Lake Biwa water quality survey Water sampling experiment with underwater drones Cost reduction, efficiency improvement (Mainichi Shimbun) - Yahoo! News

Underwater drone for water quality survey used by Lake Biwa River Office for trial. A water sampling capsule with a capacity of 500 milliliters is seen above the drone in the foreground in Tamanoura, Otsu City, on Feb. 3, 2022. (Mainichi/Manabu Niwata)

　The Lake Biwa River Office of the Ministry of Land, Infrastructure, Transport and Tourism conducted a demonstration experiment in the south lake of Otsu City in order to explore the practicality of water sampling by underwater drones in the water quality survey of Lake Biwa. Drones could cut costs compared to current ship-based surveys, and could be more efficient with fewer people, he said. In the experiment, we confirmed the operability and water sampling function of the drone. The office conducts water quality surveys once a month at 22 locations on Lake Biwa using a boat with seven or eight people on board. Underwater drones can be surveyed by only two people, and maintenance costs can be reduced compared to water quality survey ships. On the other hand, 10 liters of water is sampled from one location in a ship's water quality survey, but the drone used in the demonstration test can only sample 500 milliliters of water at a time. In order to collect 10 liters, the drone must sample water 20 times at the same location. The body of the underwater drone used in the experiment is about 38 cm long, about 33 cm wide, and weighs 5 kg. It is operated from land with a controller connected by a cable of up to 300 meters. It moves around with six screws called thrusters and can dive to a depth of 150 meters. The position is confirmed by the Global Positioning System (GPS). A water sampling capsule with a capacity of 500 milliliters can be installed, and water can be inhaled in about 15 seconds. The Lake Biwa River Office confirmed the accuracy of the drone's position and water depth in an experiment, and verified the time required for water sampling. It is equipped with a sensor that measures the amount of dissolved oxygen in water, and its accuracy will be confirmed in the future. Takayuki Ogita, general maintenance officer of the office, said, "Since drones are cable-based, their area is limited, and they are affected by weather and wave conditions, but we would like to explore the possibility of using new technology." . [Manabu Niwata]