ST/ECA/147 •¿ Cei*« GROUND WATER IN AFRICA UNITED NATIONS ^.. J UNITED NATIONS COBRIGEND SECRETARIAT Ref.: Sales No. E.71.II.A.: (Si/ECA/lk'i 2 July 197; Bíev Yorí GROUND WATER IN AFRICA Corrigendum Page U, fourth paragraph, line 1 For clearing read cleaning Page 9« fifth paragraph, lines 2 and 3 w For production; unirrigated crops tend to be only read production, considering the fact that many crops which are produced at little or no cost for irrigation water are only Page H5, ninth paragraph, lines 2 and 3 For in the (continental) sandstones of the ATbian (Algeria) and L Nutia (Egypt) read in the continental Albian sandstones (Algeria) and Nubian sandstones (Egypt) Page U6, fifth paragraph, line 3 For basins and read basins are Page 67 Seventh line from top For file read records system Seventh line from bottom For sources read resources Page 76, line 6 For drilled read dug Page 8U. line 22 For trial borings have shown read exploratory drilling has shown / / Lith" in United Nations. New York ST/ECA/1^7/CI( July 1973 - 3,500 English only/ 73-13799 -2- Page 9k % penultimate line For contains few impurities read has a low content in dissolved solids Page 106, line 10 For (acolian) read (aeolian) Page 116. final line For Mauritius read Mauritius, an independent State and member of the Commonwealth Page 117. thirteenth line from bottom t For sensulato read lato sensu \ Page 121, line 17 For contamination by brine read sea-water intrusion into the aquifer Page 12U, last paragraph, line 1 For trial bores have been made read exploration bore-holes have been drilled Page 127 First paragraph, line k For water read hydrographie Seventh paragraph, line 1 For The entire country read Most of the country Page 13U, second heading For Surface aquifer covering whole of country read Shallow aquifer covering the whole of the country Page 13$, second paragraph, line k For pressurized fcy read confined under Page 139« fourth line from bottom For (dry wells) read (nearly dry wells) -3- Page IU5, fourth paragraph For assemblages read units Page lU6, final line For results obtained, if any, are read vater obtained, if any, is Page IU9. table, first line For 0.9 to fc8 read 0.9 to U Page 150, line 8 j For tried read drilled i Page 152 Fifth paragraph, line 11 For made read are Seventh line from bottom \ For Water Borings Service read vater-drilling service Page Third paragraph, line 1 For are confined to the Mediterranean coast read are present only in the vicinity of the Mediterranean shores Fourth line from bottom For salts read solids Page 158, fifth line from bottom For sources read points Page 160, seventh paragraph, line 1 For basement collapse trough read rift valley \ \ ST/ECA/147 Department of Economic and Social Affairs GROUND WATER IN AFRICA UNITED NATIONS New York, 1973 NOTE The designations employed and the presentation of the material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the United Nations concerning the legal status of any country or territory or of its authorities, or concerning the delimitation of its frontiers. ST/ECA/147 UNITED NATIONS PUBLICATION Sales No.: E.71.II.A.16 Price: $U.S. 4.00 (or equivalent in other currencies) CONTENTS Page Foreword 1 Introduction 3 A. Historical outline 3 B. Traditional wells and drains 3 C. Drilled and dug wells of modern construction 5 D. Ground water and the water supply of large cities 6 E. Ground water and economic and social development 7 F. Conclusion ....... 10 PART I. OVERVIEW OF AFRICA'S GROUND-WATER RESOURCES Chapter I. Prospecting for ground water in Africa 12 A. Historical outline 12 B. Hydrogeological reconnaissance 13 C. Inventory of water resources 15 D. Geophysical prospecting 17 E. Drilling 20 F. Pumping tests 22 G. Water analyses, tracers, nuclear techniques 23 H. Analogue models 25 I. Ground-water organizations 25 J. Bilateral and international assistance 26 K. Conclusion: general summary and trends 31 II. Occurrence of ground water in Africa 33 A. General 33 B. Geographical and morphological conditions 3I+ C. Climatic conditions 35 D. Geological conditions 39 E. Hydrogeological domains: general summary of the principal reservoirs hk -111- CONTENTS (continued) Page Chapter III. Available yields for the principal types of aquifers ¡±g A. Aquifers with interstitial porosity I+9 B. Aquifers with fracture and channel porosity 53 C. Formations with little or no porosity except locally in certain favourably situated weathered or fissured zones 56 D. Conclusion 60 PART II. GROUND WATER IN AFRICA, ARRANGED BY COUNTRY General Sk Algeria 65 Angola 69 Botswana 71 Burundi 73 Cameroon 7I+ Canary Islands 76 Cape Verde Islands 77 Central African Republic 78 Chad 79 Comoro Islands 82 Dahomey 82 Democratic Republic of the Congo Qk Equatorial Guinea 88 Ethiopia 89 French Territory of the Afars and the Issas 91 Gabon 92 Gambia 9I+ Ghana 95 Guinea 97 Guinea (Bissau) 98 Ivory Coast 99 Kenya 101 -IV- CONTENTS (continued) Lesotho 102 Liberia 103 Libyan Arab Republic 10*+ Madagascar 107 Malawi Ill Mali 113 Mascarene Islands 116 Mauritania 117 Morocco 119 Mozambique 122 Namibia 12U Niger 125 Nigeria 127 People's Republic of the Congo 130 Rwanda 132 Senegal 133 Sierra Leone 135 Somalia 136 South Africa 138 Southern Rhodesia Spanish Sahara Sudan Swaziland Togo Tunisia 150 Uganda 153 United Arab Republic 15Î+ United Republic of Tanzania 156 Upper Volta 158 Zambia !59 -v- CONTENTS (continued) Page PAET III. CONCLUSIONS AND RECOMMENDATIONS I. Conclusions l66 II. Recommendations l68 Map Map of the aquifers of Africa -VI- FOREWORD The Economic and Social Council, by its resolution 675 (XXV) of 2 May 1958, requested the Secretary-General to take appropriate measures for the establishment, within the Secretariat, of a centre to promote co-ordinated efforts for the development of water resources. It also singled out ground-water problems as one of the priority subjects in the development of a programme of studies. Large-Scale Ground-Water Development, published in I960,— was the first study prepared in this field by the Water Resources Development Centre. During the First United Kations Development Decade many projects assisted by the United Nations Development Programme (UNDP) and other United Nations technical co-operation programmes were entirely or partially devoted to ground-water prospection, assessment or pilot development. In Africa alone, 30 such projects have been or are being executed. The utilization of ground water other than spring water has, in fact, begun only recently in many African countries, especially in humid areas, since in the tropical zones, where most of Africa's population lives, surface waters are abundant and widespread. However, the chemical peculiarities and degree of pollution of these surface waters, which sometimes contain large quantities of pathogenic agents, make them in many cases unfit for human consumption - and in some cases even unfit for animal consumption - according to the generally accepted sanitary standards for drinking water. For this reason, ground water is more and more often being used to supply towns and villages, since its quality is usually good enough to render unnecessary the costly treatment facilities required by urban centres that rely on surface water. Moreover, many African cities (including recently established or recently developed capitals) and their industrial areas are situated on or near the seacoast, and they draw their fresh water from underground sources. In the deserts, ground water constitutes the only available source - and then only at certain select locations. Lastly, ground water, whether from springs, drains, traditional wells, modern wells - i.e. wells with motor-driven pumps - or artesian bore-holes, is being more and more frequently used for the irrigation of food or industrial crops, chiefly in the arid and semi-arid zones. Thus, the exploitation of ground water in Africa is an essential factor in the development of the continent: it affects every country and every economic sector. In the following pages the reader will find, firstly, a general view of Africa's ground-water resources and their utilization. Methods of ground-water exploration and exploitation are discussed and a brief account is given of the present state of knowledge, including a description of Africa's major ground-water reservoirs, the yields of which are indicated and illustrated in the schematic map 1/ United Nations publication, Sales No.: I960.II.B.3. -1- of African ground water annexed to this report. Next, there are trief country- monographs incorporating the information submitted "by the specialized technical services of many African countries in response to a United Nations questionnaire. The study ends with a set of conclusions concerning the potential resources, the needs and the development prospects of each region and with some recommendations for the future. Preliminary general reports of the same kind are planned for Latin America, for Asia and the Far East, for the Middle East and for Mediterranean Europe. -2- INTRODUCTION A. Historical outline In Africa, as in the rest of the Old World, the existence of populous ancient civilizations, with an advanced social organization and a sophisticated way of life, is linked to the presence of large rivers. These rivers provide a plentiful supply of water, rich soil, fish and game in the valleys and deltas, ease of transport and relative safety. Two of the greatest African civilizations were those of Egypt, which Herodotus called ''the gift of the Nile", and Benin on the lower Niger, which may have been founded by peoples migrating from the upper Nile valley. The Chad civilization arose in a sort of African Mesopotamia between the Chari and the Logone.