Isotope Hydrology › The Science

Undertstanding the Basics of Water

Atoms of an element with different mass are called isotopes. Water consists of isotopes of hydrogen and oxygen, which are distributed by natural processes throughout all segments of the hydrological cycle. The journey made by each drop of water causes it to undergo small, important and measurable changes in the relative abundance of the different isotopes. Therefore, water in different environments develops characteristic isotopic labels or 'fingerprints' that allow it to be distinctly identified from water in other environments. This make it possible, for example, to trace the source of the water or to estimate how long a body of water has been in the hydrological system.

Tools to Unlock Water's Secret

Nuclear Science has developed an array of methodologies and analytical techniques which use various isotopes of water to characterize water masses and trace their history and movement through the hydrological cycle. The IAEA's Water Resources Programme has been pioneer in developing isotope hydrology as a powerful and effective scientific approach.

By tracking the isotopes of water, scientists can quickly obtain valuable information which otherwise may require decades of hydrological data collection. Isotope techniques can help determine the origin, age and renewal rate of groundwater, and whether it is at risk of salt water intrusions or contamination. It also permits the rapid and reliable mapping of non-renewable groundwater resources, the majority of which are transboundary aquifers, so that they can be abstracted rationally for equitable use.

Isotope techniques are important tools to understand surface water movement and inter-action with groundwater, dam leakages, and the impact of climate change on water resources development and management.

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