Water for development. World Water Day 2002 - March 22. A summary report

'Water for Development' was the theme of the World Water Day 2002, which the IAEA coordinated fro the United Nations system. The IAEA transfers cutting edge nuclear technologies to scientists in developing countries to help them find a way to improve efficiency of water use, to better understand climatic change, to turn salt water into fresh water, and to grow healthy crops in saline lands. A comprehensive understanding of a hydrological system is necessary for a sustainable resource development without adverse effects on the environment. Isotope techniques are effective tools fro fulfilling critical hydrologic information needs, e.g. the origin of groundwater, recharge, residence time, interconnections between water bodies, etc. The cost of such investigations is often relatively small in comparison to the cost of classical hydrological techniques, and in addition isotopes provide information that sometimes could not be obtained by other techniques. Stable and radioactive environmental isotopes have now been used for more than four decades to study hydrological systems and have proved particularly useful for understanding groundwater systems. Applications of isotopes in hydrology are based on the general concept of 'tracing', in which either intentionally introduced isotopes or naturally occurring (environmental) isotopes are employed. Environmental isotopes (either radioactive or stable) have a distinct advantage over injected (artificial) tracers in that they facilitate the study of various hydrological processes on a much larger temporal and spatial scale through their natural distribution in a hydrological system. Thus, environmental isotope methodologies are unique in regional studies of water resources to obtain time and space integrated characteristics of groundwater systems. The use of artificial tracers generally is effective fro site-specific, local applications