SUSTAINABLE GROUNDWATER RESOURCES IN AFRICA Copyright © 2010 UNESCO Sustainable Groundwater Resources in Africa Water supply and sanitation environment Editors Yongxin Xu & Eberhard Braune UNESCO Chair in Hydrogeology University of the Western Cape, South Africa Copyright © 2010 UNESCO Copyright © 2010 UNESCO Published jointly by: UNESCO UNESCO International Hydrological Programme (IHP) 1 rue Miollis 75732 Paris Cedex 15 France Tel: 33 (0) 1 4568 4004 Fax: 33 (0) 1 4568 5811 Website: http://www.unesco.org/water and CRC Press/Balkema P.O.Box 447, 2300 AK Leiden, The Netherlands e-mail: [email protected] www.crcpress.com – www.balkema.nl – www.taylorandfrancis.com – www.routledge.com CRC Press/Balkema is an imprint of the Taylor & Francis Group, an informa business, London, UK Typeset by Vikatan Publishing Solutions (P) Ltd., Chennai, India Printed and bound in Great Britain by TJ International Ltd, Padstow, Cornwall Library of Congress Cataloging-in-Publication Data Sustainable groundwater resources in Africa : water supply and sanitation environment / editors, Yongxin Xu & Eberhard Braune. p. cm. “Published jointly by UNESCO.” Includes bibliographical references. ISBN 978-0-415-87603-2 (hardcover : alk. paper) 1. Water resources development -- Africa. 2. Groundwater -- Africa. 3. Water-supply -- Africa. 4. Sanitation -- Africa. 5. Human ecology -- Africa. I. Xu, Y. (Yongxin) II. Braune, E. III. Unesco. HD1699.A1S87 2010 333.91’04096--dc22 2009036650 ISBN: 978-0-415-87603-2 (hbk) ISBN: 978-0-203-85945-2 (eBook) Disclaimer The designations employed and the presentation of material throughout this publication do not imply the expression of any opinion whatsoever on the part of UNESCO concern- ing the legal status of any country, territory, city or area or of its authorities, or concern- ing the delimitation of its frontiers or boundaries. The author is responsible for the choice and the presentation of the facts contained in this book and for the opinions expressed therein, which are not necessarily those of UNESCO and do not commit the Organization. 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Copyright © 2010 UNESCO Table of contents List of figures XI List of tables XV Preface XVII Acknowledgements XIX List of contributors XXI I – Best practice guidelines 1 Water supply and sanitation issues in Africa 3 1.1 Contribution of water supply and sanitation to African development 3 1.2 Millennium development goals and water 4 1.3 Water supply and sanitation coverage 6 1.4 Challenges and strategies to achieve the MDGs for WSS 9 1.4.1 Rural water supply 10 1.4.2 Urban water supply 10 1.4.3 Sanitation 11 1.4.4 General 11 1.5 Various programmes to achieve goal 13 1.6 From water for domestic use to a livelihoods focus 15 1.7 Conclusions 16 2 Groundwater resources in Africa 19 2.1 Characteristics of groundwater resources 19 2.1.1 Major types of aquifers 19 2.1.2 Groundwater resources in Africa 21 2.1.3 Roles and functions 24 2.2 The sustainable groundwater utilization and management in Africa 28 2.2.1 Major groundwater-related issues and problems on the African continent 28 2.2.2 The data and information management relating to groundwater resources management 32 2.2.3 Implication of climate change 33 2.3 Outlook for the sustainable utilization of groundwater in Africa 34 3 Framework of best practices for groundwater supply and sanitation provision 39 3.1 Introduction 39 3.2 Integrated water resources management 39 3.3 Groundwater and IWRM 40 3.4 Integrated water, sanitation and hygiene delivery 42 3.5 Integrated service delivery in the urban environment 43 3.6 Integrated service delivery in the rural environment 45 3.7 A framework to facilitate groundwater management 46 Copyright © 2010 UNESCO VI Table of contents 4 Best practice for groundwater quality protection 49 4.1 General introduction 49 4.2 South African borehole guidelines 49 4.2.1 Introduction 50 4.2.2 Relevant literature 50 4.2.3 Contracts and agreements 51 4.2.4 Supervision of activities 52 4.2.5 Materials and equipment 53 4.2.6 Anomalous circumstances 54 4.2.7 Straightness and verticality 55 4.2.8 Protecting the resource 56 4.2.9 Safety 58 4.2.10 Conclusions 58 4.3 Groundwater protection guidelines 58 4.3.1 Basic approaches 59 4.3.2 Concept of safe distance 59 4.3.3 Stepwise procedure from case studies 60 4.3.4 Zoning approach 61 4.3.5 Protection approach in fractured rock aquifers 64 4.3.6 Spring and shallow well protection 69 4.4 Drought proofing 71 4.4.1 Basic concepts 71 4.4.2 Types of drought 73 4.4.3 Livelihood approach 74 4.5 On-site sanitation and groundwater 74 4.6 Ecosan approach for effective groundwater resources management 77 4.6.1 Historical context of Ecosan 77 4.6.2 Main objective of Ecosan projects 78 4.6.3 The philosophy about Ecosan 78 4.6.4 Ecosan and groundwater quality 78 4.6.5 The challenge for Ecosan 79 4.7 Community participation best practice 79 4.8 Towards a comprehensive approach 80 4.8.1 Toolkit for water services 80 5 Summary and recommendations 87 5.1 Summary 87 5.2 Recommendations 89 II – Case studies 6 Groundwater dynamics in the East African Rift System 93 6.1 Introduction 93 6.2 Tectonic framework 95 6.3 Hydrology and climate 97 6.4 Hydrogeological framework 98 6.5 Hydrogeochemical feature 102 6.6 Implication on water supply and sanitation 104 6.7 Summary and recommendations 105 7 Aquifer vulnerability and its implication for community water supply of Porto-Novo region (South–East of Benin) 107 7.1 Introduction 107 7.2 Site description 108 Copyright © 2010 UNESCO Table of contents VII 7.3 Data requirements 109 7.3.1 DRASTIC and GOD methods 109 7.3.2 Evaluation of DRASTIC and GOD parameters 111 7.3.3 Validation of vulnerability maps and determination of aquifer protection 112 7.4 Results and discussion 113 7.4.1 Vulnerability maps 113 7.4.2 Discussion 114 7.5 Conclusion 116 8 Vulnerability of dolomite aquifers in South Africa 119 8.1 Introduction 119 8.2 Geological description 121 8.3 Methodology 122 8.3.1 Overlying layers map (O-Map) 123 8.3.2 Concentration of flow map (C-Map) 125 8.3.3 Precipitation map (P-Map) 128 8.4 VUKA index map 129 8.5 Summary 129 9 A low tech approach to evaluating vulnerability to pollution of basement aquifers in sub-Saharan aquifer 133 9.1 Introduction 133 9.2 The weathered basement aquifer 134 9.3 The groundwater vulnerability drivers 135 9.4 Simple field approach to vulnerability assessment 136 9.5 Scorecard validity 138 9.6 Conclusions 139 10 Preserving groundwater quality against microbiological contamination through differentiated aquifer management in Africa 141 10.1 Introduction 141 10.2 Microbiological transport within secondary aquifers 142 10.3 Extent of microbiological impacts on some Africa aquifers 143 10.4 State of microbiological monitoring networks in Africa 146 10.5 Groundwater protection zoning 146 10.6 Way forward 148 10.7 Conclusion 149 11 Fluoride in African groundwater: Occurrence and mitigation 153 11.1 Introduction 153 11.1.1 Health effects of ingested fluorine 153 11.1.2 Fluoride content as a water quality parameter 154 11.2 Sources of fluoride in groundwater 154 11.2.1 Natural sources 154 11.2.2 Anthropogenic sources 155 11.3 Formation of fluoride-rich groundwater 155 11.4 Determination of fluoride 155 11.5 Fluoride occurrence in African groundwater 156 11.5.1 Occurrence based on documented cases 156 11.5.2 Can we predict distribution pattern of fluoride in Africa? 158 11.5.3 Occurrence based on probability 160 11.6 Removal of fluoride from drinking water supplies 161 11.6.1 Removal processes 161 11.6.2 Fluoride removal methods 161 11.6.3 Critical assumptions for application 162 Copyright © 2010 UNESCO VIII Table of contents 11.7 Alternative mitigation 164 11.7.1 Improved nutrition 164 11.7.2 Fluoride-free water sources 164 11.8 Implication for rural water supplies 165 12 Practical methods to reduce Iron in groundwater with a case study 169 12.1 Introduction 169 12.2 Project area 169 12.3 Methodology 170 12.4 Iron removal 171 12.5 Results 172 12.6 Iron filter construction 173 12.7 Conclusion 174 13 Investigation of borehole failures—experience from Botswana 177 13.1 Introduction 177 13.2 Hydrogeology of the study area 178 13.3 Methodology and data uesd 179 13.3.1 Methodology 179 13.3.2 Data used 179 13.4 Results and discussion 180 13.4.1 Evidence of possible recent decline in groundwater yield 180 13.4.2 Correlation analysis 181 13.4.3 Reliability analysis of groundwater monitoring data 181 13.5 Summary, conclusion and recommendation 183 14 Cost-effective boreholes in sub-Saharan Africa 187 14.1 Introduction 187 14.2 Assertions, information and evidence of high drilling prices 189 14.3 Conceptual framework 189 14.3.1 Borehole costs and quality 189 14.3.2 Borehole price 192 14.3.3 The core factors 192 14.3.4 Key elements 192 14.4 Analysis of the thirteen elements of cost-effective boreholes 194 14.4.1 Operation