Impact of check dams on the sharp decrease of runoff in the middle Yellow River: case study in the Huangfuchuan River basin

Abstract

Soil erosion in the middle Yellow River is the most serious in China. Recently, due to the increasing human activities for several decades, the condition of runoff and sediment yields has changed obviously, which causes the sharp decrease of runoff in this region. Therefore, deep investigation on the impact of human activities on runoff process appears particularly important. In this study, the Huangfuchuan (noted as HFC hereafter) River basin, one typical tributary in the middle Yellow River, is taken as the study area; and the building of extensive check dams (i.e., sediment trapping dams) are taken as the typical type of human activities in this basin. Firstly, digital drainage network with high spatial resolution was extracted from the DEM (i.e., Digital Elevation Model) by using the TOPAZ module. Then the amount and distribution of check dams were determined through data collection from statistical reports and artificial identification from remote sensing images. Thereafter, the topological relation between the dams and river reaches was identified, which helped to find the check dams, 448 in all, control 45% of the total basin area. To estimate the effect of those dams, periods with weak or significant impact of human activities were defined, respectively, by the analysis of runoff change. Then, the Digital Yellow River Integrated Model (noted as DYRIM hereafter) is used to simulate the response of runoff process on the building of check dams, using the measured precipitation data over the basin from 1976 to 2006. By comparing simulated runoffs with and without check dams, this study shows that the interception effect of check dams is one of the most important reasons for the sharp decrease of runoff in the middle Yellow River, under the condition that the rainfall decrease is obscure.