Unmanned submarine to be deployed in fight against algae blooms at Daecheong Lake

A remote-controlled unmanned submarine will be deployed at Daecheong Lake, the main drinking water source for the Chungcheong region, which has been hit by algae alerts every summer in recent years.

The Ministry of Climate, Environment and Energy announced Wednesday it had drawn up and would begin implementing a set of measures to combat algae blooms at the lake.

Daecheong Lake has a watershed area of 3,283 square kilometers — the second largest among reservoirs created by multipurpose dams in South Korea, behind Chungju Dam at 6,677 square kilometers, and larger than Soyang Lake at 2,703 square kilometers.

The lake's wide watershed allows phosphorus to flow in from multiple directions, while its winding shape creates numerous bends and stagnant zones, making it highly susceptible to algae growth.

No algae alert has been issued this summer, but major monitoring points on the lake have seen repeated alerts over the past three years.

The ministry plans to deploy remote-controlled unmanned submarines around intake points and algae-prone areas — including Chudong, Munui, Hoenam, Daejong-ri and Chuso-ri — targeting bends and stagnant stretches to remove sediment layers containing nutrients and algae spores.

Buoyancy water wheels will also be installed to improve water circulation, and floating gardens will be created to absorb nutrients while blocking sunlight to suppress water temperature rises.

When blooms occur, vessels will be dispatched to skim algae off the surface.

Low-temperature plasma equipment — described as a new technology — will be moved to bloom-affected areas as needed. A newly installed pressurized removal device that draws in algae and destroys it through applied pressure will also be put into operation.

Measures to reduce phosphorus flowing into the lake are also being pursued.

Given that high concentrations of phosphorus are being discharged despite the relatively small population around the lake, the ministry will expand public sewage treatment facilities and install retention basins downstream of villages. Inspections and guidance for private wastewater systems, including septic tanks and sewage treatment units, will also be stepped up.

The ministry will also widen the inspection zone for stockpiled compost in the Daecheong Lake watershed to cover roughly 1,164.4 kilometers along both banks of the Geum River's main channel and 113 tributaries, with the aim of eliminating improperly stored compost.

Farmers will be encouraged to apply only the appropriate amount of nutrients to agricultural land, and best management practices will be promoted to reduce nutrient runoff from fields.

The ministry will use AI to develop an optimal operating plan for Daecheong Dam that factors in algae reduction, with a pilot run planned during this year's flood season, which runs from June 21 to Sept. 20.

If the measures are implemented as planned, the ministry projects that total phosphorus discharge in the Daecheong Lake watershed will fall by more than 30 percent from current levels by 2030, with summer algae blooms reduced by up to 50 percent.