Spatiotemporal Heterogeneity And Driving Factors Of Streamflow Variations In Jialing River Basin

In recent years,variation of meteorological and hydrological elements and changes of eco-hydrological process caused by global climate change and human disturbance have attracted widespread attention.As an important water source and sediment-producing area in the Yangtze River Basin,healthy development of the ecological environment in this basin have important sense to Yangtze River.This study used the observed data to analyze the spatial and temporal characteristics of hydrometeorological properties of Jialing River Basin and drive sensitivity and attribution analysis of runoff variation based on Budyko hypothesis.By constructing SWAT model of Jialing River Basin,monthly simulation of water yield in sub-basins were obtained to further analyze the spatiotemporal characteristics and driving factors water yield.Results were as follows:(1)Based on observed data,the trend and change point of precipitation(P),runoff depth(R)and potential evapotranspiration(E0)generation of Jialing River Bain and its sub-study regions were detected using mathematical statistics,Mann-Kendall analysis and Sen's slope estimator.Results showed that P,E0,R showed a decrease,increase and decrease trend respectively during 1954-2015.P decreased and E0 increased in the upper reaches,while showed an opposite trend in middle and lower reaches.With the exception of Qu Jiang Basin,trend of R was consistent with P with a contrary trend in upper region and middle-lower regions.(2)Using the elastic coefficient method and complementary method based on the Budyko hypothesis,the sensitivity analysis of the runoff variation in the Jialing River Basin and the contribution rate of meteorological and non-meteorological elements indicated that sensitivity of runoff variation was higher in semi-humid region than that of humid areas.Contribution rate of meteorological and non-meteorological elements to runoff changes in Jialing River Basin was about 20%and 80%,respectively.Compared with the base period(1954-1979),the contribution rate of the factors with higher contribution rate in the first impact period(1980-1993)showed a downward trend in the second impact period(1994-2015).(3)Setting 1980-1981 as warm-up period,1982-2000 as calibration period and 2001-2015 as validation period of SWAT model in Jialing River basin,simulation of monthly water yield data was carried out.R2,NSE,and PBIAS,as applicability index,showed "excellent" at Luoduxi Station,Wusheng Station and Beibei Station,and "good" at Xiaoheba Station,that is,the model was available to reflect the watershed hydrological processes and characteristics.(4)According to the simulation results of water yield in sub-basins by SWAT model,the spatial variation characteristics of runoff in Jialing River Basin at different time scales were studied.Results showed that water yield in Jialing River Basin was spatially bounded by the Longmenshan fault zone,showing less in upstream and more in midstream.With the boundary of mid-stream and downstream,the downstream region had a low water yield.With spatial difference of change trend,water yield in upstream low-yield area continued to decrease,while it showed a significant increase in downstream low-yield area.The spatial distribution of the yield of the sub-basin in spring,summer and autumn was similar to the multi-year average runoff pattern,while showed a decrease trend from upper region to lower reaches in winter.Principal component analysis and cluster analysis were used to obtain typical influencing factors and divide the whole basin into 4 typical regions according sub-basin's properties.Driving factors of water yield in these 4 typical regions were detected by standardized regression coefficient.Results indicated that morphology factor mainly affected runoff characteristics in the eastern source area and central fault zones of Jialing River Basin;Surface condition factor was the major driving factors of low-altitude area in middle and lower reaches;Rainfall factor controlled the western tributary of eastern source area with low water yield;The western source region was mainly controlled by meteorological factor and land surface condition properties.