Led by: Further Information: This leaflet has been produced by the International Water Management Institute (IWMI). For more information, contact: Karen Villholth, Principal Researcher – Groundwater Management, IWMI, Pretoria, South Africa (k.villholth@cgiar.org) Yvan Altchenko, Senior Researcher – Hydrogeologist, IWMI, Pretoria, South Africa (y.altchenko@cgiar.org) Front cover photo: Karen Villholth Led by: Transboundary Aquifer Mapping and Management in Africa Africa is heavily reliant on groundwater resources, with an estimated 75% of the population dependent on this resource for basic water supplies. However, with population growth, climate change and the need to combat growing food insecurity, the demand for groundwater is set to increase in the future. The focus on transboundary aquifers (TBAs) comes from the recognition of this increasing stress on available water resources. For the purpose of this study, a TBA (Figure 1) refers to an aquifer or an aquifer system, parts of which are situated in different states. In practical identification and verification of a TBA, the spatial delimitation, hydrogeological similarity, recharge and discharge mechanisms and zones, and significant hydraulic connectivity between the national compartments of the TBA are all important factors and should be established and agreed upon between the aquifer-sharing states. Partner Ministère de l'agriculture, République Française The CGIAR Research Program on Water, Land and Ecosystems (WLE) combines the resources of 11 CGIAR centers, the Food and Agriculture Organization of the United Nations (FAO) and numerous national, regional and international partners to provide an integrated approach to natural resource management research. WLE promotes a new approach to sustainable intensification in which a healthy functioning ecosystem is seen as a prerequisite to agricultural development, resilience of food systems and human well-being. This program is led by the International Water Management Institute (IWMI) and is supported by CGIAR, a global research partnership for a food secure future. wle.cgiar.org The International Water Management Institute (IWMI) is a non-profit, scientific research organization focusing on the sustainable use of water and land resources in developing countries. It is headquartered in Colombo, Sri Lanka, with regional offices across Asia and Africa. IWMI works in partnership with governments, civil society and the private sector to develop scalable agricultural water management solutions that have a real impact on poverty reduction, food security and ecosystem health. www.iwmi.org Phot o: Karen Villh olth Printed: July, 2014 Figure 2 builds on previous maps created by the United Nations Educational, Scientific and Cultural Organization (UNESCO), the World-wide Hydrogeological Mapping and Assessment Programme (WHYMAP) and the International Groundwater Resources Assessment Centre (IGRAC), and shows the presently known TBAs in Africa. It includes 80 aquifers and aquifer systems, which Source: UNESCO 2004 Figure 1. Schematic illustration of a transboundary aquifer. are shared internationally, superimposed on 63 international river basins. The mapping proposes a new nomenclature for the TBAs, based on three subregions, reflecting the leading regional economic communities (RECs) as shown in Table 4. The map illustrates that TBAs cover approximately 42% of the continental area and 30% of the population. Table 1. Evolution of the number of TBAs in Africa, inventoried and mapped by various efforts and subdivided into regions. AFRICAN REGIONa UNESCO WHYMAP IGRAC IGRAC Altchenko 2004 2006 2009 2012 and Villholth 2013 Northern Africa 6 6 7 9 15 Western and Middle Africa (except countries in the SADC regionb) 9 9 9 22 22 Eastern Africa (except countries in the SADC region) 5 5 5 6 8 Southern Africa (SADC countries) 18 20 20 34 35 TOTAL 38 40 41 71 80 Notes: a According to the United Nations division of regions and subregions (UNdata 2013) b SADC - Southern African Development Community Table 4. The proposed regional subdivision for TBA nomenclature in Africa. Subdivision zone Countries in the African continent Regional economic name (code name) communities (RECs) concerned Northern and Eastern Africa Algeria, Djibouti, Egypt, Eritrea, Ethiopia, Kenya, IGADa*** (AFNE) Libya, Morocco, Somalia, South Sudan, Sudan, COMESAb** Tunisia, Uganda and Western Sahara CEN-SADc** CEN-SADc** EACd** AMU/UMAe* Western and Central Africa Benin, Burkina Faso, Cameroon, Central African ECOWASf*** (AFWC) Republic (CAR), Chad, Republic of the Congo, ECCASg** Côte d’Ivoire, Equatorial Guinea, Gabon, Gambia, CEN-SAD** Ghana, Guinea, Guinea Bissau, Liberia, Mali, AMU/UMA* Mauritania, Niger, Nigeria, Senegal, Sierra Leone and Togo Southern Africa (AFS) Angola, Botswana, Burundi, Democratic Republic SADCh*** of the Congo (DRC), Lesotho, Madagascar, Malawi, COMESA** Mozambique, Namibia, Rwanda, South Africa, EAC** Swaziland, Tanzania, Zambia and Zimbabwe Notes: *** active, ** poorly active and * non-active in transboundary water resources management, according to NEPAD, AU and AfDB 2011. a IGAD – Intergovernmental Authority on Development; b COMESA – Common Market for Eastern and Southern Africa; c CEN-SAD – The Community of Sahel-Saharan States; d EAC – East African Community; e AMU/UMA – Arab Maghreb Union; f ECOWAS – Economic Community of West African States; g ECCAS – Economic Community of Central African States; h SADC – Southern African Development Community. References Altchenko, Y.; Villholth, K.G. 2013. Transboundary aquifer mapping and management in Africa: A harmonised approach. Hydrogeology Journal 21(7): 1497-1517. IGRAC (International Groundwater Resources Assessment Centre). 2009. Transboundary aquifers of the world 2009. Special edition for the 5th World Water Forum, Istanbul, Turkey, March 2009, ed., Kukuric, N. Available at http://www.un-igrac.org/publications/323# (accessed on April 16, 2013). IGRAC (International Groundwater Resources Assessment Centre). 2012. Transboundary aquifers of the world 2012. Special edition for 6th World Water Forum, Marseille, France, March 2012, ed., Kukuric, N. Available at http://www.un-igrac.org/publications/456# (accessed on April 16, 2013). NEPAD (New Partnership for Africa’s Development); AU (African Union); AfDB (African Development Bank). 2011. Study on Programme for Infrastructure Development in Africa (PIDA). Phase I. TWRM sector (Transboundary Water) Sector. 32p. Puri, S.; Appelgren, B.; Arnold, G.; Aureli, A.; Burchi, S.; Burke, J.; Margat, J.; Pallas, P. 2001. Internationally shared (transboundary) aquifer resources management: Their significance and sustainable management. A framework document. IHP-VI, Series on Groundwater No. 1. Paris, France: United Nations Educational, Scientific and Cultural Organization (UNESCO). 71p. Available at http://unesdoc.unesco.org/images/0012/001243/124386e.pdf (accessed on June 9, 2014). UNdata. 2013. Composition of macro geographical (continental) regions, geographical sub-regions, and selected economic and other groupings. UNdata, United Nations Statistics Division. Available at http://millenniumindicators.un.org/unsd/methods/m49/m49regin.htm (accessed on April 16, 2013). UNESCO (United Nations Educational, Scientific and Cultural Organization). 2004. Proceedings of the International Workshop on Managing Shared Aquifer Resources in Africa, Tripoli, Libya, June 2-4, 2002, ed., Applegreen, B. ISARM-Africa. IHP-VI, Series on Groundwater No. 8. 238p. WHYMAP (World-wide Hydrogeological Mapping and Assessment Programme). 2006. Groundwater resources of the world - Transboundary aquifer systems. Special edition for the 4th World Water Forum, Mexico City, March 2006. Hannover: Bundesanstalt für Geowissenschaften und Rohstoffe (BGR); Paris: United Nations Educational, Scientific and Cultural Organization (UNESCO). Available at http://www.whymap.org/whymap/EN/Downloads/Global_maps/spec_ed_2_map_pdf.pdf?__blob=publicationFile&v=3 (accessed on April 16, 2013). Figure 2. Transboundary aquifers and international river/lake basins in Africa. Table 2. Inventory of transboundary aquifers in Africa. ID Name Countries Population Area Aquifer type Rainfall Annual sharing the aquifer (inhabitants) (km2) (mm/year) recharge (WHYMAP) AFS1 Karoo sedimentary aquifer Lesotho/South Africa 5,568,000 166,000 Consolidated sedimentary rocks 350 – 1,200 VL to M AFS2 Coastal sedimentary basin 5 Namibia/South Africa 7,900 1,700 Quaternary and consolidated sedimentary rocks 45 – 55 VL to M AFS3 Coastal sedimentary basin 6 Mozambique/South Africa 548,000 11,700 Quaternary and consolidated sedimentary rocks 700 – 1,200 M to H AFS4 Rhyolite-Breccia aquifer Mozambique/South Africa/Swaziland 206,000 5,500 Volcanic/Quaternary 600 – 850 VL to M AFS5 Southwest Kalahari/Karoo basin Botswana/Namibia/South Africa 15,500 85,000 Kalahari groups aquifer and Karoo supergroup aquifers 200 – 350 VL to M AFS6 Ncojane aquifer Botswana/Namibia 2,300 10,300 Consolidated sedimentary rocks 300 – 350 VL to M AFS7 Khakhea/Bray dolomite South Africa/Botswana 57,000 30,000 Dolomite 300 – 450 VL to M AFS8 Ramotswa dolomite basin Botswana/South Africa 135,500 3,200 Malmani subgroup of the Transvaal supergroup 500 – 550 VL to M AFS9 Limpopo basin Mozambique/South Africa/Zimbabwe 313,800 20,000 Volcanic and basement rocks 400 – 700 VL to L AFS10 Tuli Karoo sub-basin Botswana/South Africa/Zimbabwe 70,600 14,330 Volcanic and basement rocks 300 – 450 VL to L AFS11 Northern Kalahari/Karoo basin Angola/Botswana/Namibia/Zambia 35,900 144,400 Consolidated sedimentary rocks 380 – 550 VL to H AFS12 Save alluvial aquifer Mozambique/Zimbabwe 32,600 4,500 Alluvial 400 – 600 VL to M AFS13 Eastern Kalahari/Karoo basin Botswana/Zimbabwe 54,300 39,600 Upper Karoo Sandstone 400 – 600 VL to M AFS14 Cuvelai and Etosha basin Angola/Namibia 1,032,400 202,000 Consolidated sedimentary rocks 300 – 900 L to M AFS15 Nata Karoo sub-basin Botswana/Namibia/Zimbabwe 195,000 91,000 Ecca sequence 500 – 750 VL to M AFS16 Coastal sedimentary basin 4 Angola/Namibia 20 2,200 Quaternary and consolidated sedimentary rocks 100 – 150 VL to M AFS17 Medium Zambezi aquifer Mozambique/Zambia/Zimbabwe 50,800 10,700 Quaternary and consolidated sedimentary rocks 720 – 780 VL to M AFS18 Shire Valley aquifer Malawi/Mozambique 527,000 6,200 Tertiary/Quaternary 780 – 900 M to VH AFS19 Arangua Alluvial Mozambique/Zambia 12,500 21,200 Alluvial 700 – 1,100 VL to M AFS20 Sand and gravel aquifer Malawi/Zambia 2 233,000 25,300 Unconsolidated intergranular aquifer and weathered 800 – 1,200 VL to VH basement complex AFS21 Coastal sedimentary basin 3 Mozambique/Tanzania 794,000 23,000 Quaternary and consolidated sedimentary rocks 930 – 1,200 H AFS22 Karoo-Sandstone aquifer Mozambique/Tanzania 214,500 40,000 Consolidated sedimentary rocks 900 – 1,700 M to VH AFS23 Kalahari/Katangian basin DRC/Zambia 1,006,000 15,600 Katangian and Kalahari sequence 1,200 – 1,300 H to VH AFS24 Congo Intra-cratonic Angola/DRC 1,920,000 317,200 Consolidated sedimentary rocks 1,200 – 1,650 H AFS25 Weathered basement Malawi/Tanzania/Zambia 852,000 25,842 NI 900 – 2,000 M to VH AFS26 Karoo Carbonate CAR/Congo/South Sudan 9,400,000 941,100 Limestone/Sandstone 1,000 – 1,800 H to VH AFS27 Tanganyika aquifer Burundi/DRC/Tanzania/Rwanda 11,940,000 222,300 Fractured basalt and granite 800 – 1,800 VL to VH AFS28 Dolomitic aquifer Angola/DRC 750,600 21,300 Karst weathered dolomite 1,100 – 1,450 H to VH AFS29 Coastal sedimentary basin 2 Angola/DRC 34,000 2,250 Quaternary and consolidated sedimentary rocks 800 – 1,000 VL to H AFS30 Cuvette Centale Congo/DRC 14,000,000 814,800 Alluvial Sandstones 1,400 – 2,100 H to VH AFS31 Coastal sedimentary basin 1 Kenya/Tanzania 2,150,000 16,800 Quaternary and consolidated sedimentary rocks 850 – 1,250 M to H AFS32 Kilimanjero aquifer Kenya/Tanzania 1,396,000 14,600 Volcanic alluvium 600 – 1,600 VL to M AFS33 Kagera aquifer Rwanda/Tanzania/Uganda 493,500 5,800 Alluvial unconsolidated sand and gravels 930 – 1,800 VL to M AFS34 Mgahinga DRC/Rwanda/Uganda 1,451,000 4,400 Volcanic 1,250 – 1,650 VL to M AFS35 Western Rift valley sediment DRC/Uganda 1,151,000 29,500 Volcanic 800 – 1,250 VL to H AFWC1 NN Congo/Gabon 13,300 23,000 NI 1,400 – 1,750 M to VH AFWC2 NN Congo/Gabon 48,500 7,100 NI 1,650 – 1,950 H to VH AFWC3 NN Congo/Gabon 41,000 23,500 NI 1,750 – 1,950 H to VH AFWC4 NN Congo/Gabon 1,700 19,600 NI 1,600 – 1,750 H to VH AFWC5 NN Cameroon/CAR/Gabon 178,000 66,400 NI 1,550 – 1,650 H to VH AFWC6 Rio Delrey Cameroon/Nigeria 3,300,000 24,000 Upper Miocene to Quaternary 2,500 – 3,130 VH AFWC7 Keta basin Benin/Nigeria/Togo 16,896,000 55,400 Quaternary (sand, silt, clay) 950 – 2,450 H to VH AFWC8 Tano basin Côte d'Ivoire/Ghana 4,740,000 43,000 Quaternary Terminal Continental and Maestrichtien Aquifer 1,300 – 1,930 H to VH AFWC9 NN Côte d'Ivoire/Guinea/Liberia 2,370,000 47,300 NI 1,400 – 2,050 H to VH AFWC10 Kandi sedimentary basin Benin/Burkina Faso/Ghana/Togo 1,143,000 47,800 Cambro-Ordovicien and alluvial 850 – 1,100 VL to VH AFWC11 Garoua - Chari Cameroon/Nigeria 1,870,000 38,400 Sandstone - Clay 950 – 1,400 H to VH AFWC12 NN Cameroon/CAR/Chad/Sudan 716,000 155,400 Sedimentary 700 – 1,600 H to VH ID Name Countries Population Area Aquifer type Rainfall Annual sharing the aquifer (inhabitants) (km2) (mm/year) recharge (WHYMAP) AFWC13 Disa Chad/Sudan 74,300 1,500 Sandstone 500 – 550 VL to M AFWC14 Lake Chad CAR/Cameroon/Chad/Niger/Nigeria 22,419,100 1,300,500 Sedimentary: the Upper Quaternary, the Lower Pliocene 40 – 1,400 VL to H and the TC AFWC15 Irhazer-Iullemeden Algeria/Mali/Niger/Nigeria 12,888,600 545,400 Sedimentary deposit including IC and TC 80 – 900 VL to VH AFWC16 NN Burkina Faso/Mali/Niger 333,000 3,500 NI 250 – 600 VL to M AFWC17 Liptako-Gourma aquifer Burkina Faso/Niger 7,758,300 159,500 Fractured metamorphic 400 – 900 VL to H AFWC18 NN Guinea/Mali/Senegal 4,250,000 185,500 Birrimien 850 – 1,650 VL to VH AFWC19 Senegalo-Mauritanian basin Gambia/Guinea-Bissau 11,930,000 331,450 Maestrichtien 20 – 1,850 VL to VH Mauritania/Senegal AFWC20 Taoudeeni basin Algeria/Mali/Mauritania 82,400 936,000 Multilayers 10 – 350 VL to L AFWC21 L'air Cristalline aquifer Algeria/Mali 84 28,400 NI 60 – 100 VL to M AFWC22 Tin Seririne Algeria/Nigeria 520 73,700 NI 20 – 50 VL to L AFNE1 Rift aquifer Kenya/Tanzania/Uganda 279,000 21,150 Volcanic 450 – 1,100 VL to M AFNE2 Merti aquifer Kenya/Somalia 129,000 13,500 Semi-consolidated sedimentary 350 – 750 L to M AFNE3 Mount Elgon Kenya/Uganda 806,550 5,400 Volcanic 1,000 – 1,300 VL to M AFNE4 Dawa Ethiopia/Kenya/Somalia 223,150 24,000 Volcanic rocks, alluvials and Precambrian basement 300 – 650 VL to L AFNE5 Juba aquifer Ethiopia/Kenya/Somalia 197,600 34,600 Aquifers in Precambrian and intrusive rocks 270 – 450 VL to L AFNE6 Shabelle aquifer Ethiopia/Somalia 334,000 31,000 Sedimentary and minor volcanic aquifers 280 – 400 VL to L AFNE7 Sudd basin Ethiopia/Kenya 2,926,500 331,600 Precambrian and volcanic rocks with patches of alluvials/ 450 – 1,100 M South Sudan/Sudan sedimentary AFNE8 Baggara basin CAR/South Sudan/Sudan 2,433,500 239,300 Umm Ruwaba (overlain the Nubian Formation) 300 – 900 L to M AFNE9 Awash Valley aquifer Djibouti/Eritrea/Ethiopia 627,400 50,700 Volcanic 110 – 350 VL to L AFNE10 Mareb aquifer Eritrea/Ethiopia 1,827,900 22,800 Precambrian and intrusive rocks 450 – 550 VL to M AFNE11 Gedaref Eritrea/Ethiopia 732,000 38,700 Precambrian and volcanic rocks with patches of 400 – 950 VL to M Sudan alluvials/sedimentary AFNE12 Nubian Sandstone aquifer Chad/Egypt/Libya/Sudan 67,320,000 2,608,000 Nubian and Post-Nubian 1 – 550 Mainly VL system (mainly < 30) (VL to VH) AFNE13 Mourzouk-Djado basin Algeria/Libya/Nigeria 108,000 286,200 Sedimentary < 20 Mainly VL (VL to M) AFNE14 Tindouf aquifer Algeria/Mauritania/Morocco 107,000 160,000 Alternating series of calcareous rocks and sand 30 – 200 VL to M AFNE15 Errachidia basin Algeria/Morocco 156,300 18,500 Sandstone, calcareous, dolomite 80 – 200 VL to L AFNE16 North Western Sahara Aquifer Algeria/Libya/Tunisia 4,000,000 1,190,000 Sand, Sandstone, sandy clay, calcareous, dolomite 10 – 300 VL to L system (mainly < 50) AFNE17 Djaffar Djeffara Libya/Tunisia 262,400 15,800 NI 130 – 250 L AFNE18 Figuig Algeria/Morocco 32,300 1,500 Phreatic Aquifer, Porous 100 – 170 VL to L AFNE19 Chott Tigri-Lahouita Algeria/Morocco 26,800 4,700 Porous, Karst, Dolomite Limestone and Sandstone 180 – 250 VL to L AFNE20 Ain Beni mathar Algeria/Morocco 23,100 20,000 Karstic, Dolomite Limestone and Dolomite 260 – 350 VL to M AFNE21 Angad Algeria/Morocco 25,600 3,500 Porous, Plio-Quaternary 350 – 450 VL to M AFNE22 Jbel El Hamra Algeria/Morocco 40,100 1,250 Karstic 440 – 500 VL to L AFNE23 Triffa Algeria/Morocco 920,000 13,100 PorousVillafranchian and Quaternary 370 – 450 M Notes: NN = No name referenced; NI = No information; TC = Terminal Continental; IC = Intercalary Continental; VL = Very low (0 - 2 mm/year); L = Low (2 - 20 mm/year); M = Medium (20 - 100 mm/year); H = High (100 - 300 mm/year); VH = Very high (> 300 mm/year) Table 2. Inventory of transboundary aquifers in Africa (Continued) (Continued) Table 2. Inventory of transboundary aquifers in Africa. ID Name Countries Population Area Aquifer type Rainfall Annual sharing the aquifer (inhabitants) (km2) (mm/year) recharge (WHYMAP) AFS1 Karoo sedimentary aquifer Lesotho/South Africa 5,568,000 166,000 Consolidated sedimentary rocks 350 – 1,200 VL to M AFS2 Coastal sedimentary basin 5 Namibia/South Africa 7,900 1,700 Quaternary and consolidated sedimentary rocks 45 – 55 VL to M AFS3 Coastal sedimentary basin 6 Mozambique/South Africa 548,000 11,700 Quaternary and consolidated sedimentary rocks 700 – 1,200 M to H AFS4 Rhyolite-Breccia aquifer Mozambique/South Africa/Swaziland 206,000 5,500 Volcanic/Quaternary 600 – 850 VL to M AFS5 Southwest Kalahari/Karoo basin Botswana/Namibia/South Africa 15,500 85,000 Kalahari groups aquifer and Karoo supergroup aquifers 200 – 350 VL to M AFS6 Ncojane aquifer Botswana/Namibia 2,300 10,300 Consolidated sedimentary rocks 300 – 350 VL to M AFS7 Khakhea/Bray dolomite South Africa/Botswana 57,000 30,000 Dolomite 300 – 450 VL to M AFS8 Ramotswa dolomite basin Botswana/South Africa 135,500 3,200 Malmani subgroup of the Transvaal supergroup 500 – 550 VL to M AFS9 Limpopo basin Mozambique/South Africa/Zimbabwe 313,800 20,000 Volcanic and basement rocks 400 – 700 VL to L AFS10 Tuli Karoo sub-basin Botswana/South Africa/Zimbabwe 70,600 14,330 Volcanic and basement rocks 300 – 450 VL to L AFS11 Northern Kalahari/Karoo basin Angola/Botswana/Namibia/Zambia 35,900 144,400 Consolidated sedimentary rocks 380 – 550 VL to H AFS12 Save alluvial aquifer Mozambique/Zimbabwe 32,600 4,500 Alluvial 400 – 600 VL to M AFS13 Eastern Kalahari/Karoo basin Botswana/Zimbabwe 54,300 39,600 Upper Karoo Sandstone 400 – 600 VL to M AFS14 Cuvelai and Etosha basin Angola/Namibia 1,032,400 202,000 Consolidated sedimentary rocks 300 – 900 L to M AFS15 Nata Karoo sub-basin Botswana/Namibia/Zimbabwe 195,000 91,000 Ecca sequence 500 – 750 VL to M AFS16 Coastal sedimentary basin 4 Angola/Namibia 20 2,200 Quaternary and consolidated sedimentary rocks 100 – 150 VL to M AFS17 Medium Zambezi aquifer Mozambique/Zambia/Zimbabwe 50,800 10,700 Quaternary and consolidated sedimentary rocks 720 – 780 VL to M AFS18 Shire Valley aquifer Malawi/Mozambique 527,000 6,200 Tertiary/Quaternary 780 – 900 M to VH AFS19 Arangua Alluvial Mozambique/Zambia 12,500 21,200 Alluvial 700 – 1,100 VL to M AFS20 Sand and gravel aquifer Malawi/Zambia 2 233,000 25,300 Unconsolidated intergranular aquifer and weathered 800 – 1,200 VL to VH basement complex AFS21 Coastal sedimentary basin 3 Mozambique/Tanzania 794,000 23,000 Quaternary and consolidated sedimentary rocks 930 – 1,200 H AFS22 Karoo-Sandstone aquifer Mozambique/Tanzania 214,500 40,000 Consolidated sedimentary rocks 900 – 1,700 M to VH AFS23 Kalahari/Katangian basin DRC/Zambia 1,006,000 15,600 Katangian and Kalahari sequence 1,200 – 1,300 H to VH AFS24 Congo Intra-cratonic Angola/DRC 1,920,000 317,200 Consolidated sedimentary rocks 1,200 – 1,650 H AFS25 Weathered basement Malawi/Tanzania/Zambia 852,000 25,842 NI 900 – 2,000 M to VH AFS26 Karoo Carbonate CAR/Congo/South Sudan 9,400,000 941,100 Limestone/Sandstone 1,000 – 1,800 H to VH AFS27 Tanganyika aquifer Burundi/DRC/Tanzania/Rwanda 11,940,000 222,300 Fractured basalt and granite 800 – 1,800 VL to VH AFS28 Dolomitic aquifer Angola/DRC 750,600 21,300 Karst weathered dolomite 1,100 – 1,450 H to VH AFS29 Coastal sedimentary basin 2 Angola/DRC 34,000 2,250 Quaternary and consolidated sedimentary rocks 800 – 1,000 VL to H AFS30 Cuvette Centale Congo/DRC 14,000,000 814,800 Alluvial Sandstones 1,400 – 2,100 H to VH AFS31 Coastal sedimentary basin 1 Kenya/Tanzania 2,150,000 16,800 Quaternary and consolidated sedimentary rocks 850 – 1,250 M to H AFS32 Kilimanjero aquifer Kenya/Tanzania 1,396,000 14,600 Volcanic alluvium 600 – 1,600 VL to M AFS33 Kagera aquifer Rwanda/Tanzania/Uganda 493,500 5,800 Alluvial unconsolidated sand and gravels 930 – 1,800 VL to M AFS34 Mgahinga DRC/Rwanda/Uganda 1,451,000 4,400 Volcanic 1,250 – 1,650 VL to M AFS35 Western Rift valley sediment DRC/Uganda 1,151,000 29,500 Volcanic 800 – 1,250 VL to H AFWC1 NN Congo/Gabon 13,300 23,000 NI 1,400 – 1,750 M to VH AFWC2 NN Congo/Gabon 48,500 7,100 NI 1,650 – 1,950 H to VH AFWC3 NN Congo/Gabon 41,000 23,500 NI 1,750 – 1,950 H to VH AFWC4 NN Congo/Gabon 1,700 19,600 NI 1,600 – 1,750 H to VH AFWC5 NN Cameroon/CAR/Gabon 178,000 66,400 NI 1,550 – 1,650 H to VH AFWC6 Rio Delrey Cameroon/Nigeria 3,300,000 24,000 Upper Miocene to Quaternary 2,500 – 3,130 VH AFWC7 Keta basin Benin/Nigeria/Togo 16,896,000 55,400 Quaternary (sand, silt, clay) 950 – 2,450 H to VH AFWC8 Tano basin Côte d'Ivoire/Ghana 4,740,000 43,000 Quaternary Terminal Continental and Maestrichtien Aquifer 1,300 – 1,930 H to VH AFWC9 NN Côte d'Ivoire/Guinea/Liberia 2,370,000 47,300 NI 1,400 – 2,050 H to VH AFWC10 Kandi sedimentary basin Benin/Burkina Faso/Ghana/Togo 1,143,000 47,800 Cambro-Ordovicien and alluvial 850 – 1,100 VL to VH AFWC11 Garoua - Chari Cameroon/Nigeria 1,870,000 38,400 Sandstone - Clay 950 – 1,400 H to VH AFWC12 NN Cameroon/CAR/Chad/Sudan 716,000 155,400 Sedimentary 700 – 1,600 H to VH ID Name Countries Population Area Aquifer type Rainfall Annual sharing the aquifer (inhabitants) (km2) (mm/year) recharge (WHYMAP) AFWC13 Disa Chad/Sudan 74,300 1,500 Sandstone 500 – 550 VL to M AFWC14 Lake Chad CAR/Cameroon/Chad/Niger/Nigeria 22,419,100 1,300,500 Sedimentary: the Upper Quaternary, the Lower Pliocene 40 – 1,400 VL to H and the TC AFWC15 Irhazer-Iullemeden Algeria/Mali/Niger/Nigeria 12,888,600 545,400 Sedimentary deposit including IC and TC 80 – 900 VL to VH AFWC16 NN Burkina Faso/Mali/Niger 333,000 3,500 NI 250 – 600 VL to M AFWC17 Liptako-Gourma aquifer Burkina Faso/Niger 7,758,300 159,500 Fractured metamorphic 400 – 900 VL to H AFWC18 NN Guinea/Mali/Senegal 4,250,000 185,500 Birrimien 850 – 1,650 VL to VH AFWC19 Senegalo-Mauritanian basin Gambia/Guinea-Bissau 11,930,000 331,450 Maestrichtien 20 – 1,850 VL to VH Mauritania/Senegal AFWC20 Taoudeeni basin Algeria/Mali/Mauritania 82,400 936,000 Multilayers 10 – 350 VL to L AFWC21 L'air Cristalline aquifer Algeria/Mali 84 28,400 NI 60 – 100 VL to M AFWC22 Tin Seririne Algeria/Nigeria 520 73,700 NI 20 – 50 VL to L AFNE1 Rift aquifer Kenya/Tanzania/Uganda 279,000 21,150 Volcanic 450 – 1,100 VL to M AFNE2 Merti aquifer Kenya/Somalia 129,000 13,500 Semi-consolidated sedimentary 350 – 750 L to M AFNE3 Mount Elgon Kenya/Uganda 806,550 5,400 Volcanic 1,000 – 1,300 VL to M AFNE4 Dawa Ethiopia/Kenya/Somalia 223,150 24,000 Volcanic rocks, alluvials and Precambrian basement 300 – 650 VL to L AFNE5 Juba aquifer Ethiopia/Kenya/Somalia 197,600 34,600 Aquifers in Precambrian and intrusive rocks 270 – 450 VL to L AFNE6 Shabelle aquifer Ethiopia/Somalia 334,000 31,000 Sedimentary and minor volcanic aquifers 280 – 400 VL to L AFNE7 Sudd basin Ethiopia/Kenya 2,926,500 331,600 Precambrian and volcanic rocks with patches of alluvials/ 450 – 1,100 M South Sudan/Sudan sedimentary AFNE8 Baggara basin CAR/South Sudan/Sudan 2,433,500 239,300 Umm Ruwaba (overlain the Nubian Formation) 300 – 900 L to M AFNE9 Awash Valley aquifer Djibouti/Eritrea/Ethiopia 627,400 50,700 Volcanic 110 – 350 VL to L AFNE10 Mareb aquifer Eritrea/Ethiopia 1,827,900 22,800 Precambrian and intrusive rocks 450 – 550 VL to M AFNE11 Gedaref Eritrea/Ethiopia 732,000 38,700 Precambrian and volcanic rocks with patches of 400 – 950 VL to M Sudan alluvials/sedimentary AFNE12 Nubian Sandstone aquifer Chad/Egypt/Libya/Sudan 67,320,000 2,608,000 Nubian and Post-Nubian 1 – 550 Mainly VL system (mainly < 30) (VL to VH) AFNE13 Mourzouk-Djado basin Algeria/Libya/Nigeria 108,000 286,200 Sedimentary < 20 Mainly VL (VL to M) AFNE14 Tindouf aquifer Algeria/Mauritania/Morocco 107,000 160,000 Alternating series of calcareous rocks and sand 30 – 200 VL to M AFNE15 Errachidia basin Algeria/Morocco 156,300 18,500 Sandstone, calcareous, dolomite 80 – 200 VL to L AFNE16 North Western Sahara Aquifer Algeria/Libya/Tunisia 4,000,000 1,190,000 Sand, Sandstone, sandy clay, calcareous, dolomite 10 – 300 VL to L system (mainly < 50) AFNE17 Djaffar Djeffara Libya/Tunisia 262,400 15,800 NI 130 – 250 L AFNE18 Figuig Algeria/Morocco 32,300 1,500 Phreatic Aquifer, Porous 100 – 170 VL to L AFNE19 Chott Tigri-Lahouita Algeria/Morocco 26,800 4,700 Porous, Karst, Dolomite Limestone and Sandstone 180 – 250 VL to L AFNE20 Ain Beni mathar Algeria/Morocco 23,100 20,000 Karstic, Dolomite Limestone and Dolomite 260 – 350 VL to M AFNE21 Angad Algeria/Morocco 25,600 3,500 Porous, Plio-Quaternary 350 – 450 VL to M AFNE22 Jbel El Hamra Algeria/Morocco 40,100 1,250 Karstic 440 – 500 VL to L AFNE23 Triffa Algeria/Morocco 920,000 13,100 PorousVillafranchian and Quaternary 370 – 450 M Notes: NN = No name referenced; NI = No information; TC = Terminal Continental; IC = Intercalary Continental; VL = Very low (0 - 2 mm/year); L = Low (2 - 20 mm/year); M = Medium (20 - 100 mm/year); H = High (100 - 300 mm/year); VH = Very high (> 300 mm/year) Table 2. Inventory of transboundary aquifers in Africa (Continued) (Continued) The management of TBAs has only recently been addressed as part of transboundary water management. It is critical to implement frameworks for managing already stressed, shared groundwater resources and associated dependent ecosystems, as well as for enhancing the sustainable development of Figure 2. Transboundary aquifers and international river/lake basins in Africa.‘new’ groundwater resources. While a harmonised approach is advocated, it is also acknowledged that flexible and hybrid institutional models that build on the present customary approach of making the river and lake basin organisations (R/LBOs) responsible may be necessary, as illustrated in Table 3 and Figure 3. Table 3. Configuration of TBA location in relation to international river/lake basin (R/LB) as described in Figure 3. Geographical Intersection of TBA Number of cases in Africa Example of TBA with no type with R/LB (number of cases R/LBO where R/LBO exists)a 1 None 3 Ain Beni Mathar (-) (AFNE20) 2 TBA partly inside 20 Coastal Sedimentary a single R/LB (13) Basin 1 (AFS31) 3 TBA partly inside two 12 Tano Basin (AFWC8) or more R/LBs (7) 4 TBA fully inside a 23 Figuig (AFNE18) single R/LB (22) 5 TBA fully inside two R/LBs 18 Errachidia Basin (17) (AFNE15) 6 TBA fully inside three 4 AFWC9b or more R/LBs (3) Notes: a A distinction is made between international R/LBs with and without a formalised basin organisation. b TBA has no name, according to IGRAC 2012. Figure 3. Conceptual configuration of TBA location in relation to international river and lake basins (R/LBs); polygons represent river/lake basins, squares represent TBAs. Figure 2 builds on previous maps created by the United Nations Educational, Scientific and Cultural Organization (UNESCO), the World-wide Hydrogeological Mapping and Assessment Programme (WHYMAP) and the International Groundwater Resources Assessment Centre (IGRAC), and shows the presently known TBAs in Africa. It includes 80 aquifers and aquifer systems, which Source: UNESCO 2004 Figure 1. Schematic illustration of a transboundary aquifer. are shared internationally, superimposed on 63 international river basins. The mapping proposes a new nomenclature for the TBAs, based on three subregions, reflecting the leading regional economic communities (RECs) as shown in Table 4. The map illustrates that TBAs cover approximately 42% of the continental area and 30% of the population. Table 1. Evolution of the number of TBAs in Africa, inventoried and mapped by various efforts and subdivided into regions. AFRICAN REGIONa UNESCO WHYMAP IGRAC IGRAC Altchenko 2004 2006 2009 2012 and Villholth 2013 Northern Africa 6 6 7 9 15 Western and Middle Africa (except countries in the SADC regionb) 9 9 9 22 22 Eastern Africa (except countries in the SADC region) 5 5 5 6 8 Southern Africa (SADC countries) 18 20 20 34 35 TOTAL 38 40 41 71 80 Notes: a According to the United Nations division of regions and subregions (UNdata 2013) b SADC - Southern African Development Community Table 4. The proposed regional subdivision for TBA nomenclature in Africa. Subdivision zone Countries in the African continent Regional economic name (code name) communities (RECs) concerned Northern and Eastern Africa Algeria, Djibouti, Egypt, Eritrea, Ethiopia, Kenya, IGADa*** (AFNE) Libya, Morocco, Somalia, South Sudan, Sudan, COMESAb** Tunisia, Uganda and Western Sahara CEN-SADc** CEN-SADc** EACd** AMU/UMAe* Western and Central Africa Benin, Burkina Faso, Cameroon, Central African ECOWASf*** (AFWC) Republic (CAR), Chad, Republic of the Congo, ECCASg** Côte d’Ivoire, Equatorial Guinea, Gabon, Gambia, CEN-SAD** Ghana, Guinea, Guinea Bissau, Liberia, Mali, AMU/UMA* Mauritania, Niger, Nigeria, Senegal, Sierra Leone and Togo Southern Africa (AFS) Angola, Botswana, Burundi, Democratic Republic SADCh*** of the Congo (DRC), Lesotho, Madagascar, Malawi, COMESA** Mozambique, Namibia, Rwanda, South Africa, EAC** Swaziland, Tanzania, Zambia and Zimbabwe Notes: *** active, ** poorly active and * non-active in transboundary water resources management, according to NEPAD, AU and AfDB 2011. a IGAD – Intergovernmental Authority on Development; b COMESA – Common Market for Eastern and Southern Africa; c CEN-SAD – The Community of Sahel-Saharan States; d EAC – East African Community; e AMU/UMA – Arab Maghreb Union; f ECOWAS – Economic Community of West African States; g ECCAS – Economic Community of Central African States; h SADC – Southern African Development Community. References Altchenko, Y.; Villholth, K.G. 2013. Transboundary aquifer mapping and management in Africa: A harmonised approach. Hydrogeology Journal 21(7): 1497-1517. IGRAC (International Groundwater Resources Assessment Centre). 2009. Transboundary aquifers of the world 2009. Special edition for the 5th World Water Forum, Istanbul, Turkey, March 2009, ed., Kukuric, N. Available at http://www.un-igrac.org/publications/323# (accessed on April 16, 2013). IGRAC (International Groundwater Resources Assessment Centre). 2012. Transboundary aquifers of the world 2012. Special edition for 6th World Water Forum, Marseille, France, March 2012, ed., Kukuric, N. Available at http://www.un-igrac.org/publications/456# (accessed on April 16, 2013). NEPAD (New Partnership for Africa’s Development); AU (African Union); AfDB (African Development Bank). 2011. Study on Programme for Infrastructure Development in Africa (PIDA). Phase I. TWRM sector (Transboundary Water) Sector. 32p. Puri, S.; Appelgren, B.; Arnold, G.; Aureli, A.; Burchi, S.; Burke, J.; Margat, J.; Pallas, P. 2001. Internationally shared (transboundary) aquifer resources management: Their significance and sustainable management. A framework document. IHP-VI, Series on Groundwater No. 1. Paris, France: United Nations Educational, Scientific and Cultural Organization (UNESCO). 71p. Available at http://unesdoc.unesco.org/images/0012/001243/124386e.pdf (accessed on June 9, 2014). UNdata. 2013. Composition of macro geographical (continental) regions, geographical sub-regions, and selected economic and other groupings. UNdata, United Nations Statistics Division. Available at http://millenniumindicators.un.org/unsd/methods/m49/m49regin.htm (accessed on April 16, 2013). UNESCO (United Nations Educational, Scientific and Cultural Organization). 2004. Proceedings of the International Workshop on Managing Shared Aquifer Resources in Africa, Tripoli, Libya, June 2-4, 2002, ed., Applegreen, B. ISARM-Africa. IHP-VI, Series on Groundwater No. 8. 238p. WHYMAP (World-wide Hydrogeological Mapping and Assessment Programme). 2006. Groundwater resources of the world - Transboundary aquifer systems. Special edition for the 4th World Water Forum, Mexico City, March 2006. Hannover: Bundesanstalt für Geowissenschaften und Rohstoffe (BGR); Paris: United Nations Educational, Scientific and Cultural Organization (UNESCO). Available at http://www.whymap.org/whymap/EN/Downloads/Global_maps/spec_ed_2_map_pdf.pdf?__blob=publicationFile&v=3 (accessed on April 16, 2013). Led by: Further Information: This leaflet has been produced by the International Water Management Institute (IWMI). For more information, contact: Karen Villholth, Principal Researcher – Groundwater Management, IWMI, Pretoria, South Africa (k.villholth@cgiar.org) Yvan Altchenko, Senior Researcher – Hydrogeologist, IWMI, Pretoria, South Africa (y.altchenko@cgiar.org) Front cover photo: Karen Villholth Led by: Transboundary Aquifer Mapping and Management in Africa Africa is heavily reliant on groundwater resources, with an estimated 75% of the population dependent on this resource for basic water supplies. However, with population growth, climate change and the need to combat growing food insecurity, the demand for groundwater is set to increase in the future. The focus on transboundary aquifers (TBAs) comes from the recognition of this increasing stress on available water resources. For the purpose of this study, a TBA (Figure 1) refers to an aquifer or an aquifer system, parts of which are situated in different states. In practical identification and verification of a TBA, the spatial delimitation, hydrogeological similarity, recharge and discharge mechanisms and zones, and significant hydraulic connectivity between the national compartments of the TBA are all important factors and should be established and agreed upon between the aquifer-sharing states. Partner Ministère de l'agriculture, République Française The CGIAR Research Program on Water, Land and Ecosystems (WLE) combines the resources of 11 CGIAR centers, the Food and Agriculture Organization of the United Nations (FAO) and numerous national, regional and international partners to provide an integrated approach to natural resource management research. WLE promotes a new approach to sustainable intensification in which a healthy functioning ecosystem is seen as a prerequisite to agricultural development, resilience of food systems and human well-being. This program is led by the International Water Management Institute (IWMI) and is supported by CGIAR, a global research partnership for a food secure future. wle.cgiar.org The International Water Management Institute (IWMI) is a non-profit, scientific research organization focusing on the sustainable use of water and land resources in developing countries. It is headquartered in Colombo, Sri Lanka, with regional offices across Asia and Africa. IWMI works in partnership with governments, civil society and the private sector to develop scalable agricultural water management solutions that have a real impact on poverty reduction, food security and ecosystem health. www.iwmi.org Phot o: Karen Villh olth Printed: July, 2014