Report on visit to a WaterAid project, Nigeria, to carry out workshops and assess geology of Benue State

MacDonald, Alan ORCID: 2001 Report on visit to a WaterAid project, Nigeria, to carry out workshops and assess geology of Benue State. British Geological Survey, 26pp. (IR/01/018) (Unpublished)

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This short report summarises activities and conclusions from a visit to Nigeria by Alan MacDonald (6-21 January 2001), other relevant information is attached. The terms of reference for the visit were: • to train WaterAid/WASU/BERWASSA staff to find dolerite intrusions in Obi and Oju; • to train staff in the use and interpretation of resistivity equipment in Oju and Obi; • carry out a desk study of the geological conditions of 7 LGAs in Benue State. To meet these terms of reference a seven-day workshop was undertaken in Oju/Obi comprising mainly fieldwork. Three days were spent in Makurdi consulting geological information available at the Geological Survey of Nigeria. A summary of the main activities and recommendations from the visit are given below. 1. Boreholes drilled into dolerite intrusions offer the cheapest and most sustainable water supply for much of Obi. Therefore considerable time (1-2 days per community) should be given to try to locate dolerite in communities in Obi. The best method for finding it is to use EM34 and magnetics together and then validate using EM34 with 40-m coil separations. WaterAid and WASU are competent to carry out these activities. 2. All workshop participants could competently use the magnetic and EM34 equipment. Most could interpret the data to identify areas with dolerite. However, for this year, it is advisable for the WaterAid Engineer to validate interpretations of any surveys. 3. Resistivity is not a particularly useful technique in Oju and Obi. Similar information is given by using EM34 at 20-m spacings and then repeating with 40-m coil separation. All participants recognised the pros and cons of using resistivity and as a group we decided that we do not need to continue using it in Oju and Obi. Most participants can now roughly interpret resistivity data. 4. The geological conditions of the 7 LGAs vary greatly. The most difficult area for finding groundwater is probably Gwer West. The geological conditions of all seven LGAs are summarised in Table 3. 5. The records from the 2000 drilling programme highlighted several important issues. • The boreholes were drilled and tested during the rainy season when yields are artificially high. • They were only grouted to a depth of one metre, therefore leaving the laterite unsealed. • The depth ranged from 22-51m (average 32.4 m) – well short of the minimum depth of 40 m suggested by BGS. • The bailer tests were not carried out properly (and the raw data not given) therefore it is impossible to assess the yields of the boreholes. 6. Several other issues arose during the visit, such as the future use of the drilling rig; the distribution of reports (both within the project and to other stakeholders). These are discussed later in the report. Summary

Item Type: Publication - Report
Programmes: BGS Programmes > Groundwater Management
Funders/Sponsors: NERC
Additional Information. Not used in RCUK Gateway to Research.: This item has been internally reviewed but not externally peer-reviewed
Additional Keywords: GroundwaterBGS, Groundwater, International development
Related URLs:
Date made live: 13 Dec 2010 13:45 +0 (UTC)

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