Multiple benefits20 September 2010
Hydro and multipurpose projects are being sought more due to climate concerns and are vital in regions of high water stress, such as Ethiopia. Report by Patrick Reynolds
A multiplicity of water needs can be served by hydro and multipurpose projects, and in the near- to medium-term there is going to be relatively greater demand to employ them as an adaptation strategy to the anticipated increase in weather instability, as projected from the effects of climate change, notes The World Bank Group in its Directions in Hydropower report, which was published last year.
The World Bank says it ‘is keenly aware of this timely and important period for hydropower’ though adds that this particular use of water resources will be only part of the picture in future. It says that given the increasing importance of climate change, water security, and regional cooperation, the bank has consequentially a wider view that ‘encompasses water infrastructure that serves multiple objectives, among which energy may be a subsidiary goal’.
The Directions report adds, ‘As part of a flexible, well-planned water resources infrastructure, hydropower can help countries manage floods and droughts and improve water resources allocations across a complex set of users’.
It goes on, ‘Multipurpose hydropower can also support adaptation to increasingly difficult hydrology by strengthening a country’s ability to regulate and store water and so resist flood and drought shocks.’
But before facing any climate change impact on hydrology, some countries are already experiencing great water-stress, prime among them being Ethiopia, Haiti and Niger, the World Bank said in March, when releasing an internal review of support given to water-related activities over 1997-2007. Almost a third of all projects worldwide approved by the World Bank for funding since 1997 have been water-related.
In every country, from the most water-stressed to those far less strained – possibly even with an abundance of hydrological resources, there is far more attention demanded, and being given now, to a wider range of planning factors, including strategies being developed around river basins, large and small. One such major planning initiative is underway for the river Nile – the world’s longest – and its many regional, national and local sub-catchments.
The Nile & Ethiopia
Africa holds immense untapped water resource and hydropower potential, and yet in the north it also has some of the most water-stressed regions anywhere. Also in the north is the Nile, one of the world’s longest rivers, and in the Horn of Africa is Ethiopia which, despite facing significant water-stress, ranks as one of the countries on the continent with most hydropower potential, notes its Ministry of Water Resources (MoWR).
The Nile Basin Initiative (NBI) was established just over a decade ago and is one of the largest river basin strategies in the world. The Nile’s extensive catchment area extends over parts of many countries in northeast Africa. Draining through Egypt to the Mediterranean Sea, south of Sudan the river is fed by two branches – the White Nile, which arises in east central Africa, and the Blue Nile, which rises near Lake Tana in the highlands of Ethiopia.
With so many competing visions and needs for the water resources, and the cross-border nature of the flows, it is vital to have co-operation. Like so many river basins elsewhere, the need for effective partnerships and co-operation will become increasingly important when countries and people become presented with weather instability and other foreseen impacts from predicted climate change.
NBI provides a mechanism for the shared visions, and needs, to have the Nile basin developed to deliver multiple and widespread benefits. Having formally launched the Initiative in 1999, the participating countries held their 18th Council of Ministers meeting in late June this year, in Addis Ababa, Ethiopia. The Council leads the NBI to help deliver the socio-economic benefits that are commonly, and separately, sought while helping to promote peace and security in the region where water is relatively scarce.
The development efforts on the White Nile and Blue Nile are handled under two units within NBI – the Nile Equatorial Lakes Subsidiary Action Programme (SAP) and the Eastern Nile Subsidiary Action Programme (ENSAP), respectively.
Ethiopia has 12 basins – eight river basins, one lakes basin and three that are, in effect, dry as they have insignificant flows, if any, says MoWR. Under NBI, developments in water-stressed Ethiopia fall within the function and partnership discussions enabled by ENSAP.
There have been a range of water projects developed over many years, both prior to and since NBI was established. A number of countries and foreign firms have worked on plans and schemes, and over the last couple of years the Norwegian Water Resources and Energy Directorate (NVE) has been measuring sediments and hydrology to support reservoir development on the Blue Nile, which is known as Abay in Ethiopia.
Presently, there are a series of hydro, multipurpose and various other water schemes either in studies, construction or operations, and these include the multipurpose Mandaya and Beko Abo projects, the Genale-Dawa basin development, the Gilgel Gibe III addition to the Gibe cascade scheme, and the Beles Multipurpose (Beles II) project.
Mandaya & Beko Abo
The Mandaya and Beko Abo projects are being studied as potential major developments, some 300km apart, on the Blue Nile in west/central Ethiopia. While they are being examined together and would be neighbours in the river basin, and operationally they would influence each other, the projects would be developed separately.
The study into the projects is being undertaken by a consortium of companies comprising consultants Norplan/Multiconsult, Norconsult and Scott Wilson with energy utility Electricte de France (edf). They are being supported by local firms Shebelle Consult and Tropics. The work is to be completed by mid-2012.
In the study, a full technical and economic assessment of the 2GW Mandaya project is being undertaken. The surface plant is envisaged to generate 12.100GWh per year. Planning for the 2.1GW Beko Abo scheme is proceeding with, first, a techno-economic pre-feasibility study. The Beko Abo underground plant would generate about 12,600GWh annually.
Both projects are anticipated to have large RCC dams, and at the Mandaya site the structure would impound a reservoir extending 300km upstream to the location of Beko Abo. The reservoir behind the Beko Abo dam would be about half the length, at approximately 150km long.
Mandaya was examined at the pre-feasibility stage by a joint venture of Scott Wilson and EdF, and they completed the work almost three years ago. Around the same time a separate JV of Norplan/Multiconsult, Norconsult and lahmeyer finished reconnaissance-level studies for Beko Abo.
The RCC dams to be built at Mandaya and Beko Abo have been estimated will be 200m and 285m high, respectively. At Mandaya, the structure will have a crest length of approximately 1400m and a volume of 13Mm3, and at Beko Abo the comparable figures are 880m and 10.5Mm3.
Bids are being sought by 31 August to undertake the geotechnical site investigation works for the studies underway for each project.
The Beko-Abo and Mandaya plans are complementary to the NVE’s technical support to MoWR for the Blue Nile measurement studies, which are part of the Joint Multipurpose Programme Identification Phase 1 (JMP1 ID) that is to develop an optimum cascade scenario.
Planning for development of the water resource of the Genale-Dawa river basin comprises studies for six potential projects ranging from irrigation (Lower Genale, Welmel), water supply (Negele Yabelo) and multipurpose hydropower (GD-3) to an integrated watershed management project (Bonora).
The studies are being advanced by MoWR, and planning has been underway over much of the last decade. The bulk of funding for the early studies was provided by the African Development Bank (AfDB), and the work was mostly carried out by consultant Lahmeyer with local firm Yeshi-Ber Consult. A separate task, to accelerate planning for the 357MW GD-3 project, was performed by consultant Ardico-Rodio through government resources.
In addition, Norwegian consultants Norplan and Norconsult undertook a feasibility study for the GD-6 multipurpose hydropower project, which is estimated to have an installed capacity of approximately 257MW in a surface powerhouse, an 18km long headrace tunnel and require a 39m high RCC dam. It is expected to generate 1230GWh of electricity annually.
AfDB notes that there have been expressions of interest from potential investors from Turkey, Japan and China for both the GD-3 and GD-6 projects and that they are ready for investment. It further notes that the Ethiopian government, in addition to fast-tracking the hydro projects, is pushing for rapid development of the Welmel irrigation and Negele water supply schemes, although it is the Lower Genale project that is furthest in the requirement for immediate investment.
The Genale-Dawa basin is estimated to have economically exploitable hydropower energy potential of 15.7TWh annually, says MoWR.
Gibe Cascade, Beles
The largest hydropower project under construction in Ethiopia is Gilgel Gibe III, the latest – though it won’t be the biggest – addition to the cascade development on the Omo-Gibe basin, which is one of the significant water resources in the country. There are four Gibe projects in the cascade and they constitute one of the country’s most attractive hydro developments, says EEPCo.
Gilgel Gibe III will have a surface plant with an installed capacity of 1870MW and housing 10 Francis turbines, which are to generate about 6400GWh of electricity annually from the reservoir that is be impounded by a RCC dam (231m high, 580m long). The average net head is 186m, the design flow is 950m3/sec and the plant load factor is 0.46. Extensive studies were undertaken to examine the environmental impact of the scheme and potential mitigation measures.
The dam and powerhouse are being built approximately 155km downstream of the Gilgel Gibe II plant, which has an installed capacity of 420MW and recently became operational, although there’s a short-term outage to clear and repair a rockfall blockage in the headrace tunnel. It is to generate 1635GWh per year.
Gilgel Gibe I was smaller again, but still a large development, at 184MW and generating 722GWh per year.
Planning is continuing for the Gilgel Gibe IV project, which will be the farthest downstream in the cascade. It is estimated the plant will have an installed capacity of 2GW and generate 8000GWh annually.
Also under recent development is Beles, which involved significant tunnelling works, like Gilgel Gibe II. The plant capacity is 460MW and it will tap the waters of Lake Tana, and so be one of the furthest upstream of hydro plants along the Nile.