Jowett Consulting Limited Review of Minimum Flows and Water Allocation in Taranaki Client Report: IJ1702 July 2018 Review of Minimum Flows and Water Allocation in Taranaki Ian Jowett Prepared for Taranaki Regional Council Jowett Consulting Ltd. Client Report: IJ1702 July 2018 Tairua 3208, New Zealand Phone +64-7-864 8703, Mob 021 944 447 [email protected] Contents Executive Summary ................................................................................................................................. 4 1 Introduction .................................................................................................................................... 8 2 Planning framework ...................................................................................................................... 11 3 Methods for determining minimum flow and allocation ............................................................. 13 3.1 Review of Regional Council minimum flow methods ........................................................... 13 3.2 Research on the effects of water abstraction ....................................................................... 14 3.2.1 Relationship between flow and ecology ....................................................................... 14 3.2.2 Assessment of environmental flow requirements ........................................................ 15 3.2.3 Instream habitat methods ............................................................................................ 16 3.2.4 Instream habitat validation studies .............................................................................. 17 3.2.5 Habitat observations ..................................................................................................... 18 3.2.6 Models of abundance ................................................................................................... 24 3.2.7 Water quality ................................................................................................................ 26 3.2.8 Summary of research .................................................................................................... 27 3.3 Principles for setting minimum flows and allocation ........................................................... 28 3.3.1 Minimum flow ............................................................................................................... 28 3.3.2 Protection levels ........................................................................................................... 29 3.3.3 Allocation ...................................................................................................................... 30 4 Taranaki Regional Council Minimum Flow and Allocation ........................................................... 31 4.1 Flow Management objectives for TRC .................................................................................. 33 4.2 Method of assessing the combined effect of minimum flow and allocation on benthic invertebrate abundance ................................................................................................................... 35 4.2.1 Development of suitability curves for high MCI score invertebrates ........................... 35 4.2.2 Application of high MCI score curves to Taranaki rivers ............................................... 36 5 Other matters to consider when setting environmental flow limits ............................................ 37 5.1 Submissions ........................................................................................................................... 37 5.2 Flexibility ............................................................................................................................... 37 5.3 Group schemes ..................................................................................................................... 37 5.4 Exemptions to minimum flows ............................................................................................. 38 6 Taranaki Rivers .............................................................................................................................. 38 6.1 Hydrology .............................................................................................................................. 38 6.2 Fish species ........................................................................................................................... 39 6.3 Water Quality ........................................................................................................................ 41 1 6.4 Benthic Invertebrates ........................................................................................................... 43 7 Method for determining environmental flow requirements........................................................ 44 7.1 Minimum flows and allocation to protect the state of the benthic invertebrate community 44 7.2 Habitat at 30-day low flow to protect the fish community .................................................. 48 8 Review of environmental flows in Draft Plan ............................................................................... 50 9 Recommended environmental flow limits for Taranaki ............................................................... 51 9.1 Application of environmental flow limits in freshwater management units ........................ 51 9.2 Protection levels ................................................................................................................... 51 9.3 Minimum flow and allocation ............................................................................................... 52 9.4 Flat-lining .............................................................................................................................. 53 9.5 Reliability of supply ............................................................................................................... 53 9.6 Flexibility ............................................................................................................................... 53 10 Stakeholders ............................................................................................................................. 54 11 References ................................................................................................................................ 54 12 Appendix I – Instream Habitat Analysis .................................................................................... 60 12.1.1 Habitat mapping ........................................................................................................... 60 12.1.2 Cross-section selection ................................................................................................. 60 12.1.3 Analysis ......................................................................................................................... 60 13 Appendix I ................................................................................................................................. 63 5.2 Renewable Power Ltd ........................................................................................................... 63 5.16 Contact Energy ...................................................................................................................... 63 5.24 DairyNZ .................................................................................................................................. 63 5.27 Taranaki Fish and Game ........................................................................................................ 63 5.34 Department of Conservation ................................................................................................ 64 5.4 Nga Ruahine .......................................................................................................................... 64 5.32 Methanex NZ Ltd ................................................................................................................... 64 5.38 Trustpower ............................................................................................................................ 64 14 Appendix II ................................................................................................................................ 65 14.1 Waiwhakaiho River ............................................................................................................... 65 14.2 Kaupokonui River .................................................................................................................. 66 14.3 Kapoaiaia Stream at lighthouse ............................................................................................ 67 14.4 Patea River at Stratford ........................................................................................................ 69 14.5 Tangahoe River ..................................................................................................................... 70 2 14.6 Mangaoraka River at Corbett Road ...................................................................................... 72 14.7 Waingongoro River at Normanby ......................................................................................... 73 14.8 Manganui River at Croyden .................................................................................................. 75 14.9 Waiongana Stream at SH3A .................................................................................................