渭河源区典型小流域水沙演变规律分析

根据渭河源区清源河典型小流域实测水文资料，分析了流域水文要素的年内和年际变化规律，流域降水、径流和泥沙主要集中在汛期，5-9月降水量占全年的78.5%，5-10月径流占全年的78.7%，5-8月输沙量占全年的88.9%。受上游修建水库、水土保持等人类活动的影响，流域汛期径流和泥沙1997-2013年比1980-1996年均减少了5.9%。流域面平均降水量、平均流量、平均输沙量年际变化不稳定，总体呈减少趋势，序列最大可能变异点分别为1995年、1994年和1997年。建立了流域年降水量与年径流深、次降水量P+Pa与次径流深相关模型，相关系数达到0.902和0.860。以年最大洪峰流量为参数，分别建立了流域年径流量与年输沙量、次径流量与次输沙量关系模型，相关系数达到0.835和0.917，公式模拟值与实测值接近，误差较小，可以作为以径流推算泥沙的重要依据。通过定性定量分析人类活动对流域径流、泥沙的影响程度，对区域抗旱防洪减灾、水资源管理、小流域治理及生态环境保护具有重要意义。

Water and sediment evolution in a small watershed:the headwaters of the Weihe River

Based on the hydrological data from the headwaters of the Weihe River,the annual and inter-annual variations of the hydrological elements were analyzed.It is found that precipitation,runoff and sediment in the basin is mainly concentrated in the flood season,such as precipitation from May to September accounts for 78.5％ of annual precipitation,runoff from May to October accounts for 78.7％ of annual runoff and sediment discharge from May to August accounts for 88.9％ of annual sediment discharge.Human activities,such as reservoir construction and soil and water conservation in the upstream,resulted in decrease of runoff and sediment runoff 5.9％ in 1997-2013 as compared with that in 1980-1996.Precipitation,runoff and sediment runoff in the basin change from year to year with an overall trend of decrease and some jumps in 1995,1994 and 1997.Models of annual precipitation,annual runoff depth,and P + Pa for the basin are established,of which the correlation coefficients reach 0.902 and 0.860.Based on annual maximum flood parameters,models of basin annual runoff,annual sediment runoff and P + Pa were established,respectively,of which the correlation coefficients were 0.835 and 0.917.The simulation values are close to the measured values,with a small error,showing the simulated results can be used as an important base to calculate sediment from runoff.Through qualitatively and quantitatively analyzing the influence of human activities on basin runoff and sediment,one can see that this study is helpful for the regional struggle against drought,flood and disasters,for water resources management,watershed management and ecological environment protection.