Analysis and evaluation of the spatial and temporal variabilities of river water quality parameters

This study aimed to analyze the status and evaluate the spatiotemporal variabilities of water quality in the Awash River, Ethiopia. The study also aims to identify the origin and geochemical composition of the river water. Temporal variabilities of similar water quality parameters in the Lake Beseka, a dramatically rising lake (0.2 m/year) in the Awash River basin, which is being channeled into the Awash River system in order to control the lake level rise, were also considered in this study. To do this, laboratory measurements and a 10-year consecutive record of physicochemical parameters, major ions, nutrients and minor ions of the Awash River and Lake Beseka waters, graphical methods and factor analysis approaches were used. The origin of the Awash River was found to be shallow-medium depth aquifer with a geochemical composition of Ca(HCO3)(2) and NaHCO3, while the origin of Lake Beseka was found to be deep, ancient groundwater with a geochemical composition of NaCl and NaHCO3. However, mixing the lake water with Awash River in the downstream sites shifted the geochemical composition of the river water to a mixture of Ca(HCO3)(2), NaHCO3 and NaCl water types. The results also showed that the river water quality varies spatially and temporally, controlled by three major factors: the combined effects of anthropogenic activities and mineral dissolutions (Factor-1), anthropogenic activities and ion exchange (Factor-2) and ion exchange (Factor-3). While Factor-1 was the main controlling factor of the river water quality, and Factor-3 was the least, all three factors equally controlled the temporal variabilities of water quality in Lake Beseka. The observed temporal and spatial variabilities of the river water quality suggest that frequent water quality evaluations are important in designing appropriate water management strategies in river systems near intensive agricultural, industrial, and urban development areas.