Simulation of the Effect of Land Use/Cover Change on Non-Point Source Pollution Load in Xixi Watershed of the Jinjiang Basin with SWAT Model

The nitrogen and phosphorous transport in Xixi watershed of the Jinjiang basin was modeled using the SWAT model.The model was calibrated by comparing the observed ammonia-nitrogen and mineral phosphorous with the simulated one,and the Ens of ammonia-nitrogen and mineral phosphorous was 0.69 and 0.79 with the minimum relative error 5.3% and 1.4%,respectively.The results indicated that SWAT model was appropriate for Xixi watershed.Then the effect of land use/cover change on non-point source(NPS)pollution loadings in the watershed was simulated with the mode,and the spatial and temporal variations of loadings were analyzed.The results showed that the total nitrogen and total phosphorous load increased from 1 530 tons and 266 tons in 1970s' to 2 641 tons and 542 tons in 2001,because of the land use change.The most serious region of unit area NPS pollution was located at the central watershed.The total pollution load in the Kengzikou tributary was still smaller,and it was changed and became almost the same in the other four tributaries.Due to the reduction of the area of farm and the increase of orchard,the most important land use catalog for the production of NPS pollution was the orchard in 2001 instead of the farm in 1970s'.