Simulation Of Hydrological Response To Land Use Land Cover Changes In Panjiakou Reservoir Watershed

Luanhe river is the most important source of water supply of Tianjin and The water transfer project from Luanhe River into Tianjin city is of significance in Tianjin's water supply..This project supplied Tianjin with 17 billion cubic meters of water so far and contributed a lot to the development of society and economy. But in recent years, the water resources of Luanhe River Basin have changed significantly with a sharp decrease of runoff flowing into the Panjiakou Reservoir, and put the water supply of Tianjin city in risk several times and made the government have to transfer water from Huanghe River. So a study on impacts of land use /land cover change on the runoff flowing into the Panjiakou Reservoir is of great help.SWAT(Soil and Water Assessment Tool) model, developed by the US department of agriculture, is a distributed model for large- medium size watersheds and long time scale, which is used to simulate the long term impacts of land management on the runoff, sediments and agricultural chemicals. The application experience domestic and abroad has shown that SWAT model has the extensive applicability.In this paper, the SWAT model in used to simulate the runoff flowing into the Panjiakou Resevoir, and then the measured data was applied to calibrate and validate the parameters of this model. After verification of the applicability, the model was used to analyze the characteristics of evolution of the runoff flowing into the Panjiakou Reservoir.The results reveal that average annual runoff during the period 1986-1999 is 11% lower in the land use scenarios of year 2006 while comparing to the land use scenarios of year 1980; By analyzing different typical hydrological years, we know that change of runoff is the greatest in dry years and change in wet years and mean years are equal in response; The runoff decrease because of land use changes are mainly take place during the flooding season. The result shows that water conservation capacity of Panjiakou Reservoir watershed is increasing in recent years. Designed annual runoff of 10%?50% and 90% frequency is obtained through frequency analysis on the model results in the land use scenarios of 2006,they are 4.27 billion m~3,2.03 billion m~3 and 0.76 billion m~3, respectively, and runoff distribution in relative years are calculated from the chosen typical years by magnifying or reducing it. Simulation of impacts of land use changes on the runoff in Panjiakou reservoir watershed has practical significance in reasonable land use planning and universal water management in the study area.