Exploration of submarine groundwater discharge using a drone in a coastal area of Hiji town, Oita Prefecture, Japan in summer

Abstract

In a coastal zone discharging submarine groundwater, we observed sea surface temperature using a drone equipping infrared thermography in order to verify the availability and defect on exploration of submarine groundwater using a drone. The difference of temperature between sea surface above the discharge point of submarine ground water and surrounding seawater was approximately 3 degree Celsius based on manual direct measurements using a thermometer. The difference of temperature was also observed by sea surface temperature image of a drone, showing that drone’s exploration method is successful for discovering submarine groundwater discharging at water depth of 2 meters. Furthermore, the submarine groundwater affected the temperature of surface seawater within a few square meters. On the other hand, submarine groundwater discharging at water depth of 4–5 meters was not identified by the image of drone, suggesting that the application of this method was restricted within very shallow parts of coastal area.