By Puja Daya, IAEA Office of Public Information and Communication

Groundwater provides half of all drinking water worldwide. The impact of climate change on groundwater sources is severely impacting availability and quality in many countries, including Namibia. With a drought emergency declared in 2019 and increasingly extreme weather conditions, annual rainfall may not be sufficient to replenish groundwater resources, according to experts. The growing influx of people living in and moving to the capital Windhoek and to coastal cities is adding to Namibia’s struggle to maintain water supplies.

The IAEA, Namibia’s Ministry of Agriculture, Water and Land Reform and Germany’s Institute of Geosciences and Resources are collaborating to investigate Namibia’s water resources to protect them and make sure water supplies are sufficient year-round. The project will use isotope hydrology techniques (see Science box below) to monitor groundwater resources and to assess the impact of climate change and variability in water from major aquifers in the country’s southwest.

“Using isotopes to assess our groundwater resources is of extreme importance to us for maintaining reliable sources of water throughout the country,” said  a hydrogeologist at Namibia’s Ministry of Agriculture, Water and Land Reform, Anna Kaupuko David. Faced with the potential of devastating droughts in her country, Kaupuko David wants to use isotopic techniques to assess if the country’s current plans are sufficient. “If we suffer from a drought, the Windhoek aquifer becomes our emergency water supply for the city and can last at least three years. However, it’s unclear how using the aquifer in this way would impact its future and we’ve been trying to use surface water from our dams to recharge it for times of drought. But with a growing population, it’s never enough,” she said.

Isotope hydrology techniques are a well-established tool for the assessment of groundwater resources and could be the problem solver for Namibia’s droughts, said isotope hydrologist at the IAEA, Ioannis Matiatos,. “At the IAEA, we’ve been closely collaborating with experts from all around the world on the use of environmental isotopes to improve the availability and sustainability of freshwater resources.”

Assessing aquifers

Aquifers are sensitive to both human activities and natural changes, and the IAEA has used isotope hydrology tools to assess availability and the impact of contamination, including in Bolivia and South Africa. But what impact could deviations in climate have on aquifers in Namibia?

Understanding the evolution of the country’s rain distribution during the rainy summer season and the dry winter season through isotopes will indicate how the availability of groundwater can be altered in cases of drought due to climate change. Through the improved knowledge of groundwater dynamics, experts in Namibia will be able to manage water resources better and avoid water emergencies like in 2019, Matiatos said.

Virtual capacity building

Though the COVID-19 pandemic has delayed IAEA experts from visiting Namibia as planned, the cooperation continued virtually.

An online training course launched at the end of May 2021 helped participants understand how isotope hydrology can be used to accurately assess and manage groundwater. “The training session taught us how to plan our field trips and collect samples of stable isotopes, as well as considerations and equipment needed to collect good quality samples for analysis,” said David. “We are looking forward to an upcoming fellowship in Germany where we hope to learn more about analysing samples and deriving actionable information from the data.”

The study will start by taking samples from the Kuiseb aquifer, a source under extreme stress from supplying water to the growing towns of Walvis Bay and Swakopmund. Results from these samples will be used to predict the future impact of climate change on national groundwater resources and guide protection and governance activities.

“The use of isotopes is an area of great importance in adapting to climate change. Through technical assistance and targeted capacity building, the IAEA is continuously building partnerships and bridges to coordinate responses to drought emergencies and ensure countries are able to manage water resources in a sustainable way,” said the IAEA Programme Management Officer coordinating the activities with Namibia through the Agency’s technical cooperation programme, Anna Grigoryan. Earlier this year, Namibia and the IAEA signed an agreement setting the framework for the aquifer project. This cooperation builds on previous successful projects with the country in using nuclear techniques to create new crop varieties, and ensure the safe transport of radioactive material.

The Science

Using environmental isotopes to trace groundwater origin and flow

Bodies of water are naturally labelled with unique isotopic signatures. By using these signatures, water origin and movement can be tracked through its entire cycle of existence. A laser spectroscopic analyser is used to examine groundwater samples and interpret them based on the stable isotopes present in the water molecule.

Other naturally occurring isotopes can be found in aquifers, such as carbon-14 (14C) — a radioactive isotope commonly used to date fossils and archaeological specimens. By measuring the 14C content in water samples, scientists can estimate the age of the groundwater as old as 40,000 years. Other isotopes, such as tritium (hydrogen-3) and those found as dissolved noble gases, — helium-3, helium-4, argon-39 and krypton-81, are powerful tools that allow scientists to date from young to very old groundwater systems.

This information informs water specialists on the nature, history and flow of sampled groundwater and helps them calibrate and improve groundwater numerical models that predict the aquifer’s response to climate change.