XA9950048-/£?- IAEA International Symposium on Isotope Techniques in Water Resources Development and Management Vienna, Austria 10-14 May 1999 BOOK OF EXTENDED SYNOPSES 30-23 IAEA-SM-361 The material in this book has been supplied by the authors and has not been edited. The views expressed remain the responsibility of the named authors and do not necessarily reflect those of the government of the designating Member State(s). The IAEA cannot be held responsible for any material reproduced in this book. PAPERS Keynote Address World Water Recourses and Water Use: Modern Assessment and Outlook for the 21st Century Prof. I.A. Shiklomanov, XA9950049 State Hydrological Institute, St. Petersburg, Russian Federation 1) During 1991 -1996 the scientists from the State Hydrological Institute under the guidance of the author of the present paper made a new multi-purpose assessment of the world water resources, water use and water availability in the dynamics, up to 2010-2025. Basic results and conclusions of this work are given in the present paper. 2) Observation data (monthly and annual values) from the world hydrological network have been used directly for the assessment of renewable water resources on the global scale. The assessment of water resources for all the continents and regions of the world has been made in the dynamics for the same rather long time period from 1921 to 1985. Popular hydrological methods have been used for series extension, for filling gaps in observations and for the computation of river runoff on ungauged areas, i.e. methods of correlation and hydrological analogy, hydrological models and methods of mapping runoff depth. Moreover, the world database on monthly precipitation and air temperatures has been widely applied. 3) A quantitative assessment of water resources use on the global scale for the past and for nearest decades has been made with the account of water use for the needs of population, industries (power generation including), agriculture (irrigation), as well as losses for evaporation due to reservoirs construction. These factors, explaining a unilateral decrease of surface and subsurface runoff, are observed everywhere and they are subject to an intensive development; and they can greatly affect the water resources in large regions. All the assessments have been made in the dynamics for the present century, for 1995 and for the future (2000, 2010 and 2025). Moreover, national data on water use in individual countries or in group of countries were used first of all. If such data were not available, assessment were made with the use of indirect methods based on the account of the main factors which determine the amount and dynamics of water use. To estimate the future water use a methodology has been developed which takes into account peculiarities and trends in water use in the past as well as the available long-range forecasts for the population growth and economic development in different countries of the world. A specific water availability in various regions and countries (in m^/year per capita) has been analyzed for 1950-2025 with the account of not only population number but water consumption, too. 4) Mean renewable water resources in the world have been estimated as much as 42700 km^/year and they are greatly variable in time and space. The maximum water resources are available in Asia and South America (13500 and 12000 knP/year, respectively), the minimum water resources are observed in Europe and Australia and in Oceania (2900 and 2400 km^/year, respectively). Moreover, the amount of water resources can vary within the ranges of+15 - 25 % from its mean value. Long-term variations of the world water resources are characterized by the absence of any trends to changes for the whole 65-years period. In general, it is typical of many continents, too, except Africa and South America during the last 20 years; here a trend in river runoff increase in South America and a trend in river runoff decrease in Africa are observed. The dynamics of water resources have been analyzed not only for continents but for 26 large physiographic and economic regions of the world (into which the whole land area of the world has been subdivided), and for 60 selected countries from all the continents. These selected countries include developed and developing countries, countries with transient economics, countries largest and smallest by areas and population number, northern and southern countries, as well as countries with water resources deficit and surplus. 5) The present (by 1995) total water withdrawal in the world is equal to 3700 km3/year; the water consumption equals 2300 km^/year. In future, the total water withdrawal would be higher by 10-12 % each 10 years and by 2025 it would attain 5200 km^/year (increase in 1.38 times). At present about 57 % of the total water withdrawal and 70 % of the total water consumption in the world are observed in Asia where the largest irrigated lands are cultivated. The most intensive water use in the nearest decades is expected in Africa and in South America (in 1.5-1.6 times); the least intensity of the water use is expected in Europe and in North America (1.2 times). At present 67 % of the total water withdrawal and 86 % of the total water consumption are observed in agriculture; in future, the role of agriculture would be less important mainly due to an intensive development of other water users. According to the up-dated data, the total irrigated lands in the world (by 1995) occupied 254million hectares; by 2010 the irrigated lands would occupy about 290 million hectares and before 2025 they would cover up to 330million hectares. The analysis of water use dynamics and the rate of water resources development has been made for all the continents, for physiographic and economic regions and for selected countries. In accordance with the obtained data, there are many countries in the world where water resources have been exhausted completely; not only local water resources are used in these countries but most of the freshwater imported from the adjacent areas. It should be noted that countries and regions, where the rate of water use exceeds 20 %, are inhabited by more than 75 % of the global population. 6) The analysis of the specific water availability in all the physiographic and economic regions and selected countries for 1950-2025 shows an extremely uneven water resources distribution all over our planet. The maximum water availability (1995) is observed in Canada and Alaska and in Oceania where it equals 170-180 thou m^/year per capita. Meanwhile in densely populated regions of Asia, Central and South Europe and in Africa the present water availability ranges within 1.2-5.0 thou m^/year; in the north of Africa and in the Arabian Peninsula it is as much as 0.2-0.3 thou m^/year. It should be noted that water availability less than 2 thou m^/year per capita is assumed to be very low, and if it is less than 1 thou m^/year - it is assumed as catastrophically low. At present about 35 % of the world population live in the conditions of a very low or catastrophically low water availability. This situation would be even worse at the beginning of the next century. By the 2025 the majority of the world population would live in the conditions of a very low and catastrophically low water availability or about it; about one third of the global population would have a catastrophically low water supply. 7) Important conclusions have been deduced during the analysis of trends and rates of changes in water availability in countries and regions depending on socio-economic and climatic factors. In industrially developed countries the rate of specific water availability decrease is rather low and it has been reduced in 1.8 times during 1950-2025 on average irrespective of the climate and amount of water resources. In developing countries the rates of specific water availability decrease tend to a rise in 4.5 times on average for the conditions of sufficient and surplus moistening; and in 8.5 times for the arid and semi-arid regions. Thus, if the appropriate measures are nor taken, most of the developing countries would face a catastrophic water problem in the near future. This situation may be even more acute because of the hydrological characteristics of the arid and semi-arid regions are extremely vulnerable to anthropogenic change in the global climate. Keynote Address GROUNDWATER FOR SUSTAINABLE DEVELOPMENT OPPORTUNITIES AND CONSTRAINTS Fatma Abdel Rahman Auia XA9950050 Director of the Research Institute for Groundwater Cairo, Egypt The availability of renewable water resources has played a key role in human development. The rise and decline of civilizations have been linked to climatic changes which, in turn, controlled the natural recharge of aquifers and regulated the pollution of groundwater and soils. Aquifers have specific characteristics that distinguish them from other water bodies (i) they can help in removing SUSpCfldod s<>h'ds 6nd dketee-causing organisms; (ii) they can store water in quantities exceeding those which are or conceivably could be stored in all natural and artificial surface-water bodies, (iii) they can rtgulattthe water temperature and its chemical quality; (iv) they transport water from areas of recharge to areas of need; and (v) they slow-down the natural discharge of water to the surface. As such, aquifers <san be utilized as strategic storage reservoirs for water 10 make up the bulk, of the dry-weather flow of streams In addition to secular changes in groundwatcr caused by climatic variations, there are now serious threats to both quantity and quality of groundwater resources caused by the accelerating human intervention.