Seasonal Assessment of Quality of Groundwater from Private Owned Wells in Unguja Island Zanzibar

Abstract

The Assessment of seasonal changes in groundwater quality is an essential aspect for evaluating pollution level which can be a reflection of the source environment and the activities of man, including the use and management measures. This study examined the effect of seasonal variation on the physical, chemical, and biological properties of groundwater in the Bububu constituency which is located in the West district within the Urban –West region of Unguja Island. The study was conducted using cluster sampling. Four clusters with a large number of wells were selected for further analysis. The number of wells from each cluster was sampled for physicochemical and bacteriological contamination levels. Samples were collected in two different seasons (Wet and Dry) to allow comparison between the two seasons. Analysis of water samples (N= 52) indicated that the sources are very vulnerable to microbial contamination particularly during the wet season at which 78.85% of the analyzed samples were contaminated with fecal coliform and unfit for human consumption. However, all measured physicochemical parameters were within the acceptable range except the levels of nitrate during the wet season in some samples taken at Kibweni and Sharifumsa which exceeded the recommended level by WHO. There is a need for adequate treatment of water particularly during the wet season as well as serious monitoring and proper regulation by the appropriate authorities to curb the menace and safe guard the lives of people to prevent a possible epidemic.