Role of ICT
The International Commission on Tracers (ICT) is one of the youngest commissions within IAHS. It was established at the IUGG Assembly in Vienna 1991. Unlike commissions established earlier, ICT is a methodologically based commission that cuts across all other commissions.
Before the 1950ís, applications of tracers were rare in all disciplines of science. Then, step by step, researchers discovered the potential of this method, which nature had found long before: e.g. dogs use their own tracers to mark their territory and insects use pheromones with great success. By the end of the 1980s hydrologists had found various tracer substances and tools for analysis and interpretation, but still the number of researchers dealing seriously with tracers was rather limited. Hence there was a need to promote the dissemination of tracer methods amongst the entire hydrological community, which led to the foundation of ICT.
Since then the use of environmental (naturally occurring) and artificial (intentionally injected) tracers has permeated the various sub-fields of hydrological sciences. The number and quality of publications has increased remarkably, and so has the use of tracers as tools for water resources assessment. ICT seeks to promote tracers further for basic and applied research.
ICT is responsible for the advancement and application of artificial and natural tracers in hydrology, for developing and improving the methodological framework of tracer techniques and for extending these methods within the hydrological sciences. ICT supports the integration of tracer approaches throughout hydrology by technology transfer from research to operational use.
The particular usefulness of water tracing techniques is due to the fact that the tracing of water allows a direct insight into the dynamics of surface and subsurface water flux. Tracer techniques are a useful tool in understanding the transport processes, phase changes (evaporation, condensation, sublimation) and the genesis of water quality. Tracer techniques are particularly useful in arid and semiarid regions for quantifying groundwater and vadose zone water movement. Tracer methods have become a major calibration and validation tool in catchment modeling and in the definition of runoff generation processes. Tracer approaches can be extremely useful in assessment of groundwater - surface water interactions, dating of water, quantifying water - rock interactions and evaluating water resource vulnerability.
The use of tracers has considerably changed the identification of the different runoff components. Runoff generation processes are among the most important processes in catchment hydrology, and modeling them is improving considerably thanks to tracer methods. Understanding where water goes when it rains, water and chemical species residence times and subsurface flow paths is crucial for catchment modeling and the quantification of solute and contaminant transport. In recent years, tracer methods, combined with hydrometric measurements, have proved to be effective for identifying runoff generation mechanisms in headwater catchments.
ICT also discharges its responsibilities through extensive cooperation with the other IAHS Commissions, and with other organizations, such as the International Atomic Energy Association (IAEA), UNESCO/IHP, the International Association of Tracer Hydrology, the International Association of Hydro geologists (IAH), and other groups within the hydrological community. In the relatively short time since it began in 1991, ICT has organized or co-sponsored more than 15 international and regional symposia and workshops that have disseminated results and the state-of-the-art of research findings to the hydrological science community. ICT participated in the development of the IAEA/UNESCO long-term inter-agency Joint International Isotopes in Hydrology Program (JIIHP). It has also been a leading IAHS Commission in the development of the IAHS initiative Prediction in Un-gauged Basins (PUB).
These related programmes and the ICT philosophy instilled into each of them are considered to be among the chief successes of the Commission over the past decade.
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