Groundwater Evolution in the Multilayer Aquifers of the Mekelle Sedimentary Outlier (Northern Ethiopia): A Chemical and Isotopic Approach

The study aims to evaluate groundwater geochemistry characterization of multilayer aquifers of the Sedimentary Rock in Mekelle Outlier in order to gain knowledge on the dominant geochemical processes and water quality status. Groundwater samples were collected and analyzed for major ion chemistry and stable isotopes (δ²H and δ¹⁸O). The findings reveal that the sources of ions into the groundwater are controlled by the duration of the water-rock interaction in confined and semi-confined aquifers. The chemical facies of the water evolve from Ca–HCO₃ to Ca–SO₄ along the flow direction. The stable isotope of δ²H versus δ¹⁸O signifies a source of local meteoric water. The isotopic signature of few samples depicts the effect of the evaporation process prior to infiltration.