Irrigation, Drainage and Ecological Engineering Approaches to Controlled Farmland Nonpoint Source Pollution

Farmland nonpoint source pollution (FNPSP) was considered as the chemical to river, lake or groundwater with the surface runoff, seepage or farmland drainage. It is distributed widely and scattered, and difficult to control. A framework to prevent and control FNPSP was put forward, namely irrigation, drainage and ecological engineering approaches (IDEEA), which including in water-saving irrigation, controlled drainage, bioreactor, water and fertilizer management, ecological drainage canal and wetland. In order to identity subject of responsibility of FNPSP, the total pollutants and their density should be estimated and emission permit should be implemented base on the main drainage canal catchment of farmland. The effects of different approaches were analyzed based on recent research results. Case study in Guilin, Guangxi and Qingpu, Shanghai showed that, in same region, the area of wetland for TN is larger than for TP and the area of wetland in surface is larger than in subsurface. The percentage of wetland area to paddy field is about 9-10% in surface flow and 7-8% in subsurface.