Groundwater quality evaluation for different uses in the lower Ketar Watershed, Ethiopia

摘要

Groundwater quality samples from 33 wells were collected in the lower Ketar watershed (Ethiopia) to study its suitability for domestic and irrigation purposes. Samples were evaluated for major ions and physicochemical properties. In 58% of the samples analyzed, Ca(2+)is the dominant cation and Na(+)dominates the remaining 42% of the samples. Among the anions found during analyzation, HCO(3)(-)is the solo dominant ion in all the wells sampled. The order of the concentration of the major ions was Ca2+ Na+ Mg2+ K(+)for the cations and HCO3- SO42- Cl NO(3)(-)for the anions. AquaChem analysis shows that Ca-HCO(3)and Na-HCO(3)are the major water types in the area. The analyses indicated that the dissolution of fluorite or fluorapatite is the possible source of the high fluoride concentration in the area. And, the interactions between water and rock and cation exchanges mainly determine the water quality. The suitability of the groundwater for use in irrigation was evaluated based on the salinity (EC), SAR, %Na, RSC, PI, KR, and the USSL Salinity diagram. The groundwater from most of the wells can be used for irrigation without any significant restriction except for a few of the wells downstream. Its suitability for domestic use was evaluated by comparing with the WHO standard limits. The parameters limiting the use of this groundwater for drinking purposes are F-(94%), HCO3-(45%), and Ca2+(33%). All the remaining major cations and anions complied with the WHO standard limits for drinking.