Water quality performance of SUDS ponds analysed on a WQI

Results from a three year water quality (WQ) monitoring in two SUDS ponds are presented and the use of a water quality index (WQI) as a method for determining the WQ performance of Sustainable Urban Drainage Systems (SUDS) is proposed. WQ data were collected at the inlets and outlets of the Halbeath and Linburn ponds, located in adjacent catchments in the Dunfermline Eastern Expansion Area (DEX) in Eastern Scotland. Pond inflows and outflows were analysed for DO, pH, TSS, turbidity, chloride, conductivity, NH3 and O-P. The results show that both ponds performed well in removing TSS. There was no evidence of nutrient removal in either pond. Runoff from the residential housing area in the Linburn pond catchment typically carried the highest pollutant loads and the data suggest that several pollution events occurred during construction in the catchment. Improvement of site practices and better housekeeping in residential areas would lead to significant runoff improvements. The use of a parameter-weighted WQI for WQ analysis is proposed, as it can be easily adapted to SUDS situations. A WQI also allows better evaluation of SUDS performance than evaluation from single WQ parameters and is suitable for use in modelling software and standard spreadsheet applications.