Research On Agricultural Non-Point Source Pollution In The Watershed Of The Source Areas Of The Liaohe River Based On AnnAGNPS

Water resources are the primary condition for the country sustainabledevelopment,however, Chinese water situation is not optimistic.In recent years,inorder to improve grain yield,fertilizer and pesticide application rate isincreasing.Excess fertilizer and pesticide entered the water with surface runoff hascaused the water pollution further deteriorated.Agricultural non-point sourcepollution has become one of the main reasons for the water pollution,so controlingagricultural non-point source pollution is the important goal for the water pollutioncontrol.Because of the complexity of the formation mechanism and migrationmechanism,Agricultural non-point source pollution have random and dispersivecharacteristics.Applying the mathematical model in agricultural non-point sourcepollution research can effectively solve the inconvenience which caused by therandomness of non-point source pollution,and also can quickly simulate the temporaland spatial distribution of agricultural non-point source pollution.Based on thesimulation results,decision-makers can make a reasonable management measure tocontrol the agricultural non-point source pollution. AnnAGNPS (AnnualizedAgricultural Non-point Source Pollution Model) is the computer model jointlydeveloped by the U.S. Department of Agriculture Agricultural Research Service andNatural Resources Protection Bureau to simulate the agricultural non-point sourcepollution load.This paper take the watershed of the source areas of the Liaohe River as thestudy area,analysis the variation of nitrogen,phosphorus and runoff with time,as wellas the loss of nitrogen and phosphorus under different land use by monitoring surfacerunoff.According to the land use types,soil types,application of fertilizer andpesticide,crop farming methods,and the meteorological datas of the watershed todetermine the parameters of AnnAGNPS model.Thereinfo the sub-division number ofa watershed is closely related to the spatial distribution of non-point pollution sources,the CSA (critical source area) and MSCL (the minimum channel length) wererepetitiously employed to determine the number of sub-division of watershed and itwas captured when a variety of non-point source pollution loads were stabilized.As the soil texture system of Chinese Soil Survey is different from the system of the soiltexture that AnnAGNPS needed,the soil erodibility factor was calculated by usingEPIC model after the soil textures were adapt to AnnAGNPS model by interpolationmethod, assuming the soil cumulative size follow the lognormal cumulative.The model has been calibrated and tested by comparing the simulated andmeasured values of nitrogen and phosphorus.The tested model was used to simulatethe TN and TP loads of the watershed of the source areas of the Liaohe River,whichwere used to analysis the temporal and spatial distribution of nitrogen and phosphorusloads and to identify the critical source areas of nitrogen and phosphorus nonpointsource pollution loads. According to the critical source areas,the managementmeasures were maked to control the agricultural non-point source pollution.