黄土高原典型流域水沙关系对退耕还林(草)的响应

Responses of the Water and Sediment Behavior to Vegetation Restoration in Tipical Catchments on the Loess Plateau

利用北洛河上游吴旗站实测水文资料,采用Pettitt、Mann-Kendall非参数检验以及流量历时曲线等方法,对比1963-1979年水沙特征,分析了1980-2002年间水土流失综合治理,尤其2003-2011年间退耕还林(草)工程实施等效应背景下流域水沙行为的变化规律。结论表明,近50a来,流域水沙量均呈显著减少趋势。对比1963-1979年,1980-2002年间平均径流量和平均输沙量分别减少了22.80%,45.63%,2003-2011年间减少幅度更大,分别达到53.03%,89.33%。三阶段5%,50%概率时的丰水、平水期径流量和输沙量均呈下降趋势,输沙量的减少幅度更大,而枯水期的基流量为逐阶段增加趋势,输沙量则在2003-2011年间完全消失。三阶段的年尺度水沙关系,在2003-2011年间发生了统计上的显著变化。与1963-1979年间比,单位径流的产沙能力,1980-2002年间降低了12.80%,流域泥沙赋存量减少了17.27%,而2003-2011年间则分别减少了约1/4和1/3。月尺度含沙量-流量关系表现为"8"字环形,环的延展度逐阶段下降,尤其在2003-2011年间降低幅度最大。50a来,在不断的水土流失综合治理,尤其退耕还林(草)工程实施推动下,流域径流量和输沙量、径流和输沙情势、年/月水沙关系均表现为逐阶段减少、降低或动力削弱状态。表明,退耕还林(草)生态工程发挥了良好的蓄水保土、增加基流、削弱侵蚀、减少泥沙输移的良好的生态功能和效益。

This paper compared the runoff and sediment characteristics from 1963-1979,analyzed the effects of the soil and water conservation comprehensive harness between 1980-2002,especially,the variation of runoff and sediment behavior patterns and characteristics of catchment with the effects of conversion of cropland to forest and grassland between 2003-2011 by using the hydrological data of the Wuqi hydrological station on the upper catchment of Beiluo River.The results showed that：Over the 50 years,the volume of runoff and sediment displayed obvious decreasing tendency.Contrasting with between 1963 and 1979,the mean volume of runoff and sediment between 1980 and 2002 were abated about 22.80% and 45.63%respectively.The decreasing fluctuations of the mean volume of runoff and sediment were stronger with53.03% and 89.33%respectively.The volume of runoff and sediment during high flow and median flow of the three periods showed decreasing tendency and the decreasing level of the volume of sediment is higher than the volume of runoff,however,the volume of base low increased gradually in low flow.The volumes of sediment of 2003-2011 were vanished completely.In three periods,the annual relationships between runoff and sediment manifested statistical obvious variation.Comparing with 1963-1979,the sediment of unitrunoff were decreased about 12.08% in period of 1980-2002,the capacity of runoff and sediment were declined about 17.27% and they decreased about 1/4and 1/3respectively in 2003-2011.At monthly scale,the volume of runoff and sediment showed a circle of 8,the decreasing fluctuations of extends of them were stronger,especially during 2003-2011.Over the 50 years,the volume of runoff and sediment,the conditions of runoff and sediment and the relationships of runoff and sediment were decreased gradually under the background of the water conservation comprehensive harness,especially the conversion of cropland to forest and grassland.It shows that the＂grain for green project＂played its ecological role on saving water and soil,multiplying base low and also abating runoff and sediment.