Research On The Runoff Response To Underlying Surface Changes In Upper Luanhe River Basin

Climate change and human activity are the key to water resources shortage.In recent years,the runoff that flowing into the Panjiakou reservoir has been significantly decreased due to water resources shortage in Luahe river basin,and this seriously restricts the social and economic development in Tianjin.Therefore,taking the Panjiakou Reservoir watershed as study area,this article analyzed the variation characteristics of hydrometeorological elements and the spatiotemporal variation of land use.Also,the SWAT model as well as water-energy balance equation based on Budyko hypothesis were used to quantify the driving force of runoff reduction.Besides,we evaluated the impacts of land use change on runoff based on SWAT model.The main conclusions were as follows:?1?Statistical methods were used to analyze the variation characteristics of hydrological and meteorological data.The annual potential evapotranspiration and precipitation showed an insignificant downward trend,while the annual temperature showed a significant upward trend.The annual runoff reduced significantly and the change point was in 1979.?2?Land use transfer matrix and spatial analysis model were used to analyze the spatiotemporal variation of 1970,1980,1995 and 2010 l and use data.The results showed that the spatiotemporal variation of land use types was different which major included water reduction,the increase of forest and urban area expansion.?3?The SWAT model was established in study area.The R² and E_ns of the calibration period and validation period were both higher than 0.51.Combined the SWAT model with water-energy balance equation based on Budyko hypothesis,we quantified the driving force of runoff reduction in the Panjiakou reservoir.The contribution of climate change and human activitiy to runoff reduction were above 65%and below 35%,respectively.?4?Evaluating the hydrological processes under four land use scenarios based on SWAT model.Due to the transition from agricultural land and pasture to forest,the mean annual runoff decreased by 6.37%in four land use scenarios.The influence of land use change on typical hydrological years in wulihe subbasin was:dry years>mean years>wet years.The water yield of land use types was:urban area>unused land>agricultural land>pasture>forest>water.The evapotranspiration of land use types was:water>forest>agricultural land>pasture>unused land>urban area.The spatial variation of hydrological components caused by land use change showed spatial differences.