Coupling a large-scale hydrological model (CWatM v1.1) with a high-resolution groundwater flow model (MODFLOW 6) to assess the impact of irrigation at regional scale
Coupling a large-scale hydrological model (CWatM v1.1) with a high-resolution groundwater flow model (MODFLOW 6) to assess the impact of irrigation at regional scale
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DOI：
10.5194/gmd-15-7099-2022
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发表时间：
2022-09
影响因子：
5.1
通讯作者：
L. Guillaumot;M. Smilovic;P. Burek;Jens A. de Bruijn;P. Greve;T. Kahil;Y. Wada
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文献类型：
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作者：
L. Guillaumot;M. Smilovic;P. Burek;Jens A. de Bruijn;P. Greve;T. Kahil;Y. Wada
抽象的。在气候变化和水资源需求不断增加的背景下，大规模的水文模型有助于理解和预测未来不同尺度的水资源。地下水是一种重要的淡水资源，对全年河流流量有很强的控制力。它对生态系统也是必不可少的，并有助于蒸散，从而产生气候反馈。然而，世界各地的地下水系统相当多样，包括厚的多层含水层和薄的非均匀含水层。近年来，人们努力提高地下水系统在大型水文模型中的代表性。评估这些模型输出的准确性具有挑战性，因为(1)它们的应用分辨率比山坡尺度要粗糙得多，(2)它们简化了通常在当地尺度上为人所知的地质结构，(3)它们没有充分考虑当地的水管理做法(主要是地下水抽水)。在这里，我们在两个不同的气候、地质和社会经济区域应用大型水文模型(CWatM)和地下水流动模型MODFLOW：Seewinkel地区(奥地利)和Bhima盆地(印度)。该耦合模型可以模拟地下水位对地下水-土壤和地下水-河流交换的影响，地下水通过渗漏渠道的补给，以及地下水的抽水。这种区域尺度的分析能够评估模型在精细空间分辨率(CWatM为1公里，MODFLOW为100-250米)下模拟地下水位的能力，以及在很好地估计地下水抽水量的情况下。评估大规模模型仍然具有挑战性，但结果表明，(1)平均地下水位波动和(2)无偏差地下水位深度的再现可以作为此类模型的基准目标。我们发现，网格分辨率是影响地下水位深度偏差的主要因素，因为它平滑了河流的切割，而抽水则影响时间波动。最后，我们利用该模型评估了以地下水为基础的灌溉抽水对蒸散、地下水补给和钻孔地下水位观测的影响。
Abstract. In the context of changing climate and increasing water demand, large-scale hydrological models are helpful for understanding and projecting future water resources across scales. Groundwater is a critical freshwater resource and strongly controls river flow throughout the year. It is also essential for ecosystems and contributes to evapotranspiration, resulting in climate feedback. However, groundwater systems worldwide are quite diverse, including thick multilayer aquifers and thin heterogeneous aquifers. Recently, efforts have been made to improve the representation of groundwater systems in large-scale hydrological models. The evaluation of the accuracy of these model outputs is challenging because (1) they are applied at much coarser resolutions than hillslope scale, (2) they simplify geological structures generally known at local scale, and (3) they do not adequately include local water management practices (mainly groundwater pumping). Here, we apply a large-scale hydrological model (CWatM), coupled with the groundwater flow model MODFLOW, in two different climatic, geological, and socioeconomic regions: the Seewinkel area (Austria) and the Bhima basin (India). The coupled model enables simulation of the impact of the water table on groundwater–soil and groundwater–river exchanges, groundwater recharge through leaking canals, and groundwater pumping. This regional-scale analysis enables assessment of the model's ability to simulate water tables at fine spatial resolutions (1 km for CWatM, 100–250 m for MODFLOW) and when groundwater pumping is well estimated. Evaluating large-scale models remains challenging, but the results show that the reproduction of (1) average water table fluctuations and (2) water table depths without bias can be a benchmark objective of such models. We found that grid resolution is the main factor that affects water table depth bias because it smooths river incision, while pumping affects time fluctuations. Finally, we use the model to assess the impact of groundwater-based irrigation pumping on evapotranspiration, groundwater recharge, and water table observations from boreholes.