Flow directions of stream-groundwater exchange in a headwater catchment during the hydrologic year,Hydrological Processes

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Flow directions of stream-groundwater exchange in a headwater catchment during the hydrologic year
Hydrological Processes ( IF 2.8 ) Pub Date : 2021-07-16 , DOI: 10.1002/hyp.14310
Enrico Bonanno _{1,

2} , Günter Blöschl ₂ , Julian Klaus ₁

Affiliation

Understanding near-stream groundwater dynamics and flow directions is important for predicting hillslope-stream connectivity, streamflow generation, and hydrologic controls of streamwater quality. To determine the drivers of groundwater flow in the stream corridor (i.e., the stream channel and the adjacent groundwater in footslopes and riparian areas), we observed the water levels of 36 wells and 7 piezometers along a headwater stream section over a period of 18 months. Groundwater dynamics during events were controlled by the initial position of the groundwater table relative to the subsurface structure. The near-stream groundwater table displayed a fast and pronounced response to precipitation events when lying in fractured bedrock with low storage capacity, and responded less frequently and in a less pronounced way when lying in upper layers with high storage capacity. Precipitation depth, intensity, regolith thickness above the fractured bedrock, and proximity to and elevation above the stream channel also had an effect on the groundwater dynamics, which varied with hydrologic conditions. Our high-frequency and spatially dense measurements highlight the competing influence of groundwater inflow from upslope locations, streamwater level and bedrock properties on the spatiotemporal dynamics of flowpaths in the stream corridor. Near-stream groundwater pointed uniformly towards the stream channel when the stream corridor was hydrologically connected to upslope groundwater. However, local interruptions of the water inflow from upslope locations caused flow reversals towards the footslopes. The direction of near-stream groundwater followed the local fractured bedrock topography during dry hydrologic conditions on a few occasions after events. The outcomes of this research contribute to a better understanding of the drivers controlling spatiotemporal changes in near-stream groundwater dynamics and flow directions in multiple wetness states of the stream corridor.

中文翻译：

水文年源头集水区河流-地下水交换流向

了解近流地下水动态和流动方向对于预测山坡-河流连通性、河流生成和河流水质的水文控制非常重要。为了确定河流廊道（即河道和脚坡和河岸地区的相邻地下水）中地下水流动的驱动因素，我们在 18 个月的时间里观察了沿上游河流部分的 36 口井和 7 个压力计的水位. 事件期间的地下水动力学由地下水位相对于地下结构的初始位置控制。近流地下水位位于储水能力低的裂隙基岩中时，对降水事件的响应迅速而明显，当位于具有高存储容量的上层时，响应频率较低且不明显。降水深度、强度、裂隙基岩上方的风化层厚度以及与河道的接近度和海拔高度也对地下水动态产生影响，这些动态随水文条件而变化。我们的高频和空间密集测量突出了来自上坡位置的地下水流入、河流水位和基岩特性对河流走廊流道时空动态的竞争影响。当河流走廊在水文上与上坡地下水相连时，近河流地下水均匀地指向河道。然而，从上坡位置的水流入的局部中断导致流向脚坡的逆转。事件发生后的几次干旱水文条件下，近流地下水的流向遵循当地的裂隙基岩地形。这项研究的结果有助于更好地了解控制河流走廊多种湿润状态下近河流地下水动力学和流动方向时空变化的驱动因素。

更新日期：2021-08-07

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