金沙江流域不同区域水沙变化特征及原因分析

在金沙江流域水文站控制的不同区间的水文资料和降水量资料,以及大量的长江上游水土流失重点防治区小流域综合防治工程(简称"长治"工程)拦沙减蚀量、水库拦沙量资料的基础上,对金沙江流域各水文站控制的不同区间、不同时段的来水来沙变化特征及其变化原因进行了定量分析.结果表明,金沙江流域水沙在地区分布上有明显的水沙异源特性,不同区间水沙变化特征存在很大的差异,降水/径流变化引起的沙量变化、水库拦沙、"长治"工程减沙在不同区间起着不同的作用.金沙江攀枝花以上地区以冻融侵蚀和坡面侵蚀为主,年产沙量仅0.521亿t,输沙模数200 t/(km2·a),但增沙的趋势较明显;攀枝花至屏山区间新构造运动剧烈,断层发育,岩层松软破碎,地形陡峻,植被稀少,以重力侵蚀为主,年产沙量1.58亿t,输沙模数达2 200 t/(km2·a),1991-2000年来沙量增加,2001-2004年来沙量大幅度减小.

Variations of runoff and sediment load of the Jinsha river

Using statistic methods,this paper analyzes the hydrologic data,precipitation data,soil and water conservation data and reservoir data and the causes for the variations of sediment loads at different areas.The results show that the runoffs and the sediment loads of Jinsha river are originated from different source areas and the runoffs and sediment loads from different source areas have very different variation characteristics,and the effects of precipitation,soil and water conservation and reservoir on sediment production at different source areas are also different.The sediment production upstream Panzhihua is mainly caused by the freeze-thawing erosion and slope erosion,and the sediment yield is relatively low,only about 0.521×108t,and the sediment runoff modulus is about 200 t/(km2·a).But in recent years,the sediment yield increases.The area between Panzhihua and Pingshan station lies in famous fault zones with precipitous landform.There exist a lot of fracture belts,little vegetation cover and the intense neotectonic movement that loosen the surface materials.Thus,mass erosion such as the collapse,landslide and debris flow develop largely in this area.The sediment yield in this area is very large,it is 1.58×108t annually,and the sediment runoff modulus is about 2 200 t/(km2·a).From year 2001 to 2004,the sediment yield in this area largely decreases to 1.10×108t,mainly because of the soil and water conservation and sediment trapping of the reservoirs.