Study Simudation On Non-point Source Pollution In Mishui Basin

Since the 1990s,there have been outbreaks of water pollution in our country.In recent years,with the rapid development of the social economy,the rapid development of industry and agriculture,the urbanization is intensified,the water pollution of the drainage is becoming more and more serious,bringing a serious crisis to the lives of people on both sides.Based on the topographic elevation of the basin and land use type map from 1990 to 2018,spatial data and attribute data in the basin were organized,molecular basins were delineated,WDM meteorological files were established,and UCI files were formed under WINHSPF environment to establish HSPF hydrological model.The runoff and water quality were simulated by adjusting the parameters.The impact of different development modes on non-point source pollution was studied by changing future land use scenarios.The main research results are as follows:(1)From 1990 to 2018,the agricultural land increased first and then decreased,it peaked in 2010;urban or built-up land increased by 8999.12 hm2;the forest land decreased by 11200.73 hm2;wetlands increased by 2428 hm2;the barren land decreased by 50.27 hm2.The increase of population in the study area increases the demand for construction land.(2)The CA_Markov land use prediction model was introduced,and the land use type conversion rules were calculated based on the Markov model,which provided the required rules for the simulation of cellular automata,completed the simulation of the complex and disordered state,and improved the simulation accuracy of land use change.Based on the land use data of the basin in 2010 and 2015,the simulation and verification of the land use model in 2018 were completed,and the land use scenario in 2035 was obtained.(3)The period of 2010-2013 was taken as the model rate period,and the period of 2014-2018 was taken as the model validation period.The runoff simulation results of Yanling,Chaling,Anren and Hengdong controlled areas were obtained,and the Nash coefficients were all above 0.7.The simulation results were good and met the requirements of simulation.The absolute value of the total error of runoff simulation is less than 25%,and the simulation result is reasonable.(4)In terms of NH3-N simulation,the total ammonia nitrogen error of Yanling control unit rate was 21.2%and 19.61%in the periodic and validation periods,respectively.The periodic and validation errors of the control unit rate in Hengdong were 14.62%and 18.06%respectively.In the simulation of TP,the error of control unit rate in the periodic and validation periods is 19.01%and 18.04%,respectively.The calibration and validation period errors of Hengdong control unit are-16.17%and-15.16%respectively.Nash coefficient is greater than 0.6,R2 is above 0.74,the simulation results are reasonable.In line with the current situation of water quality pollution in the river basin.(5)The influence of the dropping-surface distribution of different land use types on non-point source pollution was constructed.The land use types in 2035 were simulated based and cultivated land,and further developed three development scenarios:economic priority and environmental protection priority,and the non-point source pollution load under different scenarios was analyzed.