Abstract The arid and semi-arid regions of the world are facing limited freshwater resources, minimal amounts of rainfall, and increasing population pressure and water demands. These resources, often groundwater, are vulnerable to both natural variability and anthropogenic interventions. Here, we develop and apply an integrated approach using geophysical, geochemical, and remote sensing observations to quantify the recharge rates of arid region aquifers that are witnessing rapid groundwater depletion. Focusing on the Saq aquifer system in the Arabian Peninsula, our study was three-fold: (1) to examine the areal extent of aquifer recharge domains using geologic, climatic, and remote sensing data; (2) to investigate the origin of, and modern contributions to, the aquifer system by examining the isotopic composition of groundwater samples; and (3) to estimate the magnitude of modern recharge to the aquifer utilizing estimates from the Gravity Recovery and Climate Experiment (GRACE) data and a continuous rainfall-runoff model, the Soil and Water Assessment Tool (SWAT) model. Isotopic examination of the groundwater from Saq revealed that deeper aquifers (fossil water) are more depleted compared to shallow reserves (alluvial aquifer; mixed waters). Analysis of GRACE-derived terrestrial and groundwater storage estimates indicates that the aquifer system received an annual recharge rate of 5.21 ± 0.10 km3/yr (11.85 ± 0.22 mm/yr), equal to about half of the withdrawal rate from wells during the investigation period (2002–2016). Analysis of SWAT results indicates that, from 1998 to 2014, the investigated watersheds received an average annual precipitation of 19.20 km3, of which approximately 51% is partitioned as potential recharge. The temporal variations in storage, depletion and recharge are related to the changes in regional groundwater extraction, rainfall, and extent of irrigated areas.

中文翻译：

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使用综合地球物理、地球化学和遥感方法评估干旱地区含水层的现代补给

摘要 世界干旱和半干旱地区正面临淡水资源有限、降雨量极少、人口压力和用水需求增加的问题。这些资源，通常是地下水，容易受到自然变异和人为干预的影响。在这里，我们开发并应用了一种综合方法，使用地球物理、地球化学和遥感观测来量化正在见证地下水快速枯竭的干旱地区含水层的补给率。我们针对阿拉伯半岛的 Saq 含水层系统进行了三方面的研究：(1) 利用地质、气候和遥感数据检查含水层补给域的面积范围；(2) 通过检查地下水样品的同位素组成来调查含水层系统的起源和现代贡献；(3) 利用重力恢复和气候实验 (GRACE) 数据和连续降雨径流模型、土壤和水评估工具 (SWAT) 模型的估计值来估计含水层的现代补给量。对来自 Saq 的地下水的同位素检查表明，与浅层储量（冲积含水层；混合水）相比，更深的含水层（化石水）消耗得更多。对 GRACE 得出的陆地和地下水储量估计值的分析表明，含水层系统的年补给率为 5.21 ± 0.10 立方千米/年（11.85 ± 0.22 毫米/年），相当于调查期间井抽取率的一半左右（2002-2016 年）。SWAT 结果分析表明，1998 年至 2014 年，调查流域年均降水量为 19.20 km3，其中大约 51% 被分配为潜在的充电。储存、消耗和补给的时间变化与区域地下水抽取、降雨量和灌溉面积范围的变化有关。