According to the agricultural non-point pollution problems in Yitong River

a model of agricultural non-point pollution in this area was constructed using SWAT model with the support of GIS technology and watershed foundation database.The model was used to simulate the temporal and spatial distributions of N

P and sediment

as well as the total nitrogen delivered into groundwater in the study area.Results from the calibration and verification for the model showed that the precision of the model can meet the requirements.Through the calculation of model simulation

sediment yields in 1985and 2008were 7.031 6and 3.458 7million ton

respectively.In 1985

total nitrogen and phosphorus outputs were 20 400and 2 300ton

respectively

and in 2008

was about half of that in 1985.For one year

pollution output from June to August took up90% of the total amount.The simulation result showed that the amount of nitrogen delivered into ground water by infiltration was considerable in 1985and 2008

the amounts of nitrogen delivered into groundwater were 2.4and 5.5times of those in other forms of output.