Possible Sources of Salinity in the Upper Dibdibba Aquifer, Basrah, Iraq

Salinity increase in groundwater was investigated in the area between Al-Zubair and Safwan, and close to the Khor Al-Zubair Channel of southern Iraq. Thirty-nine groundwater samples from the shallow aquifer and one sample from the Khor Al-Zubair Channel were analyzed. The mean total dissolved solids are 7556 mg/L. The delta H-2 and delta O-18 plot in two groups are below the global meteoric water line. Group A indicates the evaporation effect of irrigation return-flow, while group B is characterized by depleted delta O-18 values due to recharge under colder climate. Deuterium excess values plot within the region of modern precipitation and dilution of groundwater by precipitating water. The groundwater residence time is between 1000 and 2000 years and combining C-14 -age with SO42- shows a contrasting effect on groundwater on both sides of Khedr Almai Fault and the Zubair anticline, which indicates the role of these geological structures on the hydrochemical evolution in the western part. Jabal Sanam shows no clear effect in this regard. The ratio Cl-/Br- and sulfate in groundwater showed that the measured salinity in groundwater is the result of a mixing process between groundwater, seawater intruding from Khor Al-Zubair Channel, and water from septic tanks in addition to dry and wet sea spray, and irrigation return-flow.

Automated summary

Groundwater salinity increase in southern Iraq is mainly the result of a mixing process between groundwater from various sources, with influences from seawater intrusion, septic tanks, sea spray, and irrigation return-flow.