Indirect detection of subsurface outflow from a Rift Valley lake

Darling, W.G.; Allen, D.J.; Armannsson, H.. 1990 Indirect detection of subsurface outflow from a Rift Valley lake. Journal of Hydrology, 13 (1-4). 297-306. https://doi.org/10.1016/0022-1694(90)90180-6

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Abstract/Summary

Naivasha, highest of the Kenya (Gregory) Rift Valley lakes, has no surface outlet. However, unlike other Rift lakes it has not become saline despite high potential evaporation rates, which indicates that there must be some subsurface drainage. The fate ofthis outflow has been the subject of speculation for many years, especially during the general decline in lake water level during the I980's. Particularly to the south of the lake, there are few opportunities to obtain information from direct groundwater sampling. However, the stable isotopic composition of fumarole steam from late Quaternary volcanic centres in the area has been used to infer groundwater composition. Using a simple mixing model between Rift-flank groundwater and highly-evaporated lakewater, this has enabled subsurface water flow to be contoured by its lakewater content. By this method, outflow can still be detected some 30 km to the south of the lake. Stable isotope data also confirm that much of the steam used by the local Olkaria geothermal power station is derived from lakewater, though simple balance considerations show that steam use cannot alone be responsible for the fall in lake level observed during the 1980's.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1016/0022-1694(90)90180-6
Programmes:	BGS Programmes > Groundwater Management
ISSN:	0022-1694
Additional Keywords:	GroundwaterBGS, Groundwater, International development
NORA Subject Terms:	Hydrology
Date made live:	03 Jun 2013 14:31 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/502063

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