Pumping optimization under uncertainty is a powerful approach for the management of groundwater resources, and its implementation would be valuable in island aquifers where freshwater lenses are affected by seawater intrusion. Sharp-interface numerical models are especially well suited for the task as they offer fast simulation times, but to date they have not been used because of a lack of guidelines and due to the specific challenges associated with this approach. This study presents a methodology for pumping optimization under uncertainty for island freshwater lenses using a sharp-interface model (MODFLOW-SWI2) and demonstrates it for a real case (Magdalen Islands, Quebec, Canada). The total pumping in a well field was maximized while avoiding well salinization due to upconing. To do so, the sharp interface simulated below the pumping wells was corrected successively for cell-to-well upconing and for dispersion. Pumping optimization under uncertainty was then conducted using PESTPP-OPT, considering parameter and observation uncertainty, and was repeated for 23 reliability levels to illustrate a large range of risk-averse, tolerant and neutral stances. The maximum pumping was obtained as a function of risk of well salinization. This approach enabled quantification of the tradeoffs between pumping and risk, allocation of pumping amongst wells, and an examination of the ability of the well field to meet the water demand while maintaining an acceptable level of risk. Ultimately, this framework allows groundwater managers to select the final pumping scenario themselves, depending on their attitude toward risk.

中文翻译：

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使用锐界面海水入侵模型的岛屿淡水透镜的不确定性泵送优化

不确定条件下的泵送优化是管理地下水资源的有力方法，其实施对于淡水透镜体受海水入侵影响的岛屿含水层具有重要价值。Sharp-interface 数值模型特别适合这项任务，因为它们提供了快速的仿真时间，但迄今为止，由于缺乏指导方针以及与这种方法相关的特定挑战，它们尚未被使用。本研究提出了一种在不确定性下使用锐界面模型 (MODFLOW-SWI2) 对岛屿淡水透镜进行泵送优化的方法，并针对真实案例（加拿大魁北克马格达伦群岛）进行了演示。井场的总抽水量最大化，同时避免了由于上锥造成的井盐碱化。为此，抽水井下方模拟的尖锐界面针对单元到井的上行和分散进行了连续校正。然后使用 PESTPP-OPT 在不确定性下进行泵送优化，考虑参数和观察的不确定性，并重复 23 个可靠性级别，以说明大范围的风险规避、容忍和中立立场。最大抽水量是作为井盐渍化风险的函数而获得的。这种方法可以量化抽水和风险之间的权衡，在井之间分配抽水，并检查井场在保持可接受的风险水平的同时满足用水需求的能力。最终，该框架允许地下水管理人员根据他们对风险的态度自行选择最终的抽水方案。