Simulation effects of clean water corridor technology on the control of non-point source pollution in the Paihe River basin, Chaohu lake

At present, water pollution is still a serious problem in some parts of China. Clean water corridor technology (which provides water quality assurance and pollution load reduction from the Major Science and Technology Program for Water Pollution Control and Treatment) is a river pollution control and treatment measure. However, due to the differences of specific river conditions, it is not initially clear which technology can be used to obtain the best effect. Numerical simulation can address this issue. The results can be used as the basis for selecting clean water corridor technology. Combined with remote sensing (RS) and geographic information system (GIS) technology, the relationship between land use and non-point source pollution load was analyzed by using the HSPF (Hydrological Simulation Program-Fortran) model. According to the distribution of pollution load, the effect of the clear water corridor technology and its combination scenario on the reduction of non-point source pollution in the basin was simulated, and the best clear water corridor technology scheme for the control of non-point source pollution was identified. Research results show that from 2015 to 2018, the non-point source pollution load of total nitrogen in the Paihe River basin showed an overall increasing trend, while the total phosphorus showed a slightly increasing trend. Agricultural land and construction land accounted for 70% and 20%, respectively, of the non-point source pollution load, and the change in land use played an important role in the load of non-point source pollution. In terms of spatial distribution, the non-point source pollution of total nitrogen and total phosphorus was mainly concentrated in the downstream region and the central region. The non-point source pollution load reduction rates of total nitrogen and total phosphorus by the three types of clean water corridor technologies of vegetation buffer zones, permeable sidewalks and constructed wetlands, and their combinations were 15.29% and 15.03%, 11.93% and 11.48%, 8.96% and 8.67%, and 24.12% and 23.20%, respectively. It is necessary to comprehensively adopt clean water corridor technology for an optimal allocation and reasonable layout and to increase the pollution load reduction rate to further achieve ecological environment restoration goals.