Programme › IAEA Programme on Water Resources (2005–2006)

G.1. Isotope Methodologies for the Protection and Management of Surface Water, Groundwater and Geothermal Resources

Project G.1.01: Exchange of information, training and cooperation with international organizations in isotope hydrology

Rationale: A multitude of efforts at various levels are required to integrate isotope techniques and benefit from their use in water resource management. These include incorporation of isotope hydrology in appropriate educational programmes and hydrological practices, as well as development of trained human resources from among practising professionals in Member States. Expertise in isotope hydrology in many countries resides in agencies that are not directly responsible for water resources management and insufficient communication between hydrogeologists and isotope scientists is a significant impediment to the integration of isotope techniques in the water sector. Through General Conference resolutions, Member States have requested the Agency to continue to help integrate isotope hydrology in their water sectors through national programmes and through collaboration with other international organizations, including UNESCO. Activities implemented in the last programme cycle have resulted in many initiatives that would produce desired results over the coming years. A joint IAEA/UNESCO International Isotopes in Hydrology Program (JIIHP) was launched in 2002 and is generating substantial interest among Member States to bring together their isotope and hydrology professionals. Similarly, progress is being made in having isotopes included in academic curricula and in building human capacity. Collaboration with international programmes in water cycle research has been established and joint projects are being formulated with UNDP/Global Environment Facility (GEF) and the World Bank. These efforts need to be continued and in some cases strengthened to meet the objectives.

Project G.1.02: Isotope methods for the assessment of groundwater sustainability

Rationale: Groundwater is the primary source of drinking water for half of the world's population and of the irrigation water used for food production. In many parts of the world, groundwater levels are rapidly declining and over wide areas, groundwater withdrawal exceeds natural recharge, particularly in arid and semi-arid areas where fossil or non-renewable waters are being mined. In more humid climates non-renewable waters may be replaced by modern recharge of poorer quality. The concept of aquifer sustainability rests firmly on the development of a sound scientific understanding of the basic hydrogeological conditions, but at the same time needs to be integrated and interfaced with a broader and integrated framework for evaluating water resources and social needs. More efficient irrigation practices depend upon the knowledge of the actual use of water by vegetation compared to that lost by evaporation and by infiltration below the root zone. Evaluation of the sustainability of groundwater requires improved understanding of the residence times of water, including origin and age distribution of river baseflow as a major sink in the continental hydrological cycle. Isotope studies in particular have been crucial in defining the occurrence of and in estimating the extent of modern recharge, including that resulting from irrigation. Similarly, they are useful for designing and monitoring artificial recharge and aquifer storage schemes. Delineation of fossil water aquifers is dependent entirely on the availability and synthesis of isotope data.

Project G.1.03: Development of isotope methodologies for water quality assessment and management

Rationale: Degradation of water quality from agricultural and other anthropogenic activities is partly responsible for the looming scarcity of freshwater. Irrigated agriculture contributes a majority of the nutrient load (nitrogen, phosphorous, etc.) to rivers, lakes and shallow aquifers. Urban and industrial activities similarly contribute a variety of contaminants to surface and groundwater. Wetlands, on the other hand, help to improve water quality by filtering out and transforming nutrients and other pollutants. Crucial knowledge gaps exist in understanding the processes related to nutrient cycling, water balance estimations, and cause-and-effect relationships. Tracing and partitioning of pollution sources is a key challenge in the development of drinking water supply strategies, as well as wastewater treatment and remediation practices.

Water resource managers need this detailed information to develop appropriate decision support tools. Recent technological advances have enabled the use of N-15, C-13, S-34 and oxygen isotopes in nitrate and sulfate as indicators of point and non-point anthropogenic loadings to natural waters. Most recent analytical techniques include the measurement of isotopes in dissolved species, such as dissolved organic and inorganic carbon and
nitrogen.

G.2. Reference Isotope Data and Analysis for Hydrological Applications

Recurrent Project G.2.01: Development of Member State capacity for isotope analysis of hydrological samples

Rationale: Reliable and accurate isotope measurements are essential for the application of isotope methodologies in the water sector. Member States, through General Conference resolutions, have requested the Agency to strengthen their ability for isotopic analyses and to help establish regional resource units. Improved quality of analysis is achieved through calibration with reference materials and continued comparison of results from different laboratories on a common sample. The Agency is the primary source of reference materials that are used for making precise isotopic measurements. These reference materials are equally necessary for isotope measurements in both the developing and developed Member States. Member States also need the assistance of the Agency to establish and maintain a laboratory network that can provide reliable analytical data and fulfil analytical needs of national and regional TC projects, as well as to develop local capacity.

Project G.2.02: Isotope methods for the study of water and carbon cycle dynamics in the atmosphere and biosphere

Rationale: An improved scientific understanding of the water cycle to better manage water resources under the current and future climatic conditions is an internationally recognized goal, as stated in the Johannesburg Plan of Implementation that resulted from the World Summit on Sustainable development. Vegetation plays a critical role in modulating atmospheric water cycle and climate processes over the continents, and has a major influence on seasonal and interannual climate variability. The biospheric regulation of vapotranspiration is an important control on moisture exchange between the atmosphere and lakes, reservoirs, and watersheds. Ecosystem exchanges are critical for tracing direct climate change impacts of anthropogenic greenhouse gas emissions on the water cycle.

The existing IAEA/WMO Global Network for Isotopes in Precipitation is a valuable resource for a quantitative understanding of precipitation inputs to the hydrological system. The reverse process of feedback to the atmosphere is difficult to measure and isotopes offer a unique means for this purpose. Wider application of quantitative water balance of lakes, reservoirs, watersheds, and irrigation efficiency using isotope techniques require better characterization of atmospheric moisture isotope signatures and variability, and improved understanding of boundary layer mechanisms which control kinetic fractionation during evaporation.

Scientific investigations have established the high potential of isotopes for evaluating water and carbon exchange in the boundary layer, although the potential has been limited by lack of interaction between the carbon and water cycle research communities, and by lack of global information exchange and coordination between Member States. Although international programmes such as the Biosphere Atmosphere Stable Isotope Network (BASIN), FLUXNET, AmeriFLUX, OZFLUX, and EuroCarbonFlux have created an opportunity for carbon cycle studies and characterization of CO2 fluxes from the terrestrial biosphere including isotope based investigations, the programmes do not specifically target the water cycle linkages and implications.

Project G.2.03: Development of helium isotope applications for water resources management

Rationale: The availability of information on groundwater ages and travel times in shallow aquifers world wide can significantly improve groundwater management and protection practices and facilitate the integration of isotopes in hydrology. Until recently, high tritium concentrations in precipitation resulting from atmospheric nuclear testing of the 1950s and 1960s provided an easy means for determining the presence of post 1950s recharge and for estimating travel times to water table. However, atmospheric tritium concentrations have been decreasing over the last 30 years and are currently almost at their low, natural levels, making tritium less useful as a hydrological tracer. To overcome this limitation, a new method has been developed over the last about 15 years using helium-3 which is a daughter product of tritium decay. Tritium-helium dating has been shown to be an effective and powerful tool for obtaining groundwater ages on the order of 1 to 50 years. In spite of their potential, the hydrological and marine applications of helium isotopes have been relatively limited to date, primarily because of the limited availability of measurement facilities and cost. There are less than ten laboratories world-wide where helium isotopes are measured for hydrological or marine applications. The capacity of these laboratories is limited and, when available, the costs of easurement are extremely high. The availability of an operational helium isotope facility at the Agency would result in advancing the use of isotopes for water resource management and would allow introduction of the helium isotope tool in both the regular budget and TC projects. Outcomes of other projects in Programme G will be enhanced by the incorporation of helium isotope measurements. In addition, an Agency laboratory can be used for training Member State scientists in sampling and analysis for helium isotope measurements. Without this analytical service and training, which is very difficult to obtain at existing non-Agency laboratories, the use of helium isotopes is unlikely to be successfully transferred over the long run.

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