Variation of runoff-sediment relationship at flood event scale in three typical watersheds of the Loess Plateau

Abstract

River runoff and sediment load are characterized by topography, climate patterns, and vegetation in the watershed. The relationship runoff and sediment load has been greatly altered in many rivers throughout the world, as well as rivers in the Chinese Loess Plateau (LP) due to large-scale ecological restoration and soil conservation measures implementation. This study attempts to identify the changes of runoff-sediment relationship in three watersheds: the Gushanchuan River watershed, Jialu River watershed and Xichuan River watershed by using the flood event data during the periods of 1974–1989 and 2007–2019 in the LP. The results indicated that both runoff depth and sediment yield of flood events during 2007–2019 reduced significantly compared with those during 1974–1989 in all the watersheds. The highest decrease was found in the Gushanchuan River watershed, exhibiting reduction of 56.48% and 95.03% in runoff and sediment yield, respectively. The ratios between sediment yield and runoff depth in all three watersheds showed significant decrease during 2007–2019 when comparing to those in 1974–1989. The correlations between runoff and sediment variables became worse in 2007–2019, compared with those during 1974–1989. The implementation of soil and water conservation (SWC) measures (vegetation restoration, terraces and check dams) accounted for the changes in runoff-sediment relationship in all three watersheds. The result of this study could provide valuable information for the influences of SWC implementation and guide soil erosion control in the LP.