The UN Educational, Scientific and Cultural Organisation’s World Heritage Committee expressed concern about the disruptive effect of Ethiopia’s Gibe III dam “on the flow and ecosystem” of Lake Turkana downstream.
The impact “poses further threat to the site,” Unesco said in a statement on Thursday issued from Bahrain.
Located in northwestern Kenya and known as the Jade Sea, Lake Turkana is the most saline lake in east Africa and the largest desert lake in the world.
Its islands are breeding grounds for the Nile crocodile, hippopotamus and several snake species while the lake itself is important to migratory birds.
The area is also a possible site of mankind’s birth, hosting the fossil deposits at Koobi Fora.
The remains of many early hominins have been found there, including Australopithecus, Homo habilis, Homo erectus and Homo sapiens.
“The Koobi Fora deposits, rich in mammalian, molluscan and other fossil remains, have contributed more to the understanding of paleo-environments than any other site on the continent,” says Unesco.
“The geology and fossil record represents major stages of earth history,” it adds.
The lake itself is 249km long and 44km wide while the protected area, known as Lake Turkana National Parks, comprises three adjacent reserves – Central Island, South Island and Sibiloi parks – covering a total area of 161 485 hectares.
The lake, however, is endangered primarily by Ethiopia’s construction of a hydroelectric and irrigation dam on the Omo River, which replenishes the lake seasonally.
The dam threatens to disrupt seasonal flooding that is essential to the reproductive cycle of the lake fish, with an estimated 300 000 people depending on fishing Turkana for their livelihoods.
The irrigation project is also expected to significantly reduce the total amount of water entering the lake.
Many fear that the two Omo River projects will cause the lake level to reduce dramatically – by several tens of metres – echoing the environmental disaster previously seen in the Aral Sea, in Central Asia, which dried up after its feeder rivers were diverted for irrigation schemes.
Unesco opposed the Gibe III dam, Africa’s highest at 243 meters, which was inaugurated at the end of 2016 and also serves to water vast new sugar cane plantations.
“The dam’s impacts on the lake water levels are already becoming evident,” Unesco warned.
“The data provided shows an overall rapid decline in water levels since January 2015 when the impounding of the Gibe III reservoir commenced, and that seasonal fluctuation patterns have been heavily disrupted.”
Unesco lamented the absence of proper environmental assessments and warned of “potential downstream impacts on [Lake Turkana], such as reduced water flow and contamination from fertilizers and pesticides”.
“Although the scale of the project has been reduced, it is likely to increase water consumption from the Omo River,” it added, meaning less water reaching the lake.
The southern part of Ethiopia’s Omo Valley is also designated a World Heritage Site.
In Kenya, Richard Leakey, a renowned palaeoanthropologist and conservationist, welcomed the endangered listing but doubted it would save the lake.
“I think the more attention we can get for the plight of Lake Turkana the better, but I don’t think necessarily that Unesco can do anything for Lake Turkana,” Leakey told AFP.
“Unesco declared it a world heritage site many years ago, (but) the situation in Turkana continued to get worse not better,” he said.