▲ The Nakdong River near the Mulgeum and Maeri water intake stations is dyed green.
It looks as if green paint was not just poured in, but dumped into the main stream of the Nakdong River near the Mulgeum and Maeri water intake stations in Yangsan, Gyeongsangnam-do, which serve as the water source for Busan residents, on July 6.
Because temperatures were not high due to the light monsoon rain, the distinct earthy, fishy odor typical of algae blooms was not severe. However, aerial footage showed that the main stream and tributaries of the lower Nakdong River had turned green, as if green paint had been poured into them.
A citizen in his 60s, surnamed Kim, who was taking a walk nearby with an umbrella, said, "I don't think I have ever seen an algae bloom this severe during the monsoon season," adding, "I am worried about how much worse it will get once the intense summer heat begins."
Algae containment booms were installed at the Mulgeum intake station, and purification facilities were in constant operation.
Moving toward the Nakdong River estuary (in the direction of Busan), which is closer to the sea, the green color faded slightly, but the main stream of the Nakdong River remained green in many areas.
The Mulgeum and Maeri points, which are the water sources for Busan and Gyeongsangnam-do residents, have been under an algae alert of "Caution" since June 22.
This is the earliest such alert has been issued since the algae alert system was introduced.
It was one day earlier than in 2022, when a record-breaking algae bloom occurred, and two months earlier than last year.
Generally, the intensity of an algae bloom tends to subside once the monsoon season begins, but that has not been the case this year.
According to the Ministry of Climate, Energy and Environment's Water Environment Information System, the number of harmful cyanobacteria cells at the Mulgeum and Maeri point between Gimhae and Yangsan, Gyeongsangnam-do, was measured at 165,880 per milliliter on July 2.
This is the highest figure recorded in July since the Mulgeum and Maeri point was designated as an algae alert monitoring site in 2020.
Even when compared to all historical observations, including those in August, it is the second-highest level on record.
The highest record at this location was 447,075 cells per milliliter, observed on August 8, 2022.
However, as monsoon rains fell over the weekend, it is expected that the figures to be released on July 6 will decrease slightly.
An algae alert is issued at the "Attention" level when the number of cyanobacteria cells is 1,000 or more per milliliter, "Caution" at 10,000 or more, and "Mass Proliferation" at 1 million or more.
An official from the Busan Metropolitan Government explained, "The situation is fluid depending on rainfall and the occurrence of typhoons, so we need to monitor the situation until the end of July," adding, "There is currently no major concern for a 'Mass Proliferation' alert."
Busan City explained that it is minimizing the inflow of algae by operating algae removal vessels near the Mulgeum and Maeri water intake points.
The city also stated that it is blocking algae toxins and odor-causing substances by strengthening water purification processes, such as installing algae containment booms at intake points, operating water spray facilities, intensifying chlorine and ozone treatment, using high-efficiency coagulants, shortening the backwashing cycle of sand and activated carbon filters, and injecting powdered activated carbon.
(Photo: Yonhap News)
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