| Abstract |
The Olkaria geothermal field is recharged from precipitation in Aberdares Ranges and Mau forest that is heated before flowing into the overlying geothermal reservoirs via structures. Mixing ratios between cold and thermal waters will be estimated with Cl, Na and B concentrations since elemental concentrations may be derived from geothermal water. Hydrogeochemical features of ground and surface water samples are reviewed in the context of hydrogeological information. Hydrogeochemical characterization of thermal and non - thermal waters discharged from flowing artesian wells will be based on thermal waters with salinity, discharge temperatures and hydrochemical facies. Hydrochemical processes are characterized by analyzing ion ratios in various waters. Geothermal waters have high lithium and boron concentrations, probably due to exchange with smectite. The objective is to assess the hydrologic and geochemical connection between the fractured bedrock geothermal reservoir and the alluvial aquifer and provide an overall assessment on the origin of the thermal waters and geochemical processes giving rise to salinities of these waters as well as estimation of the subsurface reservoir temperatures.The temperatures of the deep geothermal reservoirs are estimated based on the Na-K-Mg geothermometry, while slightly lower estimates are obtained using silica geothermometeters. Mixing of the waters provides evidence of groundwater flow paths that may be useful in investigations of thermal waters.Higher contents of some minor elements, such as water F, Si, B and Sr are probably derived from extended water rock interaction, and these elements can be regarded as indicators of flow paths and residence times. Elevated temperature, lithium, boron, chloride and silica indicate mixing may occur indicate geothermal activities. |