Hydrogeochemical characterization of groundwater in fractured crystalline basement aquifers in Dodoma, central Tanzania: implications on water quality for domestic and irrigation applications

Abstract

Assessment of groundwater hydrogeochemistry characteristics of aquifers plays a vital role in establishing water quality status and its suitability for human and industrial use. The main objective of this research was to carry out hydrogeochemical characterization of groundwater and assess its impacts on water quality and spatial variability of groundwater geochemistry in Dodoma, Tanzania. The methods used include groundwater sampling, laboratory analysis to determine physico- chemical parameters and data processing to classify the groundwater hydrochemical facies. The results show that the average value for pH is 7.2, for electrical conductivity (EC) is 1108 µS/cm and for total dissolved solids (TDS) is 620.4 mg/L. The dominant ions in the groundwater are Na+, Ca2+, Mg2+, SO42-, Cl-, and HCO3-. The groundwater evolution in the study area is from Ca–Mg– Cl-SO4 and Ca–Mg–SO4 around the Mzakwe well-field, Na–K-Cl-SO4 in the Hombolo sub- catchment, Ca–Mg-HCO3 around the Ihumwa aquifer system and from Ca–Mg-HCO3 type in the Chamwino aquifer system. Water Quality Index (WQI) was found 113.12 and it indicates that the groundwater in the study area is of bad/poor quality; hence, some treatment techniques such as the use of reverse osmosis (RO) systems are necessary especially for domestic and drinking water to improve the quality so that groundwater becomes suitable for both domestic and irrigation use.