Topographic controls on shallow groundwater levels in a steep, prealpine catchment: When are the TWI assumptions valid?
Topographic controls on shallow groundwater levels in a steep, prealpine catchment: When are the TWI assumptions valid?
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地形对陡峭的高山前流域浅层地下水位的控制：TWI 假设何时有效？
DOI：
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
Jan Seibert
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文献类型：
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作者：
M. Rinderer;H. J. V. Meerveld;Jan Seibert
像地形湿度指数（TWI）这样的地形指数已经被用来预测平均地下水位的空间格局，并在事件期间模拟饱和区的动态（例如TOPMODEL）。然而，在水文模型中使用TWI的基本假设，其中最重要的是地下水水位变化可以通过一系列稳态情况来近似，很少得到检验。目前还不清楚的是，对具有渗透性土壤的地点进行的现有山坡研究的结果能否很好地转移到土壤渗透性较差的整个集水区。因此，本研究基于瑞士20公顷低渗透土壤集水区51口地下水井的时间序列，评估了所选地形指数描述地下水位空间变化的适用性。结果表明，中位地下水位与坡度、曲率和TWI均有相关性，但相关性强弱取决于这些指标是表征当地地形还是表征上坡贡献区的地形。TWI与地下水位的相关关系在降雨事件开始时呈下降趋势，表明地下水响应存在较大的空间差异，而在洪峰过后，TWI与地下水位的相关关系增加，此时地下水位在空间上处于稳定状态。我们的研究结果表明，地形指数对于预测低渗透土壤集水区的中位地下水水位是有用的，当地下水水位变化缓慢时，TWI假设最符合。
Topographic indices like the Topographic Wetness Index (TWI) have been used to predict spatial patterns of average groundwater levels and to model the dynamics of the saturated zone during events (e.g., TOPMODEL). However, the assumptions underlying the use of the TWI in hydrological models, of which the most important is that groundwater level variation can be approximated by a series of steady state situations, are rarely tested. It is also not clear how well findings from existing hillslope studies on sites with transmissive soil can be transferred to entire catchments with less permeable soils. This study, therefore, evaluated the suitability of selected topographic indices to describe spatial groundwater level variations based on time series from 51 groundwater wells in a 20 ha catchment with low‐permeability soils in Switzerland. Results showed that median groundwater levels were correlated to slope, curvature, and TWI, but the strength of correlation depended on whether the indices characterized the local topography or the topography of the upslope contributing area. The correlation between TWI and groundwater levels was not constant over time but decreased at the beginning of rainfall events, indicating large spatial differences in groundwater responses, and increased after peak flow, when groundwater levels could be considered to be spatially in a steady state. Our findings indicate that topographic indices are useful to predict median groundwater levels in catchments with low‐permeability soils and that the TWI assumptions are best met when groundwater levels change slowly.