Daecheong Reservoir was made by the construction of a large dam (>15 m in height) on the middle to downstream of the Geum River and the discharge systems have the watergate-spillway (WS), a hydropower penstock (HPP), and two intake towers. The purpose of this study was to investigate the limnological anomalies of turbid water reduction, green algae phenomenon, and oligotrophic state in the lower part of reservoir dam site, and compared with hydro-meteorological factors. Field surveys were conducted in two stations of near dam and the outlet of HPP with one week intervals from January to December 2000. Rainfall was closely related to the fluctuations of inflow, outflow and water level. The rainfall pattern was depended on the storm of monsoon and typhoon, and the increase of discharge and turbidity responded more strongly to the intensity than the frequency. Water temperature and DO fluctuations within the reservoir water layer were influenced by meteorological and hydrological events, and these were mainly caused by water level fluctuation based on temperature stratification, density current and discharge types. The discharges of WS and HPP induced to the flow of water bodies and the outflows of turbid water and nutrients such as nitrogen and phosphorus, respectively. Especially, when hypoxic or low-oxygen condition was present in the bottom water, the discharge through HPP has contributed significantly to the outflow of phosphorus released from the sediment into the downstream of dam. In addition, HPP effluent which be continuously operated throughout the year, was the main factor that could change to a low trophic level in the downreservoir (lacustrine zone). And water-bloom (green-tide) occurring in the lower part of reservoir was the result that the water body of upreservoir being transported and diffused toward the downreseroir, when discharging through the WS. Finally, the hydropower effluent was included the importance and dynamics that could have a temporal and spatial impacts on the physical, chemical and biological factors of the reservoir ecosystem.

This study was carried out to comparatively identify characteristics of turbid water influence in Imha Reservoir, Soyang Reservoir, and Daecheong Reservoir in Korea. We used 3 years dataset from 2002 to 2004 and analyzed seasonal water quality characteristics, particular parameters in association with turbidity, and light transparency to figure out the trends. All parameters to be used in the study were total phosphate (TP), total nitrogen (TN), chlorophyll-a (Chl), suspended solids (SS), Secchi depth (SD), conductivity, and vertical light extinction coefficienct (Kd), euphotic zone (Zeu), and critical depth (Zp). All parameters depend on season and watershed. Suspended solids from Soyang Reservoir were usually caused by TP, mainly related to living wastes and agricultures in upper stream. Daecheong Reservoir was influenced by organic matters related to large phytoplankton biomass in summer and inorganic suspended solids by nutrients in the winter. However, in case of Imha Reservoir, turbid water, consisted in silt and clay through heavy precipitation remained in the waterbody to decrease water transparency along with TP and caused the light limitation in winter. Overall results suggest that it was necessary to establish various management programs because the reasons occurring turbidity were varied according to the reservoir circumstances.

어류개체군에 대한 탁수의 영향을 파악하고자, 2004년부터 2005년까지 탁수하천(대기, 자운천)과 비탁수하천(봉산천, 계방천)에 분포하는 금강모치 개체군의 체장-체중 관계와 비만도지수의 변화를 알아보았다. 탁수하천과 비탁수하천간의 금강모치 평균전장을 비교해본 결과, 유의한 차이가 없는 것으로 나타났다. 남한강에서 체장-체중 관계에 따른 회귀계수 b값은 봉산천에서 3.21, 그리고 대기천에서 3.07로 나타났다. 이에 반하여, 북한강에 위치한 탁수하천의 회귀계수 b값은 비탁수하천의 값보다 약간 높았다. 그 값은 계방천에서 3.20, 자운천에서 3.23으로 각각 나타났다. 우리의 연구 결과는 금강모치 개체군 단계에서 만성 탁수의 영향이 적음을 보여준다.

본 연구는 임하호의 고탁수 발생에 따른 식물플랑크톤군집의 변화를 조사하기 위하여 2003년 5월부터 2004년 7월까지 댐축 지점에서 매월 채집하였다. 2003년 9월과 10월의 가장 높은 탁도(1221 NTU) 형성은 태풍(매미)에 동반된 집중 호우 시기와 일치하였다. 출현한 식물플랑크톤은 모두 102분류군이고, 이 중 규조강이 63종류로 가장 많이 출현하였으며, 녹조강이 23종류, 남조강이 9종류, 시누라조강과 은편모조강이 각각 3종류 그리고 유글레나 조강이 1종류가 출현하였다. 총 현존량은 270~4,515 indls. mL-1였고, 은편모조강의 Cryptomonas ovata, 규조강의 Cyclotella sp. 그리고 남조강의 Microcystis aeruginosa 등은 고탁수의 감소후 차례로 우점하였다.

High turbid water in the River has been one of the major concerns to the downstream residence. Especially in the Nakdong River basin severe turbid water problem occurred in year 2002 and 2003 due to the typhoon Rusa and Maemi consecutively. The main objective of this study is to develop turbid water management system in reservoir downstream of the Nakdong River combining physically based semi-distributed hydrologic simulation model SWAT with 1-dimensional dynamic water quality simulation model. SWAT model covers the area from the upstream of the Imha and Andong reservoir to the Gumi gage station for the purpose of estimating flow rates and suspended sediment of the tributaries. From year 1999 to 2007 runoff simulation for 8 years Reff and R2 ranges 0.46~0.9, 0.54~0.99 respectively. Through the linkage of models, outputs of SWAT model such as suspended sediment and flow rates of the tributaries can be incorporated into the 1-dimensional dynamic water quality simulation model, KoRiv1 to support joint reservoir operation considering the turbidity released from Imha and Andong reservoir. The applicability of model simulation has been tested for year 2006 and compared with measured data.