INTEGRATED ASSESSMENT OF THE HEALTH OF RIVER SOSIANI; KENYA

Abstract

This study set out to evaluate the effect of anthropogenic activities by analyzing the physical habitat characteristics, physico-chemical water quality parameters, macrophytes and macroinvertebrates as indicators of water quality degradation and to develop an integrated index to assess the health of River Sosiani from August 2012 to February 2013. Physical habitat characteristics were observed and measured by a tape measure and a GPS. Physico-chemical water quality parameters were temperature, pH, TDS and Conductivity measured in situ while TP, TON, BOD and DO were measured in vitro using standard methods. Protocols for identification of biological communities were used for macrophytes and macroinvertebrates. Physical habitat characteristics were more of destructive practices on the riparian zone of the river ecosystem. Physico-chemical water quality parameters‘ measurement were high during dry season than wet season, except for DO which was high in wet season. However, there was strong correlation of these parameters with the stations in both seasons except for pH (r = -0.017 and p = 0.948). Huruma and Maili inne stations were distantly related to the other stations in both seasons. Principal component analysis with component 1 explaining 60.5% variance and component 2 explaining 26.1% variance evaluated TON and TP as key pollutants in both wet and dry season, with BOD levels high at Huruma and Maili inne. Varifactor 2 that explained 35.3 % of the variance in wet season and 27.1% in the dry season had a strong negative factor loading of BOD (Wet; -0.878, Dry; -0.915) and also of TP (Wet; -0.839, Dry; -0.709) in both seasons. Varifactor 3 that explained 18.4% variance in wet season and 21.7 % in the dry season also had a strong negative factor loading of TON (Wet; -0.822, Dry; - 0.861) in both seasons. Macrophytes‘ abundance with TON and TP gradient was high at stations where concentration of the nutrients was also high. Macroinvertebrates‘ response of 25 families had a tolerance level to TP of 0.1 mg/l, 15 families had the same tolerance level to TON and similarly, 11 families to BOD. Habitat Index, Macrophyte and Macroinvertebrate Index were reliable in assessment of River Sosiani. Integrated Index for River Sosiani Health evaluated it in the range moderate to poor quality class. The study recommends for appropriate environmental management measures, continuous monitoring and awareness creation for all stakeholders. The index can be used to evaluate the health of rivers in the upper catchments of Lake Victoria Basin and other high altitude streams in Kenya.