Predicting changes in rainfall distribution and improving on existing water management practices are crucial to mitigating and reducing the uncertainties impacting global water security due to climatic changes. The IAEA is supporting countries to better tackle and address some water-related challenges with the use of isotopic techniques. In agriculture, it does so in cooperation with the Food and Agriculture Organization of the United Nations (FAO).
“With more frequent extreme weather events, rainfall will become more unpredictable, affecting the livelihood of hundreds of millions in developing countries who rely mainly on rainfall for crop production,” said Lee Heng, Head of the Soil and Water Management and Crop Nutrition Section of the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture.
Adapting water use for agriculture
Agriculture consumes, on average, 70% of the total freshwater used around the world, mainly through irrigation for food production. However, less than half of this water is being used efficiently; the rest is wasted through evaporation and deep drainage and runoff. This water – whether from rainfall or irrigation – carries nutrients, pesticides and chemicals to ground and surface water resources, harming water quality and habitat, said Heng.
Isotopic and nuclear techniques are contributing to better soil and irrigation management by improving water use practices and efficiency. These techniques are becoming an integral part of agricultural water management, as isotopes (oxygen-18 and deuterium) can help determine the origin and movement of water in plants and soils (see The Science box). For instance, scientists can measure with isotopes how much water is used and “transpired” by a plant or is evaporated from the soil.
With such information, strategies can be developed to improve crop production, reduce water losses and prevent land, water and ecosystem degradation.
In Africa, which suffers from severe drought in some areas, the IAEA has run several technical cooperation projects on adaptation to climate change using drip irrigation. In Sudan for example, scientists were successfully trained to use the minimal amount of water and fertilizer crops need to flourish, and in turn they supported 1050 small scale women farmers – among them many refugees from neighbouring countries – improve subsistence agriculture production. They succeeded turning dry lands into vegetable fields that feed families and entire villages, contributing to poverty alleviation and local food security enhancement in rural areas.
In Mauritania, 400 rural women, family farmers, living in a hostile desertic environment – with water scarcity, high temperatures and sandy soils – have benefited from the support of scientists trained by the IAEA. They increased yield and varieties of vegetables grown in the desert and grew their income for improving education and health.
Supporting climate modelling
To help predict future impacts of climate change, scientists must explore and understand how complex Earth systems work and can evolve. For that, some choose climate models, systems using mathematical equations to characterize how energy and matter interact in different parts of the ocean, atmosphere and land. It is a complex process that necessitates powerful supercomputers and, among others, accurate data on water.
The IAEA offers a unique resource to climate modelers around the world: the Global Network of Isotopes in Precipitation (GNIP). Created in 1960 by the IAEA together with the World Meteorological Organization to collect hydrogen and oxygen isotope data on precipitation worldwide. These isotopes are highly sensitive indicators of climatic processes. The GNIP helps scientists to study the global water cycle and the origin, movement and history of water, and to validate climate model predictions. In over 90 countries, hundreds of monitoring sites have generated more than 130,000 isotope records worldwide.
An IAEA coordinated research project has just been launched to assess climate change impacts with hydrological modelling, said Leonard Wassenaar, Head of the IAEA’s Isotope Hydrology Laboratory. “We aim to improve the expertise among countries in the use of environment isotopes for an in-depth assessment of different types of precipitation,” he said. “This will help to better understand the possible range of climatic changes induced impacts to the rainfall characteristics, such as frequency, amount, duration and intensity.”
How stable isotopes track water
Isotopes are forms of atoms that have the same chemical properties but different molecular weight. Stable isotopes are non-radioactive, so they do not emit radiation, but their unique properties enable them to be used in a broad variety of applications, including hydrology and agricultural water management. Hydrogen and oxygen stable isotopes help record Earth’s temperature and climate over thousands of years, for example, by using ice cores.
The amounts and proportions of stable isotopes in samples, for example in water samples, are measured using a varitety of techniques. The amounts of naturally-occurring stable isotopes of water and other substances are used to trace the origin, history, sources, sinks and interactions in water as well as partitioning water losses as evaporation and transpiration in agriculture.