Mountain‐front recharge (MFR), or all inflow to a basin‐fill aquifer with its source in the mountain block, is an important component of recharge to basin‐fill aquifer systems. Distinguishing and quantifying the surface from subsurface components of MFR is necessary for water resource planning and management, particularly as climate change may impact these components in distinct ways. This study tests the hypothesis that MFR components can be distinguished in long‐screened, basin‐fill production wells by (1) groundwater age and (2) the median elevation of recharge. We developed an MFR characterization approach by combining age distributions in six wells using tritium, krypton‐85, argon‐39, and radiocarbon, and median recharge elevations from noble gas thermometry combined with numerical experiments to determine recharge temperature lapse rates using flow and energy transport modeling. We found that groundwater age distributions provided valuable information for characterizing the dominant flow system behavior captured by the basin‐fill production wells. Tracers indicated the presence of old (i.e., no detectable tritium) water in a well completed in weathered bedrock located close to the mountain front. Two production wells exhibited age distributions of binary mixing between modern and a small fraction of old water, whereas the remaining wells captured predominantly modern flow paths. Noble gas thermometry provided important complementary information to the age distributions; however, assuming constant recharge temperature lapse rates produced improbable recharge elevations. Numerical experiments suggest that surface MFR, if derived from snowmelt, can locally suppress water table temperatures in the basin‐fill aquifer, with implications for recharge elevations estimated from noble gas thermometry.

中文翻译：

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结合地下水年龄分布，稀有气体测温以及流体和能量传输模型的山前补给成分表征方法

山前补给（MFR）或全部流入其源位于山区的盆地填充含水层，是向盆地填充含水层系统补给的重要组成部分。区分和量化MFR的地下成分对于水资源计划和管理是必要的，尤其是因为气候变化可能以不同的方式影响这些成分。这项研究检验了以下假设：在长期筛选的盆地填充生产井中，MFR成分可以通过（1）地下水年龄和（2）补给中位数提高来区分。我们通过结合使用,、 85 85，氩39和放射性碳的6口井的年龄分布，开发了一种MFR表征方法，和稀有气体测温仪的中值补给高度与数值实验相结合，以使用流动和能量传输模型确定补给温度的下降速率。我们发现，地下水年龄分布提供了有价值的信息，可用于表征盆地填充生产井所捕获的主要流动系统行为。示踪剂表明在靠近山前的风化基岩中完井的井中存在旧的（即，没有可检测到的tri）水。两个生产井显示了现代水和一小部分旧水之间二元混合的年龄分布，而其余的井则主要捕获了现代流路。稀有气体测温为年龄分布提供了重要的补充信息。然而，假设恒定的补给温度下降速率产生了不可能的补给升高。数值实验表明，如果表面融化速率（MFR）来自融雪，则可以局部抑制盆地填充含水层中的地下水位温度，这对根据稀有气体测温法估算的补给高度具有影响。