Study On The Application Of SWAT Model In The Yangou Watershed On Loess Hilly Plateau

Taking Yan'gou watershed as a research object,based on nearly10years of watershedmonitoring and land use data. the purpose of this paper is to study water balance, runoff, theresponse of water yield to land use change and how the water yield varies under different landuse condition by using SWAT model. The specific results and conclusion as follows:(1) Developed a sensitive factor and its parameter of SWAT model adapt to Loessplateau region. The factors that matter the most to runoff including CN2, ESCO,ALPHA_BF,SOL_AWC,SOL_K and SLOPE. Among these factors CN2and ESCO are theprimary influences on runoff, whereas ALPHA_BF is the primary influences on undergroundrunoff. After manual and automatic calibration.(2) SWAT model can not only apply to the small watershed in Loess Plateau region butalso has a very well simulation results. The monthly runoff data of Yan'gou watershed from2007to2008are used for model validation. The validation is achieved by usingNash-Sutcliffe simulation efficiency factor Ens and r2. In the calibration period, Ens is0.81and r2is0.80. In the Validation period, Ens is0.81and r2is0.80. The simulation valuescoordinate well with the measured values.(3) The annual and monthly water balance from2002to2008in Yan'gou watershed isanalyzed. The results indicate that there is no significant variation in annual and monthlywater balance. The precipitation and runoff concentrated are mostly in summer, i.e. June, JulyAugust and September. The water yield gradually decreases from October to next June andthen begins to rise again, the maximum water yield is in September.(4) Revealed that vegetation restoration may cause the reduction of runoff. Thesimulation results show that the runoff depth was14.64mm in1997and was9.37mm in2003. The loss of runoff from1997to2003is5.27, a value of56.2%of the annual totalrunoff depth in2003, which indicates the vegetation restoration is capable to reduce the wateryield in small watershed.(5) Developed5different scenarios to explain the effect of land use/land cover changeon runoff. The results indicate that the runoff decreases with the increases of forest andgrassland. After the comparison of forest scenario and grassland scenario, it is clear that forest has more powerful influence on runoff than grassland.