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World Water Day 2022: Making Invisible Visible – Using Nuclear Techniques to Assess and Manage Groundwater in Critical Situations


Groundwater samples in plastic vials of an auto sampler. Isotopes of water molecules make the invisible visible and provide crucial information on this vital source that makes up 30% of the world’s available freshwater. (Photo: D. Calma/IAEA)

You turn on the tap to wash your hands. There is no water! What would you do? Would you know how to find water? Day in and day out, millions of people face this very question. Every year, natural and human-made disasters and mismanagement cut off safe water supplies to people in many parts of the world.

Disasters often occur suddenly and impact availability of water sources. Floods, volcanic eruptions, droughts, earthquakes, conflicts, pandemics, fires and accidents, such as oil spills and those involving waste disposal, are among the most common disasters affecting people and the environment. Climate change also leads to natural disasters occurring more frequently and intensely, requiring urgent relief measures.

In the aftermath of such extreme events, there is usually a decline in the quantity and quality of surface water, so groundwater becomes the primary water resource. Groundwater, which is the focus of World Water Day 2022, also acts as a buffer against climate variability when surface water levels are low.

However, unlike surface waters, groundwater is invisible to the eye and hence often poorly understood. How much groundwater is available? Where does it come from and where does it go? How sustainable is this water resource? How vulnerable is it to pollution? Obtaining rapid information on new water resources, particularly groundwater resources, becomes vital for ensuring supply security.

Isotopes make groundwater visible

That’s where nuclear techniques come into play, making the invisible visible. Environmental isotope tracers provide fast and reliable answers to these questions. Isotope tools, such as nitrate isotopes, are ideally suited for water quality assessment and pollution sources tracking, and information on water origin and its fate can be quickly obtained from isotopes of the water molecule. This basic information is critical to advise governments and communities on securing water sources in times of crisis, as well on protecting and conserving critical groundwater recharge zones.

Isotope hydrology has been applied in numerous IAEA technical cooperation projects to relieve populations under stress helping them identify alternative sustainable sources of water. In Honduras, where drought often has a severe impact on surface water availability, isotopic techniques were used to better understand groundwater sources, by identifying the provenance and rate at which groundwater is replenished. This information enabled local water authorities to re-assess their groundwater supply strategy, protect recharge zones and improve their strategy for a more sustainable use.

Similarly, in Africa’s Sahel region, a series of droughts connected to increasing water demand due to population growth resulted in problems with safety and availability of clean water. Despite its scarcity on the surface, this semi-arid region has rich bodies of water hidden underground. The IAEA has been working closely with water authorities to help them understand their invisible groundwater resources. This information is critical to support long term access to clean water.

In Mauritius, where water pollution became critical due to illegal waste disposals, nitrate isotopes were used to assess the origin of such waste dumps. Authorities had detected nitrate contamination in streams and rivers, threatening protected areas and fisheries due to increased toxic algal blooms in the ocean that kill fish, but were not sure where it had come from. The answer was provided by nitrate isotopes, which enabled the adaption of a targeted pollution control strategy.

Isotopes protect groundwater

In many semi-arid regions of the world, groundwater has been the main source of water not only for household use but also for irrigation. Its importance has grown due to the increasingly variable water supplies as a result of climate change. Groundwater use has grown to reach 40% of global and a third of OECD irrigation use. However, water use efficiency in agriculture is less than 50%, affecting agricultural productivity – and leading to a waste of water.

Scientists in Nigeria have been working with the IAEA and the Food and Agriculture Organization of the United Nations (FAO) in developing techniques for cultivating crops with minimal water use using drip irrigation from groundwater. This has helped women who fled from terrorists and who live in camps for internally displaced to increase yields of crops such as cucumber, watermelon and okra by 60%, while decreasing water use by 45% compared to other methods.  

Another global issue is the impact of agroecosystems on the natural environment, particularly on water quality. Pollution generated in agroecosystems is primarily transferred to the natural environment through waterways. Identifying the sources and transport of contaminants in agriculture is therefore crucial for evaluating and predicting their impact and protecting groundwater resources. Several case studies from both developed and developing countries have shown that stable isotope tracers and hydro-chemicals can help improve surface and groundwater quality protection by teasing them apart from other contaminant sources.

Isotopes at World Water Forum

The IAEA strives to improve the expertise among countries in the use of environmental isotopes for an in-depth assessment of different types of changes in water quality and quantity that help to ensure water supply sustainability and increase the resilience to disasters and climate change.

At the 9th World Water Forum taking place this week in Dakar, Senegal, the IAEA will host side two events: One on capacity building in isotope hydrology, together with UNESCO, World Bank, World Meterological Organisation, IHE Delft and several Member States, and another one on water security.

The IAEA held this month a pioneering conference for PhD students, focused on groundwater resources in one of the driest regions on earth, the Sahel.

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