The paper discusses the availability in New Zealand of generally available information in contaminant annual load data to predict loads of nutrients (Nitrogen N and Phosphorus P) and bacteria (E.coli and Faecal coliforms FC) for stormwater catchments.
The sources reviewed are; Contaminant Load Model (CLM) (Auckland Council), TP10 Stormwater management devices design guideline (Auckland Council), Waterways Wetlands and Drainage Guide (Christchurch City Council), Stormwater Treatment Standard for State Highway Infrastructure (NZTA) and On-site Stormwater Management Guideline (NZWERF).
Based on the available information, nutrients and bacterial loads are estimated for a specific stormwater catchment and compared with the wastewater discharge quality from the same catchment’s wastewater treatment plant.
The intention of this comparison is to provide an order of magnitude assessment on relative contributions of stormwater and wastewater source discharges. This determines the importance of nutrients and bacterial loads to be further investigated with respect to the impact on downstream stormwater quality.