Hydrochemistry of Olkaria and Eburru geothermal fields, Kenyan Rift Valley

Abstract

The chemical composition of waters from cold and warm boreholes, springs, Lake Naivasha, River Morendati and geothermal waters from the Olkaria and Eburru fields is presented. The study of the chemistry of the waters has been used to suggest movement and processes affecting the groundwater in the Rift Valley. The study has shown that Lake Naivasha, which is the only fresh water lake in the Kenyan Rift Valley, recharges most of the nearby boreholes. The chemical characteristics of the geothermal waters in Olkaria and Eburru geothermal fields are similar. Eburru and Olkaria geothermal reservoirs get some of their recharge from the rift groundwater. The waters from some boreholes to the north of Eburru and Elementeita spring are outflows from Eburru geothermal field and there seems to be no other geothermal resource in the Elementeita area. The escarpment warm spring waters are shallow escarpment waters that have been heated by shallow hot rock, probably below the location of the springs. They may not be related to the geothermal systems at Olkaria and Eburru. Monitoring of water levels around the lake is recommended to determine the possible effect of geothermal exploitation at Olkaria on Lake Naivasha. Further work to estimate the outflow of water from the lake and inflow into it is also recommended.