Subsurface dams, strongly advocated in the 1992 United Nations Agenda-21, have been widely studied to increase groundwater storage capacity. However, an optimal allocation of augmented water with the construction of the subsurface dams to compensate for the water shortage during dry periods has not so far been investigated. This study, therefore, presents a risk-based simulation–optimization framework to determine optimal water allocation with subsurface dams, which minimizes the risk of water shortage in different climatic conditions. The developed framework was evaluated in Al-Aswad falaj, an ancient water supply system in which a gently sloping underground channel was dug to convey water from an aquifer via the gravity force to the surface for irrigation of downstream agricultural zones. The groundwater dynamics were modeled using MODFLOW UnStructured-Grid. The data of boreholes were used to generate a three-dimensional stratigraphic model, which was used to define materials and elevations of five-layer grid cells. The validated groundwater model was employed to assess the effects of the subsurface dam on the discharge of the falaj. A Conditional Value-at-Risk optimization model was also developed to minimize the risk of water shortage for the augmented discharge on downstream agricultural zones. Results show that discharge of the falaj is significantly augmented with a long-term average increase of 46.51%. Moreover, it was found that the developed framework decreases the water shortage percentage in 5% of the worst cases from 87%, 75%, and 32% to 53%, 32%, and 0% under the current and augmented discharge in dry, normal, and wet periods, respectively.

在 1992 年联合国 21 世纪议程中大力提倡的地下大坝已被广泛研究以增加地下水储存能力。然而，迄今为止，尚未研究通过建造地下大坝来补偿干旱期间缺水的增水优化分配。因此，本研究提出了一个基于风险的模拟优化框架，以确定地下大坝的最佳水资源分配，从而最大限度地减少不同气候条件下水资源短缺的风险。在 Al-Aswad falaj 中对开发的框架进行了评估，一种古老的供水系统，其中挖出一条缓慢倾斜的地下通道，通过重力将水从含水层输送到地表，用于灌溉下游农业区。地下水动力学使用 MODFLOW UnStructured-Grid 建模。钻孔数据用于生成三维地层模型，用于定义五层网格单元的材料和高程。使用经过验证的地下水模型来评估地下大坝对falaj排放的影响。还开发了条件风险价值优化模型，以最大限度地减少下游农业区增加排放造成的缺水风险。结果表明，falaj 的排放显着增加，长期平均增长 46.51%。此外，发现开发的框架将 5% 的最坏情况下的缺水率从 87%、75% 和 32% 降低到 53%、32% 和 0%，在干流和增流下，分别为正常期和潮湿期。