降水和水土保持对黄土区流域水沙关系的影响

流域水沙关系对降水量变化和水土保持的响应可为水土保持效益评价提供科学依据。根据黄土丘陵沟壑区第三副区典型小流域桥子东沟和桥子西沟1987—2010年的水文泥沙数据,用Mann-Kendall法检验流域年降水量和水沙变化趋势,采用双累积曲线法分析径流量和输沙量之间的关系,探讨降水量变化和水土保持措施对流域水沙关系的影响。结果显示,年降水量和水沙变化趋势基本一致,降水量是流域产流和输沙的主要影响因素。桥子东沟在1987—2006年和桥子西沟在1987—2010年时期的年单位径流输沙量没有发生显著变化,表明降水量变化、坡面工程措施和植被措施对流域水沙关系没有显著影响;桥子东沟在2007—2010年期间的年单位径流输沙量显著减小,表明流域水沙关系发生显著改变,这是由于2006年建设的淤地坝通过拦蓄径流泥沙和减少下游沟道侵蚀,导致流域减沙比例大于减水比例。

Effects of precipitation and erosion control practices on the rainfall-runoff-sediment delivery relationships of typical watersheds in the hilly-gully region on the Loess Plateau

Rainfall-runoff-sediment delivery relationship is of great importance for evaluating the benefits of erosion control practices in the hilly-gully regions on the Loess Plateau. The hydrologic data （1987-- 2010） of Qiaozi East Watershed （QE） with erosion control practices and Qiaozi West Watershed （QW） without erosion control practices were collected. We analyzed the annual variations of precipitation, runoff, sediment delivery and the annual sediment delivery per unit runoff of the watersheds using the Mann-Kendall test method. The double mass curve was used to analyze the runoff-sediment delivery relationship of QE and QW. The results indicated that the variation trends of runoff and sediment delivery of the watersheds were consistent with the precipitation, which was the main factor to influence the runoff and sediment delivery. No significant change was observed in the annual sediment delivery per unit runoffof QE during 1987--2006 and that of Qw during 1987--2010, indicating that the variation in precipitation, slope erosion control practices and vegetation did not alter the runoff-sediment delivery relationship of the watersheds. However, a significant change occurred in QE during 2007--2010, after 19 check dams were built, resulting in reduction of gully erosion and alternation of the runoff-sediment delivery relationship.