Simulation of harmful cyanobacterial blooms under weir operations and climate change scenarios: A data-driven study of the Nakdong River

Kim, Jayun; Jang, Gayeon; Jo, Minkyoung; Park, Joonhong

doi:.0..

DOI: https://doi.org/10.4491/eer.2025.081

Simulation of harmful cyanobacterial blooms under weir operations and climate change scenarios: A data-driven study of the Nakdong River

Jayun Kim^1,2^†, Gayeon Jang¹, Minkyoung Jo¹, and Joonhong Park¹

¹Department of Civil and Environmental Engineering, Yonsei University, Seoul, South Korea
²Division of Environmental Health Sciences, The Ohio State University, OH, USA

Corresponding Author: Jayun Kim ,Tel: +82-2-2123-7768, Email: nature9973@gmail.com

Received: February 7, 2025; Accepted: May 18, 2025.

ABSTRACT

Climate change has caused widespread harmful cyanobacterial blooms (HCBs), worldwide. Although the hydraulic retention time affects the proliferation of cyanobacteria, changes in the frequency and intensity of HCBs under climate change in response to different water velocities are not well quantified. This study used data-driven models to simulate changes in the frequency and intensity of projected HCBs in 2100 (due to elevated temperatures) depending on the operations of weirs constructed in the Nakdong River in South Korea. Results indicated that the water velocity in the river was estimated to be three to eight times lower (a significant decrease) after the construction of weirs. The multiple linear regression model revealed a negative correlation between water velocity and cyanobacterial abundance. In the future, the demolition of weirs in the Nakdong River would result in decreased cyanobacterial density, while this density would increase under temperature-rise scenarios. Simulations indicated that increased water velocity due to weir operations decreased the frequency of HCBs at sites with a pronounced decrease in water velocity due to the construction of weirs. These findings imply that the increasing intensity and frequency of HCBs can be offset by adjusting the hydrology of the river following quantitative simulations of relevant consequences.