Uganda is a landlocked country in Eastern Africa and is home to Africa’s third-highest peak, Mount Margherita: 5,109 m (highest point in Uganda), which is a part of the Rwenzori Mountains National Park. The mountains are better known as the ‘Mountains of the moon’, is one of the most permanent sources of the River Nile and supports the richest montane flora in Africa. Along with a few national parks and sanctuaries, Uganda is home to several hot springs. Two popular ones include the Sempaya (Semiliki National Park (Western Uganda) and Amoropii Hot springs. These hot springs are rooted in worship traditions as it is believed to have divine powers, visited by women hoping for cure for infertility and by those seeking fairer/tender skin. Other known uses of geothermal resources in Uganda include cooking, but there is no recorded use for generating electricity or for industrial applications (e.g. agriculture).
Uganda, located in East Africa which is a part of the East African rift system (EARS), an active continental rift zone. The EARS is a series of rift valleys divided into the eastern, south-West and western branches. The western branch runs along the border of Uganda and the Democratic Republic of Congo and passes through Rwanda, Burundi, and Tanzania. The western branch can be divided into three sections:
The west is characterized by much less volcanism than the east and is tectonically (seismically) active characterized by large, deep-seated (27–40 km) earthquakes. Parts of this branch shows the greatest subsidence on Earth represented by deep rift lakes at or below sea level.
Uganda is in the northern section and the most important structural features are the Albert (Albertine) Rift, Rwenzori Mountains and lakes Albert, Edward, and Kyoga. The Rwenzori Mountains are the highest rift mountains on Earth rising to over 5000m formed by rift flank uplift (a hotly debated topic). Basins associated with the Albert Rift are dominated by a thick sequence of non-volcanic sediments with some volcanic rocks in southern basins where volcanic products can be found.
Figure 1: Structural Map show the Eastern (Kenya) and Western branches of the East African Rift system from Omenda 2009
Geothermal exploration dates to 1930 with brief reconnaissance investigations of resources by the Geological Survey. The main geothermal resources of Uganda are in close proximity to Lake Albert and Lake Edward. The three most promising geothermal prospects are Katwe-Kikorongo (Katwe, Kasese district), Buranga (Bundibugyo district), and Kibiro (Hoima District). These will be discussed briefly below. Several other geothermal areas exist but are in the preliminary exploration phase with predicted subsurface temperatures of 100 – 160 ̊C. Several are being considered for further work (surface exploration) including Rubaare, Panyimur, Kitagata, Ihimbo, and Kanangorok.
Figure 2. Geothermal Resources Map of Uganda; Source: Bahati, 2012
The Katwe geothermal area lies at the foot of the Rwenzori Mountains (south) in the Katwe-Kikorongo Volcanic Field (KKVF). The KKVF is bordered to the south by the Lake Edward and Lake George to the east. The main fault runs NE-SW with a few associated crates including the Katwe, Kitagata and Kyemengo craters.
Surface manifestations are generally scarce and found in the Katwe and Kitagata craters. A few warms springs with temperatures of up to 32ºC and travertine deposits are found associated with the Katwe crater lake. five hot springs are associated with Lake Kitagata having temperatures between 56 and 70 ̊C. These hot springs have been and are still being used in the cooking of Obushera, a millet porridge.
The thermal fluids from the manifestations are characterized by high carbonate and sulphate and salinity (19,000 – 28,000 mg/kg total dissolved solids). The thermal fluids from Lake Kitagata and Lake Katwe craters are characterized by the presence of high levels of hydrogen sulphide (30-40 ppm) suggesting a volcanic and hydrothermal source. Models based on hydrology studies of hot springs using hydrogen isotopes indicate that the fluid is a mixture of hot geothermal water with the lake water.
Temperature gradient wells were drilled (200-300m) and measurements suggest geothermal gradients of 30-36 ̊C/km, slightly above the global average of 30 ̊C/km. Subsurface temperatures predicted by isotopic geothermometry (sulphate water isotope) and mixing models suggest ranges of 130–200 ̊C.
Two anomalous areas (low resistivity) have been identified using transient electromagnetic (TEM) geophysical studies. The first is located around Lake Katwe and the second stretch from Lake Kitagata to Lake Kikorongo. Gravity geophysical investigations support the results of the TEM study indicating that the anomalous areas are controlled by a N-S fault (east of Lake Katwe) and an NNE-SSW fault (Lake Kitagata – Lake Kikorongo area).
The Buranga geothermal area is in the Albertine Rift in the Semliki National Park at the north-western/western end of the Rwenzori Mountains. There is no evidence of volcanism but the are tectonically active characterised by major tectonic faults (Bwamba fault). Geologically, the area is dominated by sedimentary rock. Geothermal manifestations include hot springs (37 springs with flow rates of 10-30 l/s and temperatures up to 98.4°C.), fumarolic activity and travertine deposits.
Between 1953-54 the Geological Survey of Uganda carried out a drilling program at Buranga to determine if geothermal power could be developed. Three boreholes were drilled in Buranga with depths up to 349. One borehole produced thermal water that in February 2005 the measured water temperature was 62°C. Subsurface temperatures of 120-150 ̊C were predicted using geothermometry coupled with mixing models. The fluids (surface and subsurface) are neutral with a pH of 7-8, salinity (14,000 – 17,000 mg/kg total dissolved solids) and have considerable gas, largely carbon dioxide.
Geophysical investigations (Schlumberger soundings) were carried out in 1973. Results showed that the resistivities of the rift sediments decrease towards the hot springs. Also, that high resistivity volcanic rocks (basement) dips west at the Bwamba fault.
The Kibiro geothermal area is located on the eastern shores of Lake Albert with key structures being the Kachuru and Kitawe faults (NNE-SSE). The faults intersect the Albert Rift in the Kachuru and Kibiro villages. The field is divided into two, having distinct geological features. To the east, it is dominated by crystalline volcanic rocks (granites and granitic gneisses). Where the west, is dominated by thick (~5.5 km) sequences of sediments, with no volcanic rocks at the surface.
Surface manifestations are found in the western section on the shores of Lake Albert. They include hot and warm springs at Kibiro characterised by the presence of hydrogen sulphide, fumarolic activity at Kachuru, calcite and sulphur deposits. These exhibit temperatures of up to 86.4 ̊C with flows of ~7 l/s.
Subsurface temperatures were estimated using geothermometers and mixing models and ranges from 110 ̊C and 220 ̊C. A temperature of 54 ̊C was been observed from a shallow well (600 m) close to the geothermal area. The fluids have a neutral pH and salinities of 4,000 – 5,000 mg/kg (total dissolved solids).
Geophysical studies identified low resistivity(<5m) associated with the fault lines and a low resistivity anomaly ‘trench’ traced into basement rocks. This ‘trench’ follows the fault lines to the SSW and then along W-E. A high gravity was observed in the granites suggesting the presence of intrusive igneous bodies.
In order to take advantage of the geothermal resources present, the Geothermal Resources Department was created in 2014 to spearhead the development of geothermal resources in the country. As of January 2020, a new and revised draft of the national energy policy was submitted emphasizing strategies pushing renewable energy development, including solar and geothermal power.
As of 2018, several private developers are making progress in geothermal exploration:
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Bahati, G., 2011. Status of geothermal exploration and development in Uganda. Presented at Short Course VI on Exploration for Geothermal Resources, organized by UNU-GTP, GDC and KenGen, at Lake Bogoria and Lake Naivasha, Kenya, Oct. 27 – Nov. 18, 2011. http://theargeo.org/home/files/Uganda/bahati2011_status_of_geothermal_exploration_and_development_in_uganda.pdf
Bahati, G. and Natukunda, J.F., 2008. Status of geothermal exploration and development in Uganda. Short Course III on the Exploration of Geothermal Resources, p.10.
Bahati, G., Natukunda, J.F. and Tuhumwire, J., 2003, September. Geothermal energy in Uganda, country update. In International Geothermal Conference, Reykjavik, Iceland. S04 paper (Vol. 124, pp. 48-53).
Bahati, G., Natukunda, J.F. and Tuhumwire, J., 2010. Geothermal energy in Uganda, country update. Proceedings World Geothermal Congress 2010 Bali, Indonesia, 25-29 April 2010. http://22.214.171.124/web_data/iga_db/Uganda.pdf
Bahati, G., Vincent, K. and Catherine, N., 2010. Geochemistry of Katwe-Kikorongo, Buranga and Kibiro Geothermal Areas, Uganda. In Proceedings of the World Geothermal Congress, Bali, Indonesia (pp. 25-29). https://www.geothermal-energy.org/pdf/IGAstandard/ARGeo/2010/Bahati.pdf
Bahati, G., Pang, Z., Ármannsson, H., Isabirye, E.M. and Kato, V., 2005. Hydrology and reservoir characteristics of three geothermal systems in western Uganda. Geothermics, 34(5), pp.568-591.
Chorowicz, J., 2005. The East African rift system. J. African Earth Sciences, 43, 379–410.
Harðarson, B.S., 2014. Structural geology of the Western branch of the East African Rift: tectonics, volcanology and geothermal activity. Paper presented at Short Course IX on Exploration for Geothermal Resources, organized by UNU-GTP, GDC and KenGen, at Lake Bogoria and Lake Naivasha, Kenya, Nov. 2-23, 2014. https://rafhladan.is/bitstream/handle/10802/9124/UNU-GTP-SC-19-0301.pdf
Kato, V., 2013. Geothermal exploration in Uganda: Status Report. Paper presented at Short Course VIII on Exploration for Geothermal Resources, organized by UNU-GTP, GDC and KenGen, at Lake Bogoria and Lake Naivasha, Kenya, Oct. 31 – Nov. 22, 2013. https://orkustofnun.is/gogn/unu-gtp-sc/UNU-GTP-SC-17-1004.pdf
Kato, V., 2000. Geothermal field studies using stable isotope hydrology: case studies in Uganda and Iceland. United Nations University. https://orkustofnun.is/gogn/flytja/JHS-Skjol/Yearbook2000/10Vincent.pdf
Mainza, D., 2006. The chemistry of geothermal waters of SW-Uganda. United Nations University. Geothermal Training Programme Reports 2006, Number 12. https://orkustofnun.is/gogn/flytja/JHS-Skjol/Yearbook2006/12Dan.pdf
McNitt. J.R., 1982: The geothermal potential of East Africa. Proceedings of the Regional Seminar on Geothermal Energy in Eastern and Southern Africa, Nairobi, Kenya, June 15-21 1982.
MOE, 2011. Scaling-up Renewable Energy Program (SREP) Investment Plan for Kenya. Submitted by the Government of Kenya to the Climate Investment Fund (CIF) Board, September 2011.
Mnjokava, T.T., 2014. Geothermal Development in Tanzania – Status Report. Presented at Short Course IX on Exploration for Geothermal Resources, organized by UNU-GTP, GDC and KenGen, at Lake Bogoria and Lake Naivasha, Kenya, Nov. 2-23, 2014.
Muhwezi, D.K., 2009. The Potential Relationship of some Geothermal Fields in Uganda. In Proceedings of the Third East African Rift Geothermal Conference (pp. 365-382). https://orkustofnun.is/gogn/unu-gtp-report/UNU-GTP-2009-20.pdf
MWIE, 2015. Highlights of the Ethiopian Geothermal Sector. Presentation to the Global Geothermal Alliance Stakeholder Meeting, Nairobi, by the Ministry of Irrigation and energy, Federal Democratic Republic of Ethiopia. June, 2015
Natukunda, J.F., Geology of Kibiro, Katwe and Buranga geothermal prospects of Uganda. In Proceedings of the World Geothermal Congress (pp. 1-13). https://www.geothermal-energy.org/pdf/IGAstandard/WGC/2010/1261.pdf
Ochmann, N., Lindenfeld, M., Barbirye, P. and Stadtler, C., 2007. Microearthquake survey at the Buranga geothermal prospect, western Uganda. In Proceedings of Thirty-Second Workshop on Geothermal Reservoir Engineering (pp. 22-24). http://theargeo.org/home/files/Uganda/ochmann_kraml_et.all._2010_mikroearthquake_survey_at_the_buranga_geothermal_prospect_western_uganda.pdf
Omenda, P.A., 2007. The geothermal activity of the East African Rift. Short course II on surface exploration for Geothermal Resources, organized by UNU-GTP and KenGen, at Lake Naivasha, Kenya, pp.2-17. https://orkustofnun.is/gogn/unu-gtp-sc/UNU-GTP-SC-10-0204.pdf
Onacha, S.A., 2012. Challenges and Opportunities of Geothermal Exploration and Development in the Western Branch of the East Africa Rift Valley. Proceedings 4th African Rift Geothermal Conference 2012, Nairobi, Kenya, 21-23 November 2012
Rutagarama, U., 2014. Geothermal exploration and development in Rwanda. Presentation by Geothermal Development Unit Energy, Water and Sanitation Limited (EWSA Ltd) to the Geothermal Donor Collaboration Meeting and Geothermal Workshop for Donors and Decision-makers 26th to 28th May, 2014
Rutagarama, U., 2015. Geothermal Resources Development in Rwanda: A Country Update. Proceedings World Geothermal Congress 2015, Melbourne, Australia, 19-25 April 2015.
Takouleu, J.M., 2018. UGANDA: Country wants to produce 100 MW of geothermal energy by 2025, Afrik21. https://www.afrik21.africa/en/uganda-country-wants-to-produce-100-mw-of-geothermal-energy-by-2025/
Teklemariam, M., 2008, October. Overview of Geothermal resource utilization and potential in East African rift system. In Proceedings of the 30th Anniversary Workshop of UNU-GTP, Reykjavik. https://orkustofnun.is/gogn/unu-gtp-sc/UNU-GTP-SC-08-02.pdf
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