Abstract
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•This research work is aimed at characterizing the aquifer of Hawssa city ground water system located in Ethiopian Rift valley in reference to fluoride ion concentration (F-) and Total dissolved solids (TDS). It focused on the area where high exposure to Fluoride ion leads to flourosis in its dental and skeletal forms on millions of people and animals.•Pumping test and drilling lithology data of the already drilled and productive wells are used for 25 boreholes in the city. The main water bearing geological formation in the groundwater system is classified along with the respective water bearing thickness .The spatial distribution of the two parameters along with the geochemistry of the ground water is analyzed and discussed to conclude the source and effect of the elevated concentration of the two drinking water quality parameters. The possible sources of the chemicals and the reactions that facilitate the cause are identified. To see the correlation between parameters, statistical analysis is conducted Using SPSS.•Based on this, the study concludes physical and practical solutions to minimize the effect of fluoride ion through drinking water from subsurface source. This work tries to bring the significance of deep cutting and blinding those aquifers with chemical effect to extract safe drinking water.
The Main Ethiopian Rift valley (MER) region, where millions rely on fluoride contaminated drinking water that is by far higher than the WHO standard resulting skeletal and tooth decay.
Pumping test and drilling lithology data of the already drilled and productive 25 wells (25 m–200 m depth) to characterize the aquifer. Particular emphasis is given to the spatial distribution of fluoride ion (F-) and Total dissolved solids (TDS) applying SPSS (Statistical Package for the Social Scientists) statistical tool.
The major water bearing formation is of weathered and fractured geologic formation having high porosity and permeability, which resulted in risk of shallow groundwater surface contamination. The concentration of fluoride ion, ranging from 0.65mg/l to 11mg/l is under significance influence by the geochemistry. Higher temperature at the shallow aquifer along with geological process like weathering of rocks and dissolution of CaF2 promotes the concentrated availability of fluoride ions. The deeper the strata along with igneous formation dominated by pumice, the lower the concentration showing strong inverse correlation with depth for both F- and TDS with R2 =0.78 and R2 =0.68 respectively at α< 0.001. Either drilling wells beyond such formations (=60m) or blinding the poor quality strata is recommended to minimize the effect of high fluoride and TDS concentration in drinking water for Hawassa city aquifer.