Understanding the Water Below Our Feet

Understanding the Water Below Our Feet Two billion people are dependent on groundwater moving under our feet and between borders, the amount of which is estimated to be as much as 10.5 million km3 worldwide; 99% of the world’s accessible fresh water is under the earth. In the 20th century, the human population has tripled and fresh water consumption has risen six-fold. According to the World Water Vision Unit of the World Water Council, if water is not more efficiently used, approximately half the world’s population will soon live in high water stress regions, where agricultural, industrial, and domestic users compete.

In this context, the United Nations Millennium Development Goals include the reduction by half of the number of people without adequate, affordable and safe drinking water. Reaching this goal will require better water management practices, but also a thorough understanding of available reserves and how they can be used. Recognizing the role transboundary aquifers and river basins can play in meeting human water needs, the IAEA works extensively to help Member States characterize and assess their water resources by using isotope hydrology techniques.

Stories from the Field

The Nubian Sandstone Aquifer System (NSAS), the world’s largest ‘fossil’ water aquifer system, lays under the countries of Chad, Egypt, Libyan Arab Jamahiriya and Sudan, the total population of which is over 136 million. Groundwater has been identified as the biggest and in some cases the only future source of water to meet the growing demands and development goals of each NSAS country. However, faced with increasing demand from agricultural and for drinking water, as well as pressure from climate change, over-abstraction has already begun in some areas. There amount drawn could double in the next 50-100 years. The IAEA/UNDP/GEF Nubian Project, one of the first international transboundary aquifer water projects, sought to implement modern scientific techniques in order to address the challenges of tomorrow’s water supply.

Working alongside scientists from each Nubian Aquifer country, the IAEA has developed a new and innovative 3-D model of the aquifer based on long-lived radioisotope data. Through particle tracking—which traces the movement of individual water parcels through the modelled aquifer system—scientists are able to map water movement through the aquifer and estimate the age of water in the system at any time and location. Also, the recent use of krypton isotopes promises to provide a more accurate estimate of age and validate the 3-D model.

Beneath Argentina, Brazil, Paraguay, and Uruguay, the Guarani Aquifer System (GAS) is the largest groundwater body in South America. Though most of the reserves remain intact, some areas of the aquifer are highly exploited, water consumption is rising, and the population continues to expand. Uncontrolled pollution in areas of extraction and recharge also poses a great threat. In 2009, the four GAS countries, with support from the Global Environment Facility, the World Bank and the Organization for American States, created a Strategic Action Program (SAP) in order to provide a management framework for the Guarani aquifer. Upon request, the IAEA became actively involved in the project to help assess the aquifer using isotope hydrology.

In addition to identifying recharge areas and flow patterns of the groundwater, the IAEA’s work helped indicate that the old groundwater in the aquifer is vulnerable to ground mining, thus encouraging GAS countries to modify their extraction, maintain a higher level of sustainability, and improve accessibility to groundwater for all those in the region.

In Central America, the IAEA assisted with characterizing the hydrology of both surface and groundwaters in the Upper Lempa River basin, part of the Trifino Transboundary Aquifer System that lies beneath Guatemala, Honduras, and El Salvador. The information gathered helped local stakeholders and national authorities to establish fair dialogue over the maintenance of and extraction from the aquifer. The first stage of the technical cooperation project consisted of measuring basic physical and chemical parameters of the aquifer, and then collecting samples from precipitation, surface and ground water for analysis of environmental isotopes.

As a result of these studies, a hydrological map of the Trifinio area was produced for the first time, leading to the development of conceptual flow models that map the routes of both local and regional flow systems. Such information also allows for the assessment of groundwater discharges. The IAEA has been also involved in assisting Member States in assessing other aquifer systems, including the Zarumilla Aquifer, North-Western Sahara Aquifer System, and the Iullemeden Aquifer System.

What Lies Ahead

Despite this recent progress, there is much work to be done to ensure that precious water resources are adequately understood and managed. The IAEA hopes to build upon these successes by continuing in the field collaboration with scientists and policy makers from Member States. For example, future collaboration will include the use of available data to produce large scale maps showing ranges of groundwater age. In addition, the IAEA Water Availability Enhancement Project, currently in the pilot phase, aims to strengthen Member States’ national capacity to conduct assessments, including groundwater resources, which are generally poorly understood and poorly managed.