Although the water temperature in the lower reaches of the Nakdong River has dropped, there are still many harmful blue-green algae, so the algae warning level is maintained at 'alert'.

Although the water temperature has dropped in October, the harmful blue-green algae in the downstream water supply of the Nakdong River has not sufficiently decreased, and the algae warning issued in the summer continues to be at the 'alert' level.

According to the Nakdong River Basin Environmental Office on the 4th, the bird warning alert level is maintained at the Chilseo branch between Haman and Changnyeong and the Mulgeum and Mary branches between Yangsan and Gimhae.

Chilseo was raised to the alert level on August 20, and Mulgeum and Mary were raised to the alert level on the 10th of the same month, and have remained on alert for the 46th and 56th days, respectively, to this day.

The number of harmful blue-green algae cells measured on the 1st was 39,600 per ml for Chilseo and 13,151 per ml for Mulgeum and Mary.

The number of Chilseo branches decreased from 35,533 on the 23rd of last month to 9,692 on the 28th, but increased again by about 4.1 times in three days.

Mulgeum and Mary branches showed a decline following 49,391 on the 23rd of last month and 34,681 on the 28th, but still exceeded the alert level standard of 10,000 per ml.

An algae alert is issued when the number of harmful blue-green algae cells, the cause of green algae, is more than 1,000 per ml for two consecutive times, 'Warning' when it is more than 10,000, and 'Large outbreak' when it is more than 1 million.

To escape the alert level, the number must be measured below 10,000 twice in a row, so even if the number falls below the standard once, the alert is not immediately lowered.

The water temperature at Chilseo branch went from 28.5 degrees on the 2nd of last month to 23.6 degrees on the 1st, and at Mulgeum and Mary branches from 28.7 degrees on the 1st of last month to 24.7 degrees on the 1st.

Harmful blue-green algae usually proliferate more actively as the water temperature rises, but in two locations, even as the water temperature drops, it has not decreased enough to lower the alert.

Accordingly, the Nakdong River Network, an environmental group, argued in a statement on the 2nd that the government's green algae seasonal management system was not effective due to the fact that the water gates were not sufficiently opened in the summer.

They urged, “Through a national audit, thoroughly verify the goals and actual performance of the 2026 Green Algae Seasonal Management System and reveal the reasons why effective green algae reduction was not achieved.”

Next, they disclosed the process and basis for reducing and changing the plan to open the floodgates of the four weirs downstream of the Nakdong River and requested that measures be taken to secure sufficient water flow before green algae occurs.