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Characterizing groundwater‐surface water interactions in idealized ephemeral stream systems
Hydrological Processes ( IF 3.2 ) Pub Date : 2020-07-06 , DOI: 10.1002/hyp.13847
Edisson A. Quichimbo 1 , Michael B. Singer 1, 2, 3 , Mark O. Cuthbert 1, 2, 4
Affiliation  

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 idealized 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.

中文翻译:

在理想化的短暂河流系统中表征地下水-地表水的相互作用

来自短暂溪流床的传输损失被认为是干旱和半干旱地区地下水补给的普遍机制,并支持一系列旱地水文生态。旱地面积约占地球陆地表面的 40%,地下水资源通常是淡水的主要来源。通常假设在河流下方存在非饱和带的地方,地表水和地下水之间的相互作用是单向的,地下水不会对传输损失产生显着的反馈。为了验证这一假设,我们使用理想化的二维通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、水力特性和流态的地表水和地下水之间相互作用的敏感性和程度。我们扩大了术语“河流-含水层相互作用”的使用范围,不仅指通量和水交换,还包括河流和含水层相互产生水力影响的方式。我们的结果表明,深水位、较不频繁的河流事件和/或高渗透性沉积物往往会导致河流与底层地下水之间有限的双向水力相互作用,进而导致大量渗透。随着到地下水位的初始深度更浅、更高的水流频率和/或更低的河床渗透率,来自地下水的更大“负”水力反馈发生,进而导致更低的渗透量。随着初始地下水位深度的增加,河床损失最终达到恒定速率,但在所研究的一些案例中,仅在 10 米深的地方。我们的结果强调,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。我们得出的结论是,除非有明确的相反证据,否则地下水和地表水应被视为水资源管理的连接系统。
更新日期:2020-07-06
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