Borehole site investigations in volcanic rocks of Lolmolok area, Samburu district, Kenya

Mulwa JK. "Borehole site investigations in volcanic rocks of Lolmolok area, Samburu district, Kenya.". In: Water Resources of Arid areas. London: Taylor & Francis Group, ISBN 04 1535 9139; 2004.


A systematic approach has been applied in the selection of suitable sites for borehole drilling in a quest to provide adequate water supply to a rural pastoral community in Lolmolok area. The study area lies in samburu district in Kenya and is bound by latitudes 0°56’21”N and 0°57’58”N and longitudes 36°34’42”E and 36°36’35”E. The geology of this area is comprised of tertiary volcanics. Basalts, which have weathered into residual black cotton soil, are underlain by phonolitic lavas and tuffs. The systemat-ic approach for the exploration of groundwater was followed to enable selection of an optimum drill site(s) within a quadrant with three-kilometer radius identified by the pas-toral community. The approach consisted of the following multi-steps:-
(i) Hydrogeological reconnaissance of the whole area, mapping different groundwa-ter potential areas on the basis of aerial photo interpretation;
(ii) Geophysical field surveys involving very low frequency electromagnetic (VLF-EM) and Vertical Electrical Sounding (VES).
(iii) Processing and interpretation of the data acquired in the field, which led to selection of suitable drill sites, indication of potential yield and depth of aquifers.
This paper describes the success of combined geophysical survey techniques in siting boreholes whose yield ranges between 5 m3/hr and 10 m3/hr.

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