Geochemical evolution of spring waters in carbonate dominated aquifer in Upper Shirin Tagab sub-basin, northern Afghanistan

Abstract

Spring waters originates from carbonate aquifers provides substantial water for drinking and widely used for irrigation in Afghanistan. Thus, understanding hydrogeochemical evolution in carbonate dominated aquifer is important for sustainable groundwater resource management in the country. Therefore, in this study, water from springs and dug wells from carbonate dominated aquifers were investigated to study hydrogeochemical evolution in Upper Shirin Tagab sub-basin, Northern Afghanistan. This study reveals that water in the area mainly belongs to Ca-Mg-HCO3 facies type in Upper part and Mg-(Na, Ca)-SO4-(HCO3, Cl) in the lower part. The hydrogeochemical processes in the aquifer were found to be governed by dissolution of carbonate, gypsum and halite minerals. Results shows that the chemical composition of springs is primarily controlled by local geology and water-rock interactions of limestone and dolomite with minor effects of silicate weathering. The δ2D-H2O and δ18O-H2O of springs water shows wide variations and found in the range of −64.4 ‰ to −52.6 ‰ and −10.1 ‰ to −8.6 ‰, respectively. Stable isotopes of water indicate that the water in the study area receive recharge from infiltration of recent precipitation and showing less evaporative enrichment of heavier isotopes. Overall, the quality of groundwater is safe for drinking with respect to WHO guidelines but the aquifer is suspectable to anthropogenic contamination such as sewage sludge, excessive nutrients, sulfate and pathogens. Furthermore, findings of this study will be helpful for decision makers to develop a sustainable water resource management in Shirin Tagab sub-basin in Northern Afghanistan.