黄土丘陵沟壑区坡面水保措施及植被对流域尺度水沙关系的影响

根据黄土高原高含沙水流的特点，认为次暴雨的产沙模数和径流深可用线性正比关系式来表示，关系式中比例系数表示流域单位径流深的输沙能力、次暴雨过程中流量超过临界值后的稳定含沙量以及流域历次洪水的平均含沙量。在此模型基础上，以黄土丘陵沟壑区的王家沟的两个毗邻地貌相似的两条沟为研究区，其中一条沟为经治理而另一条则未治理。探讨各种坡面水土保持措施及植被对流域水沙关系的影响。结果表明，治理流域和非治理流域具有相同的水沙关系，被治理沟的植被等坡面措施在流域尺度上仅通过减水来减沙。这主要是因为植被等坡面措施不能显著改变沟道的输沙能力，且由于植被不能很好地控制沟谷侵蚀和重力侵蚀，使得水流进入沟道后又会获取充足的泥沙补充，达到和治理前相同的径流输沙能力。因此可以认为，在仅有植被和其它坡面治理措施的情况下，治理流域的减沙率可用减水率来估计。本文的实际计算表明，在多年平均尺度、年际尺度和次暴雨尺度这一方法都有较好的精度。

Effect of vegetation and other measures for soil and water conservation on runoff sediment relationship in watershed scale

According to the characteristics of hyper-concentrated sediment flow, the relationship between runoff and sediment yield can be expressed by linear regression relation and the sediment transport capacity, stable sediment concentration during the flow discharge excess the critical value as well as the average sediment concentration for each flood in watershed can be expressed by different regression coefficients. By using this model the effect of vegetation and other measures for soil and water conservation on relationship between runoff and sediment is investigated by means of comparing the differences of sediment yield and runoff in two typical small watersheds with similar geological characteristics, in which one watershed without soil and water conservation measures and the other having the vegetation area greater by 75 % and other soil and water conservation measures. It is found that the runoff-sediment relationship in these two watersheds is the same but the sediment yield is reduced due to the reduction of runoff. The vegetation and slop prevention measure can not effectively reduce the hilly erosion. It may conclude that in case only vegetation and slope prevention measures are adopted for water and soil conservation the sediment reduction rate by means of these measures can be estimated by using reduction rate of runoff. The effectiveness of this method is verified by application examples.