Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Hydrogeological and geophysical studies on Al Qassim area, Kingdom of Saudi Arabia

Auteur : El-Sherbini, Ragab Attia Mohamed.

Etablissement de soutenance : Mansoura University

Grade : Master of Science in Hydrogeology 2021

Résumé
The kingdom of Saudi Arabia faced the extreme water demands and deficiency of water incomes. Al Qassim Province is categorized by intensive agricultural utilities and in attempts great water supply that irrigated mainly from the Cambrian-Ordovician Saq Aquifer. The Thesis aimed to determine the petrophysical parameters and evaluate hydrochemical properties of the Cambrian – Ordovician Saq-Ram aquifer system in Al Qassim province, Kingdom of Saudi Arabia. This is achieved by evaluating the chemical analysis of 26 water samples and 8 water wells logging associate with downhole cam recording. The petrophysical evaluation associated with hydrochemical analysis divided the penetrated Saq Formation into 2 zones with different hydrogeological characterizations (Aquifer zone and Aquitard zone). Moreover, the Saq-Ram aquifer system is classified into confined and unconfined. The ground water quality varies from fresh to brackish water. It is recommended to add new water wells in newly reclaimed arid area. The hydro-chemical data from 26 groundwater wells, emphasis on assessing the groundwater quality and assigning the best borehole locations. These goals achieved through full hydro-chemical analyses of water samples. Both suitability and unsuitability of the groundwater for drinking and irrigation purposes was assessed based on hydro-chemical data, according to the standard guideline’s values. The results indicate that the Cambrian-Ordovician Saq aquifer is the crucial aquifer in the province, which is detached into two sub-aquifers. The upper sub-aquifer is encountered at depths range from 110m to 130m bgl (below ground level), with overall thickness ranges from 200 to 250 m. The total dissolved solids (TDS) vary from 400 to 800mg/l indicating fresh-brackish water-bearing zones. The lower sub-aquifer is located at depths range from 360m to 400m, with extra saline water characteristics rather than the upper ones, with TDS variance from 600-1425mg/l. The results displayed the dominance of Alkaline earth (Ca2+ and Mg2+) and strong acids (SO42− and Cl−) in most water samples. The concentrations of major ions are CaeCl (34%), NaeCl (30%), NaeSO4 (10%), CaeHCO3 (8%), CaeSO4 (8%), NaeHCO3 (8%) and MgeSO4 (2%). The low electric conductivity (EC) values point to good, permissible, and doubtful Water. The total hardness (TH), established from the calcium carbonate concentration, categorize the ground water into hard to very hard. Water quality indices include such : sodium content (SC) ; Chloro-alkalinity index (CAI) ; sodium adsorption ratio (SAR) ; and Corrosively Ratio (CR) appraise the suitability of groundwater for municipal activities, agricultural purposes and irrigation utilities. Preceding exploitation further studies and simulation are highly recommended to establish a sustainable level of abstraction besides assessing the vulnerability to protect from pollution. The results of the geophysical borehole logging provide significant information about the dominating lithological nature, litho-stratigraphic zonation, hydrogeologic property assessment and salinity patterns. This leads to zoning the penetrated section into discrete intervals with distinctive properties porous aquifer and low porosity zones (aquitard), identification of permeable and impermeable zones assignment to groundwater resources and groundwater quality reserve, control of completion and production. The production of ground water from a potential water bearing aquifer can affect sustainable development and country’s economics, it is significant to determine the bulk volume water (BMW) and whether the aquifer is at irreducible water saturation (Swirr) (capillary bound water) or contain free movable water.

Présentation étendue (EULC)