Evidence for climatic and hillslope‐aspect controls on vadose zone hydrology and implications for saprolite weathering
Evidence for climatic and hillslope‐aspect controls on vadose zone hydrology and implications for saprolite weathering
复制标题
气候和山坡方面对渗流带水文控制的证据以及对腐泥土风化的影响
DOI：
10.1002/esp.3718
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发表时间：
2015
影响因子：
3.3
通讯作者：
S. P. Anderson
中科院分区：
文献类型：
--
作者：
A. Langston;G. Tucker;R. Anderson;S. P. Anderson
通过融雪中的水的输送，气候应该控制着积雪为主的山区流域腐泥岩的形成速度和程度，但水深入到雪层中的机制在很大程度上尚不清楚。在这项研究中，我们将土壤和浅腐泥岩的降雨量、积雪深度和含水率数据联系起来，记录了两个山地流域两年来的包气带动态。对积雪厚度和土壤湿度的测量表明，在浅渗带土壤显著潮湿的时间和融水输送时间上，北坡和南坡之间存在着强烈的对比。尽管积雪融化补给量相似，但北向坡面比南向坡面具有更高的持续土壤湿度。为了帮助解释这些观察结果，我们使用包气带动力学的2D数值模型来计算理想山坡上在两种湿润情景下的预期时空水分模式：单个持续的补给脉冲与一组短脉冲。模型预测，补给事件的持续时间对上层非饱和带水的深度和停留时间的控制作用强于补给事件的大小。模型计算还表明，水在地下的移动速度应该更慢，当水以几次脉冲而不是一次持续的方式施加时，向下的水通量应该大大减少。结果表明，北坡土壤较厚，岩石风化程度较深，可能反映了深层地下水的补给量较大。版权所有©2015年 John Wiley父子有限公司。
Through the delivery of water in snowmelt, climate should govern the rate and extent of saprolite formation in snow‐dominated mountain watersheds, yet the mechanisms by which water flows deeply into regolith are largely unexplored. In this study we link rainfall, snow depth, and water content data from both soil and shallow saprolite to document vadose zone dynamics in two montane catchments over 2 years. Measurements of snow pack thickness and soil moisture reveal strong contrasts between north‐ and south‐facing slopes in both the timing of meltwater delivery and the duration of significant soil wetting in the shallow vadose zone. Despite similar magnitudes of snowmelt recharge, north‐facing slopes have higher sustained soil moisture compared to south‐facing slopes. To help interpret these observations, we use a 2D numerical model of vadose zone dynamics to calculate the expected space–time moisture patterns on an idealized hillslope under two wetting scenarios: a single sustained recharge pulse versus a set of short pulses. The model predicts that the duration of the recharge event exerts a stronger control on the depth and residence time of water in the upper unsaturated zone than the magnitude of the recharge event. Model calculations also imply that water should move more slowly through the subsurface and downward water flux should be substantially reduced when water is applied in several pulses rather than in one sustained event. The results suggest that thicker soil and more deeply weathered rock on north‐facing slopes may reflect greater water supply to the deep subsurface. Copyright © 2015 John Wiley & Sons, Ltd.