Response Of Runoff And Sediment To Climatic Variabilities And Land Use Change On The Upper Sangkan River Basin

Loess Plateau area is a typical vulnerable eco-environmental zone in China,making it one of the most serious region in the world.This fragile natural ecosystem combined with long-term improper interference from human activities,resulted in water and soil erosion,land degradation,water shortage,deteriorating ecosystem and forming a vicious cycle.Detecting the relationship between the change of climatic variabilities,land use and the streamflow,sediment,and figuring out the prone area of soil erosion,can do help to the restoration of ecosystem,implement of “Grain for Green” and regional sustainable development.This study can also provide advice for ecological restoration of Yongding River and ensure the water security of the capital(Beijing).The upper Sang-kan(USK)river basin,the headwater of the Yongding River of the Haihe basin was taken as the study area in this research.The main content of this study are as the followings:(1)Temporal trends and frequency changes of climatic variabilities and streamflow in the USK basin between 1957 and 2012 were detected using linear regression,Mann-Kendall(MK)analysis,and wavelet transform methods.The results indicate that: precipitation in the USK basin over the study period did not show any trend while the temperature showed a significant increase(especially in spring and winter);streamflow flowing out from this basin indicated a significant decrease(in spring summer and autumn);Linear regression method was used to identify the contribution of climate change and human activities to the streamflow reduce was37.3% and 62.7%,respectively.(2)Using ENVI(Environment for Visualizing Images),land use maps of 1986,2000 and 2012 were interpreted from Landsat images.Based on the ArcGIS and Fragstats 4.2,the change of land use structure and land use transfer relationship,etc.,were calculated.Ann_Markov_CA model was set up with IDRISI to predict the land use in 2030.Results showed that: from 1986 to 2012,the trend of land use change stayed in status of Weak Equilibrium;agriculture land experienced obvious decline while urban land and unused land extended dramatically.In the future,the agriculture land,urban land and unused land will decline,while the forest and grassland will increase.(3)After the setting up of SWAT model,the observed streamflow and sediment data was used to calibrate and validate the model through SUFI-2 method ofSWAT-CUP.Results showed that SWAT model can perform reasonable streamflow and sediment simulation;with the “Single-Factor Transformation” method,the land use change from 1986 to 2012 led to an increase of 2.2% to 3.9% in the streamflow,and an increase of 6.86% in sediment;while the change of climatic variabilities made the streamflow decreased by 39.1%.While groundwater overdraft,water diversion irrigation and reservoir management are the main causes of river dry-up in Sang-kan River,accounting for 63.1%~64.8%.(4)The future climate data(30*30 m)was generated using the Weather Research and Forecasting(WRF)model driven by the Model for Interdisciplinary Research on Climate version 5(MIROC5)in the context of the Coupled Model Intercomparison Project Phase.Put the future land use map and climate data into the calibrated SWAT model,and the simulation results indicated that the average temperature will decline and precipitation and will increase during 2015 to 2030.Meanwhile,runoff.and sediment will increase.