Calibration and validation of water quality parameters in the Greater Sydney drinking water catchments.

WaterNSW is responsible for the management of Sydney's drinking water catchment and the prevention or reduction of water quality risks through the supply system from catchment to customer in line with the principles of the Australian Drinking Water Guidelines. WaterNSW is currently in the process of developing an integrated modelling system for both water quantity and quality that encompass the entire supply chain. This paper will focus on the water quality calibration and validation of grazing, forested, and roads and rails land uses across the drinking water catchments of Avon and Cataract. The primary land use within each catchment drove the manual calibration for the land use across all other catchments, using Event Mean Concentration and Dry Weather Concentration models in Source. The manual input process was automated with a python script. Simulation periods used for calibration and validation of each catchment were constrained by fire exclusion periods and data availability, with calibration using 80% of data and validation using the remaining 20% of data. The water quality parameters calibrated and validated within the models were selected for their impact on the receiving lake models. These include Ammonium, Nitrogen Oxides, Soluble Reactive Phosphorus, Total Kjeldahl Nitrogen, Total Nitrogen and Total Phosphorus. This paper discusses the water quality calibration and validation results through timeseries, cumulative and flow percentile box plots, and pollutograph and cumulative load graphs. It will also discuss the challenges encountered in the process, with a focus on the outcomes of calibrating for multiple land uses across multiple catchments. [ABSTRACT FROM AUTHOR]