Evaluating the potability of domestic water supply sources using water quality index in Kilombero district, Tanzania

ABSTRACT The decline in water quality in various bodies of water has led to significant health risks for individuals relying on these sources for drinking and domestic use. The prevalence of waterborne diseases in some areas is attributed by inadequate water quality assessments of supply sources. This study focused on evaluating the potability of domestic water sources in the Kilombero district of Tanzania, where approximately 70% of the population depends on untreated natural sources. Two models were utilized: the Weighted Arithmetic Water Quality Index (WAWQI) and the Canadian Council of Ministers of Environment Water Quality Index (CCME WQI), analysing 15 water quality parameters. The WAWQI identified three groundwater sources as poor quality for consumption, while indicating seasonal improvements in water quality – from 12 in the wet season to 13 in the dry season. Conversely, the CCME WQI classified all 15 sources as potable, with an increase in ‘Excellent’ ratings from 9 to 13 between seasons. The findings showed that all surface water sources were deemed potable, while 67% of groundwater sources met quality standards. The remaining 33% of boreholes were categorized as having poor quality. Overall, both models indicated better water quality during the dry season, with surface water generally exhibiting higher quality than groundwater.