SWAT-based Nutrient Source Analysis And Regulation Strategies In The Huangshui River Basin

Huangshui watershed is the political economic and cultural center of Qinghai Province. It is the most economically developed regions in Qinghai Province. In recent years, with the rapid development of the economic construction, environmental issues within the watershed have become serious increasingly. Watershed aquatic ecological environment is fragile. River runoff decreases. River self-purification capacity weakens. The river is polluted by nutrient which is mainly composed of organic ammonia. All above problem reduces water use value and functionality. Finding out scientifically the nutrient sources of Huangshui watershed can provide support for nutrient pollution control and overall ecological environment planning.This research uses distributed hydrological model SWAT to simulate the hydrological cycle and the source and spatiotemporal distribution of nutrient ammonia nitrogen and total phosphorus content in the Huangshui Watershed.Through statistical analysis and modeling, the following conclusions can be drawn. Ammonia nitrogen and total phosphorus change up and downs. The most important source of nutrients are from the effluent discharge and the use of fertilizers. The total ammonia nitrogen contribution rate are41.68%and41.71%respectively. The total phosphorus contribution rate are44.73%and44.75%respectively. The waste water and fertilizer use's ammonia load volume in2000increases by4times compared to1997. The phosphorus load volume in2000doubles by1997. Sewage is the main source of wastewater. The use of Nitrogen and phosphate fertilizers in agriculture accounts for a large proportion. Farm waste and animal dung with the water flows into the river causes nutrient pollution to a certain extent, which contribution rate is16.61%.The ammonia load volume caused by livestock in2000only doubles by1997.For the above analysis, this research puts forward the proposal to control nutrient pollution. The first is adjusting the industrial structure and optimizing the industrial layout. The second is improving sewage facilities and the sewage treatment rate. Rational application of fertilizer is the key to improve fertilizer utilization. To strengthen the livestock intensive management is the effective way from the traditional development to the modern pattern.