Hydrologic controls on hyporheic exchange in a headwater mountain stream
Hydrologic controls on hyporheic exchange in a headwater mountain stream
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源头山涧流域交换的水文控制
DOI：
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
S. Wondzell
中科院分区：
文献类型：
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作者：
N. Schmadel;A. Ward;S. Wondzell
河流廊道内潜流交换的时空尺度受河流流量和地下水流入与河床形态相互作用的控制。虽然经过几十年的研究，我们已经清楚地了解了地貌形态如何在地物尺度上控制地下水交换，但在河段尺度上，我们缺乏与河流流量和地下水流入空间结构相关的可比较的预测能力，在河段尺度上，地貌环境和水文强迫都存在空间异质性。本研究在考虑地下水流入可忽略、空间均匀或与上坡累积面积成正比的情况下，模拟了高、中、低流量下沿600 m山溪河段的垂直潜流交换。流量对潜流路径停留时间或长度的影响较小（<5%），表明相对于形态驱动的潜流交换，流量是次要控制因素。地下水入流是主要的控制因素，主要引起潜流路径停留时间和长度的减少。这一发现与文献中的预期基本一致；然而，在整个研究范围内，流路响应并不一致。相反，我们发现与大形态特征相一致的大水力梯度驱动的流道对地下水流入变化的敏感性低于与山谷梯度相似的水力梯度驱动的流道。我们的研究结果表明，有必要考虑形态特征的异质排列，以区分持续时间的隐性流道和对变化的水文条件敏感的流道。
The spatial and temporal scales of hyporheic exchange within the stream corridor are controlled by stream discharge and groundwater inflow interacting with streambed morphology. While decades of study have resulted in a clear understanding of how morphologic form controls hyporheic exchange at the feature scale, we lack comparable predictive power related to stream discharge and the spatial structure of groundwater inflows at the reach scale, where spatial heterogeneity in both geomorphic setting and hydrologic forcing are present. In this study, we simulated vertical hyporheic exchange along a 600 m mountain stream reach under high, medium, and low stream discharge while considering groundwater inflow as negligible, spatially uniform, or proportional to upslope accumulated area. Most changes to hyporheic flow path residence time or length in response to stream discharge were small (<5%), suggesting that discharge is a secondary control relative to morphologically driven hyporheic exchange. Groundwater inflow was a primary control and mostly caused decreases in hyporheic flow path residence time and length. This finding generally agrees with expectations from the literature; however, flow path response was not consistent across the study reach. Instead, we found that flow paths driven by large hydraulic gradients coinciding with large morphologic features were less sensitive to changes in groundwater inflow than those driven by hydraulic gradients similar to the valley gradient. Our results indicate that consideration of heterogeneous arrangement of morphologic features is necessary to differentiate between hyporheic flow paths that persist in time and those that are sensitive to changing hydrologic conditions.