Ngaruroro, Tutaekuri, Karamu River and Ahuriri Estuary Catchments State and Trends of River Water Quality and Ecology July 2016 HBRC Report No. RM16-08 4787 Environmental Science - Water Quality and Ecology Ngaruroro, Tutaekuri, Karamu River and Ahuriri Estuary Catchments State and Trends of River Water Quality and Ecology July 2016 HBRC Report No. RM 16-08. Plan Number 4787. Prepared By: Dr Sandy Haidekker Dr Adam Uytendaal Dr Andy Hicks Oliver Wade Heli Wade Vicki Lyon Anna Madarasz-Smith Reviewed By: Stephen Swabey – Manager – Environmental Science Approved By: Iain Maxwell – Group Manager – Resource Management Signed: . Contents Executive summary ....................................................................................................................... 9 1 Introduction ...................................................................................................................... 13 1.1 TANK Catchment Descriptions and Land Use Overview ................................................... 13 1.2 Description of the Ngaruroro River Catchment ................................................................ 15 1.3 Description of the Tutaekuri River Catchment ................................................................. 19 1.4 Description of the Karamu Stream Catchment ................................................................. 24 1.5 Description of the Ahuriri Catchment ............................................................................... 30 1.6 Recreational usage and water quality in the TANK catchments ....................................... 32 1.7 SOE Water Quality Data and Analysis ............................................................................... 32 2 Water Quality in the Ngaruroro and Tutaekuri River Catchments: Long-term SOE data ........ 37 2.1 Nutrients ........................................................................................................................... 37 2.2 Nitrate-nitrogen toxicity ................................................................................................... 49 2.3 Water Clarity – Black disc and turbidity ............................................................................ 52 2.4 Bacteriological water quality – E. coli ............................................................................... 58 2.5 Dissolved oxygen ............................................................................................................... 61 2.6 Temperature ..................................................................................................................... 70 2.7 Biological indicators .......................................................................................................... 73 2.8 Assessment against the NOF NPS-FM (2014) attribute bands ......................................... 81 2.9 Compliance with HBRC Regional Resource Management Plan 2006 surface water quality Environmental Guidelines ................................................................................................. 84 2.10 Land use intensification in the upper Tutaekuri catchment – potential impacts on the Mangatutu Stream and the Mangaone River ................................................................... 87 2.11 Summary and conclusion for the Ngaruroro and Tutaekuri River catchments ................ 88 3 Water Quality of the Karamu Stream and Ahuriri Estuary Catchments: Long-term SOE data 89 3.1 Nutrients ........................................................................................................................... 89 3.2 Toxicity: nitrate-nitrogen and ammoniacal-nitrogen ..................................................... 100 3.3 Water Clarity – Black disc and turbidity .......................................................................... 103 3.4 Bacteriological water quality – E. coli ............................................................................. 107 3.5 Dissolved oxygen ............................................................................................................. 110 3.6 Temperature ................................................................................................................... 116 3.7 Biological indicators ........................................................................................................ 118 3.8 Karamu targeted study – life-supporting capacity ......................................................... 124 Ngaruroro, Tutaekuri, Karamu River and Ahuriri Estuary Catchments 3 3.9 Stormwater ..................................................................................................................... 124 3.10 Assessment against the NOF NPS-FM (2014) attribute bands ....................................... 135 3.11 Compliance with HBRC Regional Resource Management Plan (2006) surface water quality Environmental Guidelines ................................................................................... 138 4 Recreational Water Quality in the TANK catchments ........................................................ 141 4.1 ANZECC guidelines .......................................................................................................... 142 4.2 Suitability for Recreation Grade...................................................................................... 143 4.3 Recreational Usage ......................................................................................................... 144 4.4 Faecal bacterial contamination ....................................................................................... 144 4.5 Shellfish Gathering .......................................................................................................... 146 References ................................................................................................................................ 147 Appendix A Summary statistics by flow in the Ngaruroro and Tutaekuri catchments ............. 152 Appendix B Summary statistics by flow in the Karamu and Ahuriri catchments ..................... 176 Appendix C Trend analysis results for water quality variables ............................................... 188 Appendix D Regional ranking tables for select water quality variables ................................... 198 Appendix E NPS-FW (2014) NOF attribute tables .................................................................. 209 Appendix F Summary of NOF bands for E.coli, Nitrate-nitrogen and Ammonia. ..................... 214 Appendix G MfE benthic cyanobacteria alert-level framework .............................................. 219 Tables Table 1-1: Catchment characteristics of the major Ngaruroro River catchment zones. 18 Table 1-2: Summary of relevant water quality guidelines for the TANK catchments. 35 Table 1-3: HBRC Regional Resource Management Plan (2006) water quality limits - “Environmental Guidelines – Surface Water Quality”. 36 Table 2-1: Trend analysis results for DIN and DRP for Ngaruroro and Tutaekuri catchment SOE monitoring sites 43 Table 2-2: Trend analysis results for DIN and DRP for SOE monitoring sites of the Ngaruroro and Tutaekuri catchments. 49 Table 2-3: Trend analysis results for Nitrate-nitrogen (NO3-N) for SOE monitoring sites of the Ngaruroro and Tutaekuri catchments. 52 Table 2-4: Trend analysis results for black disc clarity and turbidity for SOE monitoring sites of the Ngaruroro and Tutaekuri River. 58 Table 2-5: Trend analysis results for E. coli for SOE monitoring sites of the Ngaruroro and Tutaekuri catchments. 61 Table 2-6: Proposed temperature thresholds for discussion for the National Objectives Framework . 72 4 Ngaruroro, Tutaekuri, Karamu River and Ahuriri Estuary Catchments Table 2-7: Cox-Rutherford Index (CRI) at 6 sites in the Ngaruroro and Tutaekuri catchments. 72 Table 2-8: MCI quality classes as defined by Stark and Maxted (2007). 78 Table 2-9: NPS-FW (2014) NOF band summary for freshwater river attributes for Tutaekuri and Ngaruroro catchment monitoring sites for the period 2009 to 2013. 83 Table 2-10: Comparison of average measured dissolved oxygen, black disc, dissolved reactive phosphorus and ammoniacal-nitrogen levels with HBRC RRMP 2006 Environmental Guideline levels. 85 Table 2-11: Comparison of measured DO, BD clarity and DRP values with HBRC RRMP 2006 Environmental Guideline levels. 86 Table 3-1: Trend analysis results for DIN and DRP for SOE monitoring sites of the Karamu Stream and Ahuriri Estuary catchment. 94 Table 3-2: Trend analysis results for DIN and DRP for SOE monitoring sites of the Karamu Stream and Ahuriri Estuary catchment. 99 Table 3-3: Trend analysis results for nitrate-nitrogen (NO3-N) for SOE monitoring sites of the Karamu Stream and Ahuriri Estuary. 103 Table 3-4: Trend analysis for black disc clarity and turbidity in the Karamu Stream and Ahuriri Estuary (see Appendix E for full results). 107 Table 3-5: Trend analysis results for E. coli for SOE monitoring sites in the Karamu Stream and Ahuriri Estuary (full results in Appendix E). 110 Table 3-6: Results from 24-hour continuous DO measurements during a warm summer period.114 Table 3-7: Proposed temperature thresholds for discussion for the National Objectives Framework. 117 Table 3-8: Cox-Rutherford Index (CRI) at 4 sites in the Karamu catchment. 117 Table 3-9: MCI and MCI-sb quality classes as defined by Stark and Maxted (2007). 121 Table 3-10: Sources of stormwater derived contaminants that may affect values associated with the Karamu and Ahuriri receiving environments. 126 Table 3-11: