[en] A new methodology to determine the location and strength of SGD is proposed where the salinity distribution in the water body is simulated by a 3D numerical model. Measurement of the salinity field (or any other parameter, typical for SDG source) is needed in the region of the SGD. The applied model PCFLOW3D is a 3D, nonlinear baroclinic numerical model which was originally developed to simulate the hydrodynamic circulation and transport-dispersion of different contaminants such as mercury or radionuclides. It has been completed with the possibility of simulation of transport-dispersion of any parameter arriving with the SGD source from the bottom (e.g. salinity, nutrients, radon). The basic idea is to assume a location and strength of the SGD, simulate the parameter distribution, and compare it with the measured distribution. The final information on SGD is obtained by the trial and error procedure. Possible application of the modelling method was proven with comparison to the SGD measurements in Sicily. (author)

[en] This report details the use of four naturally occurring isotopes of radium in investigations of submarine groundwater discharge (SGD) and other applications in coastal oceanography and hydrology. The focus is an evaluation of estuarine and coastal ocean exchange rates and an estimation of SGD and associated fluxes to coastal waters. In many cases radium isotopes can be used to separate SGD fluxes into those coming from surficial and from deeper aquifers. (author)

[en] First results of the geochemical research performed in a submarine spring near Izola are presented. It was found that the spring discharge of nutrients to the southern part of the Gulf is of less importance relative to the other freshwater discharges, representing <4% of the total freshwater nutrient input. (author)

[en] Salinity, DO, nitrate, phosphate and silicate along with Ra isotopes (²²⁸Ra and ²²⁶Ra) have been measured at selected sites along the east and west coast of India in order to identify potential sites for the submarine groundwater (SGD). The result of the preliminary study does not provide unequivocal evidence for SGD due to dominant influence of local pollution on the chemical parameters. The long term seasonal measurements are essential to document SGD influence. (author)

[en] In research and management of groundwaters, an important role is played by coastal aquifers. Pollution due to salinization and human activities poses serious concerns to the economy of the related territories. Under the project, established through collaboration between the Italian Universities of Palermo, Bari, Venice and the IAEA and the UNESCO, study of coastal aquifers from Syracuse to Donnalucata on the southeastern coast of Sicily was carried out. The study area, known as Hyblean Plateau, is characterized by carbonate and vulcanite outcrops, connected to the tectonic activity during the Cretaceous and the Pliocene period. The aquifers are subjected to overexploitation due to the high water demand for intensive agricultural practices. Thus, the equilibrium between fresh groundwaters and seawater is getting disturbed with consequent salinization. The research project involved the geochemical and isotopic study of well waters, springs and submarine discharges in order to understand the relationships existing among these waters, to identify the best tracers of the natural and human-related phenomena occurring in the area as well as to estimate the presence of possible environmental effects of them on the coastal ecosystem. Hydrogeochemical surveys were carried out, every three months, from 2002 to 2004 on a net of wells, sub-aerial and submarine springs. The present report synthesizes the main results of the research. (author)

[en] Submarine groundwater discharge (SGD) of groundwater into the coastal zone has received increased attention in the last few years as it is now recognized that this process represents an important pathway for material transport. Assessing these material fluxes is difficult, as there is no simple means to gauge the water flux. To meet this challenge, we have explored the use of a continuous radon monitor to measure radon concentrations in coastal zone waters over time periods from hours to days. Changes in the radon inventories over time can be converted to fluxes after one makes allowances for tidal effects, losses to the atmosphere, and mixing with offshore waters. If one assumes that advective flow of radon-enriched groundwater (pore waters) represent the main input of ²²²Rn in the coastal zone, the calculated radon fluxes may be converted to water fluxes by dividing by the estimated or measured ²²²Rn pore water activity. We have also used short-lived radium isotopes (²²³Ra and ²²⁴Ra) to assess mixing between near-shore and offshore waters in the manner pioneered by Moore. During an experiment in the coastal Gulf of Mexico, we showed that the mixing loss derived from the ²²³Ra gradient agreed very favorably to the estimated range based on the calculated radon fluxes. This allowed an independent constraint on the mixing loss of radon - an important parameter in the mass balance approach. Groundwater discharge was also estimated independently by the radium isotopic approach and was within a factor of two of that determined by the continuous radon measurements and an automated seepage meter deployed at the same site. (author)

[en] Submarine groundwater discharge (SGD) is now recognized as an important pathway between land nd 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 chemical fluxes is a challenging enterprise. A joint project of the 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. (author)

[en] 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 nearshore waters. These discharges typically display significant spatial and temporal variability, making direct assessments difficult. Groundwater seepage is patchy, diffuse, temporally variable, and may involve multiple aquifers. Thus, the measurement of its magnitude and associated chemical fluxes is a challenging enterprise. An initiative on SGD characterization was developed by the IAEA and UNESCO in 2000 as a 5-year plan to assess methodologies and importance of SGD for coastal zone management. The IAEA component included a Coordinated Research Project (CRP) on Nuclear and Isotopic Techniques for the Characterization of Submarine Groundwater Discharge (SGD) in Coastal Zones, carried out jointly by the IAEA's Isotope Hydrology Section in Vienna and the Marine Environment Laboratory in Monaco, together with 9 laboratories from 8 countries. In addition to the IAEA, the Intergovernmental Oceanographic Commission (IOC) and the International Hydrological Programme (IHP) have provided support. This overall effort originally grew from a project sponsored by the Scientific Committee on Ocean Research (SCOR) who established a Working Group (112) on SGD. The activities included joint meetings (Vienna 2000, 2002, and 2005; Syracuse, Italy, 2001; and Monaco 2004), sampling expeditions (Australia 2000; Sicily 2001 and 2002; New York 2002; Brazil 2003; and Mauritius 2005), joint analytical work, data evaluation, and preparation of joint publications. The objectives of the CRP included the improvement of capabilities for water resources and environmental management of coastal zones; application of recently developed nuclear and isotopic techniques suitable for quantitative estimation of various components of SGD; understanding of the influence of SGD on coastal processes and on groundwater regimes; a better management of groundwater resources in coastal areas; and development of numerical models of SGD. This report examines several methodologies of SGD assessment, which were carried out during a series of five intercomparison experiments in different hydrogeological environments (coastal plains, karst, glacial till, fractured crystalline rocks 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 SGD 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 variable conditions

[en] Seepage measurements of submarine groundwater discharge (SGD) were carried out in March 2002 in the Donnalucata boat basin in southeastern Sicily. SGD rates measured by manual seepage meters ranged from 5.5 to 19.3 L/min/m (with an average of 12.1 L/min/m), which was 0.6 and 5.9 times the SGD determined in Florida and Perth, respectively. The spatial distribution of SGD was found to be highly variable along ∼300 m long coast area. Semi-diurnal SGD variations which anti-correlated with tide were found using newly developed automated seepage meters that can provide continuous SGD data with high resolution. These variations may be attributed to the tidal effect, when a greater hydraulic gradient, observed at low tide, moves groundwater from land to the ocean, and an opposite effect is observed at high tide. Groundwater discharge rates were estimated from borehole groundwater temperature and pore water temperature under the seabed to be 0.92 to 3.6 cm/day in Cockburn Sound, Western Australia. Automated and manual seepage meters measured larger groundwater discharge rates of 13.7 to 16.3 cm/day. This may be caused that observed seepage rates by seepage meters include not only terrestrial fresh groundwater discharge but also recirculated saltwater. On the other hand, the discharge rates estimated from subsurface temperature may consist of only terrestrial fresh groundwater discharge. Measurements of electric resistivity of the seabed and of the electric conductivity of submarine groundwater discharge (SGD) collected in seepage meters have been made in Ubatuba, Brazil. A diurnal variation of SGD conductivity was found under the condition of semi-diurnal tidal changes over a period of four days. SGD comprised a combination of submarine fresh groundwater discharge (SFGD) of terrestrial origin, and of recirculated saline groundwater discharge (RSGD) of marine origin. The maximum of the terrestrially derived fraction SFGD/SGD was found at a distance of 50 m offshore. A lower SFGD/SGD ratio was found closer to shore, where the highest SGD flux was measured. SGD conductivity and ground resistivity displayed a diurnal cyclicity at semi-diurnal tidal water level variations, indicating that tidal water level fluctuations may not be the primary driver of SGD flux at Ubatuba. (author)

[en] This study aims to determine the sites of SGD and their physical, chemical and isotopic properties along a 100 km long coastal zone in southwestern Turkey. The aquifer feeding coastal and submarine SGDs comprises of well karstified Mesozoic carbonate massifs that extends from coast to more than 100 km inland. The carbonate massif forms a rugged topography stretching from sea level to over 3000 m. Systematic search dives for every metre of coastal zone down to 30 m below sea level were carried out for precise determination of SGDs. Majority of karstic SGDs were found to be point wise outflows through cracks and submarine caves rather than being spatially dispersed discharges. Comparison of SGD locations detected by means of search dives with those inferred from thermal/infrared satellite images and lineament analyses revealed that systematic screening of coastal zone by divers is essential to determine all existing SGDs. Visual disturbance caused by halocline and temperature gradient felt by diver's skin were the most effective tools to locate SGDs. Stable isotope (¹⁸O and ²H) and specific electrical conductivity (SEC) data gathered from SGDs in summer and autumn revealed a freshwater contribution rate ranging from 20% to 80%. Autumn samples which had more depleted stable isotopic signal were found to have relatively high freshwater contribution based on SEC. This suggests apparently higher SGD rate in autumn while precipitation to meet such increase has not occurred. Samples from fresh groundwater indicated a local deuterium excess value of +14 which is typical of research area and neighboring coastal zone. SGDs are located fairly well along a freshwater-seawater mixing line that intersects meteoric line around -6 per mille and -30 per mille for O-18 and H-2, respectively. Tritium composition of SGDs ranges between 0 TU and 4.5 TU and is not correlated with mixing ratio. This implies that freshwater components of different SGDs have different residence times. High frequency (10 minutes) SEC and temperature observations carried out in two submarine caves at depths around 20 m bgl for a period of 9 months revealed different discharge dynamics. While one observation site showed SGD pattern that was in line with seasonal recharge, the SGD rate in the other site had an oscillating behaviour that is independent of recharge dynamics. (author)