Spatial Distribution of Non-point Source Pollution in Dahuofang Reservoir Catchment Based on SWAT Model

SWAT model was used to calculate the agricultural non-point source pollution in Dahuofang reservoir catchment,Liaoning Province.The monitoring data of hydrology and water quality series from 2006 to 2009 was used to calibrate the parameters and validate the model,and the results indicated that SWAT model was appropriate for Dahuofang reservoir catchment.The calibrated model was used to reveal the spatial distribution of agricultural non-point source pollution characteristic.The results show that the annual amount of soil erosion in the reservoir catchment was 1.54×105t.In other words,there was very light soil erosion in the investigated area.The result was consistent with the actual situation of the forest coverage in this area.The various usage of lands have various degree of soil erosion.The arable lands indicated the highest soil erosion modulus,which were 475.84 t/(km2.a);the open woodlands were the second highest contributor,followed by shrub woodlands,and the soil erosion of the forests were the smallest.The slope output of both nitrogen and phosphorus in catchment were 1 248.83 t and 102.88 t,respectively.The Hun River basin ranked first in the contribution to the load of TN and TP pollution,accounted for 52.01% and 52.43%,respectively,followed by the Suzi River basin and the She River basin.The minimum contributors were the basins around the reservoir.The pollutions of nitrogen and phosphorus were various with different types of land use.The loads of TN and TP were mainly from the arable lands,which were 1 024.33 t and 93.35 t,respectively,which were much higher than the other land use types.Overall,the non-point source pollution around the Hun River basin was higher than the Suzi River′s,while the She River basin was minimum.The output intensity of non-point source pollution of the upstream region was higher than the downstream.This study indicated the spatial spread features of non-point source pollution at target areas,and the results provide a significant support to prevent both soil erosion and non-point source pollution.