Study And Build Up Nonpoint Source Pollution Model Of Shixia Catchment In Miyun Reservoir Watershed

Sources of water pollution can be classified broadly into two categories: point sources and nonpoint sources. Nonpoint source pollution is a major contributor to water contamination. It is hard to calculate simulate and control for its unfixed characters. GIS combing with nonpoint source pollution models are widely used to calculate nonpoint sources load at present.Miyun reservoir is the most important water source in Beijing. The water quality of Miyun reservoir is at medium-eutrophication situation caused by the nonpoint source pollution in the upper watershed. Shixia catchment is selected as the research area where small units of different land use have been monitored during the runoff period.Shixia Nonpoint Source Pollution model (SXNPS) is built up with the tools of Visual Basic 6.0. It consists three parts: the first is surface runoff model with the core of SCS equation; SCS hydrologic method has widely been used for analyses of agricultural watersheds. The second is soil loss model based on USLE equation. The third is nutrient transport model. Shixia Catchment Nonpoint Source Pollution Model has standard windows and friendly interfaces.A GIS database including nonpoint source information provides basic data to SXNPS. SXNPS was first used in Shixia catchment in Miyun reservoir watershed.Some conclusions are drawn as following: The surface runoff has good correlativity with the land use, the runoff depth from the village is the highest, then from wilderness use and orchard; the soil loss has good correlativity with topography, vegetation water and soil conservation, the key area is the place in which the topography is big and the land use is wilderness and orchard; the nutrient transport has good correlativity with topography land use and acreage, the nutrient concentration in village is the highest, while the gross of wilderness orchard and village are the biggest and woodland and shrub are the smallest.SXNPS model shares databases and database files with GIS. The strongpoint is high stability and reliability, short exploitation period and low work quantity, while the shortage is overstaffed and low efficiency of system.