Lake Turkana, major Omo River developments, associated hydrological cycle change and consequent lake physical and ecological change

Abstract

Abstract This study aimed to explore Lake Turkana's ecological reliance on hydrology and to determine the hydrological changes and consequences arising from the major hydropower and irrigation developments in the lake's basin. The major developments on Ethiopia's Omo River are especially significant as this river provides over 80% of the lake's annual freshwater influx and associated nutrients. The cascade of hydropower dams permanently dampens the natural hydrological cycles and lake level variability. The driving force of the flood influx to the lake is curtailed and the pattern of lake currents will adjust. Ultimately 80% of the river inflow to the lake will be regulated. Large volumes of water are required to initially fill the hydropower dam reservoirs. During 2015–16 when the huge Gibe III reservoir was filled, Lake Turkana's water level declined 2 m. The study has shown that large-scale irrigation schemes in the Lower Omo can potentially abstract 50% of the Omo River water, and that this would cause the lake level to shrink permanently to the detriment of the lake ecology. Possible lake level drops of over 15 m are demonstrated. The basin's natural capital is being replaced by large-scale plantation developments. The hydrological changes are drastic and the ecological consequences on Lake Turkana have not been fully understood. Without serious mitigation measures, Lake Turkana is a potential African Aral Sea disaster in the making, emulating what has happened to other great lakes such as Lake Chad.