Hydro-chemical Evolution of Groundwater in Modjo River Basin, Central Ethiopia, Using Conventional and Multivariate Techniques

Abstract

Groundwater is a vital resource in the Modjo River Basin of central Ethiopia, meeting the water demands for domestic, agricultural, and industrial uses. This study aimed to assess the hydro chemical characteristics and evaluate the processes controlling the groundwater chemistry in the Modjo River Basin using conventional and multivariate techniques. These water samples were collected from 79 groundwater points from different places and analyzed for major ions and physicochemical parameters in Engineering Corporation of Oromia (ECO). The result reveals that sodium ion is the dominant cations followed by calcium in the groundwater of the study area. NO3− concentration ranges from 0.03 mg/L to 85.5 mg/L in all water samples, however, high amount of NO3− contents are observed in one deep well with a concentration of 85.5 mg/l(MM-9). The F− concentrations varied from 0.07 to 1.9 mg/L in all water samples in the study area except for two deep wells that exceeds WHO standards. The results showed that the groundwater is predominantly of calcium-magnesium-bicarbonate type. Groundwater in the Modjo river catchments shows systematic hydro-chemical evolution from Ca-HCO3 to Ca-Na-HCO3 to Na- Ca-HCO3 type water along the flow path from the upper part of the catchment to the lower part of the catchment. Interpretation of hydro-chemical data suggests that silicate hydrolysis and cations exchange are the major geochemical processes that control the hydrochemistry of the groundwater in the basin. With its integrated approach, this study provided valuable insights into the hydro-chemical evolution of groundwater in the Modjo River Basin, which can guide future groundwater development and management strategies.