Evidence for extreme variations in the permeability of laterite from a detailed analysis of well behaviour in Nigeria

Bonsor, H.C.; MacDonald, A.M. ORCID:; Davies, J.. 2014 Evidence for extreme variations in the permeability of laterite from a detailed analysis of well behaviour in Nigeria. Hydrological Processes, 28 (10). 3563-3573.

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Laterite soils are widespread in tropical Africa and have a large impact on the hydrology of the areas they cover. The permeability of laterite helps determine the partitioning of runoff and interflow and regulates groundwater recharge to underlying bedrock. Groundwater within laterite also forms a widespread source of drinking water, typically from unimproved hang-dug-wells. Despite its importance, there is little published information on laterite aquifer properties. In this study, data from a 6 m deep well in Nigeria have been analysed to characterise the hydraulic conductivity of the laterite from repeated pumping tests. Transmissivity measurements from 40 tests spread out across a hydrological year varied from 0.1 to 1000 m2/d. Further interpretation of the data demonstrate a strong non-linear decrease in horizontal hydraulic conductivity with depth, characterised by an upper horizon of extreme permeability (400 m/d), and a much lower permeability profile beneath (<0.1 m/d). These data are substantiated with observations from other wells throughout the area. This non-linear permeability structure has several implications: the upper laterite can facilitate rapid lateral throughflow in the wet season, enabling contaminants to be transported significant distances (up to 1 km); natural groundwater levels are restricted to a narrow range for much of the year; and, in the dry season, the lower permeability of the deeper laterite restricts the amount of water which can be abstracted from shallow wells, leading to well failure. The work highlights the need for a wider study to better understand laterite soils and the role they play in regional hydrology.

Item Type: Publication - Article
Digital Object Identifier (DOI):
ISSN: 08856087
Additional Information. Not used in RCUK Gateway to Research.: This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited
Additional Keywords: GroundwaterBGS, Groundwater, International development
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Date made live: 16 Aug 2013 08:53 +0 (UTC)

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