| The contradiction between supply and demand of water resources is increasingly outstanding,and has become one of the strategic issues of the world.With the serious situation of our country water environment,non-point source pollution has become the main factor of water environment deterioration and eutrophication of lakes and reservoirs,and poses a serious threat to the safety of drinking water sources.Therefore,it is of great theoretical and practical significance to control non-point source pollution and protect the ecological environment for ensuring people’s drinking water safety and realizing the harmonious development of environment and society in China.As the drinking water source of Shaoxing region,Tangpu reservoir serves for nearly 2 million people in Shaoxing city,Shangyu city.With the development of economy and society,non-point source pollution has become one of the main sources of water pollution.The analysis and research of non-point source pollution and its response to water quality of the Tangpu reservoir is very important to the comprehensive treatment of the basin.Based on this,this paper,taking Tangpu reservoir as the research area,established SWAT model for quantitative simulation and evaluation of non-point source pollution load,and on this basis built a two-dimensional hydrodynamic-water quality coupling model suitable for non-point source pollution of basin,then revealed the transport and diffusion regularity of nutrient substances in the reservoir area,providing technical support and scientific basis for improving water quality and comprehensive treatment of watershed.The main research contents and results were as follows:Based on the investigation of surface water quality in the river basin,the temporal and spatial variation of nutrient pollutants,active silicon and heavy metals were studied.The results showed that the concentration of ammonia nitrogen and total nitrogen in the water of Tangpu reservoir was of obvious difference in space,and their concentration were also influenced by season,even if at the same sampling point the concentration of ammonia nitrogen also might change due to the different sampling time.Total phosphorus concentration was greatly influenced by season,overall,the lowest TP concentration in water was in February,the second in August,and the highest in May.The concentration of soluble silicon in water was significantly positively correlated with the concentration of chlorophyll a.Heavy metals were mainly gathered in the bottom.Cd,Cr and Pb were not detected,Cu and Zn both had no large fluctuations,the concentration of Fe and Mn in the reservoir had an obvious stratification,and the concentration of different layers were of great difference.Based on the collected spatial data and attribute data of the reservoir basin,a complete and unified model for Tangpu reservoir basin non-point source pollution was established,which was suitable for the SWAT model.On the basis of this model the temporal and spatial variation of non-point source pollution load were analyzed using data of the typical hydrological year.At the time scale,the annual output of all kinds of non-point source pollution were mainly in the flood season,which were concentrated in the month of large amount of rainfall.On the spatial scale,runoff distribution in Tangpu reservoir basin gradually decreased with the terrain from north to south,with a positive correlation to rainfall,and the largest area of runoff concentrated in the middle and lower reaches of the river.There was a good correlation between the distribution of sediment load and the distribution of nitrogen and phosphorus non-point source pollution load,which mainly concentrated in Wang Yuan village,Gu Lai town,and Wang Tan town,therefore,these areas should be the key source region of pollution control.2002-2011 annual average unit area pollution load of the river basin,the overall comparison,the proportion of arable land was the largest,followed by the urban land,and forest land,orchard compared was less.With the establishment of Tangpu reservoir two-dimensional hydrodynamic and water quality model,the migration and diffusion regularities of water quality indexes of non-point source of Tangpu reservoir like TN,TP,NH3-N,BOD5 were simulated.Relevant parameters of the model like water quantity and water quality were calibrated respectively,and t he simulation results were fitted well with the actual results,showing that the model could better simulate water quality change process of Tangpu reservoir.By designing three kinds of reservoir operating conditions under different hydrodynamic conditions,the migration and diffusion of TN,TP and NH3-N in the reservoir were analyzed,and then it is concluded that at the normal water level operation condition it was not only beneficial to pollutants diffusion,but also the degradation rate reached the maximum.The results of eutrophication evaluation showed that the reservoir of Tangpu reservoir was at the level of moderate eutrophication,and the level of eutrophication was increased first and then decreased from storage to dam.In the middle of the reservoir area,the degree of water nutrition is high,and the degree of nutrition is low.Phosphorus is a limiting element,of the reservoir and the reservoir has the characteristics of synergistic effect of endogenous eutrophication and exogenous pollution eutrophication.Therefore,a variety of measures to control the non-point source pollution into the reservoir at the same time,the reservoir sediment contained in a large number of endogenous pollutants should be to prevent and control,in order to reduce the nutrient content of the storage,control the endogenous pollution release To slow the eutrophication process. |
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