黄土丘陵沟壑区典型流域径流输沙对土地利用／覆被变化的响应

Effects of land use/cover change on runoff sediment discharge in typical watershed in Loess gullied-hilly region of China

基于动力水文过程测定技术和景观生态学测度方法,对位于黄土丘陵沟壑区第三副区的甘肃天水罗玉沟流域1986—2004年土地利用/覆被变化对流域径流输沙的影响进行了研究.结果表明:研究期间,罗玉沟流域土地利用/覆被变化对年径流输沙有显著影响,1995—2004年的输沙量比1986—1994年减少约63.0%,且随着年降水量的增多,其减沙效应明显;土地利用/覆被变化对流域径流输沙的影响具有季节性特征,相对于1986—1994年而言,研究区1995—2004年的减沙效应主要集中在5—10月,且月降水越多,后期的月均输沙量较前期减少得越多.降雨和洪峰流量频率分析表明,若具有相同频率分布的雨强,则任一重现期下罗玉沟流域1995—2004年的洪水平均含沙量小于1986—1994年.

By using the measurement technique of dynamic hydrological process and the estimation method of landscape ecology, this paper studied the effects of 1986-2004 land use/cover change （LUCC） on the runoff sediment discharge in the Luoyugou watershed in Tianshui of Gansu Province in third sub-region of Loess Plateau. The results showed that the LUCC in Luoyugou watershed had significant effects on the annual sediment yield. In 1995-2004, the sediment discharge was reduced by approximately 63.0%, compared with that in 1986-1994, and the reduction effect was more significant with increasing annual precipitation. The effects of LUCC on sediment discharge demonstrated seasonal fluctuation characteristic. Relative to that in 1986-1994, the reduction effect of sediment discharge in 1995-2004 was more concentrated in the period from May to October, and, the more the monthly precipitation, the more the reduction of monthly average sediment discharge in 1995-2004 than in 1986-1994. The analysis on precipitation and flood peak discharge frequency indicated that under the same frequency distribution of precipitation intensity, the average sediment concentration in any recurrence period in Luoyugou watershed was smaller in 1995-2004 than in 1986-1994.