Comprehensive aquifer characterization requires the development of a three-dimensional (3D) geological model and estimation of hydraulic and hydro-geochemical properties. This can be used to discern the governing processes of groundwater flow and chemistry, and plan pertinent groundwater management approaches. This study evaluated the influence of geological settings and groundwater flow on the groundwater development potential and chemistry in a Quaternary aquifer system in the Raya Valley, Ethiopia. Surface geology, digital elevations, groundwater-level measurements, and data from drill logs, pumping tests and vertical electrical soundings were combined to characterize the physical properties of the aquifer system. 3D geological and hydrogeological models were developed and used to delineate subsurface formations and to quantify groundwater flow. The aquifer was characterized as a heterogeneous and anisotropic unconfined system. The available groundwater volume was estimated to be 80 ± 1 km³ with a maximum sustainable yield of 530,409 ± 16,800 m³/day. The use of geochemical models and principal component analysis revealed that the origin and geochemical composition of the groundwater were spatially variable. Rock weathering, mineral dissolution, ion-exchange and anthropogenic activities were the major processes governing the hydro-geochemical characteristics of the aquifer, while evaporation processes caused groundwater salinity enrichment. However, even though mineral saturation of the groundwater at specific locations was highly influenced by the geologic matrix, advective groundwater transport led to areas with mixed groundwater chemistry. The observed and modelled complexity of this aquifer system suggests that such evaluations are important to design appropriate groundwater management strategies in heterogeneous and structurally complex aquifer systems.

全面的含水层表征需要开发三维（3D）地质模型并估算水力和水力地球化学特性。这可用于识别地下水流量和化学作用的控制过程，并规划相关的地下水管理方法。这项研究评估了埃塞俄比亚拉雅谷第四纪含水层系统中地质环境和地下水流量对地下水发育潜力和化学性质的影响。地表地质，数字高程，地下水位测量以及来自钻探测井，抽水试验和垂直电测深的数据相结合，以表征含水层系统的物理性质。开发了3D地质和水文地质模型，并将其用于描绘地下地层并量化地下水流量。含水层的特征是一个非均质各向异性的无限制系统。可用地下水量估计为80±1 km³最大可持续产量为530,409±16,800 m ³/天。地球化学模型和主成分分析的使用表明，地下水的来源和地球化学组成在空间上是可变的。岩石的风化，矿物溶解，离子交换和人为活动是控制含水层水文地球化学特征的主要过程，而蒸发过程引起了地下水盐分的富集。但是，尽管特定位置的地下水矿物质饱和度受到地质基质的强烈影响，但平流地下水的运输还是导致了地下水化学成分混合的地区。对该含水层系统进行观测和建模的复杂性表明，这种评估对于在非均质和结构复杂的含水层系统中设计适当的地下水管理策略非常重要。