| Title | Geochemistry of Katwe-Kikorongo, Buranga and Kibiro Geothermal Areas, Uganda |
|---|---|
| Authors | Godfrey Bahati, Kato Vincent, Nyakecho Catherine |
| Year | 2010 |
| Conference | ARGeo |
| Keywords | Western Rift Valley, Katwe, Buranga, Kibiro, Geothermometry |
| Abstract | 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 basement rocks rather than from the young overlying sediments. Stable isotope data suggests a similar origin of the geothermal fluids and the meteoric water. The high carbonate contents and salinity in the range of 25,000 - 30,000 and 14,000 - 17,000 mg/kg total dissolved solids of the geothermal waters from Katwe and Buranga respectively, affect their magnesium and calcium concentrations hence throwing the validity of some conventional methods of interpretation into doubt. Taking these doubts into account, reservoir temperatures of 150 - 220°C and 120 - 150°C are inferred by geothermometry for Katwe and Buranga respectively. Mixing models applied to the Katwe waters predict a reservoir temperature of about 230°C. The chemistry of the surface fluids from Kibiro on the other hand suggests a mixture of thermal and cold waters with a pH of 6 to 8, and salinity of up to 4,000 - 5,000 mg/kg total dissolved solids. The fluids are relatively dilute compared to those of Katwe and Buranga and would probably cause a few problems on exploitation. Geothermometry and mixing models predict a reservoir temperature of 200°C and above for Kibiro. The predicted reservoir temperatures for the three areas could be suitable for electric power generation and direct use in industry and agriculture. |