Planned hydropower development
The Zambezi River Basin has considerable hydropower potential, estimated at greater than 13,000 MW basinwide. In addition to the 5,000 MW of developed capacity, 6,634 MW is proposed for development before 2025 and several other major sites are identified for construction over a longer time-frame. Major projects that have received serious consideration for each region are described below. Many additional project concepts persist in various reports and memos scattered across the region.
Upper Zambezi region
Significant hydropower generating potential has been identified in the Zambezi headwaters region, including key tributaries in Angola, but no hydropower projects are currently in planning. Large-scale irrigation projects are under consideration in Angola's Upper Zambezi sub-basin that could affect water availability downstream, however. The hydropower project that has received the most attention in the Upper Zambezi region is the proposed Katombora Dam, located 60 km upstream ofFalls on the mainstem Zambezi. Katombora would stabilize water levels for firm energy production at two large power plants located downstream at Victoria Falls – a 390 MW station on the north bank (Zambia) to replace the existing Victoria Falls power plant and a second 300 MW station on the south bank (Zimbabwe). Katombora would also firm up energy production at the proposed Batoka Gorge and Devils Gorge hydropower stations downstream (World Bank 2010). However, development of hydropower at Katombora would have a serious impa ct on water flows over Victoria Falls, a World Heritage Site and major source of tourism revenue, and is unlikely to secure support.
Middle Zambezi region
The Middle Zambezi region has substantial hydropower potential, with new hydropower projects totaling more than 5,000 MW in various stages of consideration. Potential new power generation schemes include the 1,600 MW Batoka Gorge, 1,200 MW Devils Gorge, and 640 MW Mupata Gorge hydropower dams on the mainstem Zambezi, and the 450 MW Kafue Gorge Lower Dam on the Kafue River. Proposed extensions to existing power stations would increase power output by about 600 MW at Kariba and 80 MW at Itezhi-Tezhi.
Batoka Gorge, a bilateral hydropower project between 4 Climate change considerations have not been incorporated into project design, although Harrison and Whittington (2002, 2003) raised concerns about the financial susceptibility of the Batoka Gorge scheme to reduced runoff under future climate change scenarios, discussed further below.and Zimbabwe, would be located 50 km downstream of Victoria Falls. The proposed dam has a 181 m high wall, and its would have a surface area of 25.6 km2. North and south bank power stations would provide up to 800 MW of capacity each for Zambia and Zimbabwe. A full was completed in 1993 (Batoka Joint Venture Consultants 1993). Project design is based on the long-term time series of daily flows at Victoria Falls, dating back to 1907. The project received renewed media attention in mid-2012, with word of resumed high level talks and financial agreements between Zambia and Zimbabwe.
Two other bilateral projects on the mainstem Zambezi are less likely in the foreseeable future. The proposed hydropower dam at Devils Gorge (1,200 MW) located between Batoka Gorge and Kariba, would include north and south bank power stations, each with a capacity of 600 M W. The project is not considered economically viable and has been postponed indefinitely (World Bank 2010). Mupata Gorge, located downstream of Kariba Dam on the Zambezi River near theborder, would have an installed capacity of between 640 and 1,200 M W. The Mupata Gorge reservoir would inundate Mana Pools, a UNESCO World Heritage Site located on the south bank (Zimbabwe), and also Lower Zambezi National Park on the north bank (Zambia), and therefore is not under serious consideration at present (World Bank 2010).
In addition to new dam construction, additional generating capacity is proposed for Kariba North Bank (360 MW) and Kariba South Bank (300 MW) in the near future (World Bank 2010). Adequate space for two additional units at Kariba North powerhouse was allocated when the original plant was constructed.
Among the major Zambezi tributaries, the Kafue River has the greatest hydropower development potential. The Kafue Gorge Lower Hydropower Project is proposed for construction two km downstream of the existing Kafue Gorge Upper Hydropower Project. A feasibility study for developing 600 MW capacity in the Kafue Gorge Lower, with an additional bay for 150 M W, was completed in 1995 (HARZA Engineering Company 1995). This project is under serious consideration by the International Finance Corporation (MHW/IFC 2009).
The Itezhi-Tezhi hydropower extension would be located at the existing dam site and consist of an underground powerhouse with two 60 MW Kaplan units. A feasibility study was completed in 1999 (HARZA Engineering Company 1999) and the project has been fast-tracked to meet existing power shortages. As discussed above, Itezhi-Tezhi reservoir is operated mainly for regulation of the Kafue Gorge Upper and is subject to various operational constraints. At this writing, construction of the hydropower plant was underway.
Additional multipurpose dams for irrigation and hydropower production have been proposed, most notably the Gwayi Shangani Dam on the Gwayi River (for water supply to Bulawayo, Zimbabwe) and the Lower Lusemfwa Dam (35WM) in Zambia and mainstem Luangwa Dam (40MW) in the Luangwa River Basin (SWRSD 2010).
Lower Zambezi region
The Lower Zambezi region also has considerable hydropower potential, including large mainstem hydropower schemes and many smaller tributary dams. Proposed hydropower dams on the mainstem Zambezi include Mphanda Nkuwa, Boroma, and Lupata Gorge dams. The proposed Mphanda Nkuwa project site is located 61 km downstream of the Cahora Bassa Dam. The project comprises a 101-meter-high roller-compacted concrete dam impounding a reservoir with a surface area of approximately 96.5 km2 at full supply level. Proposed generating capacity is 1,300 M W, composed of four 325 MW units (LI-EDF-KP Joint Venture Consultants 2000). Climate change considerations have not been incorporated into project design. Development of up to 2,275 MW for peak power production is possible with an extension to the north bank power station or construction of a separate underground power station on the south bank. Operation of Mphanda Nkuwa Dam for peaking power would require the construction of Boroma dam downstream to stabilize (re-regulate) fluctuating river flows downstream (LI-EDF-KP Joint Venture Consultants 2000). Boroma itself would have a generating capacity of 444 M W. The feasibility studies for Mphanda Nkuwa rejected an alternative, mutually exclusive dam site at Cambewe Foz, due to higher construction costs (LI-EDF-KP Joint Venture Consultants 2000). Further downstream, the Lupata Gorge Dam site, with 654 MW generating potential, is not under serious consideration at present.
The 1,200 MW Cahora Bassa North Bank power station is proposed for peaking power. The project consists of a new underground powerhouse on the north bank of the Zambezi River with three 283.3 MW Francis units (Norconsult 2003). A new spillway, designed to increase the total discharge capacity of Cahora Bassa Dam by 3,600 m3/s, would eliminate the need for the present design flood rule curve (Beilfuss 2010).
The Zambezi Valley Development Authority of Mozambique proposed 53 small-scale hydropower development projects on tributaries in the Tete sub-basin, including 15 dams in the Luia Basin, 12 in the Revuboe basin, 12 in the Luenha basin, and 14 on other tributaries (Hidrotechnica Portuguesa 1965). Detailed follow-up studies of individual projects larger than 4 MW suggested that only two of the tributary projects were worth considering, the Luia 6 (16.5 MW) and the Luenha 7 (13.2 MW). Neither is currently in planning.
In the Lake Malawi/Shire River sub-basin, several hydropower projects are proposed on tributaries to Lake Malawi. Songwe I, II, and III were identified for hydropower development on the Songwe River, with a combined generating capacity of 340 MW (NORPLAN 2003). The Rumakali Hydropower Scheme (222 MW generating capacity) would be located on the Rumakali River, 85 km west of Njombe in southwestern(SwedPower and Norconsult 1998). The Lower Fufu dam would regulate runoff from the north Rukuru and south Rumphi rivers, routed through an underground power station with 70-145 MW generating capacity. None of these projects would significantly alter inflows to Lake Malawi.
Substantial evaporative water losses from large reservoirs, especially Kariba and Cahora Bassa, reduce water availability in the basin and will increase with climate change.
The 180 MW Kholombidzo, 40 MW Tedzani 1 & 2 refurbishment, and 64 MW Kapichira II dams are proposed for the Shire River. Two alternatives have been analyzed for hydropower development at Kholombidzo – the High Kholombidzo Dam would partially control the outflow of Lake Malawi,5 whereas the Low Kholombidzo Dam would not affect Lake water levels (Norconsult 2003). The second phase of the Kapichira hydroelectric power project entails a doubling of generation capacity from 64 to 128 MW as planned in the original design specifications.
4. For example, The Times of Zambia headline on 16 February 2012 proclaims "Zim, Zambia ink $4bn Batoka deal."
5. This proposed project replaces the original high dam design, which featured a higher crest level that would have allowed full control of the Lake Malawi drawdown with higher generating capacity. The original proposal was abandoned, however, as it would have flooded prime agricultural land and infrastructure, displaced a large population, and increased the potential for severe flooding downstream.