
土壤渗透系数各向异性对我国西南山区小流域产汇流过程的影响研究
陈苍乙, 冉启华, 刘琳, 潘海龙, 叶盛
土壤渗透系数各向异性对我国西南山区小流域产汇流过程的影响研究
The Influence of Anisotropy of Soil Hydraulic Conductivity on Rainfall-runoff Process in a Mountainous Catchment in Southwest China
土壤渗透系数各向异性在自然界中广泛存在,但当前大多数研究中没有考虑其对产汇流过程的影响。选取四川省都江堰市的山区小流域碱坪沟为研究区域,利用基于物理概念的模型(InHM)模拟了考虑土壤渗透系数各向异性条件下的降雨径流过程。研究结果表明,土壤渗透系数各向异性对流域产汇流过程有着显著影响。随着各向异性比(Kr)的增加,洪峰流量明显提高,当Kr为10时,峰值流量比基础工况(各向同性)下高出约70%;此外,较大Kr值工况下,峰现时刻也相对提前。这些影响可以归因于较大的Kr增大了坡面和河道中的流速,使更多的土壤水分在坡面出渗,并补充到河道中。由此可见,土壤渗透系数各向异性的特性不能被忽略,水文模拟过程中合理考虑各向异性能够提高降雨径流模拟的精确度,对于山洪预警预报等工程实践具有重要的应用价值。
The anisotropy of soil hydraulic conductivity is widespread in nature, but the influence of such soil characteristics on runoff generation is not considered in most studies, making it difficult to reproduce the hydrograph of real flood events. In this paper, a physics-based model (InHM) is applied to Jianpinggou, a mountainous catchment in China, to simulate the rainfall-runoff process under different scenarios of anisotropic hydraulic conductivity. The results show that the anisotropy of soil hydraulic conductivity have a significant impact on the runoff process. With the increase in anisotropic ratio(Kr), the peak discharge can be substantially elevated: when Kr is 10, it can be 70% higher than the isotropic base case. In addition, under the condition of larger Kr value, the peak occurrence time is also relatively earlier. These impacts can be attributed to the increased flow velocity both at the hillslope and under stream channel due to the larger Kr, which drains more soil water down the hillslope and recharges streamflow in the channel. Our results suggest that the anisotropy of soil hydraulic conductivity cannot be ignored, and reasonable consideration of anisotropy in hydrological simulation can improve the accuracy of rainfall runoff simulation, which has important application value for flash flood early warning and prediction.
山区流域 / 土壤渗透系数 / 各向异性 / InHM {{custom_keyword}} /
mountainous catchment / soil hydraulic conductivity / anisotropy / InHM {{custom_keyword}} /
表1 各采样点土壤纵向和横向渗透系数对比Tab.1 Comparison between vertical and horizontal hydraulic conductivity of sampling points |
采样点号 | Kv /(m·s-1) | Kh /(m·s-1) | Kr (Kh/Kv ) |
---|---|---|---|
1 | 4.44×10-5 | 3.20×10-4 | 7.21 |
2 | 2.35×10-5 | 6.53×10-6 | 0.28 |
3 | 9.05×10-6 | 6.20×10-6 | 0.69 |
4 | 3.04×10-4 | 1.91×10-5 | 0.06 |
表2 模型设定中的土壤饱和渗透系数和孔隙率Tab.2 The porosity and saturated hydraulic conductivity used in the model |
分区 | 土壤分层 | 饱和渗透系数/(m·s-1) | 孔隙率 |
---|---|---|---|
Ⅰ (>1 300 m) | 表层(0~0.5 m) | 2.35×10-5 | 0.51 |
中间层(0.5~3 m) | 1.86×10-4 | 0.45 | |
底层(3~13 m) | 1.00×10-8 | 0.30 | |
Ⅱ (1 180~1 300 m) | 表层(0~0.5 m) | 1.44×10-5 | 0.61 |
中间层(0.5~3 m) | 1.86×10-4 | 0.45 | |
底层(3~13 m) | 1.00×10-8 | 0.30 | |
Ⅲ (<1 180 m) | 表层(0~0.5 m) | 9.79×10-5 | 0.65 |
中间层(0.5~3 m) | 1.86×10-4 | 0.45 | |
底层(3~13 m) | 1.00×10-8 | 0.30 |
表3 不同各向异性比工况Tab.3 The simulated scenarios with different anisotropy |
模拟工况 | Kh /(m·s-1) | Kv /(m·s-1) | Kr(Kh/Kv) |
---|---|---|---|
工况1 | 1.86×10-3 | 1.86×10-4 | 10 |
工况2 | 9.30×10-4 | 1.86×10-4 | 5 |
工况3 | 3.72×10-4 | 1.86×10-4 | 2 |
基础工况 | 1.86×10-4 | 1.86×10-4 | 1 |
工况4 | 9.30×10-5 | 1.86×10-4 | 1/2 |
工况5 | 3.72×10-5 | 1.86×10-4 | 1/5 |
工况6 | 1.86×10-5 | 1.86×10-4 | 1/10 |
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