The Research On Characteristics Of Non-point Source Pollution In Xiangjiang River Basin Based On SWAT Model

Under the situation that the point source pollution contro l ability is increasing,non-point source pollution proble ms ha ve become increasingly prominent. Currentlyquantification and contro l of nonpoint source pollution proble m has become a hotissue in the fie ld. Xia ngjiang river basin is an important agricultura l base andagric ultural activity is freque nt, resulting to a lot of pestic ide che mical fertilizer loss.Unfortunatly, a ris ing proportio n of livestock and poultry breeding pollutionaggrevated nitroge n and phosphorus po llutio n of Xiangjiang. With waterenvironme nta l quality declining, non-point source pollution is becoming more andmore serious.According to SWAT mode l universa lity, under the support of arcgis9.3software,us ing SWAT2009model, the s imulatio n research about characteristics o f non-pointsource pollution was conducted in the upstream wa tershed of Xiangjiang in Xia ngtanhydro logica l station. This research a ims to vertify the model adaptive performa nce tored soil hilly re gion and stud y of the status of non-point source pollution. The ma inresearch conte nts and conc lus io ns are as fo llows:1. Xiangtan xiangjia ng river basin hydro logical statio ns serves as the river basinexport. According to the SWAT model with database format requireme nts, this paperestablis hed a non-point source database about xia ngta n station upstream watershed ofxiangjiang. The database cons ists of two parts, spatia l database and attribute database.Under the support of ArcGIS software, DEM map, la nd use map and soil type mapwere processed and a spatia l database was estaplis hed. SWAT attrib ute database wasestablis hed through SPAW software, SwatWeather model and a large number ofemp irical formula.2. With database support, calibration and va lidation o f the model was conducted.Research showed that SWAT mode l to simulate sediment effect was the best. Theevaluation index relative error (Re) was within6%, and the determinatio n coefficie nt(R~2) and Nash-Suttcliffe coefficient (Ens) were higher than0.93. what’s more,Runoff and total nitro gen no n-point source simulatio n effect is good. The eva luationindex Re was within5%, and R~2and Ens were higher tha n0.85. However Non-pointsources phosphorus simulation effect is genera l. Re evaluation indexes within8%, and R~2and Ens were higher than0.72, but the overa ll s imulation results meeted the needsof the mode l.3. Taking Xia ngjia ng Xiangtan hydro logica l statio n upstream watershed as theresearch object, this paper use SWAT model to s imulate non-point source nitrogen andphosphorus pollutants s imulation study results show that:(1) In the study area, Variatio n of po int so urce pollution o f nitrogen a ndphosphorus load time was s imilar to the variatio n of precip itation time. There is astrong positive relationship a mong non point source pollution load, sediment load andprecip itation. From1994to2004, total nitro gen and to ta l phosphorus of non pointsource pollution load va lue was the largest in1997and M inimum load va lue appearedin2003. The overall trend was decrease, but not severe.(2) The non-point so urce po llutio n load of total nitroge n and total p hosphorus inthe spatia l d istribution was different in stud y area. Nonpoint so urce po llutio n loadspatia l distrib ution of total nitroge n is similar to that of the rainfall spatia l distrib ution,ma inly concentrated in the ind ustria l, dense ly populated northern regions. Non-pointsource phosphorus pollutio n load distribution of space and sed iment load distrib utionwas simila r, and ma inly concentrated in agriculture and livestock exposed developedcentra l and southern regions. The total nitroge n concentratio n was who le ly on thehigh s ide and more than grade V standard. The highest concentration appeared inxiangtan c ity zhuzhou c ity and hengyang city urban area. Total phosphorusconcentration in most areas in the basin is good, only in chenzho u and totalphosphorus concentratio n of he ngyang regio n was over V c lass water qualitystandards.(3) Non-point source nitrogen and phosphorus pollution load of the research areawas related to different land use types. Through the mode l simulation resultsstatistical ana lys is, cropland contr ibuted the most to nonpoint source pollution load,forest land followed and grassla nd was the minima l.