Application of water quality index to assess water quality in river chania, kiambu county, kenya

ABSTRACT

Human-related activities are known to have deleterious effects on the water quality of aquatic ecosystems globally. However, there is limited information on the impact of similar perturbations in tropical regions, especially the River Chania in Kiambu County, Kenya, which is an important source of water for humans and animals and also provides habitat for a variety of flora and fauna along its length. The aim of this study was to determine the spatial and temporal variations of selected water quality parameters in seven sampling sites along a section of River Chania, to evaluate water quality of the river using Water Quality Index (WQI) and to assess the effect of socio-economic factors on water quality of the river. The study used a longitudinal study design in water sample collection. The sample collection was done between October 2018 and February 2019 to cater to the dry and wet seasons. A paired t-test (p< 0.05) was used to compare the water quality variables collected in both the wet and dry seasons across sites to see if these differed longitudinally down the river. The data were subjected to analysis of variance (ANOVA) using Statistical Analysis Software (SAS) version 9.2 and means separated using LSD at p< 0.05 confidence level. The mean values of the physico-chemical parameters were compared with the World Health Organization (WHO) water quality guidelines. The parameters used to compute WQI were nitrates, Total Dissolved Solids (TDS), potassium, sulphates, chlorides, copper, manganese, pH and total phosphates. The study revealed a decline in water quality from the most upstream site (Site 1) from excellent (WQI=23.17) to poor (WQI=>50) and very poor (WQI=>76) water quality at the two downstream sites during the wet season. On the other hand, the socio-economic factors were assessed using a survey employing cross-sectional survey design. The study observed that the education level of the respondents was a positive and significant predictor of the ability of an individual to identify water quality changes in River Chania in the last 10 years with an associated significance of 0.014. Age, household size, change in household number, gender and household income had no significant correlation with the identification of water quality changes in River Chania in the last 10 years. The study recommends that the riparian zone of River Chania, especially at downstream sites, should be protected from interference by human activities (e.g., deforestation, farming) and human interactions with the river ecosystem should be regulated for sustainable utilization, hence protect the water quality from further deterioration. Further research can be conducted to develop models for predicting water quality of the river over time.