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Open AccessArticle

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

1
School of Engineering, University of Glasgow, Glasgow G12 8QQ, UK
2
Scottish Universities Environmental Research Centre (SUERC), East Kilbride G75 0QF, UK
3
Geothermal Training and Research Institute (GeTRI), Dedan Kimathi University of Technology, Nyeri 657-10100, Kenya
4
Geothermal Development Company, P.O. Box 17700-20100 Nakuru, Nakuru County, Kenya
*
Authors to whom correspondence should be addressed.
Energies 2019, 12(16), 3131; https://doi.org/10.3390/en12163131
Received: 28 June 2019 / Revised: 7 August 2019 / Accepted: 7 August 2019 / Published: 15 August 2019
(This article belongs to the Special Issue Innovation in Geothermal Energy Exploration and Production)
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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 δ18O and δ2H 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. View Full-Text
Keywords: geothermal; hydrology; hydrochemistry; water; Kenya; East Africa; Menengai Caldera; Nakuru geothermal; hydrology; hydrochemistry; water; Kenya; East Africa; Menengai Caldera; Nakuru
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Montcoudiol, N.; Burnside, N.M.; Györe, D.; Mariita, N.; Mutia, T.; Boyce, A. Surface and Groundwater Hydrochemistry of the Menengai Caldera Geothermal Field and Surrounding Nakuru County, Kenya. Energies 2019, 12, 3131.

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