Impacts of rainfall intensity and urbanization on water environment of urban lakes

Abstract

The climate change and urbanization have interacted synergistically to impact the water environment problem of urban lakes in the late twentieth century. In this paper, an integrated model describing hydrology, hydrodynamics and water quality was developed based on SWMM and the DEM-based hydrodynamic and water quality model. The Tangxun Lake was used as a testbed here, and the impacts of rainfall intensity and urbanization on lake water quality was discussed through the scenario analysis. The results showed that the runoff volume and the pollution load of TN and TP into the Tangxun Lake increased significantly with the increase of the rainstorm intensity. In the prophase rainfall, the TP and TN concentration gradually increased. The greater the rainstorm intensity was, the worse the lake water quality would become. While in the late rainfall, the lake's water quality improved slightly. After the rainstorm, the water fluidity in the lake was obviously improved. Spatially, the water flow presented a directional flow from the runoff inlets to the lake outlet, and the contaminants gradually diffused from the boundary area to the center of the lake. On the other hand, with the rapid development of urbanization, the runoff depth, runoff coefficient and pollutant loads had obviously increased, thus the average TN and TP concentration in the lake also increased. Compared with the early urbanization stage, the total pollution loads of TN and TP increased by 53.49t and 8.88t respectively after the 24-hour rainstorm in the late urbanization stage.