In this study, we focused on water supply reservoirs in South Korea where the algae alert system has been implemented. Here, monitoring data from the algae alert system from 23 reservoirs were collected from 2016 to 2020. Among these reservoirs, a total of eight reservoirs were selected for modeling by excluding those without water quality monitoring sites (seven reservoirs) and those without cyanobacterial bloom (nine reservoirs). The selected reservoirs include the Paldang and Gwanggyo reservoirs in the Han River watershed, Daecheong reservoir in the Geum River watershed, and Yeongcheon, Angye, Unmun, Sayeon, and Jinyang reservoirs in the Nakdong River watershed (Table 1). A total of 15 cyanobacteria monitoring sites are present in these eight reservoirs. The number of monitoring sites differed among the reservoirs: a single monitoring site for Gwanggyo, Angye, and Yeongcheon reservoirs, two sites for Sayeon, Unmun, and Jinyang reservoirs, and three sites for Daecheong and Paldang reservoirs (Figure 1 and Table 1).