• Journal of Korea Water Resources Association
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• v.49 no.9
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• pp.761-771
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• 2016

The GloSea5 (Global Seasonal forecasting system version 5) is provided and operated by the KMA (Korea Meteorological Administration). GloSea5 provides Forecast (FCST) and Hindcast (HCST) data and its horizontal resolution is about 60km ($0.83^{\circ}{\times}0.56^{\circ}$) in the mid-latitudes. In order to use this data in watershed-scale water management, GloSea5 needs spatial-temporal downscaling. As such, statistical downscaling was used to correct for systematic biases of variables and to improve data reliability. HCST data is provided in ensemble format, and the highest statistical correlation ($R^2=0.60$, RMSE = 88.92, NSE = 0.57) of ensemble precipitation was reported for the Yongdam Dam watershed on the #6 grid. Additionally, the original GloSea5 (600.1 mm) showed the greatest difference (-26.5%) compared to observations (816.1 mm) during the summer flood season. However, downscaled GloSea5 was shown to have only a -3.1% error rate. Most of the underestimated results corresponded to precipitation levels during the flood season and the downscaled GloSea5 showed important results of restoration in precipitation levels. Per the analysis results of spatial autocorrelation using seasonal Moran's I, the spatial distribution was shown to be statistically significant. These results can improve the uncertainty of original GloSea5 and substantiate its spatial-temporal accuracy and validity. The spatial-temporal reproducibility assessment will play a very important role as basic data for watershed-scale water management.

• Clean Technology
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• v.20 no.4
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• pp.449-456
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• 2014

There has been increasing concerns for the problems of water security in countries, caused by the frequent occurrence of localized drought due to the climate change and uncertainty of water balance. The importance of fresh water is emphasized as considerable amount of usable fresh water is utilized for power generation sector producing electricity. PV power system, the source of renewable energy, consumes water for the every steps of life cycle: manufacturing, installation, and operation. However, it uses relatively less water than the traditional energy sources such as thermal power and nuclear power sources. In this study, to find out the use of water for the entire process of PV power system from extracting raw materials to operating the system, the footprint of water in the whole process is measured to be analyzed. Measuring the result, the PV water footprint of value chain was $0.989m^3/MWh$ and the water footprint appeared higher specially in poly-Si and solar cell process. The following two reasons explain it: poly-Si process is energy-intensive process and it consumes lots of cooling water. In solar cell process, deionized water is used considerably for washing a high-efficiency crystalline silicon. It is identified that PV system is the source using less water than traditional ones, which has a critical value in saving water. In discussing the future energy policy, it is vital to introduce the concept of water footprint as a supplementary value of renewable energy.

• Journal of Korea Water Resources Association
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• v.39 no.2 s.163
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• pp.139-150
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• 2006

In recent, increasing of the impervious area gives rise to short concentration time and high peak discharge comparing with natural watershed and it is a cause of urban flood damage. Therefore, we have performed for structural and non-structural plans to reduce the damage from inundation. The Gulpo-cheon basin had been frequently inundated and damaged due to the water level of Han river. So, the Gulpo-cheon floodway was constructed with 20 meters width for flood control in the basin but it was not enough for our expectation and now we have a plan to expand the floodway to 80 meters. We use a XP-SWMM model developed based on EPA-SWMM version for analyzing the capacity of flood conveyance by the expansion of Gulpo-cheon floodway with the same 100 years return period design storm and the same tidal conditions of the Yellow sea. The flood conveyance after the expansion of floodway becomes three times comparing it with before the expansion. Also we simulate the flood discharge at the diversion point of Gulpo-cheon for the expanded condition of floodway and know that the discharge of about 300 m3/sec is flowing backward to the expanded floodway. Therefore we may need some kinds of hydraulic structures to prevent the back water.

• Journal of Korea Water Resources Association
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• v.39 no.5 s.166
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• pp.467-478
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• 2006

Water supply reliability for a dam is defined with a concept of probabilistic reliability. An evaluation procedure of the water supply reliability is shown with an analysis of long term firm yield reliability. The water supply reliabilities of Soyanggang Dam and Chungju Dam were evaluated. To evaluate the water supply reliability, forty one sets of monthly runoff series were generated by SAMS-2000. HEC-5 model was applied to the reservoir simulation to compute the firm yield from a monthly data of time series. The water supply reliability of the firm yield from the design runoff data of Soyanggang Dam is evaluated by 80.5 % for a planning period of 50 years. The water supply reliability of the firm yield from the historic runoff after the dam construction is evaluated by 53.7 %. The firm yield from the design runoff is 1.491 billion $m^3$/yr and the firm yield from the historic runoff is 1.585 billion $m^3$/yr. If the target draft Is 1.585 billion $m^3$/yr, additional water of 0.094 billion $m^3$ could be supplied every year with its risk. From the similar procedures, the firm yield from the design runoff of Chungju Dam is evaluated 3.377 billion $m^3$/yr and the firm yield from the historic runoff is 2.960 billion $m^3$/yr. If the target draft is 3.377 billion $m^3$/yr, water supply insufficiency occurs for all the sets of time series generated. It may result from overestimation of the spring runoff used for design. The procedure shown can be a more objective method to evaluate water supply reliability of a dam.

• Journal of Korea Water Resources Association
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• v.36 no.2
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• pp.195-209
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• 2003

Spatial-Stochastic Neural Networks Model(SSNNM) is used to estimate long-term streamflow in the parallel reservoir groups. SSNNM employs two kinds of backpropagation algorithms, based on LMBP and BFGS-QNBP separately. SSNNM has three layers, input, hidden, and output layer, in the structure and network configuration consists of 8-8-2 nodes one by one. Nodes in input layer are composed of streamflow, precipitation, pan evaporation, and temperature with the monthly average values collected from Andong and Imha reservoir. But some temporal differences apparently exist in their time series. For the SSNNM training procedure, the training sets in input layer are generated by the PARMA(1,1) stochastic model and they covers insufficient time series. Generated data series are used to train SSNNM and the model parameters, optimal connection weights and biases, are estimated during training procedure. They are applied to evaluate model validation using observed data sets. In this study, the new approaches give outstanding results by the comparison of statistical analysis and hydrographs in the model validation. SSNNM will help to manage and control water distribution and give basic data to develop long-term coupled operation system in parallel reservoir groups of the Upper Nakdong River.

• Journal of Korea Water Resources Association
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• v.48 no.6
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• pp.511-522
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• 2015

This study assessed the impact of uncertainties in flood data on the results of flood frequency analysis for Han river basin. To meet this aim, this study quantified assessment focused on the index flood and quantile by regional flood frequency analysis using the flood data from 17 water level gauges in Han river basin. We analysed the results categorized by three cases according to the characteristics of the measured data. Firstly, we analyzed the regional flood frequency for the water level gauge in the Pyungchang river basin to investigate the impact of water level data. The results has the error of 0.240 with respect to the mean flood. Secondly, we examined the impact of uncertainty in measurement data generated by the application of rating on the results of regional flood frequency analysis. We have compared the results by applying the rating estimated for each year to the one by the recently estimated rating. The results showed that the mean error has 0.246 in terms of the mean flood. Finally, we have inferred the regional flood frequency analysis results with the regulated flow in the downstream area of dams. The regulated specific discharge in the downstream area of dams controlled by dam operation showed a large difference to the estimated specific discharge in the downstream area of dams by extension of the natural specific discharge in the upstream area using the regionalization method.

• Journal of Korea Water Resources Association
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• v.42 no.3
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• pp.191-200
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• 2009

A localized torrential rainfall and flash floods which are more frequently occurred by extraordinary atmospheric phenomena and rising sea surface temperature require more hydrological data collecting and analysis for small watershed. Urban watershed hydrological data monitoring system is needed because of big flood potential damage and lack of urban watershed hydrological data. Therefore, Urban Flood Disaster Management Research Center operates small experimental catchments(Sinnae1, Gunja, and Children's Park) observing and analyzing hydrological data(rainfall, stage, and discharge). In this study, the discharge of combined sewage for Gunja experimental drainage is analyzed with weekly data and day of the week data. Through several analyses in analyzing the urban runoff characteristics and managing the urban sewage system, direct runoff is calibrated and verified by the estimated values of rainfall-runoff model(SWMM).

• Journal of Korea Water Resources Association
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• v.41 no.3
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• pp.293-303
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• 2008

Reservoir turbidity flows degrade the efficiency and sustainability of water supply system in many countries located in monsoon climate region. A decision support system called RTMMS aimed to assist reservoir operations was developed for the real time monitoring, modeling, and management of turbidity flows induced by flood runoffs in Daecheong reservoir. RTMMS consists of a real time data acquisition module that collects and stores field monitoring data, a data assimilation module that assists pre-processing of model input data, a two dimensional numerical model for the simulation of reservoir hydrodynamics and turbidity, and a post-processor that aids the analysis of simulation results and alternative management scenarios. RTMMS was calibrated using field data obtained during the flood season of 2004, and applied to real-time simulations of flood events occurred on July of 2006 for assessing its predictive capability. The system showed fairly satisfactory performance in reproducing the density flow regimes and fate of turbidity plumes in the reservoir with efficient computation time that is a vital requirement for a real time application. The configurations of RTMMS suggested in this study can be adopted in many reservoirs that have similar turbidity issues for better management of water supply utilities and downstream aquatic ecosystem.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.908-908
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• 2012

국내 기후 특성상 하절기에 집중되는 강우로 인해 댐의 건설을 홍수조절, 용수확보 및 전력생산 등의 목적에 있어서 불가피하다. 이와 같은 저수지와 하류하천은 댐 수문 개폐에 따라 흐름변화로 인하여 수체의 거동 및 수질 변화가 발생하며, 일반적인 하천과는 다른 특성을 지니게 된다. 또한 수심이 깊은 저수지의 경우에는 흐름방향과 더불어 수심 방향의 특성도 중요하며, 수리 및 수질 모형의 연계를 통한 3차원적인 해석을 필요로 한다. 유역 내 지상 또는 대기에서 발생한 모든 오염물질은 강우에 의해 하천과 호수와 같은 수체로 유입되며, 강우가 발생했을 때 유역의 토지피복 상태와 수리, 지형, 강우강도, 토양의 특성에 의해 하천으로 유입되는 오염물질의 농도와 부하특성이 달라진다. 비점오염물질의 축적이 가능한 호수나 저수지에서는 비점오염원의 유입이 더 큰 문제가 되며, 유량이 극히 미미한 하천의 경우에는 강우초기에 일시에 집중적으로 유입되는 초기 오염 부하량이 문제가 된다. 강우유출수의 하천 유입은 강우 현상과 밀접한 관계를 맺고 있으므로 그 제어가 쉽지 않다. 이러므로 이를 총괄하는 유역통합관리기술이 필요로 하며, 기존의 유역통합관리기술은 댐 상류유역을 중심으로 개발되고 있으며, 댐 상류유역과 저수지, 하류하천으로 구분되어 연구되어 왔다. 또한 각각의 모형이 개별적으로 적용되어 통합적인 평가시스템이 표준화되지 않은 관계로 댐 상하류 모니터링 자료가 연계된 실무 적용이 이루어지지 않고 있다. 따라서 하천 수리 수문학적 역학구조를 이해하고 그 특성에 적합하게 평가할 수 있는 표준화된 시스템이 구축되어야 한다. 또한 효과적인 유역통합관리를 위해서는 하천의 현재 뿐만 아니라 장래에 대한 예측부분도 포함되어야 한다. 본 연구에서는 댐 유역에서의 유출과 수질 변화를 모의하고 이를 이용하여 저수지 내에서의 오염물질 거동에 대해서 해석하였다. 또한 기후변화에 따른 유역, 저수지 및 하천에 미치는 영향을 고려하기 위하여 고해상도 지역기후전망 모의자료를 이용하여 수문학적 스케일로 통계적 상세화한 후 지역별 상세수문시나리오를 생산하여 미래 예측에 활용하였다. 기후변화 시나리오의 상세화를 통한 상세지역의 기후를 예측하고, 예측된 기상자료를 이용하여 유역모델을 모의하여 미래의 유출 및 수질 변화를 파악할 수 있는 기술 개발로 인해 저수지의 운영에 도움을 주고, 주수지의 치수증대 사업 등 유출의 변화에 따른 하류하천 변화를 파악할 수 있고, 기후변화에 따른 하류하천에 대한 홍수기 때 치수, 이수 및 방재에 대하여 기초자료를 제공할 수 있을 것으로 판단된다.

• Journal of Korea Water Resources Association
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• v.45 no.12
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• pp.1259-1273
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• 2012

In this study, a watershed-based surface water and groundwater integrated model, SWAT-MODFLOW was used to quantify the stream flow depletion due to groundwater pumping for the Sinduncheon watershed. Complex water use conditions such as water taken from a stream, sewage disposal release, irrigation from agricultural reservoir, groundwater pumping were considered for simulations. In particular, the model was revised to reflect the effects of reservoir operation and return flow from the used groundwater on streamflow variation. The simulated results showed that the groundwater pumping at current status has induced the decrease of more than 10% in annual average streamflow and 40% in drought flow at the outlet of the Sinduncheon watershed, The simulated results also revealed that the vast water withdrawals at green house areas during winter season have dramatically changed streamflow from April to June. The streamflow depletion was mainly attributed to pumping wells located within the distance of 300 m from the stream for Sinduncheon watershed.