Groundwater fluxes to many surface water systems are spatially heterogeneous with discharge focused into discrete, high-flux zones. Quantifying fluxes in these preferential discharge zones is critical to a range of surface water habitat and water quality processes, but characterization can be difficult due to short-scale spatial and temporal variability. Passive heat-as-a-tracer methods employing vertical temperature profiler (VTP) data can provide the necessary spatial and temporal resolution, but upward fluid flow strongly attenuates the thermal signals used for estimating fluxes. In preferential discharge zones it becomes difficult to measure the signals in the subsurface and the flux parameter can become insensitive in the analysis models, leading to large uncertainties. We use data from a high-flux site of contaminant-loaded groundwater discharge to the Quashnet River on Cape Cod, Massachusetts, USA, to demonstrate how recent advances in VTP instrumentation that allow for the acquisition of high-resolution (0.001 °C) temperature data at short (1 cm) offsets near the ground surface, combined with advances in flux estimation methods that exploit the information content of the high-resolution data, facilitate heat-as-a-tracer approaches for characterizing groundwater-surface water exchanges and make it possible to obtain accurate and statistically robust results in a preferential discharge zone with a specific discharge of ∼1 m/d.

中文翻译：

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垂直温度剖面仪仪器和通量估计方法的最新进展促进了地下水 - 具有强排放区的环境中的地表水交换研究


许多地表水系统的地下水通量在空间上是不均匀的，排放集中在离散的高通量区域。量化这些优先排放区的通量对于一系列地表水栖息地和水质过程至关重要，但由于短期的空间和时间变化，表征可能很困难。采用垂直温度剖面仪 (VTP) 数据的被动热示踪方法可以提供必要的空间和时间分辨率，但向上的流体流动会强烈衰减用于估计通量的热信号。在优先排放区，测量地下信号变得困难，并且分析模型中的通量参数可能变得不敏感，从而导致很大的不确定性。我们使用来自美国马萨诸塞州科德角 Quashnet 河的高通量污染物地下水排放点的数据，来展示 VTP 仪器的最新进展如何支持采集高分辨率 (0.001°C) 温度靠近地表的短（1厘米）偏移数据，与利用高分辨率数据信息内容的通量估计方法的进步相结合，促进了热作为示踪剂的方法来表征地下水-地表水交换，并使得在比流量为~1m/d的优先排放区域中可以获得准确且统计稳健的结果。