Ethiopia's GIBE III hydropower dam is now operational. However, rights groups have raised concerns over the impact that it is having on downstream communities and the environment. The Conversation Africa's Samantha Spooner asked expert Sean Avery about the dam and the huge controversy that has surrounded this project.
Why was the dam constructed?
Ethiopia's highlands enjoy high rainfall that generates huge rivers, with much of this water flowing out into other countries. This includes almost 70% into the Nile Basin and 14% to Kenya's Lake Turkana.
Because of this huge resource, the country's hydropower potential, at 45,000 MW, is the second highest in Africa, second only to the Democratic Republic of Congo.
Hydropower is a renewable energy resource. Dams are constructed to raise the river's water to a high level for release to drive turbines within the dam's power station that generate electricity.
Ethiopia is the second most populous country in Africa and is developing its hydropower potential to meet its domestic electricity demand and also to export power to neighbouring countries. It is developing various sources, including the Omo-Gibe basin's potential through the Gibe cascade of hydropower dams along the length of the Omo river.
Gibe III is the most recently commissioned project in the Gibe cascade and at 243m height is the tallest dam in Africa. Its power station's installed generating capacity of 1,870 MW is not far short of the electricity generating capacity of the whole of Kenya in 2015 - 2,295 MW.
How long did it take and how much did it cost?
The dam construction started in 2006 and was officially inaugurated in December 2016.
The project cost is stated to be 1.47 billion Euros (USD$1.75 billion) with funding coming from the Government of Ethiopia and Exim bank of China.
What is it expected to produce in terms of energy output and which countries are set to benefit?
Gibe III's powerlines will feed into the Ethiopian national grid and onwards to the southern African electricity grid through Kenya. Gibe III will contribute roughly half its power output of 1,870 MW to Ethiopia itself. The rest will be exported to neighbouring countries - namely, 500 MW to Kenya, 200 MW to Djibouti and 200 MW to Sudan.
The project has been labelled as the "world's most controversial dam", why is this?
At the start, the procurement of the dam contractor was determined to be non-transparent by the World Bank, and international donors shunned the dam. Construction also started without a license from Ethiopia's Environmental Protection Agency.
There have since been ongoing complaints about environmental and social impacts downstream, including villagisation and displacement of indigenous people.
There is also controversy regarding Kenya's Lake Turkana. This is because the Omo river, on which Gibe III dam is built, is its umbilical cord. 90% of the inflow to Lake Turkana depends on the river, which conveys fresh water and vital nutrients (such as nitrogen) that sustain the lake, and whose floods provide stimulus for fisheries breeding.
At least half a million people depend of the lake. Lake Turkana is also the world's largest desert lake and has three national parks that together form a World Heritage site. Due to these concerns, the Friends of Lake Turkana Trust challenged the project in Kenyan Courts, but the case stalled.
The project also lacked adequate social and environmental assessments. A downstream environmental and social impact assessment was produced three years after construction started, but it didn't study its impact over the border in Kenya, and wrongly stated that the dam would create a positive water balance for the lake with consequential irrigation abstraction impacts on the lake were not not taken into account.
There were independent efforts by international donors, namely the European Investment Bank and the African Development Bank, to assess the impacts of the project. But these were gazumped when Chinese donors agreed to fund the power station. The Chinese donors did no independent environmental or social reviews.
A final controversy is that the Omo's cascade of power stations has replaced the river's natural flow cycle with regulated, man-made cycles. These depend on the electricity demands from the Ethiopian national electricity grid and its international connections. A consequence of this is that the river's annual floods are smoothed out and the low flows will be increased.
It has been claimed that this flood management is beneficial as floods can lead to loss of life. However, local people in Lower Omo depend on the annual flood, as they traditionally cultivate the riverbanks following inundation by the flood.
What will its impact on the environment be?
There are serious environmental concerns.
Firstly, Gibe III's flow regulation and water abstractions will permanently alter the Omo's natural hydrology. This will potentially destroy Lake Turkana's ecology and fisheries.
Secondly, Gibe III's river regulation has enabled irrigated plantation development. A potential of 450,000 hectares of agricultural development in the Omo-Gibe Basin has been mentioned. So far, 100,000 hectares from within the Omo and Mago National Parks and Tama Wildlife Reserve are being developed into sugar plantations. And downstream, 50,000 hectares has been allocated to a foreign cotton plantation developer. There will be other schemes requiring water too.
Through abstracting irrigation water, these plantations will deplete the Omo river influx to Lake Turkana. The lake is already semi-saline, said to be on the salinity brink for some species, and depletion of inflows will increase the salinity levels. Also, chemical releases from plantation developments may adversely affect the lake.
Thirdly, the dams will cause a massive drop in Lake Turkana's water level. When the Gibe III reservoir was filled in 2016, it caused the lake to fall two metres. The Gibe IV dam, also called Koysha, will be next in the Gibe cascade to be built, and this in turn will deplete the lake by 0.9 metres during its filling, forecast for 2020.
In 1996, the Omo-Gibe River Basin Integrated Development Plan had forecast that the Basin's water demand in 2024 would require 32% of river's discharge, 94% being for irrigation purposes. This is becoming a reality, with recent studies demonstrating that as a consequence, the lake level could fall 10-20 metres. As the lake is on average about 30 metres deep, the potential environmental consequences are significant.
And what of the future for Lake Turkana?
Warnings of environmental impact have been sounded for decades. The Omo-Gibe River Basin Integrated Development Plan had in 1996 warned that a bilateral agreement was needed between Kenya and Ethiopia before tampering with the Omo river discharges.
Time will tell, but at least there is now a trans-boundary forum brokered by UNEP, albeit belated, and somewhat lethargic in its progress. It is hoped that this initiative will be sustained and will critically review the development options and impacts.
Sean Avery is affiliated with; University of Leicester, Water Resource Associates, GIBB Africa Ltd, Kenya Wetlands Biodiversity Research Team and National Museums of Kenya