Copper concentration simulation in a river by SWAT-WASP integration and its application to assessing the impacts of climate change and various remediation strategies

Abstract

The present study aimed to investigate the copper distribution in a river through the integrated utilization of the soil hydrological assessment model and water quality model. The Erren River was selected as the investigated river system because an apparent heavy metal pollution was observed. The Soil and Water Assessment Tool (SWAT) was employed to estimate the soil flux. The Water Quality Analysis Simulation Program Model (WASP) was used for water quality simulation. The copper was selected as the model chemical and scenarios of various copper effluent control measures and impacts of the heavy rainfall by climate change on copper concentration were simulated. The results showed that the aqueous copper was adsorbed to suspended solids and the high aqueous copper concentration resulted in a high copper concentration in the sediment. In dry seasons, the aqueous copper concentration increased 215% comparing to the 2006–2016 average (baseline) concentration and a 20% decrease in copper concentration in the sediment was observed due to less wash-out solid. Under the impact of enhanced rainfall by climate change, the aqueous copper concentration decreased due to the increased river flow, which also reduced the copper deposition causing the copper concentration in the sediment lower than that in the baseline condition. In the middle and downstream river sections, the copper concentration in the water and sediment phases decreased around 66% by implementing a more-stringent effluent standard. The suspended solid played a key role for copper movement in a river. The copper accumulation in the sediment might be alleviated by reducing its aqueous concentration.