs – text data.

Reach Area Weighted Suitability (m2⁄m) 1:- Brown trout adult (Hayes and Jowett 1994) 2:- Brown trout adult (Raleigh et al. 1986) 3:- Brown trout yearling (Raleigh et al 1986) 4:- Brown trout fry to 15cm (Raleigh et al 1986) 5:- Brown trout spawning (Shirvell and Dungey 1983) Flow (m3⁄s) Brown trout Brown trout Brown trout Brown trout Brown trout 0.000 0.000 0.000 0.000 0.000 0.000 0.100 0.251 1.416 2.155 0.911 0.097 0.200 0.416 1.764 2.851 1.549 0.193 0.300 0.560 2.055 3.345 2.038 0.321 0.400 0.701 2.288 3.734 2.461 0.492 0.500 0.837 2.477 4.063 2.850 0.635 0.600 0.968 2.640 4.353 3.201 0.788 0.700 1.096 2.791 4.608 3.518 0.929 0.800 1.219 2.934 4.840 3.819 1.066 0.900 1.340 3.058 5.043 4.096 1.212 1.000 1.458 3.172 5.215 4.342 1.353 1.100 1.576 3.283 5.365 4.554 1.497 1.200 1.692 3.383 5.499 4.737 1.652 1.300 1.811 3.477 5.614 4.888 1.825 1.400 1.929 3.559 5.719 5.015 1.999 1.500 2.046 3.626 5.815 5.122 2.168 1.600 2.162 3.683 5.903 5.209 2.321 1.700 2.272 3.731 5.984 5.281 2.461 1.800 2.378 3.778 6.055 5.328 2.587 1.900 2.479 3.820 6.118 5.355 2.702 2.000 2.576 3.859 6.172 5.365 2.805 2.100 2.670 3.893 6.220 5.364 2.889 2.200 2.763 3.921 6.261 5.355 2.964 2.300 2.855 3.941 6.294 5.336 3.033 2.400 2.946 3.956 6.319 5.309 3.093 2.500 3.034 3.968 6.335 5.271 3.134 2.600 3.119 3.974 6.343 5.226 3.162 2.700 3.200 3.981 6.345 5.177 3.178 2.800 3.276 3.989 6.349 5.142 3.187

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

2.900 3.350 3.988 6.341 5.092 3.193 3.000 3.422 3.983 6.329 5.042 3.201 3.100 3.493 3.977 6.313 4.992 3.206 3.200 3.562 3.967 6.293 4.938 3.205 3.300 3.629 3.953 6.271 4.884 3.197 3.400 3.691 3.935 6.245 4.828 3.182 3.500 3.747 3.918 6.219 4.771 3.162 3.600 3.802 3.897 6.190 4.714 3.136 3.700 3.853 3.874 6.158 4.661 3.108 3.800 3.904 3.849 6.125 4.609 3.077 3.900 3.952 3.825 6.089 4.555 3.042 4.000 3.996 3.802 6.050 4.499 2.996

Chinook Salmon Reach Area Weighted Suitability (m2⁄m) Proportion of reach: 100.00 % 1:- Chinook salmon adult spawning (Bovee 1978) 2:- Chinook salmon migration holding (Raleigh et al. 1986) 3:- Chinook salmon fry < 55 mm (Glova and Duncan 1985) Flow (m3⁄s) Chinook salmon Chinook salmon Chinook salmon

0.000 0.000 0.000 0.000 0.100 0.112 0.000 2.213 0.200 0.265 0.000 3.493 0.300 0.425 0.002 4.477 0.400 0.592 0.004 5.187 0.500 0.763 0.007 5.690 0.600 0.899 0.010 6.083 0.700 1.021 0.015 6.368 0.800 1.148 0.022 6.550 0.900 1.285 0.031 6.672 1.000 1.428 0.040 6.749 1.100 1.577 0.051 6.824 1.200 1.716 0.062 6.869 1.300 1.843 0.075 6.888 1.400 1.958 0.088 6.906 1.500 2.070 0.102 6.921 1.600 2.175 0.116 6.924

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

1.700 2.277 0.131 6.948 1.800 2.370 0.146 6.973 1.900 2.457 0.162 6.985 2.000 2.542 0.179 6.982 2.100 2.624 0.195 6.984 2.200 2.699 0.212 6.961 2.300 2.767 0.229 6.933 2.400 2.833 0.246 6.879 2.500 2.888 0.263 6.805 2.600 2.934 0.280 6.719 2.700 2.972 0.298 6.624 2.800 3.002 0.316 6.560 2.900 3.027 0.335 6.467 3.000 3.044 0.355 6.375 3.100 3.054 0.376 6.290 3.200 3.057 0.398 6.201 3.300 3.054 0.421 6.113 3.400 3.045 0.444 6.026 3.500 3.031 0.468 5.945 3.600 3.012 0.492 5.866 3.700 2.991 0.516 5.788 3.800 2.968 0.542 5.707 3.900 2.945 0.567 5.627 4.000 2.922 0.593 5.546

Macroinvertebrate model output Proportion of reach: 100.00 % 1:- Nesameletus (mayfly) (Jowett et al. 1991) 2:- Hydrobiosidae (free-living caddis) (Jowett et al. 1991) 3:- Aoteapsyche (net-spinning caddis) (Jowett et al. 1991) 4:- Pycnocentrodes (stony-cased caddis) (Jowett et al. 1991) 5:- Deleatidium (mayfly) (Jowett et al. 1991) 6:- Food producing (Waters 1976) Flow Nesameletus Hydrobiosidae Aoteapsyche Pycnocentrodes Deleatidium Food (m3⁄s) (mayfly) (free-living (net-spinning (stony-cased (mayfly) producing 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.100 2.147 1.130 0.084 0.822 2.930 0.181 0.200 3.382 1.736 0.132 1.430 3.696 0.407 0.300 4.279 2.191 0.176 1.928 4.274 0.634

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

0.400 4.865 2.510 0.228 2.335 4.687 0.883 0.500 5.283 2.749 0.285 2.674 5.020 1.137 0.600 5.593 2.942 0.349 2.964 5.288 1.361 0.700 5.817 3.099 0.416 3.222 5.517 1.576 0.800 5.998 3.242 0.491 3.478 5.742 1.785 0.900 6.163 3.375 0.560 3.710 5.942 1.988 1.000 6.308 3.502 0.634 3.916 6.127 2.187 1.100 6.466 3.632 0.706 4.132 6.312 2.390 1.200 6.594 3.751 0.778 4.329 6.484 2.590 1.300 6.717 3.870 0.850 4.509 6.649 2.800 1.400 6.824 3.982 0.924 4.678 6.805 3.011 1.500 6.914 4.091 0.997 4.846 6.965 3.222 1.600 7.002 4.200 1.072 5.018 7.128 3.440 1.700 7.102 4.313 1.140 5.166 7.276 3.634 1.800 7.188 4.416 1.202 5.308 7.412 3.822 1.900 7.253 4.510 1.260 5.444 7.541 3.998 2.000 7.303 4.606 1.327 5.596 7.671 4.191 2.100 7.349 4.697 1.386 5.721 7.785 4.346 2.200 7.383 4.781 1.444 5.833 7.891 4.490 2.300 7.421 4.867 1.502 5.952 7.997 4.631 2.400 7.452 4.953 1.562 6.085 8.110 4.784 2.500 7.466 5.021 1.623 6.183 8.205 4.924 2.600 7.477 5.085 1.683 6.270 8.295 5.063 2.700 7.485 5.142 1.739 6.346 8.380 5.195 2.800 7.516 5.209 1.789 6.422 8.460 5.319 2.900 7.521 5.258 1.833 6.487 8.535 5.441 3.000 7.525 5.304 1.872 6.549 8.603 5.559 3.100 7.530 5.352 1.914 6.610 8.668 5.671 3.200 7.528 5.388 1.950 6.666 8.723 5.775 3.300 7.522 5.421 1.984 6.717 8.771 5.871 3.400 7.518 5.452 2.016 6.765 8.817 5.958 3.500 7.511 5.481 2.044 6.810 8.858 6.035 3.600 7.504 5.508 2.071 6.853 8.894 6.104 3.700 7.494 5.532 2.098 6.892 8.925 6.166 3.800 7.483 5.554 2.123 6.928 8.953 6.225

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

3.900 7.469 5.576 2.148 6.961 8.976 6.280 4.000 7.452 5.595 2.173 6.992 8.997 6.331 Reach Average CSI Proportion of reach : 100.00 % 1:- Nesameletus (mayfly) (Jowett et al. 1991) 2:- Hydrobiosidae (free-living caddis) (Jowett et al. 1991) 3:- Aoteapsyche (net-spinning caddis) (Jowett et al. 1991) 4:- Pycnocentrodes (stony-cased caddis) (Jowett et al. 1991) 5:- Deleatidium (mayfly) (Jowett et al. 1991) 6:- Food producing (Waters 1976) Flow Aoteapsych Food Nesameletu Hydrobiosida Pycnocentrode Deleatidiu (m3⁄s e (net- producin s (mayfly) e (free-living s (stony-cased m (mayfly) ) spinning g 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.100 0.205 0.108 0.008 0.079 0.280 0.017 0.200 0.278 0.143 0.011 0.117 0.303 0.033 0.300 0.326 0.167 0.013 0.147 0.326 0.048 0.400 0.357 0.184 0.017 0.171 0.344 0.065 0.500 0.372 0.194 0.020 0.188 0.354 0.080 0.600 0.385 0.202 0.024 0.204 0.364 0.094 0.700 0.389 0.207 0.028 0.215 0.369 0.105 0.800 0.391 0.211 0.032 0.227 0.374 0.116 0.900 0.393 0.215 0.036 0.237 0.379 0.127 1.000 0.394 0.219 0.040 0.245 0.383 0.137 1.100 0.398 0.223 0.043 0.254 0.388 0.147 1.200 0.396 0.225 0.047 0.260 0.389 0.155 1.300 0.398 0.229 0.050 0.267 0.394 0.166 1.400 0.397 0.232 0.054 0.272 0.396 0.175 1.500 0.394 0.233 0.057 0.276 0.397 0.183 1.600 0.395 0.237 0.060 0.283 0.402 0.194 1.700 0.397 0.241 0.064 0.289 0.407 0.203 1.800 0.399 0.245 0.067 0.295 0.412 0.212 1.900 0.400 0.249 0.070 0.300 0.416 0.221 2.000 0.399 0.251 0.072 0.306 0.419 0.229 2.100 0.398 0.254 0.075 0.310 0.421 0.235 2.200 0.396 0.257 0.078 0.313 0.423 0.241 2.300 0.396 0.259 0.080 0.317 0.426 0.247 2.400 0.395 0.263 0.083 0.323 0.430 0.254 2.500 0.394 0.265 0.086 0.326 0.433 0.260

Water Ways Consulting Ltd Ashley River/Rakahuri minimum flow assessment

2.600 0.393 0.267 0.088 0.330 0.436 0.266 2.700 0.392 0.269 0.091 0.332 0.439 0.272 2.800 0.392 0.272 0.093 0.335 0.441 0.277 2.900 0.391 0.273 0.095 0.337 0.443 0.283 3.000 0.389 0.274 0.097 0.339 0.445 0.288 3.100 0.389 0.276 0.099 0.341 0.447 0.293 3.200 0.387 0.277 0.100 0.343 0.449 0.297 3.300 0.386 0.278 0.102 0.345 0.450 0.301 3.400 0.385 0.279 0.103 0.347 0.452 0.305 3.500 0.384 0.280 0.105 0.348 0.453 0.309 3.600 0.383 0.281 0.106 0.350 0.454 0.312 3.700 0.382 0.282 0.107 0.351 0.455 0.314 3.800 0.381 0.283 0.108 0.352 0.455 0.317 3.900 0.379 0.283 0.109 0.354 0.456 0.319 4.000 0.378 0.284 0.110 0.354 0.456 0.321