Korea Water Resources Corporation (K-water) is the primary governmental water management agency in South Korea responsible for comprehensive water resource development and providing both public and industrial water supplies. Established in 1967, K-water implements national water resources management policies regarding multipurpose dams, water supply dams, and regional water supply systems.
From 2013 to 2014, K-water conducted a first-of-its-kind study to assess impacts of water resources management on a southern coastal ecosystem of South Korea. Led by K-water principal researcher Dr. Won, Nam-Il, the purpose of the research was to examine the effect of hydroelectric dam water discharges on the salinity and temperature of downstream and coastal waters. The study also investigated temperature changes occurring in tidal mudflat systems including what, if any, impact these changes have on marine bivalve populations.
The project was initiated in response to complaints from fisheries management.
“Fisheries management was concerned that freshwater releases from a small control dam downstream from the hydroelectric dam are causing lower water temperatures and salinity changes in the tidal mudflat area, impacting bivalve production,” Dr. Won said.
Dr. Won’s team set out to measure changes in temperature and conductivity across 15 sites in the coastal bay region, which included the dam reservoir, estuary, tidal flat, coastal waters, and three different watershed streams characterized as urban, natural, and controlled. For data collection, Dr. Won and his research colleagues relied on a variety of HOBO data loggers from Onset (including water level, conductivity, and water temperature loggers) across the monitoring sites.
“To investigate the potential ecological impacts from dam discharges, continuous and long-term data covering both temporal and spatial changes over daily, weekly, seasonal, and yearly time regimes is required,” Dr. Won said. “HOBO data loggers are the most cost-effective way to accomplish this and they were easy and reliable to secure,” he said.
The monitoring instruments were deployed in streams by submerging them under the water surface with a buoy secured to a suitable place with a rope. In coastal areas, loggers were secured to aquaculture facilities in a similar fashion. In the tidal flats, cable ties were used to attach HOBO Water Temp Pro v2 loggers to a plate, with the plate buried and secured to a pole.
Over the study period, deployment was mostly continuous, with downloads conducted every two months. Salinity was measured every 10 minutes at each site. Air, seawater, tide, and discharge temperature data were also collected. Onset’s HOBOware graphing and analysis software was employed for quick assessments in the field and data export to Microsoft Excel, which was utilized for further analyses.
Findings from the study revealed that temperature regimes are different among the various natural, dam-dependent, urbanized, and seawater-dependent streams and that the low temperature effects are possibly caused by the limited seasons. The researchers also concluded that discharges from the hydroelectric dam have little effect on ocean water temperatures. The results of the study are being used to negate the fisheries’ complaints.
“Freshwater inputs do not always lead to a unidirectional impact, such as decreasing stream temperature,” Dr. Won said. “Seasonal changes should be considered and ocean conditions are also important for coastal application.”
For further studies, Dr. Won said watersheds connected to coastal bays can be evaluated by similar approaches. “Possible environmental impacts can be determined by detecting small changes in temperature and conductivity,” he said. “Continuous data are very important for evaluating ecological impacts.”
Dr. Won has published a paper in a domestic Korean scientific journal and presented his project and results at a recent conference. He will soon be writing another paper to be published in international scientific journals.
The results of the project will be used by the Ministry of Fisheries in a 10-year study of estuaries, which is currently being planned. The project is also likely to be replicated across other areas of Korea where K-water manages dams.