Research on runoff sub-model of non-point source pollution model

In light of the current ability to treat point source pollution, nonpoint source (NPS) pollution has become the primary cause of water pollution. In order to manage and control NPS pollution, we must conduct research on NPS pollution. An effective means for such an endeavor is to construct a mathematical model. However, in the present continuous time and distributed parameter NPS models, such as SWAT, parameter requirements are so numerous that their application is very difficult. In order to make such a model convenient for application, research was first conducted before constructing a new continuous time and distributed parameter NPS pollution model based on hydrodynamics. In this paper, as one of its sub-models, the runoff sub-model is introduced. This sub-model is composed of the SCS model and the water routing model that was constructed by the authors of this paper. This water routing model is based on Saint-Venant equations. Through Laplace transform and inverse Laplace transform mathematical modeling, the outflow hydrograph that is an S-curve was obtained. Then, the authors built the relation between S-curve and water-collecting area coefficient, from which the water routing model is derived. In order to calibrate and validate the new model, the authors applied it in the Guishuihe watershed with satisfactory results. The results show that it has value in application, especially in the area where data are scarce.