Study on pollution control zoning and measures for non-point sources in Three-Gorge Reservoir area using SWAT model

Non-point source pollution is becoming a very serious problem affecting water quality in Three Gorges Reservoir( TGR)area. In this study,we simulated the situation of non-point pollution in this region using SWAT model. First of all,we made efforts to prove SWAT model feasible and practicable for this region,then we made thorough analysis of current distribution of total sediment,TN and TP,and discovered that non-point source pollution are concentrated on the western part of Daning River and Xiao Jiang watershed. The total sediment, the total nitrogen( TN) and total phosphorus( TP) are 0.724 million t/a,8.82 million t /a and 1. 761 million t /a,Yulin River valley,Garonne River and Wu Jiang River basin,respectively. It can be divided into four control areas based on the total pollution load of sediment and the load per area,with TN and TP taken as the indicators for each sub-basin. Among the control areas,the key and sub-key control area are supposed to account for 12. 3% and 38. 4% of the total,respectively. Finally,we examined the effect of non-point source pollution control in TGR watershed by setting five scenarios,that is,Q1: Returning farmland to forests,Q2: No-tillage,Q3: Less fertilization measures,Q4: Applying the filter strip,and Q5: Comprehensive measures. The results stated that the considerable effect can be got from the scenarios. The comprehensive measures can reduce the sediment,TN and TP by 38. 6%,35. 5% and 36. 5%,respectively. Therefore,the given measures can help to reduce non-point source pollution effectively and be of great significance to improve the water quality in TGR watershed.