Effects of sewage waste disposal on the groundwater quality and agricultural potential of a floodplain near Jeddah, Saudi Arabia

The area of Wadi Bani Malik located to the east of Jeddah (Kingdom of Saudi Arabia) is commonly known as Al Misk Lake. It is one of the many floodplains present along the dry wadi beds. As the floodplains are cultivable areas irrigated by the shallow groundwater present in the alluvium, the quality of groundwater must be investigated before determining its irrigation potential. Historically, the area of Al Misk Lake remained a dumping ground for untreated sewage for many years. Although this activity has been abandoned, but leaching of contaminants might have contaminated the groundwater, and it is not clear how much of the area of Al Misk Floodplain has been compromised. To determine the effects of sewage waste disposal on the groundwater quality, this study was undertaken to evaluate the irrigation potential of the area. The investigation focused upon the hydrogeological and geophysical studies whereby 19 groundwater samples obtained from dug wells were analyzed, geochemically. Results of chemical analysis show that all the wells are contaminated with high concentration of major ions. Electromagnetic survey carried out at the site revealed that the longitudinal extent of the plume (in the direction of groundwater flow) is much larger than perpendicular to flow. Sodium adsorption ratio, salinity hazard, and sodium percentages were found to be much higher than the irrigation water quality standards thus making the Al Misk Lake area unsuitable for irrigation purposes.