Isotope hydrology and water resources management in Africa

Transcription

1 Isotope hydrology and water resources management in Africa Current status and challenges Cheikh B. Gaye

2 International initiatives At the Millennium Summit in 2000 and during the 2002 World Summit on Sustainable Development (WSSD) in Johannesburg, world leaders recognized the integral importance of fresh water to human development, and committed themselves to a precise, time-bound agenda for addressing the world s current and future water resource and sanitation problems.

3 African initiatives New Partnership for Africa s Development (NEPAD) Water Agenda and the constitution of the Africa Ministers Council on Water (AMCOW) exemplify political developments in the pursuit of this MDG. Recognition of the multi-sectoral nature of water resources development in the context of socioeconomic development, as well as the multi-interest utilization of water resources for water supply and sanitation, agriculture, industry, urban development, low and flat lands management.

4 Stress on water resources Limited fresh water resources worldwide Growing global demand for water Continental disparities

5 Water resources and isotope techniques Development of nuclear analytical tools known as isotope hydrology over last 40 years ISOTOPES Nuclides of a single element that have different atomic weights (F. Soddy ) Isotopes come in two varieties: stable radioactive (radionuclides, radioisotopes)

6 Water fingerprinting The natural isotopic composition of a given body of water varies according to its history and its pathway through the hydrological cycle Isotopes work in hydrology as tracers of various processes in the hydrological cycle as time indicators

7 Deuterium Water fingerprinting Meteoric Water Line Sea Water Original Composition Surface Evaporation Palaeowaters Oxygen-18

8 Major areas of application Groundwater replenishment - Identification of sources and areas of recent recharge ( 2 H, 18 O, tritium, CFCs) FP - Mixing between surface and groundwater (proportion of components: 2 H, 18 O, art. tracers) QE - Determination of recharge rates (unconfined, shallow aquifers: tritium, CFCs, art. tracers) QE - Evaporative discharge of groundwater ( 2 H, 18 O, 14 C) FP - Identification of sites for artificial recharge ( 2 H, 18 O, 3 H, CFCs) F

9 Major areas of application Groundwater flow dynamics - Flow rate in deep, confined aquifers (especially great artesian aquifer systems: low flow rates, leakage between aquifers: 14 C, long-lived radioisotopes such as 36 Cl, 234 U/ 238 U etc.) QE - Verification of groundwater flow models (especially through parameter identification: 3 H, 14 C (+ 13 C) QE

10 Major areas of application Non-renewable groundwater in arid regions - Mapping (delineation) of resources ( 14 C, 13 C, 2 H, 18 O, noble gases) FP- - Interconnection of aquifers ( 14 C, 2 H, 18 O, 87 Sr/ 86 Sr, noble gases) FP - Estimation of available resources (flow rate: 14 C (+ 13 C), other long-lived radioisotopes) QE

11 Major areas of application Erosion studies * Use of 137 Cs, 10 Be, 14 C, 32 Si, 39 Ar gives quantitative information on soil erosion and aggradation rate * The differential penetration depth of 40 K, 238 U, 232 Th, Pu, 210 Pb, 129 I, 137 Cs, 7,10 Be suggest the original location of sediment in the soil profile and recognize dominant erosion processes in the catchment * 87 Sr/ 86 Sr is a powerful tracer to determine solute sources and mineral weathering rates

12 Major areas of application Sedimentation studies * use of 210 Pb and 137 Cs is the most appropriate technique for the study of sedimentation in water bodies * radionuclides ( 210 Pb, 137 Cs) in sediments and associated catchments (river suspended sediment) give critical information on sedimentation rates, bioturbation, horizontal movement of sediments, resuspension rates, and residence time of particles. Dam safety and sustainability Leakage of reservoirs: ((2H, 18O, 3H and artificial tracers) FP/QE

13 Major areas of application Surface water management (2H, 18O, 3H 3H/3He and 222Rn; CFC's and strontium isotopes) for : Rainfall-runoff studies (hydrograph separation) Water balance calculations Relation between rivers and aquifers (infiltration rate, discharge)

14 Current status of isotopes techniques in Africa More and more African countries are engaged in efforts to integrate isotope hydrology in the water sector for a sustainable development and management of their water resources National project Regional project Regional and national project IAEA Technical cooperation programme

15 Current status of isotopes techniques in Africa About 40 ongoing projects in 25 countries ~ 75 % Groundwater resource assessment 12% surface and groundwater pollution 1% Surface water dynamics and sediment transport, 2% Support to analytical capability

16 Some success stories Examples of the country projects where the application of isotope hydrology methodologies has provided information of prime importance for determining the long-term productive capacity of an aquifer, protecting vulnerable recharge areas from pollution, limiting salt water intrusion or constraining and validating groundwater models used for water management can be seen in Ethiopia, Uganda, Morocco or Senegal.

17 Groundwater and geothermal resource exploration, Rift valley and adjacent areas, Ethiopia Isotopes to enhance aquifer productivity Investigations carried out in several areas, including the Raya Valley, Dira Dawe and the Afar depression in the north using isotope techniques have helped to identify new groundwater resources and enhance aquifer productivity. Development of a national groundwater database (ENGDA). This database, has been successfully implemented and is operating at the Ministry of Water resources and will serve for the purpose of building a National Groundwater Assessment Programme. Could be a model for other African countries

18 Isotopes for improved groundwater management in Morocco An isotope investigation was conducted in the Tadla Plain (Central Morocco) to clarify the sources and areas of recharge and discharge. Results have been used to refine a groundwater flow model developed using conventional techniques. The revised model is an important contribution to the development of a groundwater resource management tool for the Tadla Plain.

19 Kisoro Town Water Supply, Uganda Isotopes for protecting vulnerable recharge areas Isotope investigations were conducted to delineate the source and flowpath of water in the Chuho springs used for the water supply of Kisoro town, South West Uganda. The isotopic composition of surface water (crater and other lakes, swamps in the mountains around Kisoro), water from Chuho springs, and other springs to the northwest, southeast, and northeast of Kisoro were measured and proved that Lakes Cyahafi and Kayumbu and the Muhavura Crater Lake are not the source of Chuho water and that the groundwater flowpath to Chuho seems to be in the northeast from Kigyezi swamp area. This information has helped secured a 3 millions dollars investment.

20 Focus of shared water resources Investigations using isotopes are being carried out to complement ongoing efforts of the international community for a fair sharing of water resources circulating across national borders. These include The North-western Sahara Aquifer System (Algeria, Libya, Tunisia) The Nubian Aquifer (Chad, Egypt, Libya, Sudan) The Iullemeden Aquifer System (Mali, Niger, Nigeria) Nile River Basin

21 Capacity building - Human resources Over the last five years more than 260 scientists and professionals from the water sector from 35 countries participated in about 15 regional training events. On-the-job training associated with technical cooperation projects was also used to enhance the skills of hundreds of already trainees. Efforts have been oriented towards the inclusion of isotope hydrology topics in the curricula of African universities and engineering schools

22 Capacity building - Analytical facilities Country Algeria Egypt Ethiopia Morocco Sudan South Africa Tanzania Tunisia Zimbabwe Capabilities for isotope analyses Deuterium, O-18, Tritium, C-14, C-13 Deuterium, O-18, Tritium, C-14, C-13, N-15 Tritium, C-14 Deuterium, O-18, Tritium, C-14, C-13 Tritium Deuterium, O-18, Tritium, C-14, C-13, N-15 Tritium Tritium, C-14 Tritium, C-14

23 Strengths: SWOT ANALYSIS Enhanced efforts to implement isotope investigations for water resources development and management, indicating a wider scale recognition and use of the nuclear technology in the water sector Isotope hydrology laboratories (9) installed or upgraded (establish necessary capability for water resources assessment using isotope techniques on a national/regional scale). Numerous scientists and technicians trained to effectively disseminate the knowledge of good analytical practices and to build up the know-how in Africa for successful application of the analytical techniques Build up of regional cooperation and concept of integrated regional management of shared water resources

24 SWOT ANALYSIS Weaknesses: Relatively poor communication partners when they belong to two or more institutions at the national level and different regional counterparts in regional projects (usually coordination meetings are the only forum for exchange) Results of isotope investigations not always translated in simple terms usable by decision makers Long delays for reparation of breakdowns in most of the isotopes analytical facilities Difficulties in provision of small equipment and consumables due to lack of running costs.

25 SWOT ANALYSIS Opportunities: Commitment of the IAEA to further increase and continue its support for the integration of isotope hydrology methods in water resources management practices in Africa Water issue high on the international agenda with involvement of major funding Agencies including the ADB (African water facility) African water vision NEPAD centers of excellence AMCOW and Threats: A major threat is related to high mobility of staff in Governmental structures (changes of position) and also lack of incentive salaries to keep the well trained scientists and technicians