GroMoPo Metadata for Nubian Aquifer System model

Parsimonious groundwater modeling provides insight into hydrogeologic functioning of the Nubian Aquifer System (NAS), the world's largest non-renewable groundwater system (belonging to Chad, Egypt, Libya, and Sudan). Classical groundwater-resource issues exist (magnitude and lateral extent of drawdown near pumping centers) with joint international management questions regarding transboundary drawdown. Much of NAS is thick, containing a large volume of high-quality groundwater, but receives insignificant recharge, so water-resource availability is time-limited. Informative aquifer data are lacking regarding large-scale response, providing only local-scale information near pumps. Proxy data provide primary underpinning for understanding regional response: Holocene water-table decline from the previous pluvial period, after thousands of years, results in current oasis/sabkha locations where the water table still intersects the ground. Depletion is found to be controlled by two regional parameters, hydraulic diffusivity and vertical anisotropy of permeability. Secondary data that provide insight are drawdowns near pumps and isotope-groundwater ages (million-year-old groundwaters in Egypt). The resultant strong simply structured three-dimensional model representation captures the essence of NAS regional groundwater-flow behavior. Model forecasts inform resource management that transboundary drawdown will likely be minimal-a nonissue-whereas drawdown within pumping centers may become excessive, requiring alternative extraction schemes; correspondingly, significant water-table drawdown may occur in pumping centers co-located with oases, causing oasis loss and environmental impacts.简约地下水模拟（Parsimonious groundwater modeling）可为努比亚含水层系统（Nubian Aquifer System, NAS）的水文地质功能提供解析视角——该系统是全球规模最大的不可再生地下水系统，覆盖乍得、埃及、利比亚与苏丹四国。该区域存在典型的地下水问题：抽水中心附近的降深规模与横向分布范围，同时伴随跨界降深相关的跨国联合管理议题。努比亚含水层系统大部分区域厚度可观，蕴藏大量优质地下水，但补给量微乎其微，因此水资源可利用性具有时间限制性。当前缺乏能够反映含水层大规模响应的有效监测数据，仅能获取抽水中心附近的局地尺度信息。代用数据（Proxy data）是理解区域地下水响应的核心支撑：全新世时期，自前多雨期以来的地下水位下降历经数千年，形成了当前绿洲与萨布哈（sabkha，盐沼）的分布格局——这些区域的地下水位仍与地表相接。研究表明，地下水消耗受两个区域参数控制：水力扩散度（hydraulic diffusivity）与渗透率的垂向各向异性（vertical anisotropy of permeability）。可供参考的辅助数据包括抽水中心附近的降深数据与地下水同位素年龄（如埃及境内存在百万年历史的地下水）。最终构建的简洁结构化三维模型，精准捕捉了努比亚含水层系统区域地下水流动的核心特征。模型预测结果可为水资源管理提供决策参考：跨界降深大概率极小，几乎不构成管理难题，但抽水中心内部的降深可能会过度发展，需采用替代取水方案；相应地，与绿洲重合的抽水中心可能出现显著的地下水位降深，进而导致绿洲消失并引发一系列环境影响。