Godfrey Bahati - Academia.edu (original) (raw)

Papers by Godfrey Bahati

Water-Rock Interaction, 2021

Recent studies on the Uganda geothermal systems have focused on three geothermal prospects, Katwe... more Recent studies on the Uganda geothermal systems have focused on three geothermal prospects, Katwe, Buranga and Kibiro, all located in the tectonically active and Recent volcanic belt in the Western Rift valley along the border of Uganda and the Democratic Republic of Congo. Geothermal systems and saline and fresh water lakes characterize the Rift Valley. The three areas were chosen for study because of their volcanic and tectonic features that indicate a powerful heat source and high permeability. The objective is to develop geothermal energy as an alternative energy source to hydro and others to meet the energy demand of rural areas in sound environment. The geology and geochemistry results for the surface hot springs indicate that potential geothermal systems exist at depth. The subsurface temperatures of 160-200°C, 200°C, and above 200°C for the Katwe, Buranga and Kibiro prospects, respectively, have been inferred by geothermometry and mixing models. These temperatures are suitable for electric power production and direct use in industry and agriculture. Other areas outside the tectonically active and recent volcanic belt have typical fluid temperatures suitable for direct application to domestic use, agriculture and industrial heating. Surface exploration studies have reached advanced stages in the three areas with the execution of the ongoing geophysical survey, the results of which will be used to upgrade the current geothermal model of geology and geochemistry and develop an integrated model that will be a basis for siting the exploration wells.

Exploration for geothermal energy in Uganda has been in progress since 1993. The studies have foc... more Exploration for geothermal energy in Uganda has been in progress since 1993. The studies have focused on three major geothermal areas namely Katwe, Buranga and Kibiro. The three areas are in an advanced stage of surface exploration and will soon be subjected to exploratory drilling that will pave the way for a feasibility study. The overall objective of the study is to develop geothermal energy to complement hydro and other sources of power to meet the energy demand of rural areas in sound environment. The methodology of the study has focused on geology, geochemistry, hydrology and geophysics with the aim of elucidating subsurface temperatures and the spatial extent of the geothermal systems. The results indicate that the geothermal activity in the three areas is related to the volcanic and tectonic activities of the Rift Valley, which has a higher heat flow than the surrounding Precambrian crust. Subsurface temperatures of approximately 140-200˚C, 120-150˚C and 200-220˚C for Katwe, Buranga and Kibiro respectively have been predicted by geothermometry. Anomalous areas have been delineated in Katwe and Kibiro prospects using geophysical methods. Drilling of shallow boreholes to a depth of 200-300m for temperature gradient measurement has been completed and the temperatures measured (30-36˚C/km) are slightly above the global average of 30˚C/km. These results and proposed additional geophysical measurements will be used to update the geothermal models in three areas that will be a basis for the drilling of deep exploration wells. The results of the preliminary geothermal investigations of the other areas predict subsurface temperatures of 100-160˚C suitable for electricity production and direct uses. The areas have been graded based on predicted subsurface temperatures and other geothermal features for further exploration and development.

The three main Ugandan geothermal fields namely, Kibiro, Katwe and Buranga are located in East Af... more The three main Ugandan geothermal fields namely, Kibiro, Katwe and Buranga are located in East African Rift System (EARS) particularly in its western arm the Albertine Rift. The general strike of the Albertine Rift is NE-SW. Geophysical surveys indicate 2500 to 3000m thickness of Pleistocene sediments in the rift floor. The Kibiro geothermal prospect, which is located at the Eastern escarpment of Albertine Rift, comprises of hot springs that emerge at the base of the escarpment at the intersection of three oblique faults. The escarpment forms a boundary between the old basement rocks (to the east) and the young sedimentary formation of the rift (to the west). The basement consists of Precambrian acidic granites, granitic gneisses, gneisses and N-S striking basic amphibolite intrusives. Mylonitic gneisses characterise the faultcontrolled valleys. The NE striking faults in the area are oblique to main rift fault and crosscut E-W striking faults. All rocks are heavily fractured with crosscutting joints. The geothermal manifestations include; hot springs, solfatara, extinct clayey alterations and secondary hydrothermal minerals that include gypsum and calcite filling joints in altered mylonitic gneisses on escarpment among others. The maximum temperature of hot springs is 86.4 0 C. The Katwe volcanic field is on the SE of Rwenzori massif and consists of 78 randomly distributed craters of which seven have water. The volcanics are deposited on Pleistocene sediments. Precambrian rocks of Toro system lie on the western side while on the eastern side; the sediments are underlain by Karagwe-Ankolean (K-A) meta-sediments. In the southeastern side of Katwe field, there is Bunyaruguru volcanic field that consists of tuffs mixed with K-A rock fragments. The Katwe volcanics are mainly phreatomagmatic pyloclastic deposits consisting of ash, tuff, lapilli, volcanic bombs and xenoliths of basement rocks. Basaltic lava flows and ejected lava blocks occur around Kyemengo and Kitagata craters. The volcanic material pile rises up to 420m above surrounding sediments. NE-SW striking faults in the same strike as the main rift fault characterize the field. The carbon dating puts the age of volcanism as Pleistocene to Holocene. The Katwe geothermal manifestations include travertine deposits that indicate extinct hot springs, warm springs (30 0 C) at L. Katwe and hot springs (70 0 C) at L. Kitagata. The Buranga field is located at the NW end Rwenzori massif near the base of Bwamba escarpment. The hot springs emerge through Pleistocene sediments. Precambrian rocks underlie the sedimentts. The main rift fault strikes 45 0 and dips 60 0-65 0. The three hot spring areas namely Mumbuga, Nyansimbe and Kagoro lie on a line striking 40 0 parallel to main rift fault. Precambrian rocks form northern half of Rwenzori massif that strike 10 0-30 0 and consists of migmitites and gneisses. The sediments consist of fine to medium-grained, poorly consolidated sands and clays, some of which are coated with calcareous material. The geothermal manifestations of Buranga field include three hot spring areas with a maximum temperature of 98 0 C, travertine cones and some sulphur deposits at Kagoro spring area. The area is seismically active and frequent earthquakes in the region reactivate and create new manifestations like new hot springs near Nyansimbe pool.

Exploration for geothermal energy in Uganda has been in progress since 1993. The studies have foc... more Exploration for geothermal energy in Uganda has been in progress since 1993. The studies have focused on three major geothermal areas namely Buranga, Katwe and Kibiro. The three areas are in advanced stages of surface exploration and will soon be subjected to exploratory drilling that will pave the way for a feasibility study. The overall objective of the study is to develop geothermal energy to complement hydro and other sources of power to meet the energy demand of rural areas in sound environment. Recent studies in Buranga have used geological, geochemical, hydrological and geophysical methods to elucidate subsurface temperatures and the spatial extent of the geothermal system. The results indicate that the geothermal activity at Buranga is related to the volcanic and tectonic activities of the Rift Valley, which has a higher heat flow than the surrounding Precambrian crust. The geothermal surface manifestations include hot bubbling springs, water pools, gas vents, H2S gas, travertine tufas and geothermal grass. The main geological structure is the Bwamba escarpment that forms the western part of the Rwenzori horst mountain massif. This main rift fault is cut by numerous perpendicular and oblique striking faults which together with other faults/fractures contribute to the recharge and up-flow permeability for the geothermal fluids at Buranga. Subsurface temperatures of 120-150˚C have been predicted by geothermometry. The results also indicate that hot springs show isotopic composition compatible with the local meteoric water line, confirming the meteoric origin of the water circulating in the geothermal system. Results from isotopes of hydrogen and oxygen (δDH2O, δ18OH2O) suggest that the recharge is from high ground in the Rwenzori Mountains. Sulphur isotopes (34SSO4) of hot water samples show magmatic contributions of sulphate, while strontium isotopes of water and rock samples (87/86SrH2O, 87/86SrRock) identify the rock type as granitic gneisses, suggesting that the major source of salinity is from water-rock interaction with a magmatic input. Micro-seismic surveys have located a subsurface anomaly within the vicinity of the thermal activity at Buranga, but is yet to be confirmed by additional geophysical surveys and drilling. Recently, TEM and MT surveys have been conducted at Buranga; the results indicate a low resistivity anomaly associated with the geothermal surface manifestations, the main rift escarpment and the faults associated to the main rift escarpment.

Exploration for geothermal energy in Uganda has been in progress since 1993. The studies have foc... more Exploration for geothermal energy in Uganda has been in progress since 1993. The studies have focused on three major geothermal areas namely Katwe, Buranga and Kibiro. The three areas are in advanced stages of surface exploration and will soon be subjected to exploratory drilling that will pave the way for a feasibility study. The overall objective of the study is to develop geothermal energy to complement hydro and other sources of power to meet the energy demand of rural areas in sound environment. The current study has focused on geology, geochemistry, hydrology and geophysics with the aim of elucidating subsurface temperatures and the spatial extent of the geothermal systems. The results indicate that the geothermal activity in the three areas is related to the volcanic and tectonic activities of the Rift Valley, which has a higher heat flow than the surrounding Precambrian crust. Subsurface temperatures of approximately 140-200˚C for Katwe, 120-150˚C for Buranga, and 200-220˚C for Kibiro have been predicted by geothermometry and mixing models. Anomalous areas have been delineated in Katwe and Kibiro prospects using geophysical methods. Drilling of shallow boreholes to a depth of 200-300m for temperature gradient measurement has been completed and the temperatures measured (30-36˚C/km) are slightly above the global average of 30˚C/km, which suggests deep reservoirs in Katwe and Kibiro or geothermal reservoirs offset from the drilled areas. Additional geophysical measurements to locate the deep reservoirs and drill sites in the two areas are recommended. The results will then be used to update the geothermal models that will be a basis for drilling of deep geothermal wells in the two areas. The Buranga area still needs detailed geophysical surveys to delineate anomalous areas that could be targets for drilling. The fourth area, Panyimur in Nebbi district, West Nile region, has indications of a geothermal prospect following the results of the petroleum drilling programme that has encountered high temperature gradients (maximum 80˚C/km) in the vicinity of the thermal area. The results of the preliminary geothermal investigations on other areas predict subsurface temperatures of 100-160˚C suitable for small scale electricity production and direct uses. These areas have been ranked based on predicted subsurface temperatures and other geothermal features for further exploration and development.

Exploration for geothermal energy in Uganda has been in progress since 1993. The studies have foc... more Exploration for geothermal energy in Uganda has been in progress since 1993. The studies have focused on three major geothermal areas namely Katwe, Buranga and Kibiro. The three areas are in advanced stages of surface exploration and will soon be subjected to exploratory drilling that will pave the way for a feasibility study. The overall objective of the study is to develop geothermal energy to complement hydro and other sources of power to meet the energy demand of rural areas in sound environment. The current study has focused on geology, geochemistry, hydrology and geophysics with the aim of elucidating subsurface temperatures and the spatial extent of the geothermal systems. The results indicate that the geothermal activity in the three areas is related to the volcanic and tectonic activities of the Rift Valley, which has a higher heat flow than the surrounding Precambrian crust. Subsurface temperatures of approximately 140-200˚C for Katwe, 120-150˚C for Buranga, and 200-220˚C for Kibiro have been predicted by geothermometry and mixing models. Anomalous areas have been delineated in Katwe and Kibiro prospects using geophysical methods. Drilling of shallow boreholes to a depth of 200-300m for temperature gradient measurement has been completed and the temperatures measured (30-36˚C/km) are slightly above the global average of 30˚C/km, which suggests deep reservoirs in Katwe and Kibiro or geothermal reservoirs offset from the drilled areas. Additional geophysical measurements to locate the deep reservoirs and drill sites in the two areas are recommended. The results will then be used to update the geothermal models that will be a basis for the drilling of deep geothermal wells. The Buranga area still needs detailed geophysical surveys to delineate anomalous areas that could be targets for drilling. The results of the preliminary geothermal investigations on other areas predict subsurface temperatures of 100-160˚C suitable for small scale electricity production and direct uses. These areas have been ranked based on predicted subsurface temperatures and other geothermal features for further exploration and development.

Geothermics, Oct 1, 2005

Several sampling surveys have been carried out in three geothermal areas in western Uganda, known... more Several sampling surveys have been carried out in three geothermal areas in western Uganda, known as Katwe-Kikorongo (Katwe), Buranga, and Kibiro. Sixty-three water samples from hot and cold springs, dug wells, rivers, and lakes, and 14 rock samples from surface outcrops have been collected and analyzed. They were then analyzed for chemistry and isotopes of hydrogen (δ 2 H H 2 O , 3 H H 2 O), oxygen (δ 18 O H 2 O , 18 O SO 4), carbon (δ 13 C DIC , 14 C DIC), sulfur (δ 34 S SO 4), and strontium (87/86 Sr H 2 O , 87/86 Sr Rock). The results suggest a meteoric origin for the geothermal waters, with little secondary alteration. Based on isotope data, Katwe and Buranga are recharged from the Rwenzori Mountains, and Kibiro from high ground represented by the Mukihani-Waisembe Ridge in Kitoba Sub-county, 20 km to the southeast. Oxygen isotope geothermometry, based on aqueous sulfate and water equilibrium fractionation, indicates a subsurface temperature of 200 • C for Buranga, which is higher than that inferred from chemical geothermometry (160-170 • C), and lower temperatures (140-150 • C) for Katwe and Kibiro that are similar to the results of chemical geothermometry. Tritium concentrations indicate some involvement of modern cold water close to the surface at Kibiro but not at Buranga and Katwe, where hot springs discharge tritium-free waters. Sulfur isotope ratios (δ 34 S SO 4) of hot water suggest magmatic contributions of sulfate in all three areas, confirming the results of earlier ଝ This paper is the sixth of a set of articles describing the use of isotope and hydrochemical methods in geothermal R&D, published in Vol. 34, No. 4 and guest-edited by Zhonghe Pang and Alfred Truesdell.

Several sampling campaigns have been carried out in three geothermal areas in western Uganda, nam... more Several sampling campaigns have been carried out in three geothermal areas in western Uganda, namely Katwe-Kikorongo (Katwe),Buranga and Kibiro. 118 water samples from hot and cold springs, dug wells, rivers, lakes and 13 rock samples from surface outcrops have been collected and analyzed for chemistry and isotopes of hydrogen (8HH20, 3HH20), oxygen (8180H20, 180S04), , ·b· (~DC 14C I h (~'34'" ) d '(87/86S 87786s ) Th I cal on U Dlt', Die), su p ur u SS04, an strontIum rH20, rRock ' e resu ts suggest a meteoric origin of the geothermal water with minimal secondary alteration. Based on isotope data, Katwe and Buranga are recharged from the Rwenzori Mountains while Kibiro is rcdlargcd from high ground represented by the Mukihani-Waisembe Ridge in Kitoba Subcounty 20 km to the southeast. Oxygen isotope geothermometry based on aqueous sulphate and walcr cqui lihriunl fractionation, indicates a subsurface temperature of 200°C for Buranga, which is highcr than th...

Uganda presently has a total installed capacity of 417 MW of electricity of which 300 MW is from ... more Uganda presently has a total installed capacity of 417 MW of electricity of which 300 MW is from Nalubaale and KUra hydropower dams at Jinja, 17 MW from small hydros and 100 MW of thermaL The production at Jinja has been reduced to a mere 120 MW due to climatic fluctuations caused by a long spell of drought in the Lake Victoria basin. The peak demand is approximately 360 MW. The country is in a dire need of energy with electricity demand growing by 10% per anuum. Despite its considerable hydro resources in excess of 2000 MW, the Ugandan government recognizes that it must diversify its energy resources. The present level of uncertainty regarding the future of large hydro power projects and increasing environmental awareness, has prompted the government to take a closer look at the country's geothermal potentiaL The government is especially interested in including village-scale geothermal power plants as part of its rural electrification-program. At present, two geothermal prospec...

Theme: Science, Technology and Innovation (STI) as a Catalyst Towards Achievement of East African... more Theme: Science, Technology and Innovation (STI) as a Catalyst Towards Achievement of East African Community Vision 2050. Venue: MUNYONYO COMMONWEALTH RESORT Date: 23th 25th OCTOBER, 2019, KAMPALA UGANDA Under the Auspices of the East African Community Jointly organised by: The Inter-university Council for East Africa (IUCEA) in collaboration with the East African Business Council (EABC), East African Development Bank (EADB), East African Science and Technology Commission (EASTECO) and GIZ CATALOGUE

Reconnaissance surveys have been carried out on the geothermal areas of Uganda since 1935 when th... more Reconnaissance surveys have been carried out on the geothermal areas of Uganda since 1935 when the first documentation of Uganda's hot springs was made. Recent studies have focused on three geothermal systems of Katwe, Buranga and Kibiro all located in the active volcanic belt in the Western Rift valley along the border of Uganda and the Democratic Republic of Congo. The Western Rift Valley is characterised by geothermal systems and saline and fresh water lakes. The three areas were chosen for the study because of their volcanic and tectonic features that indicate a powerful heat source and high permeability. The objective of the study is to develop geothermal energy to supplement hydro and other sources of power to meet the energy demand of rural areas in sound environment. The results from geological and geochemical studies indicate that all the three areas are potential geothermal prospects. Their hydrothermal systems appear to be relatively old and rise from volcanic basemen...

Water-Rock Interaction, 2021

Exploration for geothermal energy in Uganda has been in progress since 1993. The studies have foc... more Exploration for geothermal energy in Uganda has been in progress since 1993. The studies have focused on three major geothermal areas namely Buranga, Katwe and Kibiro. The three areas are in advanced stages of surface exploration and will soon be subjected to exploratory drilling that will pave the way for a feasibility study. The overall objective of the study is to develop geothermal energy to complement hydro and other sources of power to meet the energy demand of rural areas in sound environment. Recent studies in Buranga have used geological, geochemical, hydrological and geophysical methods to elucidate subsurface temperatures and the spatial extent of the geothermal system. The results indicate that the geothermal activity at Buranga is related to the volcanic and tectonic activities of the Rift Valley, which has a higher heat flow than the surrounding Precambrian crust. The geothermal surface manifestations include hot bubbling springs, water pools, gas vents, H2S gas, travertine tufas and geothermal grass. The main geological structure is the Bwamba escarpment that forms the western part of the Rwenzori horst mountain massif. This main rift fault is cut by numerous perpendicular and oblique striking faults which together with other faults/fractures contribute to the recharge and up-flow permeability for the geothermal fluids at Buranga. Subsurface temperatures of 120-150˚C have been predicted by geothermometry. The results also indicate that hot springs show isotopic composition compatible with the local meteoric water line, confirming the meteoric origin of the water circulating in the geothermal system. Results from isotopes of hydrogen and oxygen (δDH2O, δ18OH2O) suggest that the recharge is from high ground in the Rwenzori Mountains. Sulphur isotopes (34SSO4) of hot water samples show magmatic contributions of sulphate, while strontium isotopes of water and rock samples (87/86SrH2O, 87/86SrRock) identify the rock type as granitic gneisses, suggesting that the major source of salinity is from water-rock interaction with a magmatic input. Micro-seismic surveys have located a subsurface anomaly within the vicinity of the thermal activity at Buranga, but is yet to be confirmed by additional geophysical surveys and drilling. Recently, TEM and MT surveys have been conducted at Buranga; the results indicate a low resistivity anomaly associated with the geothermal surface manifestations, the main rift escarpment and the faults associated to the main rift escarpment.

Exploration for geothermal energy in Uganda has been in progress since 1993. The studies have foc... more Exploration for geothermal energy in Uganda has been in progress since 1993. The studies have focused on three major geothermal areas namely Katwe, Buranga and Kibiro. The three areas are in advanced stages of surface exploration and will soon be subjected to exploratory drilling that will pave the way for a feasibility study. The overall objective of the study is to develop geothermal energy to complement hydro and other sources of power to meet the energy demand of rural areas in sound environment. The current study has focused on geology, geochemistry, hydrology and geophysics with the aim of elucidating subsurface temperatures and the spatial extent of the geothermal systems. The results indicate that the geothermal activity in the three areas is related to the volcanic and tectonic activities of the Rift Valley, which has a higher heat flow than the surrounding Precambrian crust. Subsurface temperatures of approximately 140-200˚C for Katwe, 120-150˚C for Buranga, and 200-220˚C for Kibiro have been predicted by geothermometry and mixing models. Anomalous areas have been delineated in Katwe and Kibiro prospects using geophysical methods. Drilling of shallow boreholes to a depth of 200-300m for temperature gradient measurement has been completed and the temperatures measured (30-36˚C/km) are slightly above the global average of 30˚C/km, which suggests deep reservoirs in Katwe and Kibiro or geothermal reservoirs offset from the drilled areas. Additional geophysical measurements to locate the deep reservoirs and drill sites in the two areas are recommended. The results will then be used to update the geothermal models that will be a basis for drilling of deep geothermal wells in the two areas. The Buranga area still needs detailed geophysical surveys to delineate anomalous areas that could be targets for drilling. The fourth area, Panyimur in Nebbi district, West Nile region, has indications of a geothermal prospect following the results of the petroleum drilling programme that has encountered high temperature gradients (maximum 80˚C/km) in the vicinity of the thermal area. The results of the preliminary geothermal investigations on other areas predict subsurface temperatures of 100-160˚C suitable for small scale electricity production and direct uses. These areas have been ranked based on predicted subsurface temperatures and other geothermal features for further exploration and development.

Exploration for geothermal energy in Uganda has been in progress since 1993. The studies have foc... more Exploration for geothermal energy in Uganda has been in progress since 1993. The studies have focused on three major geothermal areas namely Katwe, Buranga and Kibiro. The three areas are in advanced stages of surface exploration and will soon be subjected to exploratory drilling that will pave the way for a feasibility study. The overall objective of the study is to develop geothermal energy to complement hydro and other sources of power to meet the energy demand of rural areas in sound environment. The current study has focused on geology, geochemistry, hydrology and geophysics with the aim of elucidating subsurface temperatures and the spatial extent of the geothermal systems. The results indicate that the geothermal activity in the three areas is related to the volcanic and tectonic activities of the Rift Valley, which has a higher heat flow than the surrounding Precambrian crust. Subsurface temperatures of approximately 140-200˚C for Katwe, 120-150˚C for Buranga, and 200-220˚C for Kibiro have been predicted by geothermometry and mixing models. Anomalous areas have been delineated in Katwe and Kibiro prospects using geophysical methods. Drilling of shallow boreholes to a depth of 200-300m for temperature gradient measurement has been completed and the temperatures measured (30-36˚C/km) are slightly above the global average of 30˚C/km, which suggests deep reservoirs in Katwe and Kibiro or geothermal reservoirs offset from the drilled areas. Additional geophysical measurements to locate the deep reservoirs and drill sites in the two areas are recommended. The results will then be used to update the geothermal models that will be a basis for the drilling of deep geothermal wells. The Buranga area still needs detailed geophysical surveys to delineate anomalous areas that could be targets for drilling. The results of the preliminary geothermal investigations on other areas predict subsurface temperatures of 100-160˚C suitable for small scale electricity production and direct uses. These areas have been ranked based on predicted subsurface temperatures and other geothermal features for further exploration and development.

Geothermics, Oct 1, 2005