Characterising groundwater–surface water interactions in idealised ephemeral stream systems
Characterising groundwater–surface water interactions in idealised ephemeral stream systems
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DOI：
10.1002/hyp.13847
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发表时间：
2020-07
影响因子：
3.2
通讯作者：
E. A. Quichimbo;M. Singer;M. Cuthbert
中科院分区：
文献类型：
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作者：
E. A. Quichimbo;M. Singer;M. Cuthbert
短暂河流河床的传输损失被认为是干旱和半干旱地区地下水补给的一种普遍机制，并支持一系列旱地水文生态。干旱地区约占地球陆地面积的40%，地下水资源往往是淡水的主要来源。通常认为，在河流下方存在非饱和区的情况下，地表水和地下水之间的相互作用是单向的，地下水不会对输电损失产生显著的反馈。为了验证这一假设，我们使用理想化的二维河道横断面进行了一系列数值模型实验，以评估典型旱地短暂河流几何形状、水力特性和水流状态下地表和地下水之间相互作用的敏感性和程度。我们扩大了“溪流-含水层相互作用”一词的使用范围，不仅指通量和水交换，而且还包括溪流和含水层相互产生水力影响的方式。我们的结果表明，地下水位较深、水流事件较少和/或高渗透性沉积物往往导致河流与地下地下水之间的双向水力相互作用有限，这反过来又会导致大量的渗透。地下水位的初始深度越浅、水流频率越高和/或河床渗透率越低，地下水的“负”水力反馈越大，进而导致入渗量减少。随着初始地下水位深度的增加，河床损失最终达到一个恒定的速率，但在所研究的一些情况下，仅在10米以下的深度。我们的结果突出表明，短暂河流中的双向河流-含水层水力相互作用可能比通常假设的更广泛。我们的结论是，地下水和地表水应被视为水资源管理的相互关联的系统，除非有明确的相反证据。
Transmission losses from the beds of ephemeral streams are thought to be a widespread mechanism of groundwater recharge in arid and semi‐arid regions and support a range of dryland hydro‐ecology. Dryland areas cover ~40% of the Earth's land surface and groundwater resources are often the main source of freshwater. It is commonly assumed that where an unsaturated zone exists beneath a stream, the interaction between surface water and groundwater is unidirectional and that groundwater does not exert a significant feedback on transmission losses. To test this assumption, we conducted a series of numerical model experiments using idealised two‐dimensional channel‐transects to assess the sensitivity and degree of interaction between surface and groundwater for typical dryland ephemeral stream geometries, hydraulic properties and flow regimes. We broaden the use of the term ‘stream–aquifer interactions’ to refer not just to fluxes and water exchange but also to include the ways in which the stream and aquifer have a hydraulic effect on one another. Our results indicate that deep water tables, less frequent streamflow events and/or highly permeable sediments tend to result in limited bi‐directional hydraulic interaction between the stream and the underlying groundwater which, in turn, results in high amounts of infiltration. With shallower initial depth to the water table, higher streamflow frequency and/or lower bed permeability, greater ‘negative’ hydraulic feedback from the groundwater occurs which in turn results in lower amounts of infiltration. Streambed losses eventually reach a constant rate as initial water table depths increase, but only at depths of 10s of metres in some of the cases studied. Our results highlight that bi‐directional stream–aquifer hydraulic interactions in ephemeral streams may be more widespread than is commonly assumed. We conclude that groundwater and surface water should be considered as connected systems for water resource management unless there is clear evidence to the contrary.