Sediment Yield Deduction from Check-dams Deposition in the Weathered Sandstone Watershed on the North Loess Plateau, China

As the basic unit of erosion and sediment yield, it was critical to determine the amount of soil erosion and sediment yield in the small watersheds for sustaining a reasonable water resource and sediment regulation system. In this study, we determined the sediment yield from the dams-controlled watershed on the North Loess Plateau. Three check dams in the watershed were investigated by drilling ten-hole sedimentation cores. The corresponding flood couplets were dated according to thickness of deposition layers, distribution of sediment particle size and historical erosive rainfall events. On the basis of the check dams capacity curve, the soil bulk density and the thickness of couplets, the deposit mass of check dams, and then the sediment yield of watershed at different temporal and spatial scale were deducted. In total of the 33, 60 and 55 couplets were corresponded to individual flood events in the dam MH1# from 1976 to 1984, the dam MH2# from 1985 to 2007, and the dam MH4# from 1981 to 2009, respectively. The specific sediment yield for flood events was 1,188.5-11,527.9Mgkm(-2), 1,278.6-17,136.7Mgkm(-2), and 3,395.9-33,698.5Mgkm(-2), and the annual average sediment yield was 10,728.6Mg(km(2)<bold>a</bold>)(-1), 12,662.9Mg(km(2)<bold>a</bold>)(-1), and 16,753.3Mg(km(2)<bold>a</bold>)(-1) in dam MH1#, MH2# and MH4# controlled watershed, respectively. The sediment yields were inversely proportional to the dams-controlled areas. For the whole watershed, the annual average sediment yield was 14,011.1Mg(km(2)<bold>a</bold>)(-1) from 1976 to 2009. There were large amounts of sediments (42.3-50.5%) were intercepted gradually along the way from small watersheds to the river channel. And the minimum rainfall for sediment deposited in the dams was greater than 20mm in this watershed. The results of this study suggested that the sediments retained behind check dams were helpful to quantifying the amount of erosion sediment yield and understanding the soil erosion evolution in the small and ungauged watersheds. Copyright (c) 2016 John Wiley & Sons, Ltd.