Whängärei Harbour Water Quality Improvement Strategy November 2012 Prepared by Northland Regional Council and Whängärei District Council Cover image © Bee Scene Photography Table of contents Executive summary .................................................................................................................................................. 4 1 Introduction ...................................................................................................................................................... 5 1.1 Background .............................................................................................................................................. 5 1.2 Purpose of this strategy ...................................................................................................................... 6 1.3 Document structure .............................................................................................................................. 6 1.4 Integration with other initiatives ...................................................................................................... 6 1.4.1 Waiora Northland Water ........................................................................................................... 7 1.4.2 Whāngārei District Council Wastewater Management Strategy ................................ 7 2 The harbour and its catchment ................................................................................................................. 8 2.1 Overview.................................................................................................................................................... 8 2.1 Catchment description ........................................................................................................................ 9 2.1.1 Sub-catchments ......................................................................................................................... 11 2.2 Values and uses of the harbour .................................................................................................... 16 2.2.1 Ecology .......................................................................................................................................... 16 2.2.2 Recreation..................................................................................................................................... 25 2.2.3 Economic and municipal ......................................................................................................... 27 2.2.4 Maori cultural values ................................................................................................................ 27 2.3 Managing harbour water quality .................................................................................................. 30 2.3.1 Direct discharges ....................................................................................................................... 30 2.3.2 Diffuse discharges ..................................................................................................................... 32 3 Water quality in the harbour ................................................................................................................... 33 3.1 Current monitoring of the harbour .............................................................................................. 34 3.2 Water quality and the harbour ecosystem ................................................................................ 36 3.2.1 Sediments ..................................................................................................................................... 37 3.2.2 Sediment contamination ........................................................................................................ 40 3.2.3 Nutrients ....................................................................................................................................... 42 3.3 Water quality and human health .................................................................................................. 48 3.3.1 Contact recreation ..................................................................................................................... 50 3.3.2 Shellfish gathering .................................................................................................................... 59 3.4 Summary and considerations ......................................................................................................... 61 4 Key sources of contamination ................................................................................................................. 62 4.1 Urban wastewater ............................................................................................................................... 62 4.1.1 Whāngārei Wastewater Treatment Plant .......................................................................... 62 4.1.2 Network overflows and leakage .......................................................................................... 62 4.2 Urban stormwater ............................................................................................................................... 64 4.2.1 Stormwater quality .................................................................................................................... 68 4.2.2 Future pressures ......................................................................................................................... 69 4.2.3 Roads and walkways ................................................................................................................. 69 4.3 Pastoral activities and rural stormwater ..................................................................................... 70 4.3.1 Rural upper harbour sub-catchments ................................................................................ 71 4.3.2 Mixed land use upper harbour catchments .................................................................... 72 4.4 Farm dairy effluent ............................................................................................................................. 74 4.5 Forestry ................................................................................................................................................... 74 4.6 Urban development ........................................................................................................................... 75 1 4.7 Septic systems ...................................................................................................................................... 76 4.8 Parks and reserves .............................................................................................................................. 77 4.9 Boats ........................................................................................................................................................ 77 4.10 Harbour dredging ............................................................................................................................... 79 4.11 Industrial discharges .......................................................................................................................... 79 4.12 Landfills ................................................................................................................................................... 80 4.12.1 Quarries ......................................................................................................................................... 81 4.13 Summary and considerations ......................................................................................................... 81 5 Proposed water quality objectives for the harbour ........................................................................ 82 6 Actions and recommendations ............................................................................................................... 82 6.1 Overview................................................................................................................................................. 83 6.1.1 Direct discharges ....................................................................................................................... 83 6.1.2 Diffuse discharges ..................................................................................................................... 83 6.1.3 Integrated catchment management .................................................................................. 83 6.2 Detailed actions ................................................................................................................................... 87 6.2.1 Enforcement of and compliance with current regulation .......................................... 87 6.2.2 Undertaking, promoting, and supporting good/best management practices .. 88 6.2.3 Other .............................................................................................................................................. 91 6.2.4 Monitoring and research ........................................................................................................ 93 6.2.5 Improving the regulatory framework ................................................................................. 94 7 Conclusion ...................................................................................................................................................... 97 Appendix 1 – Whāngārei