56. Investigation of Submarine Groundwater Discharge Using Several Methods in the Inter-Tidal Zone

To accurately estimate the flux of terrestrial groundwater discharge into the sea, a study using several methods was done in the coastal zone of Osaka Bay, Japan. The seepage-meter method and the measurement of temperature near and seabed were applied based on the hypothesis that seawater temperature in summer would decrease, reflecting the extent of active mixing with colder fresh groundwater. As a result, it was confirmed from the seepage-meter method that submarine groundwater discharge rates decreased with the distance from the coast. Evaluations of groundwater discharge rates from seabed temperature showed similar values to the results using the seepage meter, which means that the values were reasonable. Finally, the total groundwater discharge flux from this beach was estimated at 36.7% of the river discharge rate.