SWAT model-based runoff simulation in Banchengzi Reservoir Catchment,Beijing

The runoff in the Banchengzi Reservoir Catchment,Beijing,was simulated using a SWAT(the Soil and Water Assessment Tool)model,and our emphasis was placed on impacts of vegetation changes on the hydrological responses.The monthly and yearly runoff was simulated during the period of 1990--1999,and the sensitivity of the model was calibrated with three indices,i.e.,efficiency coefficient,relative error,and correlation coefficient of monthly runoff.Then the monthly runoff during the period of 2000--2006 was also validated.Results show that SWAT model was fit for the runoff simulation in the Banchengzi reservoir catchment with a high accuracy.Based on the simulation with SWAT model,we applied the spatial analysis functions of GIS and analyzed the runoff distribution in the year of 1990,1995,2000 and 2005 as well as the impacts of different landuse types on hydrological responses.Results indicate that precipitation and landuse changes had considerable impacts on the runoff.The months of more rainfall produced more runoff and vice versa.The landuse changes were mainly characterized by the decrease of shrub and coniferous forest areas and increase of broad-leaved forest areas.The corresponding hydrological changes were represented by the decline of runoff volume,of which,the runoff volume produced was the largest in coniferous forests and broadleaf-conifer mixed forests.