Evaluation of the impacts of turbidity on Gilgel-Gibe I reservoir storage, Omo-Gibe River Basin, Ethiopia

Quantity and quality of the water held in the reservoir fluctuates due to turbidity alterations. The influence of turbidity on the amount of the water held in a reservoir was described explicitly in this research. This study aimed to evaluate turbidity's impact on the Gilgel-Gibe I reservoir water. The samples were obtained by longitudinally stratifying the reservoir water throughout its course. Ten burrowed pools wrapped in transparent white plastic were used to retain water, for detection of the association between turbidity and surface water temperature, and to demonstrate the vertical variation in water temperature. The pan evaporation rate was measured using two Class A pans placed in the field to indicate the disparity in the amount of water evaporated from reservoir owing to reservoir turbidity variation. SPSS and MS Excel spreadsheet softwares were used to analyze the data. According to the results of this study, turbidity and water temperature have a significant direct relationship that is positive at 9:00 and 13:00 and negative at 17:00 observation hours. From the top layer of pool water to the bottom layer, the water temperature decreased vertically. Intensity of the light rays absorbed and scattered alters with turbidity variation and significant amounts of light rays was absorbed and scattered in the most turbid water. The reported water temperature differences between the top and bottom layers at 13:00 observation hour were 9.78 °C and 1.53 °C, for the most and least turbid pool water, respectively. Turbidity directly affects reservoir water by increasing both the water temperature and evaporation rates. Among all turbid-water samples, substantial quantity of water evaporated from the most turbid-water. For the most and least turbid water samples, the volume difference of the evaporated water from the reservoir was approximately 65.812 m³. According to these findings, if the reservoir water turbidity increases, the amount of water held in the reservoir significantly reduced due to substantial water loss.