Abstract
Rivers are among the most vital freshwater resources supporting mining and sugar processing industries. In Kenya, River Kuja plays a crucial role in sustaining industrial, agricultural, and domestic activities. However, increasing industrial activities related to artisanal gold mining and sugar processing runoff have severely affected the river’s water quality. This study was therefore undertaken to assess the impacts of mining and sugar processing activities on the physicochemical parameters and nutrient loads of River Kuja, thereby providing essential baseline data for sustainable watershed management. Water samples were collected weekly from nine sampling stations along the river, immediately upstream and downstream of major mining and sugar processing zones. Samples were analysed for temperature, pH, dissolved oxygen, electrical conductivity (EC), total dissolved solids (TDS), total hardness, alkalinity, Na⁺, K⁺, and ammonia. Descriptive and inferential statistics and multivariate analyses were applied to interpret spatial and temporal variations in water quality. The results revealed significant degradation of water quality downstream of mining sites. The mean pH was 5.8, indicating acidic conditions below the WHO-recommended range (6.5–8.5), suggesting acid mine drainage influence. EC and TDS showed a pronounced downstream increase (EC ≈ 1185 µS/cm; TDS ≈ 788 mg/L). There were high ammonia levels at the upstream in Macalder. The study concludes that mining and industrial activities are major contributors to River Kuja’s water quality deterioration. It underscores the urgent need for improved watershed management, stricter regulation of mining effluents, and adoption of sustainable land-use practices to safeguard this critical freshwater ecosystem.