MANAGING OUR ENVIRONMENT Identifying Point Source and Non-Point Source Contributions to Nutrient Loadings in Water Ways in Three Catchments in the Manawatu-Wanganui Region : Technical Report to Support Policy Development Identifying Point Source and Non-Point Source Contributions to Nutrient Loadings in Water Ways in Three Catchments in the Manawatu-Wanganui Region : Technical Report to Support Policy Development February 2007 Authors Emilie Ledein1, Olivier Ausseil2 and Jon Roygard3 1Visiting Scientist, 2Senior Scientist – Water Quality, 3Manager Science Horizons Regional Council Internally Reviewed and Approved by Kate McArthur and Alistair Beveridge Environmental Scientist – Water and Manager Water Quality and Biodiversity Horizons Regional Council External Review by Graham McBride Principal Scientist NIWA, Hamilton Acknowledgements to Maree Clark February 2007 ISBN: 1-877413-65-8 Report No: 2007/EXT/771 CONTACT 24hr Freephone 0508 800 800
[email protected] www.horizons.govt.nz Kairanga Cnr Rongotea and Kairanga-Bunnythorpe Rds Palmerston North Levin Palmerston North 11 Bruce Road Marton 11-15 Victoria Avenue SERVICE REGIONAL Cnr Hammond and Hair Sts DEPOTS CENTRES HOUSES Taihape Taumarunui Wanganui Torere Road 34 Maata Street 181 Guyton Street Ohotu Woodville Cnr Vogel (SH2) and Tay Sts POSTAL Horizons Regional Council, Private Bag 11025, Manawatu Mail Centre, Palmerston North 4442 | 06 9522 929 ADDRESS F EXECUTIVE SUMMARY Many rivers in the Manawatu-Wanganui Region are affected by excessive algal growth during summer. This phenomenon is mainly driven by high concentrations of nutrients (nitrogen and phosphorus) in the rivers. Nutrients in the waterways can come from both point sources (eg. discharges of treated wastewater) and non-point sources (eg.