Sayeong Lake, in Ulju County, Ulsan, appears green due to algal blooms on Tuesday afternoon. / Yonhap



By Lee Jin-a, Park Si-soo

The protracted heat wave has turned Korea into a sauna. And this has created the ideal environment for toxic algae in rivers to bloom rapidly.

The result is tragic: major rivers that used to be bright blue have turned green. The green hue is so deep that those who see it often compare the greenness to that of "green tea latte," a popular drink here.

The algae pose an increasing threat to fish and other aquatic creatures.

Algal warning issued

An algal warning was issued Thursday in three spots of Daechung Lake in North Chungcheong Province and two spots of Nakdong River in South Gyeongsang Province as over 1000 blue-green algae cells were found per milliliter in those areas. Paldang Lake, the upper region of the Han River, recorded 431 toxic algae cells per milliliter on Monday.

As the mercury in most parts of the country reached around 35 degrees Celsius, blue-green algae are proliferating.

According to an environmental official, warm and stagnant water is an ideal environment for the algae to spread while heavy rain is the best way to solve the problem. But "no large amount of rainfall is forecast in the near future, so the algal blooms may continue," said the Nakdong River Basin Environmental Office.

The nation's tap water supplier is on red alert because toxic algae blooms can cause odor, taste problems, respiratory illnesses and neuron paralysis.

But it emphasized tap water is safe to drink because it is purified.

"We have installed walls to block algae from entering pipes, and purified water by using ozone," K-water said.