岔巴沟流域水土保持减水减沙作用

Effects of soil and water conservation on reduction of runoff and sediment in Chabagou Watershed

运用经验公式法、双累积曲线法和不同系列对比法计算岔巴沟流域1971—1980年水土保持措施的减水作用分别为10.55%、6.18%和26.67%,减沙作用为58.74%、63.40%和72.77%;经过对计算结果和前人研究成果的分析得到如下结论:1)岔巴沟流域库坝等工程措施为主的水土流失治理方式在措施生效期间能够有效减少流域输沙量,减沙作用为65%左右,能够有效拦截洪水,减少洪峰流量,汛期减水作用大于25%;2)库坝等工程措施对流域年径流量的影响不大,减水作用在7%左右,地下径流占总径流比例提高了20.4%,对地下水的补充起到了很好的作用;3)库坝等工程措施不能改善流域坡面和沟坡侵蚀条件,故而无法真正改善流域水土流失的状况,其减沙效果随着淤积量的增加而减小,需要不断投入以维持其减沙作用,而限于自然条件,库坝等工程措施对流域的治理是不可持续的。解决水土流失问题的根本途径在于恢复流域自然植被,顺应自然规律的发展,并采取适当的人工辅助措施。

In this study,effects of soil and water conservation measures on runoff and sediment reduction in Chabagou Watershed from 1971 to 1980 are calculated by three methods： rainfall-runoff and rainfall-sediment statistical model,double-accumulative curve method and time series contrasting method separately.As a result,runoff reduction are 10.55%,6.18% and 26.67% and sediment reduction are 58.74%,63.40% and 72.77% accordingly.By analyzing the results of calculation and comparison with results of previous studies,three main points are concluded： 1） Governance model emphasizing on sediment storage dam has remarkable sediment reduction effects which is averaging about 65% and can effectively reduce peak discharge with an averaging runoff reduction effect more than 25% in the flood season;2） Annual runoff reduction effect is only averaging about 7% and the ratio of groundwater runoff to total runoff raised by 20.4%,which shows that sediment storage dam affect runoff by adjusting the ingredient proportion rather than reducing total runoff;3） The aim of water and soil conservation can not realized only by sediment storage dam for it does not change the conditions of hill slopes where soil erosion occurs,and instead vegetation restoration is an effective approach for ecosystem restoration and enhancement in eroded area of loess.