Non-point source pollution transport of a typical agricultural watershed in Taihu Basin

The generation and transport of the agricultural non-point source pollution are closely related with hydrologic processes. The mechanisms of the hydrologic responses are the basis for the research of the non-point source pollutant transport. Based on the detailed field observations, the paper studied the interacting patters between the non-point source pollution transport and the hydrologic processes. The distributed model is applied to quantify the temporal and spatial variation of flow and pollutants. Based on the field experiments, the mechanism of hydrologic responses was analyzed and the hydrologic processes were simulated in Meilin watershed. The main components and the seasonal characteristics of N and P output were investigated. Nitrate and ammonia nitrogen are the main N lost forms in Meilin watershed. Soluble N is more easily flow out with the runoff in the rainfall event, but P is more likely lose with soil particles. Although the fertilizer application is maily in summer in accordance with plant growth, but the high flow rate diluted the output concentration of N and P. Driven by the distributed hydrologic model, the non-point source pollution forecasting model is established by simplifying N and P dynamics. The simulated results compare well with observed ones and the distribution of the critical source area of N and P output are obtained for Meilin watershed.