Abstract Water movement in hillslopes is determined by the subsurface characteristics that control flow paths connecting precipitation to stream flow. The hydrological response of hillslopes is notoriously non-linear and non-stationary; with the relative importance of vertical and lateral flow paths also depending on event characteristics and antecedent conditions. In northern boreal regions, climate change projections indicate that wetter and warmer winter conditions are likely to generate more extreme flood events. Here, we report a study from an upland catchment in northern Scotland where a monitoring year provided an opportunity to contextualise observations during the hillslope response to a winter rainfall event that locally caused the most extreme flooding for over 200 years. Monitoring the hillslope water table, soil moisture and isotopes in precipitation, groundwater and stream flow provided invaluable insight into hillslope–riparian coupling. Groundwater with a shallow water table ( 1 day in the upper hillslope. In contrast, shallower wells in the soil profiles in the riparian area showed a more responsive perched groundwater system with transmissivity feedback in the upper soil layers resulting in much more rapid responses which generally peaked before the stream and exhibited clockwise hysteresis. Analysis of stable isotopes in precipitation, groundwater and streamflow, indicated that groundwater was remarkably well mixed with limited fractionation effects, inferring precipitation on the upper, unconfined hillslopes was the dominant source of recharge - particularly during the winter. The study shows that groundwater plays two roles in generating stream flow: a constant baseflow supply to the stream and time varying-exfiltration into the edge of the riparian zone, which contributes to surface runoff during storm events.

中文翻译：

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极端冬季降雨的一年中山坡-河岸界面的地下水动态

摘要 山坡中的水运动是由控制连接降水和溪流的流动路径的地下特征决定的。众所周知，山坡的水文响应是非线性和非平稳的；垂直和横向流动路径的相对重要性也取决于事件特征和先行条件。在北方北方地区，气候变化预测表明，更潮湿和更温暖的冬季条件可能会产生更多的极端洪水事件。在这里，我们报告了一项来自苏格兰北部高地集水区的研究，在该研究中，监测年份提供了一个机会，可以将山坡​​对冬季降雨事件的观测结果背景化，该事件在当地造成了 200 多年来最极端的洪水。监测山坡地下水位，降水、地下水和溪流中的土壤水分和同位素提供了对山坡-河岸耦合的宝贵见解。地下水位较浅的地下水（上山坡 1 天。相比之下，河岸地区土壤剖面中较浅的井显示出更敏感的栖息地下水系统，上层土层的透射率反馈导致更快的响应，通常在河流之前达到峰值并表现出顺时针滞后。对降水、地下水和河流中的稳定同位素的分析表明，地下水混合得非常好，分馏效应有限，推断上部无侧限山坡的降水是补给的主要来源 - 特别是在冬天。