Even after the seasonal management system ends, green algae in the Nakdong River remains on alert... More than 90,000 units of blue-green algae per ㎖

Although the seasonal green algae management system implemented by the government for the first time this year ended on the 15th, the algae warning 'alert' level continues in water sources downstream of the Nakdong River.

According to the Nakdong River Basin Environmental Office on the 18th, the number of harmful blue-green algae cells in the Mulgeum and Mary branches between Yangsan and Gimhae as of the 15th was 96,339 per ml.

This number significantly exceeds the bird warning alert level standard of 10,000 per ml.

At the Mulgeum and Mary branches, the number of harmful blue-green algae increased from 30,655 on the 8th to 98,750 on the 12th and then exceeded 90,000 on the 15th.

At the Chilseo branch between Haman and Changnyeong, 44,140 per ml were observed on the 15th.

Mulgeum and Mary were raised to the alert level on August 10th, and Chilseo was raised to the alert level on the 20th of the same month, and have remained under alert status for 70 and 60 days, respectively.

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.

The Ministry of Climate, Energy and Environment operated the green algae seasonal management system together with related ministries and local governments for five months starting May 15.

This is a system that manages discharge sources such as compost and sewage and wastewater to prevent phosphorus, which is a nutrient for green algae, from flowing into the river, and gradually opens the Nakdong River weir when green algae worsens.

However, the Ministry of Climate Change explained that even at the time of introducing the system, the weir could not be fully opened until the improvement of the intake and pumping station was completed.

There are limitations in lowering the dam water level because water intake for residential and industrial water supply must be maintained.

On the 15th, during the audit of the National Assembly's Climate, Energy, Environment and Labor Committee, it was pointed out that the improvement of intake and pumping facility facilities should be expedited to resolve these restrictions.

Rep. Geon-tae Lee of the Democratic Party of Korea (Bucheon County, Gyeonggi Province) pointed out, “Around the opening of the four weirs downstream of the Nakdong River in the summer, the number of harmful blue-green algae at the Hwamyeong branch in Busan increased from about 40,000 to 184,000 per ml,” adding, “Because the intake ports are installed high, lowering the weir water level makes water intake difficult, so it is not possible to open the floodgates sufficiently.”

At the same time, he urged improvement of facilities and securing of budget, saying, “Of the 171 facilities for intake and pumping of the four major rivers, 128 are located in the Nakdong River, but only 15 have had facility improvements.”

Some say that the seasonal management system's preventative measures are focused on open compost management, etc., and that a more detailed response is needed at each branch.

Seungjun Lee, a professor in the Department of Applied Life Sciences at Kyungpook National University, explained, "Blue-green algae can survive even in low water temperatures, so green algae does not disappear immediately when the temperature drops. That's why it's important to manage green algae even before they appear."

He added, “The causes of green algae are different at each point, such as sections with slow flow and areas where a lot of pollutants flow, so a prediction and management system that reflects the characteristics is necessary. We need to establish a tight surveillance network for livestock waste and wastewater, and improve the system so that the opening of floodgates can be done before green algae occurs.”