In most bucket-type hydrological models, water can only flow from the groundwater to the stream and the flux is based on the groundwater storage. However, many catchments have losing stream sections, where streamflow recharges the groundwater. We developed a formulation to represent groundwater recharge by streamwater in a bucket-type model and tested this formulation for the Panola Mountain Research Watershed to demonstrate its function and assess its performance. The upper reach of the Panola catchment is often dry and highly affected by flow from a bedrock outcrop; further downstream the stream is perennial. We simulated streamflow with the fully lumped version of a bucket-type model and compared it to (a) a variant with sub-catchments to more realistically represent the low storage and quick response from the bedrock outcrop and (b) a variant that also includes the bi-directional exchange between the groundwater and the stream. For all three model variants, we compared simulated and observed streamflow and groundwater dynamics. Although the gain in overall model performance by including the bi-directional exchange between the groundwater and the stream was small, the explicit representation of this exchange led to better streamflow simulations during drying-down and wetting-up periods. For Panola the fluxes along the stream appeared less important than subsurface drainage from the upper sub-catchment to the downstream sub-catchment. We recommend considering the bi-directional fluxes between groundwater and the stream in bucket-type hydrological models where these processes are important, and the focus of the simulations is on low flow conditions.

中文翻译：

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桶型水文模型中地下水和地表水之间双向通量的表示

在大多数桶式水文模型中，水只能从地下水流向溪流，流量取决于地下水存储量。然而，许多集水区都失去了河流部分，在那里河流补充地下水。我们开发了一种用桶型模型表示地下水补给的公式，并在 Panola 山研究流域测试了该公式，以展示其功能并评估其性能。帕诺拉集水区的上游经常干燥，受基岩露头的水流影响很大；更下游的河流是多年生的。我们使用桶型模型的完全集总版本模拟水流，并将其与 (a) 带有子集水区的变体进行比较，以更真实地表示基岩露头的低蓄水量和快速响应，以及 (b) 变体还包括地下水与河流之间的双向交换。对于所有三个模型变体，我们比较了模拟和观察到的水流和地下水动态。虽然通过包括地下水和河流之间的双向交换来提高整体模型性能的收益很小，但这种交换的明确表示导致了在干涸和湿润期间更好的河流模拟。对于 Panola 而言，沿溪流的通量似乎不如从上部子集水区到下游子集水区的地下排水重要。