Quantifying the sediment reduction efficiency of key dams in the Coarse Sandy Hilly Catchments region of the Yellow River basin, China

Abstract

With the implementation of a series of soil and water conservation measures, especially vegetation restoration projects and check dam construction, the sediment export in the Coarse Sandy Hilly Catchments (CSHC) region has decreased significantly. Quantifying the impact of check dams on sediment reduction in the CSHC region can provide a basis for regional management and decision–making of check dam construction. In this study, data from12 main tributaries in the region were collected, and the sediment reduction efficiency (SRE) of key dams was quantified by evaluating the sediment retention capacity (SRC) of key dams in different periods. The results showed that there were 3703 key dams in the CSHC region, among which the Wuding River watershed had the largest number of key dams (1139) and the largest total storage capacity (1332.9 Mm3). The annual sediment load of all tributaries showed a significant decreasing trend (P less than 0.01) over the past six decades. By 2018, the sediment reduction of the selected tributaries was basically more than 80%, which was mainly caused by human activities. Although the construction area of key dams in the CSHC region was increasing, the annual SRC of key dams was decreasing. In period 1, the average SRE of key dams on the west side was much higher than that on the east side. We determined that the influence of check dams in this area was weakening since the average SRE of key dams for the selected watersheds decreased from 24.38% of period 1 (1980–1999) to 11.24% of period 2 (2000–2018). In the future, the management strategy and construction planning of the CSHC region should consider the appropriate density and distribution of check dams, and explore how to maintain a sustainable vegetated ecosystem.