Assessment of Temporal Variations in Shallow Well Water Quality Using Graphical Analysis and Water Quality Index in Half-London Ward, Tunduma, Tanzania

Abstract

Shallow wells are vital for water supply in regions lacking centralized systems, but they are highly susceptible to contamination from anthropogenic activities and natural processes. This study investigated seasonal variations in water quality from five shallow wells in Half-London Ward, Tunduma, Tanzania, over a 12-month period to assess biological, chemical, and physical parameters, identify contamination drivers, and propose sustainable management solutions. Using WHO and EPA guidelines, monthly water sampling was conducted from June to May. Parameters analysed included faecal and total coliforms, nitrate, phosphate, total iron, Biological Oxygen Demand (BOD), pH, electrical conductivity (EC), turbidity, Total Dissolved Solids (TDS), and Total Suspended Solids (TSS). The National Sanitation Foundation Water Quality Index (NSFWQI) was employed to classify seasonal variations in water quality. Results revealed significant seasonal trends. Microbial contamination peaked during the rainy season, with shallow well WW3 and WW5 recording faecal coliform levels of 5 CFU/100 ml and total coliforms of 18 CFU/100 ml, exceeding WHO and East African Standards. Phosphate levels in shallow well WW4 and WW5 exceeded the threshold of 2.2 mg/l, attributed by agricultural runoff. Elevated iron concentrations (1.85 mg/l) in WW4 reflected natural geological leaching. BOD and turbidity increased during wet periods due to organic pollutants and sediment influx, while physical parameters such as pH and TDS remained within permissible limits. The NSFWQI ranged from "Excellent" (18.6) in shallow well WW5 during winter to "Medium" (65.4) in shallow well WW3 during summer, highlighting contamination risks from surface runoff and poor land management. The study concludes that rainfall and proximity to pollution sources significantly impact shallow well water quality. It recommends implementing community-driven sanitation measures, protecting shallow wells, and conducting routine monitoring. These findings provide a framework for improving groundwater quality for domestic use in urbanizing regions globally.