Surface and Groundwater Hydrochemistry of the Menengai Caldera Geothermal Field and Surrounding Nakuru County, Kenya

Nelly Montcoudiol, Neil M. Burnside, Domokos Györe, Nicholas Mariita, Thecla Mutia and Adrian Boyce
Additional contact information
Nelly Montcoudiol: School of Engineering, University of Glasgow, Glasgow G12 8QQ, UK
Neil M. Burnside: School of Engineering, University of Glasgow, Glasgow G12 8QQ, UK
Domokos Györe: Scottish Universities Environmental Research Centre (SUERC), East Kilbride G75 0QF, UK
Nicholas Mariita: Geothermal Training and Research Institute (GeTRI), Dedan Kimathi University of Technology, Nyeri 657-10100, Kenya
Thecla Mutia: Geothermal Development Company, P.O. Box 17700-20100 Nakuru, Nakuru County, Kenya
Adrian Boyce: Scottish Universities Environmental Research Centre (SUERC), East Kilbride G75 0QF, UK

Energies, 2019, vol. 12, issue 16, 1-21

Abstract: In order to assess the sustainability and impact of production from geothermal reservoirs on hydrological systems, a thorough understanding of local and regional hydrogeological systematics is a prerequisite. The Menengai Caldera in the Kenya Great Rift Valley is one of the largest explored geothermal fields in the country. This paper presents a hydrochemical investigation of the Menengai Caldera geothermal field and the ground and surface waters of the surrounding Nakuru County. Our results demonstrated a similar, sodium-alkaline dominated, ionic composition across all water types. Geothermal wells return the highest cation/anion concentrations and largely demonstrate a meteoric source from their δ 18 O and δ 2 H signature. Wells MW-09 (central part of the caldera), MW-18 (eastern part) and MW-20 (central part) showed a more evaporitic signature, closely matching with our own calculated Lake Evaporation Line, suggesting an increased mixing influence of Lake Nakuru waters. MW-09 also showed evidence of high-temperature oxygen isotopic exchange and significant water-rock interaction. Lake samples largely demonstrated seasonal shifts in ionic and isotopic values. Lake Nakuru ionic composition and isotopic values increased throughout the 12-month wet–dry–wet season sampling period. This correlated with a decrease in area which suggests a lessening of water inflow and facilitates increased evaporation. Groundwaters demonstrated clear evidence of mixing between meteoric, irrigation and lake waters. These observations enhanced the understanding of the hydrological system surrounding the Menengai Caldera and, when combined with future studies, will provide a powerful tool to assess the sustainability and impact of soon-to-be completed geothermal power production operations.

Keywords: geothermal; hydrology; hydrochemistry; water; Kenya; East Africa; Menengai Caldera; Nakuru (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2019
References: View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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