Radioisotopes in Water Resources and the Environment

• The use of environmental tracers and isotope hydrology techniques help to characterize ground and surface water resources.
• The use of nuclear technologies has helped to improve the management of water resources across many countries worldwide.

The attributes of naturally decaying atoms, known as radioisotopes, give rise to their multiple applications across many aspects of modern day life (see also information page on The Many Uses of Nuclear Technology).

Environmental tracers

Radioactive tracers (or radiotracers) are chemical compounds in which one or more atoms are radioisotopes. Radiotracers are one of a number of environmental tracers that can be used, but they play an important role in detecting and analysing pollutants since even very small amounts of a given radioisotope can easily be detected, and the decay of short-lived isotopes means that no residues remain in the environment. Hydrologists use radiotracers to determine the passage and pace of pollutants moving through groundwater to assess the level of vulnerability.

Water resources

Adequate potable water is essential for life. Yet in many parts of the world fresh water has always been scarce and in others it is becoming so. For any new development, whether agricultural, industrial, or human settlement, a sustainable supply of clean water is vital.

Groundwater is the largest source of freshwater, constituting 30% of the world's total. Isotope hydrology utilises the natural variance in the composition of water resources. A given source of water will have a certain isotopic 'fingerprint' or composition. The isotopes within a source may be natural or artificial, and may be stable or unstable. Radioisotopes are used to determine the age of water, whilst stable isotopes can be used to determine the source’s history, rainfall conditions, mixing/interaction characteristics of related water bodies, pollution processes, and evaporation processes. The results permit planning and sustainable management of these water resources. For surface waters they can give information about leakages through dams and irrigation channels, the dynamics of lakes and reservoirs, flow rates, river discharges, and sedimentation rates. Neutron probes can measure soil moisture very accurately, enabling better management of land affected by salinity, particularly in respect to irrigation.

There are some 60 countries, developed and developing, that have used isotope techniques to investigate their water resources in collaboration with the International Atomic Energy Agency (IAEA). In Central Africa, scientists from 13 countries, with the support of the IAEA, have carried out the first ever regional assessment of groundwater using nuclear techniques. The region depends on rich underground aquifers, and the findings from the study have helped to map and characterise the nature of these resources. The results from this work will be used to draw up regional management plans for the continued sustainable use of the shared aquifer systems.

In October 2021 the IAEA began a research project to assess the hydrological changes to wetland-groundwater ecosystems driven by land use changes and climate change. Stable and radioisotopes will be used, together with conventional hydrogeological tools (e.g. remote sensing, geographic information system) to analyze hydrological processes in these environments.