PSIPW Chair, Prince Sultan Institute for Environmental, Water and Desert Research, King Saud University, Riyadh, Saudi Arabia.
Geology Department, Faculty of Science, Mansoura University, Mansoura, Egypt.
Environ Monit Assess. 2018 Apr 12;190(5):277. doi: 10.1007/s10661-018-6640-4.
Groundwater is the key for life in arid areas. Aquifer overexploitation and climatic conditions can significantly deteriorate groundwater quality. The Al-Qassim area in central Saudi Arabia is characterized by dense agricultural use and is irrigated mainly by fossil groundwater from the Saq Aquifer. Understanding the area's hydrochemistry, major factors governing groundwater quality, and alternative uses of the groundwater are the main goals of this study. Groundwater samples were collected and examined for major, minor, and trace elements. Ionic relationships, hydrochemical facies, geospatial distributions, and multivariate analyses were conducted to assess the hydrochemical processes at play. The salinity and nitrate concentrations of the Saq Aquifer's groundwater were found to increase in the outcrop areas more than the confined areas. The spatial distributions were fragmented by three main factors: (i) modern recharge by relatively brackish water, (ii) irrigation return flow in intensive farming areas, and (iii) overexploitation and draining of deep and relatively saline zones of the aquifer. Seven water types were found representing the alkaline water with a predominance of sulfate-chloride ions and earth alkaline water with a predominance of sulfate and chloride. Mixing between fresh and brackish water, dissolution of mineral phases, silicate weathering, and reverse ion exchange were recognized as the evolutionary processes, while evaporation played a minor role. Cluster analyses characterized the fresh groundwater zone, modern groundwater recharge zone, and anthropogenic influence zone. In the confined areas, nearly all the groundwater was appropriate for domestic use and irrigation. In the outcrop areas, some limitations were found due to unsuitable conditions.
地下水是干旱地区生命的关键。含水层过度开采和气候条件会显著恶化地下水质量。沙特阿拉伯中部的盖西姆地区以密集的农业利用为特征，主要依靠来自萨格含水层的化石地下水进行灌溉。本研究的主要目标是了解该地区的水化学、控制地下水质量的主要因素以及地下水的替代用途。采集并检测了地下水的主要、次要和微量元素。进行了离子关系、水化学相、地理空间分布和多元分析，以评估起作用的水文化学过程。发现萨格含水层地下水的盐度和硝酸盐浓度在露头区比在承压区增加得更多。三个主要因素导致了空间分布的破碎化：（i）相对微咸水的现代补给，（ii）集约农业区的灌溉回流，以及（iii）含水层深部和相对咸水区的过度开采和排水。发现了七种水型，代表了以硫酸盐-氯化物离子为主的碱性水和以硫酸盐和氯化物为主的地球碱性水。混合淡水和微咸水、溶解矿物相、硅酸盐风化和反向离子交换被认为是演化过程，而蒸发作用的影响较小。聚类分析描述了淡水区、现代地下水补给区和人为影响区。在承压区，几乎所有的地下水都适合家庭使用和灌溉。在露头区，由于条件不合适，发现了一些限制。
