黄河上游西柳沟流域淤地坝系对径流影响的模拟分析

Simulation of the Impact of Check Dams on Runoff in Xiliugou Watershed in the Upper Yellow River

黄河上游西柳沟流域水土流失情况严重,流域内修建了不同规模的淤地坝,以改善研究区因水土流失而引起的水沙灾害问题.为探讨淤地坝对流域径流过程的影响,根据淤地坝运行机理,本文在SWAT模型的基础上开发了淤地坝水循环模块,构建了适用于西柳沟流域的分布式水文模型,并根据流域出口断面实测月流量数据对改进的模型进行参数率定及模型验证.分析表明,改进后的SWAT模型率定期与验证期的确定系数R2均在0.70以上,纳什效率系数ENS均在0.5以上,相对误差Re均小于20%,模型模拟效果较好.同时,综合考虑淤地坝地理位置、规模等特性,设置不同情景,利用改进的SWAT模型对不同淤地坝情景下西柳沟水文过程的响应进行了模拟分析.结果表明,西柳沟淤地坝系减水效果明显,随着淤地坝数量的增加,流域出口流量明显减少:与现状淤地坝情形(39座骨干坝)相比,无淤地坝情形下流域出口年均流量将会增加25%左右;未来新建79座骨干坝后的流域出口流量比现状情形减少约75%.本研究利用改进后的SWAT模型量化了淤地坝工程对径流的影响,为进一步研究淤地坝坝系影响下的水沙关系奠定基础.

Different check dams have been constructed in Xiliugou watershed in the upper Yellow River to solve the flood and sediment disaster caused by soil and water losses.In order to figure out the role of check dams on the runoff,a modified Soil and Water Assessment Tool(SWAT)model was set up by coupling with a new water balance module of check dam.The results showed that the monthly runoff simulated agreed well with the observed values in both calibration and validation periods.The coefficients of determination(R2)were larger than 0.70,the Nash-Sutcliffe Efficiencies(ENS)were greater than 0.50,and the relative error(Re)were smaller than 20%indicating that the modified SWAT model performed well in the simulations.Based on the modified SWAT model,this study used three scenarios to simulate the effects of different numbers of check dams on the runoff.Results showed that check dams were efficient in controlling the runoff,and the runoff at the outlet of the study region decreased obviously with the increasing check dams.Compared with the present scenario(i.e.,including 39 key dams),the annual runoff would increase by 25%under the scenario with no check dams,and would reduce by 75%under the future scenario(118 key dams).This study quantified the impact of the check dams on the runoff based on the modified SWAT model,which offers a foundation for investigating the relation between water and sediments influenced by the check dams.