Response of Erosion and Sediment Producing Processes to Soil and Water Conservation Measures in the Wudinghe River Basin

Abstract

Based on data from the Wudinghe River, a tributary of the Yellow River in the major coarse sediment source area of the middle Yellow River Basin, a study has been made of the effect of soil and water conservation measures on sediment yield in the condition of changing precipitation. Both annual sediment load and annual river flow show a decreasing trend with time, and the areas of soil and water conservation measures. The area-weighted annual and high-flow season precipitations over the drainage basin also show a mild trend of decreasing, less significant than the above variables. It has been found that specific sediment yield is negatively correlated with the areas of land terracing, tree planting and grass planting. The period between 1956 and 1969 and the period between 1970 and 1996 are taken as baseline period without measures and the compared period with measures, respectively. Comparison between these two periods indicates that, during the former period, the percentages of the variation in specific sediment yield, runoff to precipitation ratio and high-flow season water yield can be explained by the variation in precipitation were 69%, 80% and 77%, respectively. However, in the latter period, these percentages decreased to 26%, 31% and 54%, respectively. This change means that, in the latter period, soil and water conservation measures played a great role, and thus the contribution of the variation in precipitation to the variation in sediment yield was greatly reduced. Based on the 41-year data from 1956 to 1996, a multiple regression equation has been established.