The National Water Model (NWM) is a high‐resolution hydrological model capable of providing streamflow forecast at 2.7 million reaches across the conterminous United States (U.S.). It utilizes a conceptual (not physically explicit) module for estimating groundwater discharge (baseflow) to streams, and the baseflow module only allows for one‐way flux from the aquifer to the streams, with no interflow between surficial or groundwater catchments. This study evaluated the ability of the NWM to simulate baseflow in different geologic conditions with a case study in the Northern High Plains region. The study also evaluated two alternative formulations for the baseflow module in the NWM with the goal of improving simulated baseflow accuracy. The NWM simulated baseflow more accurately in a clayey catchment than in a sandy catchment. The model, however, over simulated baseflow during storm runoff events and under simulated during low flow events in both catchments. Analysis of groundwater recharge simulation showed that the NWM over simulated groundwater recharge for both catchment types, and reducing groundwater recharge using U.S. Geological Survey Baseflow Indexes improved the model performance for baseflow simulation, especially in the sandy catchment. Evaluation of the alteranative formulations showed that a modified Rorabaugh‐Rutledge formulation was able to improve the baseflow simulation with RMSE of 7.98 m³/s and R² of 0.41 and also improved the timing of peak flows.

中文翻译：

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在国家水模型中评估基流模拟：以美国北部高平原地区为例

国家水模型（NWM）是一种高分辨率水文模型，能够在整个美国（美国）的270万个河段提供流量预测。它使用概念性（非物理上明确的）模块来估算地下水向河流的排放量（基流），并且基流模块仅允许从含水层到河流的单向通量，而在表层或地下水集水区之间没有互流。这项研究以北部高平原地区为例，评估了NWM在不同地质条件下模拟基流的能力。该研究还评估了NWM中基流模块的两种替代公式，目的是提高模拟基流精度。NWM在粘土质流域比在砂质流域中模拟地基流更准确。该模型，但是，在两个流域的暴雨径流事件中，模拟的基础流量都超过了模拟值；在低流量事件中，模拟的基础流量却超过了模拟值。对地下水补给模拟的分析表明，两种集水类型的NWM都高于模拟地下水补给，使用美国地质调查局基础流量指数减少地下水补给，可以改善基础流模拟的模型性能，尤其是在沙质流域。对替代配方的评估表明，改进的Rorabaugh-Rutledge配方能够以7.98 m的RMSE改善基流模拟。地质调查基础流指数改善了基础流模拟的模型性能，尤其是在沙质流域。对替代配方的评估表明，改进的Rorabaugh-Rutledge配方能够以7.98 m的RMSE改善基流模拟。地质调查基础流指数改善了基础流模拟的模型性能，尤其是在沙质流域。对替代配方的评估表明，改进的Rorabaugh-Rutledge配方能够以7.98 m的RMSE改善基流模拟。³ / s和R ²为0.41，并且还改善了峰值流量的时序。