依据1956~1996年的资料,计算出了无定河流域历年的人工沉积汇、侵蚀量、泥沙输移比,进行了时间序列分析,并运用回归分析方法,建立了统计关系,揭示了无定河流域人工沉积汇对泥沙输移比的影响。研究表明,无定河流域侵蚀量和产沙量有明显的减小趋势;人工沉积汇先是增大,达到峰值后再减小;泥沙输移比先减小而后增大。这说明,无定河泥沙输移比的时间变化趋势,主要受人工沉积汇的控制。建立的多元回归方程表明,坝地面积增大对流域泥沙输移比减小的贡献最大;地表径流系数减小对流域泥沙输移比减小的贡献居第二位;在3个降水因子中,最大30日降水的贡献最大,汛期降水次之,最大1日降水再次之。在坡面措施和沟道措施中,沟道措施对流域泥沙输移比减小的影响要大于坡面措施。

As an important measure to reduce the sediment entering the Yellow River, a great number of reservoirs and check-dams have been built in the Wudinghe River basin, trapping huge amount of sediment. As a result, artificial sediment sink formed, which greatly reduced sediment delivery ratio of the river. The influence of artificial sediment sink on sediment delivery ratio is an important issue in fluvial geomorphology, but so far there has been little research devoted to this issue. Based on data from 1956 to 1996 in the Wudinghe River basin, artificial sediment sink, erosion amount and sediment delivery ratio (SDR) have been calculated, temporal variation in these variables has been analyzed, and multiple regression equations have been established. These results show that (1) sediment yield and erosion amount decreased; (2) artificial sediment sink increased to a peak and then decreased; (3) SDR decreased to a minimum and then increased. This indicates that the temporal variation in SDR is mainly controlled by the variation in artificial sediment sink. To reveal quantitatively how the water and soil conservation measures and other factors influence sediment delivery ratio, multiple regression analysis has been conducted. The multiple regression equation shows that SDR increases with the increases in high-flow season precipitation (P_6-9), the annual maximum 1-day rain amount (P₁), the annual maximum 30-day cumulative rain amount (P₃₀), and the runoff to precipitation ratio (C_r), but decreases with the increases in the areas of land terracing, tree and grass planting (A_tfg) and the area of land created by check-dams (A_c). The increase in A_c makes the largest contribution to the decrease in SDR, and the decrease in C_r makes the second contribution. Among the three indices of precipitation, P₃₀ makes the largest contribution, P_6-9 the second and P₁ the third. In two types of soil-water conservation measures, the effect of A_c on SDR is much larger than that of A_tfg.