Quantifying hydrological processes that control the upper critical zone water balance and contaminant transport in drained landscapes is needed, especially as precipitation patterns driving water balance dynamics continue to shift due to climate change. Here, hydrometric data are integrated with stable isotope signatures to quantify water storage, mixing, and fluxes to subsurface tile drainage at an agricultural field located in Indiana, USA. Over a 2-yr period, precipitation, soil water sampled with suction lysimeters (10–80 cm depth), groundwater (below tile depth; >1 m), and subsurface tile discharge were sampled 97 times. Results showed that isotopic variability in near-surface soil water (10–20 cm) reflected the seasonality of the precipitation input signal, while groundwater values were relatively consistent indicating that water stored below tile drain depth was recharged during winter. Soil water between 20 and 80 cm depth was a mixture of near-surface water and groundwater that varied seasonally depending upon groundwater hydrodynamics. Mean transit time of water ranged from 12 to 20 d for 10-cm soil water to 225–334 d for groundwater, with tile drainage exhibiting a mean transit time of 245 d. Both two- and three-component hydrograph separation indicated that groundwater was the primary source of water to the tile drain followed by soil water. Tile drain hydrograph response (i.e., celerity) was largely controlled by antecedent wetness. Comparison of tile drain celerities and velocities revealed however varying mechanisms controlling hydrograph response across a range of environmental conditions. Data sets of both water and tracer flux were, thus, useful to track the spatiotemporal variability of water fluxes within and from the critical zone. Such data provide valuable information to improve the representation of critical zone processes in these landscapes within spatially distributed hydrological models.

需要对控制上部临界区水平衡和排水环境中污染物运移的水文过程进行量化，尤其是由于气候变化导致驱动水平衡动态的降水模式不断变化时。在这里，水文数据与稳定的同位素特征相结合，以量化位于美国印第安纳州的一个农田的储水量，混合量以及通向地下瓷砖排水的通量。在2年的时间里，对降水，抽水渗漏仪（深度为10-80厘米），地下水（低于瓷砖深度；> 1 m）和地下瓷砖排水进行了97次采样。结果表明，近地表土壤水（10–20 cm）中的同位素变化反映了降水输入信号的季节性，而地下水值则相对一致，这表明在冬季，低于瓷砖排水深度的水被补充了水。20至80厘米深度的土壤水是近地表水和地下水的混合物，其随地下水动力变化而季节性变化。水的平均传播时间从10 cm土壤水的12到20 d到地下水的225-334 d，瓦砾排水的平均传播时间为245 d。两分量和三分量水位图的分离都表明，地下水是瓦砾排水的主要水源，其次是土壤水。瓷砖排水水位曲线的响应（即速度）在很大程度上受之前的湿度控制。瓷砖排水速度和速度的比较表明，在各种环境条件下，控制水位响应的机制各不相同。因此，水和示踪剂通量的数据集可用于跟踪关键区域内和来自关键区域的水通量的时空变化。这些数据提供了宝贵的信息，可以改善空间分布水文模型中这些景观中关键区域过程的表示。