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 drones 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.