Application of Build-up and Wash-off Models for an East-Australian Catchment

Abstract

Estimation of stormwater pollutants is a pre-requisite for the protection and improvement of the aquatic environment and for appropriate management options. The usual practice for the stormwater quality prediction is performed through water quality modeling. However, the accuracy of the prediction by the models depends on the proper estimation of model parameters. This paper presents the estimation of model parameters for a catchment water quality model developed for the continuous simulation of stormwater pollutants from a catchment to the catchment outlet. The model is capable of simulating the accumulation and transportation of the stormwater pollutants; suspended solids (SS), total nitrogen (TN) and total phosphorus (TP) from a particular catchment. Rainfall and water quality data were collected for the Hotham Creek Catchment (HTCC), Gold Coast, Australia. Runoff calculations from the developed model were compared with the calculated discharges from the widely used hydrological models, WBNM and DRAINS. Based on the measured water quality data, model water quality parameters were calibrated for the above-mentioned catchment. The calibrated parameters are expected to be helpful for the best management practices (BMPs) of the region. Sensitivity analyses of the estimated parameters were performed to assess the impacts of the model parameters on overall model estimations of runoff water quality. This paper demonstrates the calibration of a catchment water quality model to obtain a set of parameters for which the predicted pollutant concentrations are close to the measured concentrations. Two major pollutants were analysed for the calibration of the model: TN and TP. These pollutants were chosen for the calibration of the model because of the data availability. Nonetheless, these parameters are generally used as indicators of water quality in receiving water bodies (13). For the evaluation of the hydrologic outputs of the model, the peak discharges were compared with the calculated discharges from the WBNM and DRAINS models, which are widely used in Australia. Water quality data (TN and TP) was collected from several locations within the HTCC on the Gold Coast, Australia. The calibration of the model was demonstrated using the collected water quality data from the Gold Coast, Australia. The calibrated parameters are expected to be useful for the future use of the model to develop BMPs for pollution