『Abstract
　Submarine groundwater discharge (SGD) is now recognized as an important pathway between land and sea. As such, this flow may contribute to the biogeochemical and other marine budgets of near-shore waters. These discharges typically display significant spatial and temporal variability making assessments difficult. Groundwater seepage is patchy, diffuse, temporally variable, and may involve multiple aquifers. Thus, the measurement of its magnitude and associated fluxes is a challenging enterprise.
　A joint project of UNESCO and the International Atomic Energy Agency (IAEA) has examined several methods of SGD assessment and carried out a series of five intercomparison experiments in different hydrogeologic environments (coastal plain, karst, glacial till, fractured crystalline rock, and volcanic terrains). This report reviews the scientific and management significance of SGD, measurement approaches, and the results of the intercomparison experiments. We conclude that while the process is essentially ubiquitous in coastal areas, the assessment of its magnitude at any one location is subject to enough variability that measurements should be made by a variety of techniques and over large enough spatial and temporal scales to capture the majority of these changing conditions.
　We feel that all the measurement techniques described here are valid although they each have their own advantages and disadvantages. It is recommended that multiple approaches be applied whenever possible. In addition, a continuing effort is required in order to capture long-period tidal fluctuations, storm effects, and seasonal variations.

Keywords: Submarine groundwater discharge; coastal zone management; Seepage meters; Radon; Radium isotopes; Tracers』

Contents
1. Introduction
　1.1. Background
　1.2. Significance of SGD
　1.3. Definition of submarine groundwater discharge
　1.4. Drivers of SGD
2. A short history of SGD research
　2.1. Overview
　2.2. Worldwide studies
　2.3. The IAEA/UNESCO SGD initiative
3. Methods used to measure SGD
　3.1. Seepage meters
　3.2. Piezometers
　3.3. Natural tracers
　3.4. Water balance approaches
　3.5. Hydrograph separation techniques
　3.6. Theoretical analysis and numerical simulations
4. Coastal zone management implications of SGD
5. The UNESCO/IAEA joint SGD intercomparison activities
　5.1. Cockburn Sound, Australia
　　5.1.1. Introduction
　　5.1.2. Seepage meters
　　5.1.3. Radium isotopes
　　5.1.4. Radon
　　5.1.5. Summary
　5.2. Donnalucata, Sicily
　　5.2.1. Introduction
　　5.2.2. Study area and geophysical characterization
　　5.2.3. Isotopic analyses
　　5.2.4. SGD evaluations
　5.3. Shelter Island, New YORK
　　5.3.1. Introduction
　　5.3.2. Seepage meters
　　5.3.3. Radon and radium isotopes
　　5.3.4. Geophysical studies
　　5.3.5. Summary
　5.4. Ubatuba, Brazil
　　5.4.1. Introduction
　　5.4.2. Geophysical studies
　　5.4.3. Seepage meters
　　5.4.4. Artificial tracer approach
　　5.4.5. Radon and radium isotopes
　　5.4.6. Summary
　5.5. Mauritius
　　5.5.1. Introduction
　　5.5.2. Water balance estimate
　　5.5.3. Seepage meters
　　5.5.4. Radon
　　5.5.5. Summary
6. Overall findings and recommendations
Acknowledgments
References