Use of Long-lived Radionuclides for Dating Very Old Groundwaters

Closed for proposals

Project Type

Coordinated Research Project

Project Code




Approved Date

9 December 2015


Active - Ongoing

Start Date

11 July 2016

Expected End Date

31 December 2022

Completed Date

26 May 2023

Participating Countries



This CRP addresses the use of new tools for the estimation of very old groundwater ages (> 50000 years), which is one of the most elusive hydrological parameter to assess in the case of groundwater resources. With an increasing population and potential impact of climate change, groundwater extracted from deeper horizons is becoming the most important fresh water resource in many areas. Despite significance of age information for water resources, waste management, subsurface reactive transport, and paleoclimate, this parameter is always very difficult to assess. Additionally,  comprehensive dating tools are not often available to many Member States.The main focus of this new CRP will be the implementation of several isotope hydrology assessments of deep/large aquifer systems using long-lived radionuclides, isotope age tracers and noble gases (carbon-14, krypton-81, chlorine-36, helium-4, etc…). These techniques are either hard to access or to implement in many member states.       Following the recent increase in the analytical capacity of the IAEA’s noble gas facility, this CRP will provide the possibility to improve Member States’ capabilities in the assessment of deep groundwater systems by offering the combined use of the paleo-temperature estimates from isotopes of neon, argon, krypton and xenon and the age dating by helium-4 cross calibrated with other isotope techniques. Other noble gas isotopes, such as krypton-81, will also be analysed in selected samples. The case studies to be conducted as part of this CRP will provide a unique data set and excellent information for expanding the use of these age dating tracers to TC projects aiming at assessing deep aquifer systems in Member States.


The overall objective of the CRP is to investigate the use of long-lived radionuclides, particularly 4He and 81Kr, to assess their reliability as age tracers of ‘old’ groundwaters. The estimated groundwater age produced from these long-lived radionuclides tracers will be compared with traditional isotopic and hydrochemical tracers in a variety of hydrogeological and climatic environments. Large, well-studied aquifers will be preferentially targeted by this CRP.  The results obtained from this CRP will be used to produce a global database of long-lived radionuclides age estimations of groundwater. Once this database is compiled, the CRP will explore how groundwater residence times can be used to validate regional-scale groundwater flow models. The second important application is to use the calculated groundwater residence times to estimate the sustainable groundwater resource available into the future.

Specific objectives

Evaluate the performance of different sampling techniques and analytical methodologies for long-lived radionuclides.

Evaluate the usefulness of long-lived radionuclides in deep groundwater system for estimating groundwater ages. This will be completed through a structured program targeting different hydrogeological settings.

To understand the processes controlling the 4He accumulation rates in aquifers from different hydrogeological settings to reliably estimate the groundwater residence time (i.e. 4He vs. 81Kr).

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