Hydrochemistry and geochemical evolution of unconfined aquifer in Kalal Badrah Basin, Wasit, East of Iraq

Abstract

Chemical composition of 38 groundwater samples from wells penetrating the unconfined aquifer of the Quaternary deposits throughout Waist governorate, east of Iraq, were analyzed to describe the hydrochemical behavior of this aquifer through the area. The hydrochemical parameters include the major cations and anions, TDS, EC, pH, as well as calculating Na%, Total Hardness (TH), and Sodium Absorption Ratio (SAR). Significant spatial variations in these parameters were noticed and Ca-SO₄ water type was found to be the predominant one. According to the available standards, the present study samples were unsuitable for drinking purposes but adequate for irrigation purposes depending on Na%, TDS, EC, and SAR values. Geochemical modeling approach enabled calculation of the saturation state of some selected minerals i.e. explaining the dissolution and precipitation reactions occurring in the groundwater as well as calculating the amount of mineral mass transfer of the selected mineral phases along some specific flow paths. Based on this approach, the present samples were found to be oversaturated with carbonate minerals and under-saturated with sulfate minerals. Strong correlations between the concentrations of SO₄ and the SI’s of sulfate minerals and weak correlation with carbonate minerals were observed. The present study revealed also that calcite precipitation and dissolution of dolomite and gypsum is the main chemical reaction controlling the chemical changes of the groundwater aquifer in the study area.

Keywords: Groundwater,  Water Suitability, Saturation Index, Inverse Modeling, Wasit, Iraq.