无定河坡面措施减沙和拦粗泥沙量分析

提出了一个新的反映降雨侵蚀作用的指标,并利用无定河实测输沙量资料和前人用水保法估算的水利水保措施年减沙量,建立了流域产沙与降雨和风蚀气候因子的关系。通过与前人用水保法估算的水利水保措施年减沙量对比分析,发现坡面措施拦沙量应比水保法所得的估计量大。进一步计算出产沙中的粗泥沙量,并与坡面和沟道措施拦沙量建立关系,发现坡面措施的拦沙中粗泥沙比例平均在42%以上,而坝库拦沙中只有约32%。无定河流域坡面措施在措施拦减粗泥沙中所占的比例越来越高。由于坡面措施效益期长,拦粗效率高,所以未来应大力发展坡面措施,以达到长期有效控制水土流失的目的。

Sediment yield reduction by soil conservation measure on slopes in the Wudinghe River catchment

The Wudinghe River catchment is one of the main sediment sources of the Yellow River.With the development of soil conservation practices and changes in climate in recent decades,sediment yield from the catchment decreased gradually.This study tries to separate the contributions of soil conservation measure and climatic changes to sediment yield reduction and to separate the effects of two groups of soil conservation works,one on slopes and the other in gullies and valleys(or slope protections and dams),on sediment yield reduction.A new index reflecting the role of precipitation in soil erosion is created by this study.Based on the measured sediment discharge,climatic records in the Wudinghe River catchment on the Loess Plateau,a relationship of sediment yield with the index and wind erosion factor is developed.There is a noticeable difference between the sediment yield reduction due to soil conservation practices calculated from the proposed relationship and that estimated by a previous study,which just gave the in situ sediment yield reduction induced by soil conservation works.Through analyzing the relationship between the extra sediment yield reduction and in situ sediment yield reduction induced by slope protections and dams,it is found that the extra sediment yield reduction is mainly resulted from slope protections.Furthermore,the sediment yield reduction of coarse particles larger than 0.05 mm is calculated and related with the sediment yield reduction due to slope protection and damming.The results show that coarse particles in the sediment yield reduction accounted for about 42% by slope protection and 32% by damming.From the 1960s to the 1990s,the proportion of coarse sediment reduction due to slope protection increased gradually.The findings of this study suggest that soil conservation on slopes should be greatly developed in the future for effectively controlling soil losses on the Loess Plateau.