A high-resolution water quality model coupled sediment and suspended sediment module

Water environment numerical models considering detailed hydrodynamic processes are effective tools to better understand the pollutant transport and transformation mechanisms and the influences of sediment and suspended sediment on pollutants in rivers in complex terrain. However, these models can hardly achieve simultaneous high-efficiency and high-accuracy simulation of large-area rivers in complex terrain. Therefore, a high-resolution water quality model was developed coupled with a sediment and suspended sediment module (GAST). The Compute Unified Device Architecture (CUDA) parallel computing architecture and robust model algorithms were used, and the model performance and functionality were improved. This model was based on detailed physical processes, while water environment parameter spatial heterogeneity also was considered. A simulation function of multiphase pollutant transport and mutual transformation was established by solving the pollution adsorption kinetic equation applicable to high-resolution terrain. The transport and mutual transformation processes of multiphase pollutants in still water and steady uniform flow were verified by considering the Nash–Sutcliffe efficiency (NSE) coefficient which exceeded 0.99. The validated high-resolution water quality model was applied to simulate a river network water environment in a sulfurous iron ore area, and the numerical results for the sulfate ion concentration spatial distribution and pollution sources of sulfate ions in the sediment and water phases were explored. The results show that the concentration of sulfate ions in the Xiaowenyu River varies between 120 and 180 mg/L. The contribution rates of the 5 tributaries with slag heaps in the lower reaches to the sulfate ion load in the Xiaowenyu River followed the order of Guojiagou (15.7%) > Baoquansi (14.6%) > Zhuyuangou (9.2%) > Qingshigou (2.8%) > Sunjiagou (1.4%). On an RTX30700d computer, only 0.55 h was needed to simulate the hydrodynamic and water quality evolution process involving 653,112 cells for a 6-h model setting. The model attained a high computational efficiency and high operation speed. This study provides a reliable tool for further study of river pollution mechanisms and river water environmental management.