Seasonal subsurface water quality variation of physiochemical and bacteriological characteristics in Kamutwa-Kigali, Rwanda

The study was conducted to assess subsurface water quality on a seasonal basis in dry (January–February and June–August) and rainy (March and October–December) seasons. Samples were collected in the rainy and dry seasons of the year 2022. The results of this study were compared with global drinking water guidelines of the World Health Organization (WHO) to understand its status in terms of threshold levels of pollution and protect public health. Total hardness (TH), pH, alkalinity, electrical conductivity (EC), total dissolved solids (TDS), nitrate, sulfate, heavy metals (Zn, Mn, and Fe), fecal, and total coliforms were examined, and the water quality index (WQI) was calculated to assess the level of water contamination. The results indicated that during the rainy season, all physiochemical parameters gradually increased and the values were well within the permissible limit as prescribed by the WHO. The bacteriological test showed that there were no fecal coliform (FC) and total coliform (TC) in all trials performed, and the calculated WQI showed excellent water quality characteristics and thus proving fit for human consumption.