水土保持措施对无定河流域沟道-河道系统泥沙收支平衡的影响

流域系统可以分为坡面系统和沟道-河道系统2大单元，可以分别建立泥沙收支平衡关系。结果表明：1）实施水土保持措施以后，无定河流域系统泥沙收支平衡中各变量均随时间而变化。沟道-河道系统泥沙输移比发生了极显著的减小趋势，泥沙存储量发生了显著的增大趋势，流域产沙量的变化发生了较显著的减小趋势，坡面净侵蚀量有所减少，但变化趋势不显著。2）对于不同的泥沙收支平衡变量的变化而言，水土保持措施变化和降雨变化的贡献率是不同的；对坡面净侵蚀量的变化而言，汛期降雨的变化起着决定性的作用，贡献率高达90.82%，坡面水土保持措施的贡献率仅为9.18%；对沟道河道系统泥沙存储量的变化而言，淤地坝拦沙的变化起着决定性的作用，贡献率高达76.16%，汛期降雨变化的贡献率仅为23.81%；对流域产沙量的变化而言，汛期降雨和水土保持措施的变化都起着重要作用，前者贡献率为57.84%，后者贡献率为42.16%。3）对沟道-河道系统泥沙输移比RSDRc的变化而言，淤地坝拦沙的变化起着决定性的作用，贡献率高达87.27%，汛期降雨变化的贡献率仅为12.73%。

Influence of soil and water conservation on sediment budget of channel system: A case study of the Wudinghe River Basin

A fluvial system can be divided into two sub-systems,i.e.,hillslopes and channels.For the two sub-systems,sediment budget can be established separately.The results show: 1) After the implementation of soil and water conservation,all components of the sediment budget of channel system of the Wudinghe River Basin varied markedly.Channel sediment delivery ratio decreased significantly,and sediment storage in gullies and river channels increased significantly.Sediment yield of drainage basin decreased sharply,but net erosion from hillslopes decreased mildly.2)The contribution of soil erosion control measures and high-flow season rainfall(P6—9) to the variation in various components of sediment budget have been estimated,using multiple regression analysis.For the variation in net erosion on hillslopes,the contribution from P6—9 is estimated as 90.82%,and that from hillslope soil conservation measures is only 9.18%.However,for the variation in sediment storage in gully and channel system,the contribution from sediment trapping by check dams is estimated as 76.16%,and that from P6—9 is only 23.81%.For the variation in sediment yield of drainage basin,both the variations in rainfall and in sediment and soil conservation played important roles.For the variation in sediment yield of drainage basin,the contribution from P6—9 is estimated as 57.84%,and that from sediment and soil conservation is 42.16%.3)For the variation in channel sediment delivery ratio,the contribution from sediment trapping by check dams is estimated as 87.27%,but that from P6—9 is only 12.73%.