中文摘要：

河流水沙特征与流域降水量和下垫面变化密切相关。为揭示流域降雨以及退耕还林对延河流域水沙特征的影响,本文以延河甘谷驿站控制区1960—2010年流域降水量、河流径流量和输沙量实测数据为基础,统计分析了延河水沙变化特征及其对流域降水量的响应,并对比分析了退耕前、后（以2002年为界）延河水沙变化。结果表明：在1960—2010年间,延河甘谷驿站控制区年及汛期（6—9月）降水量、径流量和输沙量呈波动递减趋势,汛期降水量、径流量和输沙量值约占年值的64.8%、71.7%和98.1%;年及汛期输沙量与径流量呈极显著正相关关系,径流量变化可分别解释年及汛期87.6%和92.2%的输沙量变化,降水量变化可分别解释年及汛期22.7%和23.6%的输沙量变化;退耕后流域年及汛期平均输沙量、径流量和径流系数显著低于退耕前,剔除退耕前后降水量差异影响,退耕工程对年及汛期累计输沙量变化分别贡献87.5%和86.9%,对年及汛期累计径流量变化分别贡献77.4%和75.4%。研究阐明退耕可显著降低年及汛期平均径流量、径流系数和输沙量。

英文摘要：

[Background] Analysis on the trends of runoff and sediment transport and their driving forces,such as precipitation,human activities and other factors,is the basis for watershed management.Previous studies showed that the dynamics of river runoff and sediment transport were closely related to soil erosion and precipitation. The relationship of rainfall-runoff-sediment delivery is important for evaluating the benefits of erosion control practices. In recent years,the sediment discharge of the Yellow River is decreasing dramatically,which has caused wide public attention. [Methods]In this study,on the basis of runoff and sediment data measured at Ganguyi station,and the precipitation data of 5meteorological stations in Yanhe River basin,we analyzed the dynamics of precipitation,runoff,sediment discharge,runoff coefficient,and the response of runoff and sediment dynamics to watershed precipitation in Yanhe River during 1960- 2010. Meanwhile,in order to explain the effect of Grain for Green Project on runoff and sediment transport,the difference of river runoff and sediment delivery between 1960-2001 and 2002- 2010 were also studied. Based on precipitation-runoff curve and precipitation-sediment transport cumulative curve, the relationship between precipitation and runoff and sediment was determined in 1960- 2001,and with the determined relationship,the simulated runoff and sediment transport were predicted in the period of 2002- 2010,then were compared to the measured data in the same period of 2002- 2010,thus,the effect of Grain for Green Project on river runoff and sediment transport was determined. [Results]1） The annual precipitation,runoff and sediment transport at flood season decreased with fluctuation from 1960- 2010. The flood season accounted for 64. 8%,71. 7% and98. 1% of average annual precipitation,runoff and sediment transport,respectively. 2） The sediment transport were significantly related to runoff per year and in flood season. The variation of runoff caused87. 6% and 92. 2% sediment load chang