Early Summer Heat Triggers Algal Blooms; Nakdong River Under 'Caution' Alert

The early arrival of summer heat this year is leading to an early proliferation of algal blooms.

The Ministry of Climate, Energy and Environment held a meeting of the Central Task Force for Seasonal Algae Management this morning (June 17) at the Gangjeong Goryeong Weir in Dalseong-gun, Daegu, presided over by First Vice Minister Keum Han-seung, to assess the current situation.

At the Gangjeong-Goryeong section of the Nakdong River, where the meeting was held, a "Caution" level algae alert has been issued as of the 15th, with harmful cyanobacteria reaching 17,014 cells per milliliter (mL).

The number of harmful cyanobacteria at the Gangjeong-Goryeong section, which was placed under an "Attention" level alert on May 18, has surged to 4,133 cells on June 1 and 11,231 cells on June 8.

Comparing the dates of the first algae alerts at the Gangjeong-Goryeong section, this year's alert (May 15) is the earliest since 2021, following July 10 in 2025, June 27 in 2024, June 22 in 2023, June 16 in 2022, June 17 in 2021, and April 16 in 2020.

"Attention" level algae alerts are also in effect for other sections of the Nakdong River, including Haepyeong, Chilseo, and Mulgeum-Maeri.

As of the 15th, the number of harmful cyanobacteria per mL was 7,661 at Haepyeong, 18,956 at Chilseo, and 21,868 at Mulgeum-Maeri.

Currently, an "Attention" level algae alert has also been issued for Sayeon Lake, a major source of drinking water for Ulsan.

On the 15th, the concentration of harmful cyanobacteria was measured at 1,250 cells per mL at the Sayeon Lake water intake tower and 1,050 cells per mL at Banyeri.

Outside of the Nakdong River basin, an "Attention" level alert has also been issued for Boryeong Lake on the Geum River, which recorded 1,695 harmful cyanobacteria cells per mL as of the 15th.

Algae alerts (based on water supply sources) are categorized into "Attention," "Caution," and "Mass Proliferation." An "Attention" alert is issued if cyanobacteria counts exceed 1,000 cells per mL in two consecutive measurements, "Caution" for over 10,000 cells, and "Mass Proliferation" for over 1 million cells.

Cyanobacteria thrive in conditions with high water temperatures, slow flow rates, and high concentrations of phosphates in the water.

The Ministry of Climate, Energy and Environment stated, "Due to early heat starting from the spring, algae alerts are being issued earlier than in previous years," adding, "We will work to minimize the inconvenience and environmental impact caused by the algal blooms."

(Photo: Provided by Nakdong River Basin Environmental Office, Yonhap News)
※ Please note: This article was translated by AI and may contain errors.