A Developed Method of Water Pollution Control Based on Environmental Capacity and Environmental Flow in Luanhe River Basin

To solve increasingly serious water pollution problems, it is necessary to systematically manage water resources, water environment, and water ecology as elements of a watershed. Comprehensive watershed water pollution control should regard the basin as a whole, respect the natural laws of the river and lake system, and focus on the protection and restoration of its natural ecological environment so that the comprehensive ecological service functions of rivers and lakes can be fully realized. Based on the concepts of environmental capacity (EC) and environmental flow (EF), this study established watershed water pollution control scheme prediction and evaluation methods to explore the changes in the water environment and water ecology in the basin under different water pollution control schemes. The MIKE11 model was used to construct a hydrologic and water quality model of the study area, the one-dimensional water quality model was used to calculate the water environmental capacity, and the Tennant method was used to evaluate the environmental flow. In this study, the method was applied to the Luanhe River Basin of Chengde, Hebei Province, China. It simulated the concentration changes of four pollutants-namely, NH3-N, COD, TN, and TP-under eight different water pollution control schemes, and the responses of EC and EF were compared and analyzed. Some conclusions are as follows: (1) Reducing point source pollution has the most obvious effect on water pollution prevention, especially on NH3-N and COD, while reducing nonpoint source pollution is weaker and the effect of increasing upstream water is the weakest. (2) The increase in up-stream water inflow and reducing point source pollution can greatly increase the EC of NH3-N and COD. The EC of TN can be greatly increased by reducing point source pollution, and the EC of TP can be greatly increased by reducing nonpoint source pollution. (3) The increase in upstream water inflow can improve the EF level to a certain extent. This method can also be applied to other similar river basins, providing valuable suggestions for rationally formulating water environmental management strategies and for promoting the sustainable development of the ecological environment and social economy in the river basin.