考虑两流区影响的分布式水文模型及其应用

Distributed Hydrological Model Considering Influence of Two-flow Zone and Its Application

黄土塬区土层巨厚,土壤入渗过程包括优先流和基质流,但其两流区入渗过程不同于山区等区域。目前,分布式水文模型在黄土高原应用时未考虑优先流对降雨入渗过程的影响,造成模型在黄土高原应用时模拟失真,精度较低,大大限制了流域分布式水文模型的广泛适用性。基于传统降雨入渗模型(Green-Ampt模型),研究通过引入总土壤饱和含水量和土壤总饱和导水系数,改进分布式水文模型,构建黄土塬区两流区WEP分布式水文模型。选择黑河流域作为研究区域,分别利用改进前、后的WEP模型模拟研究区的降雨径流过程,对比验证WEP模型改进后的适用性。结果表明:与传统WEP模型相比,通过考虑两流区影响:对于月径流而言,流域断面逐月径流量相对误差绝对值均小于0.05%,Nash-Sutcliffe效率系数均大于0.69;而未改进模型的相对误差为0.06%~0.24%,Nash-Sutcliffe效率系数在0.66~0.70之间;改进后的模型率定期Nash-Sutcliffe效率系数由0.66升高至0.69,相对误差绝对值由0.24%降低到0.05%,在验证期内Nash-Sutcliffe效率系数由0.70提升到0.73,相对误差由0.06%减小到0.01%。针对日径流过程而言,模型改进后,Nash-Sutcliffe效率系数由-4.22提升到0.64,相对误差由57.17%降低到19.80%。通过考虑两流区对降雨入渗的影响,WEP模型对黑河流域断面月径流量以及日径流量过程的模拟效果明显改善,表明改进后的WEP模型在黄土塬区具有较好适用性,有助于增强对水分入渗过程的认识。

The soil layer in the Loess Plateau is extremely thick,and the soil infiltration process includes preferential flow and matrix flow,but the infiltration process in the two-flow zone is different from that in mountainous areas.At present,when the distributed hydrological model is applied in the Loess Plateau without considering the effect of preferential flow on the rainfall infiltration process,resulting in the simulation distortion and low accuracy of the model,which greatly limits the wide applicability of the watershed distributed hydrological model.Based on the traditional rainfall infiltration model(Green-Ampt model),this paper improves the distributed hydrological model by introducing the total soil saturated water content and the total soil saturated hydraulic conductivity,and constructs the WEP distributed hydrological model in the two-flow region of the Loess Plateau.The Heihe River Basin is selected as the study area,and the rainfall-runoff process in the study area is simulated by using the WEP model before and after the improvement to verify the applicability of the improved WEP model.The results show that compared with the traditional WEP model,by considering the influence of the two-flow zone,for the monthly runoff,the absolute values of the relative error of monthly runoff of the basin section are less than 0.05%,and the Nash-Sutcliffe efficiency coefficient is more than 0.69.The relative error of the unimproved model is 0.06%~0.24%,and the Nash-Sutcliffe efficiency coefficient is 0.66~0.70.The Nash-Sutcliffe efficiency coefficient of the improved model increases from 0.66 to 0.69 and the absolute value of relative error decreases from 0.24%to 0.05%within the rate period.During the verification period,the Nash-Sutcliffe efficiency coefficient increases from 0.70 to 0.73,and the relative error decreases from 0.06%to 0.01%.In terms of the daily runoff process,the Nash-Sutcliffe efficiency coefficient of the model increases from-4.22 to 0.64,and the relative error decreases from 57.17%to 19.80%after the improvement of WEP model.By considering the influence of two-flow zone on rainfall infiltration,the simulation effect of WEP model on monthly runoff and daily runoff process in the Heihe River Basin has obviously improved,which shows that the improved WEP model has better applicability in Loess Plateau region and helps to enhance the understanding of water infiltration process.