黄土丘陵沟壑区典型治理小流域水沙输移的尺度效应

Scale effects on sediment transport in small cascading dammed Loess HillyGully watershed

近年来,水土流失的尺度特征及尺度效应一直是土壤侵蚀研究的前沿。文中通过对黄土丘陵沟壑区第一副区不同空间尺度互为嵌套的小流域(5.97km^2的王茂沟小流域和70.1km^2韭园沟小流域)监测数据的分析,比较了流域治理措施实施后不同空间尺度小流域产流产沙过程及其对降雨事件的响应,揭示该流域淤地坝建设等措施对小流域泥沙输移特征的影响及其尺度效应。研究结果表明:两个尺度小流域径流对降雨响应过程均十分迅速,且退水后几乎没有基流,这同南方丘陵区小流域不同;王茂沟和韭园沟小流域径流量迅速增大,达到峰值后逐渐回退,大致在降雨停止6小时后完全消退;源头小流域(王茂沟)地表径流系数相较更大尺度小流域(韭园沟)略低,土壤流失量则相反;治理后的韭园沟小流域高含沙水流现象减少。重力侵蚀仍是源头区域发生高含沙径流的潜在影响因素,小流域尺度水土流失防治应重点治理源头区域。

In recent years, the scale effect of soil erosion has been the frontier of soil erosion subject. Choosing the Wangmao gully（ 5.97km^2） and Jiuyuan gully（70, 1km^2） in Loess hilly - gully region as the studied areas, the runoff production and soil erosion processes responding to storm events were researched for comparison of the scale effects at small watershed scale. The results showed that both watershed runoff responded to the rainstorm rapidly without base flow lasting during the remaining period, and both watershed ＂s runoff receded within 6 hours, which is quite different from hilly watershed in southern China. Runoff coefficient of headwater watershed （ Wangmao gully） was lower than the larger Jiuyuan gully watershed, while vice versa for soil erosion. After construction of plenty of warping dams, the soil erosional processes had been altered significantly. Land use policy and erosional mechanisms made the scale effects an important issue even in these cascading dammed watersheds. Gravitational erosion was still the potential to trigger hyper - concentration flow. Thus the headwater watershed should be the hotspot for soil and water conservation.