Daejeon, South Korea — The Geum River Basin Environmental Office has officially upgraded the algae alert for the Chudong water body of Daecheong Reservoir from 'Caution' to 'Warning', effective 6:00 p.m. on September 21.

The environmental authority operates an intensive algae alert system covering key intake points near Munui, Chudong, and Hoenam to protect public health and ensure safe drinking water across the Chungcheong region. According to officials, the decision to elevate the alert level was triggered after harmful cyanobacterial cell counts in the Chudong area exceeded the threshold of 10,000 cells per milliliter for two consecutive weeks.

Factors Driving the Proliferation

Environmental experts attribute this late-season algal expansion primarily to a combination of heavy rainfall in late August and persistently high water temperatures. The late-summer downpours washed massive amounts of nutrient salts—such as nitrogen and phosphorus—into the reservoir. Coupled with high ambient temperatures that have kept water temperatures elevated, these conditions created an optimal environment for the rapid reproduction of harmful cyanobacteria.

Geum River Basin Environmental Office chief Ma Jae-jung noted that weather forecasts from the Korea Meteorological Administration predict temperatures in the Daejeon, Sejong, and South Chungcheong provinces to remain higher than or similar to normal averages throughout September and October. Consequently, authorities anticipate that the proliferation of harmful algae within Daecheong Reservoir may persist for some time. 

Intensified Response and Monitoring Measures

Following the issuance of the 'Warning' alert, the Geum River Basin Environmental Office immediately disseminated the status to relevant municipal and government agencies to coordinate continuous reduction and response measures.

As part of enhanced safeguards for drinking water safety, water quality analysis frequency for the Chudong sector has been drastically increased from once a week to at least twice a week. Authorities are closely monitoring real-time changes in algae concentrations and deploying advanced technical assets.

Comprehensive Long-Term Strategies

This year's persistent algal blooms have prompted comprehensive governmental intervention. Daecheong Reservoir, spanning a massive watershed area, is structurally vulnerable to algae due to its winding morphology and stagnant water zones. To combat these recurring issues, environmental authorities have integrated modern countermeasures, including: 

Remote-Controlled Unmanned Submarines: Deployed in vulnerable sectors to dredge and clean contaminated sediment from the lakebed. 
Algae Removal Vessels and Equipment: Operating skimming boats and low-temperature plasma machinery from early stages of occurrence.
Water Circulation and Purification: Installing buoyancy water wheels and expanding advanced water purification processes.
Nutrient Source Control: Intensifying inspections on agricultural compost storage sites and strengthening municipal sewage treatment facilities within the watershed.

"We are fully committed to coordinating with affiliated organizations and deploying every necessary countermeasure," said Ma Jae-jung, head of the Geum River Basin Environmental Office. "Our primary goal is to ensure that there are absolutely no disruptions or safety issues in supplying clean, safe tap water to the public".