Friends of Lake Turkana, a Kenyan organisation representing indigenous groups in northwestern Kenya whose livelihoods are dependend on the Lake Turkana, had previously estimated that the Gilgel Gibe III Dam could reduce the level of the lake by up to 10 meter affecting up to 300,000 people. This could cause the brackish water to increase in salinity to where it may no longer be drinkable by the indigenous groups around the lake.

Currently, the salinity of the water is about 2332 mg/L, and it is estimated that a 10-meter decrease in the water level of Lake Turkana could cause the salinity to rise to 3397 mg/L. Raising salinity could also drastically reduce the number of fish in the lake, which the people around the lake depend on for sustenance and their survival. According to critics, this "will condemn the lake to a slow death."