Integrated Spatiotemporal Assessment of Shallow Well Water Quality Using PCA-NSFWQI in Tunduma Town, Tanzania

Understanding the seasonal controls and contamination pathways affecting shallow groundwater in rapidly urbanising environments remains a major scientific and public-health challenge in East Africa. This study applied an integrated multivariate approach particularly Principal Component Analysis (PCA) as well National Sanitation Foundation Water Quality Index (NSFWQI) to characterise the spatiotemporal dynamics of shallow well water quality in Tunduma Town, Tanzania, where groundwater serves as a primary domestic source but remains highly vulnerable to sanitation and land-use pressures. Monthly samples were collected from five shallow wells (WW1,WW2, WW3, WW5) between June 2022 and May 2023 and analysed for physicochemical and microbial parameters using standard APHA (2017) procedures. Results revealed strong seasonal contrasts, with microbial and nutrient contamination markedly elevated during the rainy season. Faecal coliforms reached 5 CFU/100 mL and total coliforms 18 CFU/100 mL in WW3, exceeding WHO and EAS limits of 0 CFU/100 mL. Phosphate concentrations rose above 2.5 mg/L in WW4 and WW5 dramatically surpassing the eutrophication threshold of 0.1 mg/L while nitrate levels similarly increased during peak rainfall months. In contrast, dry-season samples showed lower microbial loads and more stable physicochemical behaviour. PCA effectively separated contamination-dominated wet months from baseline dry months, identifying rainfall-driven runoff, pit latrine seepage, and inadequate sanitary protection as dominant pollution drivers. NSFWQI scores ranged from Excellent (18.6 to 23.4) in relatively protected wells (WW5) to Medium (57.0 to 65.4) in vulnerable wells (WW3). By integrating PCA with NSFWQI, the study provides a rigorous framework for diagnosing contamination sources, quantifying overall water quality, and informing groundwater safety planning. The findings emphasize the urgent need for enforced sanitary setback distances, improved well construction, and targeted seasonal monitoring to safeguard shallow groundwater resources in Tunduma and similar tropical urban environments, supporting progress toward Sustainable Development Goal 6 (SDG 6).