In the light of progressive depletion of groundwater reservoir and water quality deterioration of the Wadi Marwani alluvial aquifer, an investigation on chemical data of dissolved major and minor constituents in 16 recent groundwater samples was performed. The main objective was the detection of processes responsible for the geochemical evolution and mineralization throughout the area. Wadi Marwani is one of the most important wadis in the central western part of Suadi Arabia to the northeast of Jeddah City. It is intensively inhabited during the last decenniums, leading to expansion of the residential and agricultural areas. The recharge rate of the shallow unconfined aquifer of Wadi Marwani was estimated to be 18% of the annual precipitation using the chloride mass-balance method. Groundwaters of the study area are characterized by the dominance of Ca + Mg over Na + K. HCO 3 was found to be the most dominant anion in the upstream and replaced by Cl towards downstream reflecting geochemical evolution along flow path and the influence of agricultural activities and residential areas. TDS is positively correlated with most of major ions, which suggested the impact of agricultural activities on groundwater chemistry through leaching of readily soluble salts from the soil zone. NO 3 and TDS showed similar trend which suggested leaching of nitrate fertilizers applied in the agricultural areas. Anomalously high nitrate concentration in few water samples is mainly attributed to leakage of domestic wastewater from the residential area that is very close to these wells. Fluoride concentration showed uniform spatial distribution, which revealed that it is mainly derived from dissolution of silicate minerals forming the aquifer matrix. Most of the groundwater samples are undersaturated with respect to the common carbonate and sulfate minerals, whereas oversaturated with respect to quartz and chalcedony.Groundwater quality assessment revealed that the groundwater can be safely used for drinking. However, further microbiological examination should be carried out where signs of sewage contamination were detected.

No abstract

No abstract

No abstract

A classification approach has been implemented in the present work by integrating traditional water sample analysis methods and Geographic Information System (GIS) capabilities in order to classify zones with acceptable groundwater quality for drinking. GIS extrapolation capabilities with their multi-conditional layering facilities were integrated together in order to assess in the determination of areas suitable for drinking purposes. This technique was implemented in Wadi Rabigh, Western Saudi Arabia, due to its significance as one of the most promising areas in the Western Province in the Kingdom of Saudi Arabia, owing to the establishment of King Abdullah Commercial City and King Abdullah University for Science and Technology (KAUST) nearby. Results show that only a limited area in the aquifer can be used for domestic purposes. This area is located in two separate patches in the upstream part of the aquifer while most of the aquifer water is categorized as brackish which might be used for agriculture purposes to a certain extent. The downstream area of the aquifer is very saline due to sea water intrusion effect.