UNICEF IWASH Project, Northern Region, Ghana: an Adapted Training Manual for Groundwater Development Groundwater Science Programme Open Report OR/11/047
Total Page:16
File Type:pdf, Size:1020Kb
UNICEF IWASH Project, Northern Region, Ghana: An Adapted Training Manual for Groundwater Development Groundwater Science Programme Open Report OR/11/047 BRITISH GEOLOGICAL SURVEY GROUNDWATER SCIENCE PROGRAMME OPEN REPORT OR/11/047 UNICEF IWASH Project, Northern Region, Ghana: An Adapted Training Manual for Groundwater Development Ó Dochartaigh BÉ, Davies J, Beamish D and MacDonald AM Keywords Northern Region, Ghana, groundwater development, Voltaian Basin. Front cover Logging borehole chip samples using a colour chart Bibliographical reference Ó DOCHARTAIGH BÉ, DAVIES J, BEAMISH D AND MACDONALD AM. 2011. UNICEF IWASH Project, Northern Region, Ghana: An Adapted Training Manual for Groundwater Development. British Geological Survey Open Report, OR/11/047. 51pp. Copyright in materials derived from the British Geological Survey’s work is owned by the Natural Environment Research Council (NERC) and/or the authority that commissioned the work. You may not copy or adapt this publication without first obtaining permission. Contact the BGS Intellectual Property Rights Section, British Geological Survey, Keyworth, e-mail [email protected]. You may quote extracts of a reasonable length without prior permission, provided a full acknowledgement is given of the source of the extract. © NERC 2011. All rights reserved Keyworth, Nottingham British Geological Survey 2011 BRITISH GEOLOGICAL SURVEY The full range of our publications is available from BGS shops at British Geological Survey offices Nottingham, Edinburgh, London and Cardiff (Welsh publications only) see contact details below or shop online at www.geologyshop.com BGS Central Enquiries Desk Tel 0115 936 3143 Fax 0115 936 3276 The London Information Office also maintains a reference collection of BGS publications, including maps, for consultation. email [email protected] We publish an annual catalogue of our maps and other publications; this catalogue is available online or from any of the Kingsley Dunham Centre, Keyworth, Nottingham NG12 5GG BGS shops. Tel 0115 936 3241 Fax 0115 936 3488 email [email protected] The British Geological Survey carries out the geological survey of Great Britain and Northern Ireland (the latter as an agency service for the government of Northern Ireland), and of the Murchison House, West Mains Road, Edinburgh EH9 3LA surrounding continental shelf, as well as basic research projects. Tel 0131 667 1000 Fax 0131 668 2683 It also undertakes programmes of technical aid in geology in email [email protected] developing countries. The British Geological Survey is a component body of the Natural Natural History Museum, Cromwell Road, London SW7 5BD Environment Research Council. Tel 020 7589 4090 Fax 020 7584 8270 Tel 020 7942 5344/45 email [email protected] Columbus House, Greenmeadow Springs, Tongwynlais, Cardiff CF15 7NE Tel 029 2052 1962 Fax 029 2052 1963 Maclean Building, Crowmarsh Gifford, Wallingford OX10 8BB Tel 01491 838800 Fax 01491 692345 Geological Survey of Northern Ireland, Colby House, Stranmillis Court, Belfast BT9 5BF Tel 028 9038 8462 Fax 028 9038 8461 www.bgs.ac.uk/gsni/ Parent Body Natural Environment Research Council, Polaris House, North Star Avenue, Swindon SN2 1EU Tel 01793 411500 Fax 01793 411501 www.nerc.ac.uk Website www.bgs.ac.uk Shop online at www.geologyshop.com Contents Contents .......................................................................................................................................... v Forward .......................................................................................................................................... 1 1 Introduction ............................................................................................................................ 2 1.1 Background to groundwater development in the Northern Region, Ghana ................... 2 1.2 Background to this report ............................................................................................... 4 2 Guidelines for groundwater development in the Northern Region ................................... 5 2.1 General groundwater development ................................................................................. 5 2.2 Selecting sites for boreholes and geophysical surveys: reconnaissance desk and field surveys ...................................................................................................................................... 7 2.3 Geophysics ...................................................................................................................... 8 2.4 Drilling and constructing boreholes ............................................................................. 17 2.5 Data management and interpretation ............................................................................ 23 3 Hydrogeology of the main geological units in the Northern Region ............................... 24 3.1 General geology ............................................................................................................ 24 3.2 General hydrogeology .................................................................................................. 25 3.3 Hydrogeology of individual geological units ............................................................... 27 3.4 Groundwater quality ..................................................................................................... 34 3.5 A groundwater development potential map for the Northern Region .......................... 37 4 Improving hydrogeological understanding in the long-term ........................................... 41 References .................................................................................................................................... 42 Appendix 1 Geophysical methods for locating groundwater in low permeability sedimentary rocks ....................................................................................................................... 44 v FIGURES Figure 1 Location of the Northern Region in Ghana ................................................................. 2 Figure 2 The training manual ‘Developing Groundwater: a guide for rural water supply’ (MacDonald et al 2005), which should be used in conjunction with this report as a comprehensive reference for groundwater development techniques ....................................... 3 Figure 3 Geophysics is one part of a triangle of useful groundwater development approaches 8 Figure 4 Cables should be regularly inspected for damage ..................................................... 10 Figure 5 Care should be taken to ensure good connections between cables and control box during resistivity surveys ........................................................................................................ 10 Figure 6 As electrode separation is increased in a resistivity survey, the depth of current penetration increases. .............................................................................................................. 12 Figure 7 Typical geophysical results from different rock types .............................................. 13 Figure 8 Examples of interpreted resistivity survey results over mudstone (top) and sandstone (base) 14 Figure 9 EM34 equipment with coils in vertical and horizontal orientation ........................... 15 Figure 10 Working closely with the drilling crew is important to ensure good quality data are collected and recorded ............................................................................................................ 17 Figure 11 Using a stopwatch to accurately record drilling penetration rate .............................. 18 Figure 12 Different kinds of marked and labelled container for systematically storing rock chip samples for logging ......................................................................................................... 19 Figure 13 Rock chip samples from drilling should be washed and carefully examined, using a hand lens if possible ............................................................................................................... 19 Figure 14 Using colour charts to standardise the description of rock chip samples .................. 19 Figure 15 Measuring borehole yield using a stopwatch, bucket (left) and/or V notch weir (right) 20 Figure 16 Example of a detailed ‘photo log’ for a section of a dry borehole drilled at Kpachaa village, Northern Region, during the training course. Numbers are depth below the ground surface in metres ..................................................................................................................... 21 Figure 17 The geology of the Northern Region (based on recently revised geological mapping and nomenclature; extended specifically for this project to cover the Northern Region, by reference to national geological map of Ghana at 1:1 million scale). .................................... 26 Figure 18 Borehole depths and measured yields in the Obosum Group, Bunya Sandstone Member, Chereponi Sandstone Member and Bimbila Formation. Note the different vertical scales. 30 Figure 19 Borehole depths and measured yields in the Afram Formation, Anyaboni Sandstone Formation and Panaboko Sandstone Formation. Note the different vertical scales ............... 31 Figure 20 Percentage of non-dry boreholes (i.e. any yield more than zero) from the three main datasets (HAP database of abstraction boreholes – including data from EU and AFD projects; IWASH boreholes; and monitoring boreholes) ......................................................