Hydrogeochemical and stable isotope characteristics of the Shinile and Fafen-Jerer catchment of eastern Ethiopia

Abstract

Abstract The use of tracers, particularly isotope geochemistry tracers, is the most efficient method for understanding and providing fresh perspectives on hydrologic processes. The purpose of this study is to determine the stable isotope and geochemical characteristics of groundwater alluvial aquifers in eastern Ethiopia. Samples of water from rainfall, surface water, and groundwater sources were gathered and analyzed. The research discovered that EC, pH, and TDS fluctuated from 871 to 6090 μS/cm, 6 to 8.2, and 558 to 3898 mg/L, correspondingly. In both regions major cation and anion concentrations fall in the order of Ca2+ > Na+ > Mg2+ > K+ and SO4 2− > HCO3 − > Cl− > NO3 − respectively. The most common water types are mixed Na-Mg-Ca, Ca-Cl, Na-Cl, and Ca- HCO3 −. Hydrogeochemical experiments revealed that carbonate and silicate weathering and ionic exchanges primarily govern the supply of important ions in the waters and the geochemical history. The stable isotopic compositions vary from − 2.772 to − 0.418 ‰ with a mean value of− 1.772 ‰, for oxygen and from− 10.37 to 1.01 ‰ with a mean value of− 4.306 ‰ for hydrogen. The results show precipitation has been found to have more enriched isotope compositions than groundwater. In other words, both the hydrogen and oxygen isotope of groundwater are depleted than the precipitation isotope composition. The findings contribute to our knowledge of the stable isotope and geochemistry and are useful in determining the primary compositions of groundwater, water type, and the hydrogeochemistry of semi-arid areas.

Keywords

• Stable isotope
• Geochemistry
• Gibbs plot
• Piper diagram
• Groundwater
• Alluvial aquifers