为了查明人为影响程度较低时期无定河流域内不同地貌区的水沙过程及其变化规律,选取1970年以前一段时期该流域内风沙区和黄土丘陵沟壑区河流的有关水文站的水文泥沙实测数据进行对比分析。结果表明,风沙区河流的流量变率较黄土丘陵沟壑区的小;风沙区河流的含沙量远小于黄土丘陵沟壑区河流的含沙量。黄土丘陵沟壑区河流具有极高的输沙率,而风沙区河流的输沙率微不足道。风沙区和黄土丘陵沟壑区河流的产流模数基本相近,但产沙模数非常悬殊,前者的产沙模数很小,为118.58~725.38t /km2 · a,而后者的达到1879.36~25112.15t /km2 · a。显然,无定河流域黄土丘陵沟壑区的河流是侵蚀产沙的主要来源区,因而是水土保持工作的重点区域。
The Wudinghe River Basin is a representative basin in the eolian-loess transitional zone of the Loess Plateau. Some projects actualized during the last three decades for soil and water loss has led the sediment and runoff processes of the river basin no longer being in a pure natural state but also affected by anthropogenic activities.In order to put forward effective measures to prevent soil and water loss, it is necessary to find the natural processes of sediment and runoff yield of the Wudinghe River Basin. In this work the varying processes and rules of sediment and runoff yield in the eolian and loess hilly-gully regions of the river basin were analyzed systematically according to the data measured in a certain period of time before 1970 because limited human activities had been thrown to the river system during this period. The results are as below. In the near natural state the varying ratio of discharge of the river in the eolian region is smaller than that in the loess hilly-gully region.The river sediment concentration in the eolian region is far smaller than that in the loess hilly-gully region, accordingly, sediment delivery ratio is very high in the rivers of the loess hill gully region but inappreciable in the rivers of the eolian region. The specific runoff yield of the rivers in both eolian and loess hilly-gully regions is very close, but great disparities of the specific sediment yield occur in different regional rivers: it is 118.58~725.38 t/km2 · a for the eolian region and 1879.36~25112.15 t/km2 · a for the loess hilly-gully region. Obviously, the tributaries located in the loess hilly-gully region are the main source of the sediment yield in the Wudinghe River Basin. So, these tributary basins are the main regions needed to prevent soil and water loss and the control of sediment yield in gullies of these tributaries is the key task.
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