气候及下垫面变化对嘉陵江流域径流与输沙的影响

Influences of climate and land surface change on runoff and sediment in Jialing River Basin

为定量评价气候、下垫面2种驱动因子的变化对嘉陵江流域产流输沙变化的贡献率,采用SWAT模型,对嘉陵江流域1975年以来的径流和输沙过程进行模拟,通过模型控制变量的方法,分析嘉陵江流域径流和泥沙变化的驱动因子。结果表明:1988—2010年的23年间,由于下垫面变化,导致嘉陵江流域径流总量比1956—2010年的平均径流总量减少了1 718.54亿m^3,输沙总量减少了14.62亿t,下垫面变化对径流量减少的贡献率为76.19%,对输沙量减少的贡献率高达91.8%;因此,说明下垫面变化是造成嘉陵江流域径流量和输沙量变化的主要原因。

[Background] The Jialing River Basin is one of the important sources of runoff and sediment in the upper reaches of the Yangtze River Basin. Investigation on the mechanism of the influence of climate and underlying surface conditions on runoff and sediment discharge reveal the reason for the change of runoff and sediment discharge in Jialing River Basin in recent decades,therefore,analyzing the influence contribution rates from 2 factors of climate and underlying surface conditions on the changes of runoff and sediment has the important significance in the Jialing River Basin,and it also can be used as certain significant guidance to control the basin sediment variability of soil and water conservation work.[Methods]SWAT model was adopted to simulate the process of runoff and sediment in the Jialing River Basin since 1975,and was calibrated by processing the basic data（ including land use,DEM,soil data and meteorological data） and using the sediment data of the hydrologic stations,furthermore the driving factors resulting in the changes of runoff and sediment as well as their contribution rates to the changes of runoff and sediment were analyzed by the method of model control variables. [Results] The study showed that： during the 23 years from 1988 to 2010,1） the total runoff in Jialing River Basin was3. 59% less than the average runoff,and the total amount of sediment decreased by 5. 14% and onlyresulted from the change of climate condition. The contribution rate of climate changes on the decrease of runoff was 23. 81% and on the decrease of sediment was 8. 2%. 2） Compared with the average total amount of runoff and sediment discharge,the total runoff in Jialing River Basin had been a decrease of171. 854 billion cubic meters and the sediment discharge had been a decrease of 1 462 million tons. The contribution rate of underlying surface changes on the decrease of runoff was 76. 19% and on the decrease of sediment was 91. 8%. [Conclusions]1） The influence of weather change on runoff and sediment in Jialing River Basin is little. 2） The changes of runoff and sediment in Jialing River Basin are mainly caused by the changes of underlying surface conditions. Although this paper shows the underlying surface is the main reason on the change of runoff and sediment in Jialing River Basin,by the model precision it is infeasible to accurately distinguish the contribution rate of varied driving factors of underlying surface to the change processes of runoff and sediment. The underlying surface factors include soil and water conservation measures,land use change,reservoir hydropower station and the construction of large water conservancy facilities,and their influences on the runoff and sediment need further studying.