Assessing the hydrological effect of the check dams in the Loess Plateau, China, by model simulations

摘要

Check dams are commonly used for soil conservation. In the Loess Plateau of China, check dams have been widely constructed as the principal means to retain floodwa-ter and intercept soil sediments since the 1970s. For instance, there are more than 6572 check dams in the Yanhe watershed with an area of 7725 km~2 in the Loess Plateau. However, little research has been done to quantify the hydrological effects of the check dams. In this research, the SWAT model (Soil and Water Assessment Tool) was applied to simulate the runoff and sediment in the Yanhe watershed. We treated the 1950s to 1960s as the reference period since there were very few check dams during the period. The model was firstly calibrated and validated in the reference period. The calibrated model was then used in the later periods to simulate the hydrological effects of the check dams. The results showed that the check dams had a regulation effect on runoff and a retention effect on sediment. From 1984 to 1987, the runoff in rainy season (from May to October) decreased by 1.54 m~3 s~ (-1) (14.7 %) to 3.13 m~3 s~(-1) (25.9 %) due to the check dams; while in dry season (from November to the following April), runoff increased by 1.46 m~3 s~(-1) (60.5%) to 1.95 m~3 s~(-1) (101.2 %); the sediment in rainy season decreased by 2.49 × 10~6 ton (34.6 %) to 4.35 × 10~6 ton (48.0 %). From 2006 to 2008, the runoff in rainy season decreased by 0.79 m~3 s~ (-1) (15.5 %) to 1.75 m~3 s~(-1) (28.9 %), and the runoff in dry season increased by 0.51 m~3 s~(-1) (20.1 %) to 0.97 m~3 s~(-1) (46.4 %); the sediment in rainy season decreased by 2.03× 10~6 ton (79.4 %) to 3.12 × 10~ 6 ton (85.5 %). Construction of the large number of check dams in the Loess Plateau has enhanced the region's capacity to control the runoff and sediment. In the Yanhe watershed, the annual runoff was reduced by less than 14.3 % due to the check dams; and the sediment in rainy season was blocked by up to 85.5 %. Thus, check dams are effective measures for soil erosion control in the Loess Plateau.