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.