Application of Digital Filtering Theory in Baseflow Separation in Xiangxi River Watershed of Three Gorges Reservoir Area

After the impoundment of the Three Gorges Reservoir,the water quality and quantity of the inflow have been focused.Baseflow separation was widely applied in the rainfall-runoff model,water resources allocation,identification of point and non-point source pollutions.In Xiangxi River watershed of Three Gorges Reservoir area,digital filtering theory was employed to separate baseflow from river runoff to examine the effects of parameters and number of filtering equations on results of baseflow separation.The results indicate that the filtering parameter β and the number are inversely proportional to the separated baseflow.Using the minimum value method as a standard,the differences of the baseflow separation results of digital filtering with the results of the minimum smoothing were compared.According to the features of Xiangxi River watershed,the baseflow separation results that use positive-negative-positive three times filtering is most appropriate when β is set to 0.925.