Effect of Artificial Structures of Selected River on Waterblooms throughout Long-term Monitoring

The study investigated the effect of artificial structures on waterbloom in a river, focused on Dalsung Weir located in the middle of the Nakdong River in South Korea. Results from five years of long-term monitoring showed that species of green algae were the most abundant, although cyanobacteria were the dominant species during waterblooms. The waterblooms were mainly affected by the following factors: 1) the reversal phenomenon of air temperature and water temperature, 2) long periods of sunshine, and 3) rainfall events. The results of the principal component analysis for waterblooms in the study area suggested that multiple factors, such as water quality and meteorological conditions, should be taken into account. The results of the analysis for pollution sources around the study area indicated that the pollution of the river was aggravated when flows from large-scale constructions in the adjacent watershed were not properly managed. Overall, waterblooms at the study area occurred due to various causes, not just one simple reason, such as lowering the flow velocity of the river because of artificial structures. In addition, the value of water resources secured by weirs should be considered. The study provides a scientific basis for elucidating the mechanism of waterblooms in rivers.