Non-point Source Pollution Modeling In Anji County Based On SWAT

Water safety as one of the most important environmental issues has been drawing a lot of attentions and highly concerned by human. Many troubling environmental problems, especially those in water, have inevitably come along with booming economics and developing living standards since the Chinese Reformation. Non-point source pollution has been indentified as an important source of water pollutions by many researches. Single Factor Analysis and Nemerow Complex Assessment method were applied in water qualities during both flood and no-flood seasons in Anji County. Premier results showed that total nitrogen (TN) and total phosphorus (TP) were mainly from agricultural non-point pollutions. Based on the Export Coefficient Model,60.8%of TN in water was from agricultural non-point pollutions, in which70.5%was from rice paddy fields.On the basis of understanding pollution types in Anji, we employed the widely used SWAT model to simulate, analyze and forecast the pollution situation. After data collection, pollution source investment and situ supervision, we used GIS technology to build the non-point source pollution spatial database and then the tempo-spatial change trend of non-point pollution situation in Tiaoxi watershed is obtained. There has a good simulation values of monthly runoff comparing with surveying values after modeling parameters calibration, in which the Ens of calibration period is0.807and the R2is0.822. The Ens of validation period is0.881and R2is0.882. The total sand capacity of the whole watershed is4.33-10t·a-1and the loss intension is23.7t·hm-2·a-1. The up river of the watershed (hilly area with dense forest cover) has small sand loss intention and the middle river of the watershed (plain area with farmland) has serious sand loss intention. The river inflow of total nitrogen (TN) in Anji County is about1210t·a-1and the TN inflow of unit area is6.61kg·hm-2·a-1. The river inflow of total phosphorus (TP) in Anji County is about16.9t·a-1and the the TP inflow of unit area is0.92kg·hm-2·a-1. Similar with the loss situation of TN, the serious area of TP loss in mainly in the farmland area.