[Anchor]

As record-breaking heatwaves continue day after day alongside a prolonged drought, algal blooms are rapidly spreading across the Nakdong River. The situation has become severe enough to threaten citizens' drinking water sources.

Reporter Kim Su-yun investigated the scene.

[Reporter]

Samnak Ecological Park Watersports Town, located in the lower reaches of the Nakdong River.

Parts of the boat mooring area are covered in dense green particles.

I scooped up some river water myself like this.

It looks just like a matcha latte sold at a cafe.

At the Samnak Ecological Park sampling point, the concentration of toxic blue-green algae cells exceeded 20,000 cells per milliliter twice consecutively, prompting the issuance of a "Caution" level algae alert.

Banners have been hung across the park urging people to refrain from water leisure activities and the gathering of fish and shellfish.

Around this time of year, spaces like this should be bustling with water leisure sports such as kayaking, but operations have virtually halted due to the algal blooms.

[Official at Samnak Watersports Town: We have suspended the experience programs because of the algal blooms. I hope the algae clears up soon so that citizens can make use of the facility.]

Heading upstream along the Nakdong River to the Mulgeum-Maeri area between Yangsan and Gimhae in South Gyeongsang Province, the situation is severe.

As of August 3, the number of toxic blue-green algae cells surged elevenfold in just one week, triggering a "Caution" level alert.

[Sagong Hye-sun / Steering Committee Member, Gimhae-Yangsan Korea Federation for Environmental Movements: With the lack of rain continuing, the algae situation seems much more serious right now compared to last year.]

Experts analyze that high water temperatures in the Nakdong River caused by heatwaves, combined with slowed water velocities due to the drought, have created an environment ideal for algae to proliferate.

[Lee Seung-jun / Professor, Department of Applied Biosciences, Kyungpook National University: At temperatures of 28 degrees Celsius (82 degrees Fahrenheit) or higher, cyanobacteria have no choice but to multiply very rapidly. As heatwaves continue, the intensity, frequency, and severity of algal blooms are expected to increase.]

With a "Caution" level algae alert issued for Hoehwan Lake, the drinking water source for Ulsan citizens, for the first time in 17 years since 2009, algal blooms are even threatening the water supply sources for the Busan-Ulsan-Gyeongnam region.

(Video by Jeong Kyeong-mun | Design by Lee Ga-jin | Footage provided by Ulsan City Hall)