Impact of agro-industrial activities on the water quality of River Nyando, Lake Victoria Basin, Kenya

Abstract

The impact of agro-industrial activities on the water quality within River Nyando, Lake Victoria Basin was studied at different hierarchical levels between August 1997 and June 1999. Triplicate water samples were collected on a monthly basis from various stations ranging from the source to the mouth of the river and analyzed for selected physical and chemical water quality parameters using standard analytical methods. Statistical analysis was performed using MINITAB and STATISTICA computer packages. Agricultural land use was found to be the major factor contributing to changes in water quality. Salinity and pH varied at river basin scale, turbidity, TDS and conductivity at catchment scale, while DO, alkalinity and pH at subcatchment and river reach scale. The nutrient loads increased downstream. Anthropogenic sources contribute to high levels of nutrients within the basin. The changes recorded in water quality along the river were comparable to the modified Index of Biotic Integrity (IBI) and Nyando Habitat Evaluation Index (NHEI) derived for the river during the same period of study. Findings of this study can be used to design measures for mitigating and monitoring environmental impacts arising from agro-industrial activities within the Lake Victoria Basin. The study recommends a comprehensive Nyando River Basin Management Programme to address the multiple issues environmental within the basin.