Application of sensitivity analysis module of SWAT model in typical watershed of the Loess Plateau.

The soil and water assessment tool(SWAT) is a physically-based continuous event hydrologic model.Besides all the features included in SWAT2000,the latest SWAT2003 version also includes sensitivity analysis,automatic model calibration and uncertainty analysis.The sensitivity analysis of the SWAT model was expatiated and applied to simulate the rainfall and runoff relationship in Luoyugou Watershed in the Loess Plateau.Based on the sensitivity analysis, the main parameters affecting the simulated values in this watershed were determined.The results showed that the CN2 and(SOL_-AWC) parameters had the most significant influences on the simulated values of runoff and sediment yield in Luoyugou Watershed.Besides,the effect on sediment yield was higher than that of runoff.In addition,other parameters,such as(ALPHA_-BF,) ESCO,SLOPE and SLSUBBSN,had striking influences on the simulated sediment yield either,but little on the simulated runoff.Adjusting the parameters based on the analyzed results,satisfied simulation results were obtained with both of Nash-suttcliffes coefficient(E_(ns)) and correlation coefficients R~2 exceeding 0.8,and the relative error was under 15% over 15 years continuous simulations on monthly discharges.Therefore,the application of sensitivity analysis module of SWAT model in typical watershed in the Loess Plateau has improved the accuracy of simulation dramatically.