Climatic and Anthropogenic Controls on Groundwater Dynamics in the Mekong River Basin
Climatic and Anthropogenic Controls on Groundwater Dynamics in the Mekong River Basin
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DOI：
10.1016/j.jhydrol.2023.129761
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发表时间：
2023-06
影响因子：
6.4
通讯作者：
Tamanna Kabir;Y. Pokhrel;Farshid Felfelani
中科院分区：
文献类型：
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作者：
Tamanna Kabir;Y. Pokhrel;Farshid Felfelani
地下水枯竭是全世界关注的问题，也是湄公河流域 (MRB) 等地区的一个新问题。然而，即使是 MRB 地下水的自然动态也尚未得到充分探索，这使得地下水对气候变化和人类活动的响应的量化成为一项重大的科学挑战。在这里，我们研究了 MRB 中的各种地下水机制，重点关注受气候变化、地形特征和地下水与地表水相互作用的关键驱动因素调节的地下水流过程。我们进一步量化了人类活动对地下水动态的影响。我们使用空间分辨率为 0.05°（∼5km）的社区土地模型版本 5 (CLM5)，改进了地下水过程的表示，包括横向地下水流和用于灌溉的含水层抽水。结果表明，受气候和地下特征影响，整个流域地下水补给和排放存在高度空间异质性。由于降水，地下水补给具有明显的季节性；约 52% 的雨季降水补充了地下水，并大量转移到连续的旱季，从而减轻了土壤湿度。重要的是，地下水排放是全年径流的主要来源，这表明 MRB 中存在强烈的地表水-地下水耦合。最后，我们的结果表明灌溉抽水直接改变地下水流量和储存量；气候变化会平滑长时间的抽水效应，但该模型模拟了干旱年份湄公河三角洲地区范围内的地下水枯竭（高达 1 m/年）。我们的研究提供了关于 MRB 中不断变化的地下水系统的重要见解，同时也提高了基于过程的地下水建模能力。
Groundwater depletion is a worldwide concern and an emerging issue in regions such as the Mekong River Basin (MRB). However, even the natural dynamics of groundwater in the MRB is yet to be fully explored, making the quantification of groundwater response to climate variability and anthropogenic activities a major scientific challenge. Here, we examine various groundwater mechanisms in the MRB, focusing on groundwater flow processes that are modulated by climate variability, physiographic features, and key drivers of groundwater-surface water interactions. We further quantify the influence of anthropogenic activities on groundwater dynamics. We use the Community Land Model version 5 (CLM5) at 0.05° (∼5km) spatial resolution with an improved representation of groundwater processes, including lateral groundwater flow and aquifer pumping for irrigation. Results indicate high spatial heterogeneity in groundwater recharge and discharge across the basin governed by climate and subsurface characteristics. A pronounced seasonality is found in groundwater recharge due to precipitation; ∼52% of wet season precipitation recharges groundwater, with substantial carryover to the consecutive dry season that alleviates soil moisture. Importantly, groundwater discharge is a dominant source of streamflow all year round, which suggests a strong surface water-groundwater coupling in the MRB. Finally, our results indicate that irrigation pumping is directly altering groundwater flows and storages; climate variability smoothens pumping effects over long times, but the model simulates region-wide groundwater depletion (up to 1 m/year) in the Mekong Delta during dry years. Our study provides key insights on the evolving groundwater systems in the MRB, also advancing process-based groundwater modeling capabilities.