Search Results (3)

Climate change has increased the frequency and intensity of extreme weather events worldwide. In South Korea, annual precipitation in 2014–2015 was only 50% of the long-term average, resulting in severe drought conditions. This drought extended water residence time in dam reservoirs, enhancing internal nutrient recycling, degrading water quality, and promoting harmful cyanophyta blooms in downstream reservoirs. Using the Standardized Precipitation Index—for drought assessment, and monthly water sampling—for environmental factors and phytoplankton analyses, this study examined the impacts of drought on water quality and phytoplankton communities in a series of interconnected dam reservoirs (Uiam, Cheongpyeong, Sambong-ri, and Paldang Lakes) within the Bukhan River system from 2013 to 2016. The prolonged residence time during drought facilitated nutrient accumulation and recycling within the reservoirs, intensifying eutrophication and water quality deterioration, alongside a pronounced cyanobacterial dominance and harmful algal blooms. These findings suggest that changes in upstream dam discharges directly influence water quality and ecosystem health in downstream reservoirs and that diverse hydrological changes associated with drought pose a significant threat to water source management. These findings may inform the development of integrated water management strategies for maintaining water quality and protecting water sources during droughts and extreme climatic events. Full article

Salmo trutta, commonly known as brown trout, is an invasive species that has established itself in various regions, including South Korea, where it poses ecological risks to native freshwater fish populations. To enable natural habitat restoration, S. trutta needs to be monitored, but traditional monitoring techniques are associated with several limitations. Therefore, in this study, we aimed to apply a sensitive and specific real-time PCR (qPCR) assay using a set of primers and a hydrolysis probe specific to the mitochondrial cytochrome b gene of S. trutta. Environmental DNA (eDNA) was extracted from river-water samples collected downstream of the Soyang Reservoir and around the Uiam Reservoir between January and March 2023. The qPCR assays successfully detected S. trutta eDNA in 11 of the 24 samples, with high concentrations found upstream and downstream of the Soyang River. Our results demonstrate the effectiveness of qPCR assay for the S. trutta detection in aquatic environments and highlight its potential for monitoring the spread of this species, especially in areas that are difficult to survey using traditional methods. This molecular approach offers a more efficient tool for S. trutta population management, mitigating its impact on native biodiversity. Full article

This study analyzes quantitative algae mitigation, using chlorophyll-a as an indicator, through waterbody management techniques such as pulses released from upstream dams, employing a three-dimensional numerical model. Numerical simulations focused on algae reduction through dam operations by investigating nine scenarios based on Chuncheon Dam, Soyang Dam, and Uiam Dam, located in the upper and lower reaches of Uiam Reservoir of Korea. These scenarios, aligned with actual dam operation manuals, aimed to differentiate the impact of each dam’s operation by decreasing water residence time for Uiam Reservoir. The Uiam Reservoir, smaller than the upstream Chuncheon Dam and Soyang River Dam, is significantly influenced by their discharge rates. During summer, temperature differences exceeding 7 °C between discharges from Chuncheon Dam and Soyang Dam inflowed into the right side and the left side, respectively, of the reservoir, leading to poor mixing, which was further hindered by islands within the reservoir. Consequently, due to the influence of the different base water temperatures of the Bukhan River and Soyang River and the topographical characteristics, the impact range varied depending on the operation of each dam, and the amount of algae mitigation differed at each point. In emergency situations where algae blooms proliferate rapidly, appropriate dam operations in water bodies with large dams upstream and downstream, like Uiam Reservoir, can be effective in mitigating algae at specific regions of the reservoir. Full article