Dynamic Coevolution of Baseflow and Multiscale Groundwater Flow System During Prolonged Droughts
Dynamic Coevolution of Baseflow and Multiscale Groundwater Flow System During Prolonged Droughts
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DOI：
10.1016/j.jhydrol.2022.127657
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发表时间：
2022-03
影响因子：
6.4
通讯作者：
Chao Wang;J. Gomez‐Velez;John L. Wilson
中科院分区：
文献类型：
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作者：
Chao Wang;J. Gomez‐Velez;John L. Wilson
实地和数值研究表明，基流是由沃茨从地下水流路径的频谱称为地下水流系统（GWFS）-从浅山坡的贡献，流域规模的深循环起源于头沃茨和排放到低地河流。在这里，我们将探讨长期干旱下的GWFS的演变，以了解其动态和多尺度性质，并阐明其在基流生成和衰退的流域尺度的作用。我们考虑三种不同严重程度的干旱情况，并模拟地下水流在一个2-D横截面的理想化的流域深渗透基岩，跟踪流径的演变，基流，在衰退过程中的停留时间。我们发现，基流生成在不同的排水阶段，并在不同的子流域，是明显的影响不同尺度的流动路径，取决于相对强度的流动路径和子流域的位置相对于补给/排放区的更深的流域尺度的地下水循环。尽管有相同的当地救济，地质和气候，基流从每个子流域有一个独特的衰退行为和时间依赖的停留时间分布。此外，水力和运输特性的基流生成共同发展，并强烈影响地下水位子流域的连接状态。这些研究结果表明，在流域尺度上解释基流衰退数据和建立概念性基流模型时，必须考虑流域尺度地下水流影响下坡面基流生成的多样性和不相似性，以及与局部尺度和中间尺度地下水流的相互作用。
Field and numerical studies suggest that baseflow is composed of waters from a spectrum of groundwater flow paths termed the Groundwater Flow System (GWFS) – from shallow hillslope contributions to watershed-scale deep circulation originating in headwaters and discharging into lowland rivers. Here, we explore the evolution of the GWFS under prolonged droughts to understand its dynamics and multiscale nature, and to elucidate its role in baseflow generation and recession at the watershed scale. We consider three drought scenarios of varying severity and simulate groundwater flow in a 2-D cross-section of an idealized watershed with deep permeable bedrock, tracking the evolution of flow paths, baseflow, and residence times during the recession process. We find that baseflow generation at different drainage stages, and within different subwatersheds, is influenced distinctly by flow paths of different scales, depending on the relative strength of the flow paths and the position of the subwatersheds relative to the recharge/discharge zones of the deeper watershed-scale groundwater circulation. Despite having the same local relief, geology, and climate, baseflow from each subwatershed has a distinct recession behavior and time-dependent residence time distribution. Also, the hydraulic and transport characteristics of baseflow generation co-evolve and are strongly affected by the connection state of the water table to subwatersheds. These findings suggest that asynchrony and dissimilarity of baseflow generation from hillslopes under the impact of the watershed-scale groundwater flow, and interactions with local-scale and intermediate-scale groundwater flow, must be taken into account when interpreting baseflow recession data and building conceptual baseflow models at the watershed scale.