• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1249-1253
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• 2008

본 연구의 목적은 대청댐 수문방류에 의한 하류 주요지점까지의 방류수 도달시간을 검토하여 수문방류에 따른 홍수피해 예방 및 방류 증가 등 홍수조절업무에 만전을 기하고자 함이며, '06년 홍수기 대청댐 수문방류량에 의한 하류 주요 수위국 지점별 수위상승과의 연관성을 가지고 하류 홍수도달시간을 실측, 산정하고 기존 도달시간 산정 자료의 신뢰성을 검토하고자 한다. 도달시간 산정방법은 평균유속 상승에 따른 검토, 하류 수위상승 기점에 따른 검토, 수리학적 홍수추적에 따른 검토(FLDWAV, LOOPNET, HEC-RAS, Muskingum), 수문학적 홍수추적에 따른 검토(Progressive lag method)을 시행하고자 한다.

• Journal of Korean Society on Water Environment
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• v.28 no.1
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• pp.10-17
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• 2012

The middle and lower reaches of the Kum River system become stagnant in dry seasons with florishing of phytoplankton. In this study primary productivity of phytoplankton were measured by the C-14 uptake method and the P-I model method at seven main stream sites of the Kum River from the Daechung Dam outet to the river mouth. Nutrients (TN, TP, DIP, TIN) concentrations were measured in the mainstream and tributaries and compared with the variation of assimilation number. The range of primary productivity was $40{\sim}4,558mgC{\cdot}m^{-2}{\cdot}day^{-1}$ and it was higher than those of lentic ecosystems in Korea. Average TN and TP were $4.1mgN{\cdot}L^{-1}$, $70.6mgP{\cdot}m^{-3}$, respectively. Tributaries showed higher nutrient concentrations than the main stream. After two major tributaries merged with the discharging water of the Daechung Dam phyotplankton biomass and productivity increased drastically and remained at the similar eutrophic level through the downstream reach to the river mouth. Both dissolved phosphorus and nitrogen concentrations showed positive correlation with assimilation number of phytoplankton. In conclusion phytoplankton productivity is at the level of eutrophic water and it was higher than usual lentic habitats. Nutrient concentrations are critical factors in controlling productivity in the lower reach of the Kum River.

• Journal of Korea Water Resources Association
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• v.39 no.7 s.168
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• pp.627-636
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• 2006

This study estimates adequate discharge to meet the specified target water quality concentration using the pollutant load of the Geum river basin given in TMDL (Total Maximum Daily Load) report. During the 1st phase, BOD is chosen as a target water quality constituent under regulation of the Ministry of Environment in Korea. BOD, TN, and TP loads estimated based on the TMDL and provincial zones were re-distributed for 10 major tributaries, and the remaining areas along the main river are classified as 15 incremental flow areas. Water quality modeling was conducted using Qual2E for the low flow period of a year (i.e. $March{\sim}April$). The results of the model simulation showed that about 30 cms from the Daechung dam would be sufficient to satisfy the target water quality in the Geum river downstream of the Daechung multipurpose Dam.

• Journal of Korea Water Resources Association
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• v.35 no.1
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• pp.37-49
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• 2002

The application of conventional method for optimizing firm water supply and hydro-electric power generation has some limitation during abnormal or extreme drought periods. Hashimoto et al. (1982) suggested there risk evaluation criteria such as reliability, resilience, and vulnerability. These three criteria have been incorporated into a mixed-integer programming model for evaluating the possible performance of water- supply reservoir (Moy et al., 1986; Srinivasan et al., 1999). However, till now, these kind of researches have been conducted only for water-supply reservoir. Therefore there have been no other study for multi-purpose dam including hydro-electric power generation. This study presents an improved formulation of the previous model for evaluating a multi-purpose reservoir system operation considering water supply and hydro-electric power generation. The modified model was applied to the Daechung multi-purpose reservoir system in the Keum river basin to demonstrate the efficiency of the improved formulation.

• Water Engineering Research
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• v.3 no.2
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• pp.143-153
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• 2002

As the natural flows in rivers dramatically decrease during drought season in Korea, a deterioration of river water quality is accelerated. Thus, consideration of downstream water quality responding to changes in reservoir release is essential for an integrated watershed management with regards to water quantity and quality. In this study, water quality models based on artificial neural networks (ANNs) method were developed using historical downstream water quality (rm $\NH_3$-N) data obtained from a water treatment plant in Geum river and reservoir release data from Daechung dam. A nonlinear multiple regression model was developed and compared with the ANN models. In the models, the rm NH$_3$-N concentration for next time step is dependent on dam outflow, river water quality data such as pH, alkalinity, temperature, and rm $\NH_3$-N of previous time step. The model parameters were estimated using monthly data from Jan. 1993 to Dec. 1998, then another set of monthly data between Jan. 1999 and Dec. 2000 were used for verification. The predictive performance of the models was evaluated by comparing the statistical characteristics of predicted data with those of observed data. According to the results, the ANN models showed a better performance than the regression model in the applied cases.

• Korean Journal of Ecology and Environment
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• v.34 no.4 s.96
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• pp.277-284
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• 2001

Since a substantial part of the total planktonic primary production is due to the activity of the picoplankton, seasonal change of chlorophyll a in the picoplankton, nanoplankton and microplankton was determined at four locations in Daechung Reservoir from September in 1998 to September in 1999. Chlorophyll a concentration (<$200\;{\mu}m$) was $0.7{\sim}36.9\;{\mu}g/l$ In TAE (Taejeon site), $0.5{\sim}23.5\;{\mu}g/l$ in MAN (Man site), $1.9{\sim}20.1\;{\mu}g/l$ in HOE (Hoenam site), and $0.5{\sim}17.4\;{\mu}g/l$ in DAM (Dam site). Generally it was observed the highest concentration of chlorophyll a was in September and the lowest in April to June. The relative contribution of chlorophyll a of each fraction was changed dramatically through the year. Relative contribution of chlorophyll a of microplankton was high from June to October, and low in March in all locations except HOE. However chlorophlyll a concentration of picoplankton fraction was $2.0{\sim}24.3%$ of total chlorophyll a (<$200\;{\mu}m$) through the year and did not show any dramatic changes at all locations.

• Journal of Korea Water Resources Association
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• v.34 no.3
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• pp.217-229
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• 2001

The purpose of the present study was to evaluate the hydrologic changes and the effect of runoff characteristics of a large river basin due to construction of a dam. The changes of land use and vegetation are quantified from remote sensing film taken before and after dam construction. Evapotranspiration, runoff and soil moisture were calculated using water balance equation. It was found that the albedo of watershed upstream of the dam is decreasing due to the decreasing of vegetation and the increasing of water surface and forest, and the increasing of potential evpotranspiration and soil moisture led to increasing actual evpotranspiration and runoff ratio after dam construction.

• Journal of Korea Water Resources Association
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• v.44 no.9
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• pp.765-776
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• 2011

Flood discharge capacity in a dam downstream reach has been decreased after dam construction because of the river cross section reduction impacted by farm lands, sand-bars and parking lots, etc. in river flood plains. Those obstacles being in the river inside areas have caused negative influences to the dam operation policy. Therefore, the dam downstream river improvement work associated with the dam operation improvement plan is under construction for removing reduction factors on the dam effective storage, assuring flood safety in the dam downstream river and incrementing dam operation benefits. But the project has issued some problems such as project feasibility, economic evaluation, cost allocation and benefit share, etc. Since a dam enterpriser has not committed such kind of project before, it is necessary to set up an objective analysis process and a quantitative financial valuation. This study examines the measurable economic benefits and the cost allocation of the project for the fairness between benefit owners (central government and water electricity enterprisers). As a result, the total economic benefit from 3 dams (Imha, Daechung and Youngdam Dam) accounts for 14.41 Billion Won/year. The financial valuation of K-water as a project enterpriser is approximately estimated at 40% of the total value and the government is 60%.

• Journal of Korea Water Resources Association
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• v.44 no.9
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• pp.753-763
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• 2011

Allocated water storage of dam at the planning and design stage does not seem to be maintained well at the operation stage because of unexpected critical reasons. A dam is likely to be subject to negative effects caused by changes of dam operation conditions and it is hardly avoidable. Therefore, it must be timely improved to recover its original functions and looked for better alternatives to keep its original roles. Specifically the improper management of river condition degrades flood control capability in a dam and river eco-system. The dam downstream river improvement work is needed for normalizing dam functions and its valuations. This study focuses on estimating water use benefits from recovering its own effective storage buffer restricted for flood control. As the results, the water supply and the hydropower benefits in Imha, Daechung and Youngdam Dam are recovered totally by 19.9 million $m^3$/year and 20.8 GWh/year respectively. Also those results are used for the basic information of the economic analysis in the dam downstream river improvement work.

• Journal of Korea Water Resources Association
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• v.33 no.6
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• pp.745-755
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• 2000

The dam operation system of KOWACO for flood control doesn't have capability to account for the downstream hydrologic conditions and any feasible index to decide the pre-release from the forecasted rainfall and inflow. In this study, a dam operation model for flood control was developed to account for the flood flow condition of its downstream to give users the dam release schedules. Application test of EV ROM to Keum River showed that EV ROM is superior to the Rigid ROM and Technical ROM which are currently used by KOWACO. EV ROM developed in this study provides a release schedule accounting for the cumulative lateral flow hydrograph at the downstream control points where the discharge does not depend only on the dam operation. but also on lateral inflow from the tributaries. In order to reduce the peak discharge at the control points, it suggests the preliminary release during the early rising phase of the predicted hydrograph, holding the flood flow inside the dam during a peak phase, and afterward resuming the release. Three case studies of flood control by the operation of Daechung Multipurpose Dam in Geum River Basin show that the EV ROM is superior to the Rigid ROM and Technical ROM. This must be due to its nature to account for the downstream flow condition as well as the inflow and water level of the dam. It was also conceived that further case studies of EV ROM and more accurate rainfall prediction would improve the dam operation for flood control.ontrol.