In order to evaluate submarine groundwater discharge (SGD) rates continuously and automatically, a“continuous heat-type”automated seepage meter was newly developed, and it was applied to Tannowa, Osaka Bay, Japan. The meter is based on the measurements of the temperature gradient of the water between the downstream and upstream positions in a pipe. According to two months continuous measurements of SGD every 10 minutes, semi-diurnal periodical changes in SGD were found in Tannowa. This is attributed to the tidal effects on SGD. The time delay of the SGD from tidal records was also found to be about 5 hours. The newly developed automated seepage meter can provide longer-term and higher-resolution measurements of SGD, which helps us to understand temporal scale issues on SGD and the relevant hydrological and coastal oceanographic processes.

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A new technique to collect groundwater samples from submarine formations was developed. This technique makes it possible to collect more than one liter of groundwater without any seawater contamination and is applicable in water depths of 0 to 40 m.
This technique was used at one submarine groundwater discharge site of offshore Kurobe alluvial fan. We confirmed that this technique worked, and we obtained more than one liter of water sample by single operation. Major ion chemistry and stable isotope data were very similar with that reported onshore Kurobe alluvial fan.

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Sub-seabed disposal in coastal areas is regarded as one of the most promising concepts for high-level waste disposal. This is because this concept has advantages such as lower hydraulic gradients and less possibility of human intrusion compared with inland disposal. In this study, groundwater flow considering the density effect of saline water was simulated for topographically gently sloping and steeply sloping sites in coastal areas. Relative sea level changes were taken into account. The results show that groundwater in a saline water region flows downward, and that its velocity is one to twoorders of magnitude slower than in a fresh water region. The retention time of saline groundwater was also estimated to be longer than that of fresh groundwater. Since groundwater flow depends on saline concentration, it is important to predict the location of the fresh water-salt water interface affected by site characteristics, such as topography and permeability.

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Development of an effective device for extracting both soil and underground water contamination is the goal and“a Launcher-type”well is proposed as it combines both functions of injection and withdrawal at the same time in a single well. It can wash out and withdraw contaminant at areas around the aquifer as well as vadose zone where there is little pore water. Launcher-type well is expected to withdraw contaminant effectively throughout the underground.
Two launcher-type wells were devised to withdraw contaminant. One is a verticaltype well which has two ports vertically. One for injection and one for withdrawal. The other is a horizontal-type well which has ports on either side of the well. Since their fundamental functions and characteristics haven' t become clear, the experiments for these wells have only been conducted on indoor models. Because secondary contamination may be caused by using injurious materials in the experiment, organic compounds were not used. However, the transfer characteristics were experimented by heat transfer which is analogous with contaminant transfer.
The experiment showed that the vertical-type well enabled wider cleaning performance than the horizontal one. The horizontal-type well performed better with additional wing than wing-less. The experiment results agree with our numerical results and a possibility of practical application of launcher-type well is obtained.

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This paper presents a numerical analysis and visualization experiments of a steadystate two-dimensional groundwater flow passing through a borehole with a cylindrical obstacle at its center.
In the numerical analysis, Darcy's Law was applied to simulate the flow in porous media, while Navier-Stokes Equations were applied to simulate the flow in the borehole. These equations were discretised with the finite difference method and were solved using the alternative direction implicit method under various flow conditions.
The results of numerical analysis were validated with velocity and streamline measurements in laboratory experiments. Effects of Reynolds Number and obstacle sizes on the flow in the borehole were observed in the velocity and streamline profiles. The applicable ranges of the Stokes' Approximation in the Navier-Stokes Equation were also investigated through the numerical analysis.

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Groundwater exchange affects the ecology of surface waters by sustaining stream baseflow and stabilizing the water level of groundwater-fed lakes. It also provides stabletemperature habitats, and supplies nutrients and inorganic ions. Groundwater input of nutrients can even determine the trophic status of lakes and the distribution of macrophytes. In streams the mixing of groundwater and surface water in shallow channel and bankside sediments creates a unique environment called the hyporheic zone, an important component of the lotic ecosystem. Localized areas of high groundwater discharge in streams provide thermal refugia for fish. Groundwater also provides moisture to riparian vegetation, which in turn supplies organic matter to streams and enhances bank resistance to erosion. As hydrologists and ecologists interact to understand groundwater' s impact on aquatic ecology, a new research field called“ecohydrology”is emerging.

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