Abstract
Abstract. Soil erosion not only results in the destruction of land resources and the decline of soil fertility, but also contributes to river channel sedimentation. In order to explore the spatiotemporal evolution of erosion and sediment yield before and after returning farmland in a typical watershed of the hilly and gully region (Chinese Loess Plateau), a distributed-dynamic model of sediment yield based on the Chinese Soil Loss Equation (CSLE) was established and modified to assess the effects of hydrological factors and human activities on erosion and sediment yield between 1995 and 2013. Results indicate that (1) the modified model has the characteristics of a simple algorithm, high accuracy, wide practicability and easy expansion, and can be applied to predict erosion and sediment yield in the study area, (2) soil erosion gradations are closely related to the spatial distribution of rainfall erosivity and land use patterns, and the current soil and water conservation measures are not efficient for high rainfall intensities, and (3) the average sediment yield rate before and after model modification in the most recent 5 years (in addition to 2013) is 4574.62 and 1696.1 Mg km−2, respectively, decreasing by about 35.4 and 78.2 % when compared to the early governance (1995–1998). However, in July 2013 the once-in-a-century storm is the most important reason for maximum sediment yield. Results may provide an effective and scientific basis for soil and water conservation planning and ecological construction of the hilly and gully region, Chinese Loess Plateau.
Highlights
Soil erosion is one of the main environmental risks that restrict the survival and development of human beings (Ongley et al, 2010), affect regular land development, and have been reported as the main cause of land degradation (Sun et al, 2012)
The annual erosion rate of the Majiagou River watershed in 2008 is 2485.46 Mg km−2 yr−1 and the corresponding simulated value is 2278.2 Mg km−2 yr−1 with relative error 8.34 %. These results demonstrate that the dynamic erosion and sediment yield model has scientific rationality and good reliability
Previous research results of sediment variations in Ganguyi hydrological station between 1961 and 2012 (Ren et al, 2012) and the simulation results of sediment yield in this study confirmed that sediment yield showed a decreasing trend; there were fluctuations of different degrees in individual years (Fig. 5), it indicates that the overall changing trends of sediment yield in the study area are consistent with the background of returning farmland policy (Zhao et al, 2013); the current simulation accuracy basically meets the requirements of changing tendency evaluation
Summary
Soil erosion is one of the main environmental risks that restrict the survival and development of human beings (Ongley et al, 2010), affect regular land development, and have been reported as the main cause of land degradation (Sun et al, 2012). According to Miao et al (2010), soil erosion in the Chinese Loess Plateau is serious. Recent studies on the Loess Plateau are mainly focused on water erosion control in the water–wind crisscrossed erosion region, soil quality indicators in relation to land use and topography, overland flow on abandoned slopes, effects of longterm fertilizer applications on soil organic carbon and hydraulic properties, soil water content, interrill erosion on unpaved roads, and temporal variations of flow–sediment relationships (Zhao et al, 2015, 2016a; Yu et al, 2015, 2016; Shi et al, 2016; Li et al, 2016a, b; Cao et al, 2015; Gao et al, 2016), but there is little research on the distributed-dynamic simulation of erosion and sediment yield at watershed scales. Wu et al.: Application of a modified distributed-dynamic erosion and sediment yield model
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