• Journal of Wetlands Research
• /
• v.20 no.4
• /
• pp.353-362
• /
• 2018

The purpose of this study is to suggest a structure plan for improving the utilization of inactive storage in the dam for overcoming the drought. Inactive storage in the dam is composed of the emergency storage and dead storage. The emergency storage can be used for the case of emergency such as drought. But, in general, the dead storage for sedimentation is not used even for the emergency. Therefore, this study considers the part of dead storage that the sedimentation is not progressed yet can be used during the severe drought period and is called "drought storage in a dam". The accurate Sediment Level(SL) analysis for the computation of the drought storage should be performed and so the present and future SL in the dam reservoir is estimated using SED-2D linked with RMA-2 model of SMS. After the consideration of additionally available storage capacity based on the estimated SL, the drought storage is finally determined. Present data based on historical data, future predicted future climate factors by Representative Concentrarion Pathways(RCP) 8.5 scenario. Then, using the TANK model, dam inflows were determined, and future period such as SL and drought storage were suggested. As the results, we have found that the available drought storage will be reduced in the future when we compare the present drought storage with the future one. This is due to a increase variability of climate change. Therefore, we should take the necessary study for the increase of available drought storage in the future.

• Journal of Korea Water Resources Association
• /
• v.50 no.1
• /
• pp.55-64
• /
• 2017

This study presents a numerical model for simulating turbidity currents using the ULTIMATE scheme. For this, the layer-averaged model is used. The model is applied to laboratory experiments, where the flume is composed of sloping and flat parts, and the characteristics of propagating turbidity currents are investigated. Due to the universal limiter of the ULTIMATE scheme, the frontal part of the turbidity currents at a sharp gradient without numerical oscillations is computed. Simulated turbidity currents propagate super-critically to the end of the flume, and internal hydraulic jumps occur at the break-in-slope after being affected by the downstream boundary. It is found that the hydraulic jumps are computed without numerical oscillations if Courant number is less than 1. In addition, factors that affect propagation velocity of turbidity currents is studied. The particle size less than $9{\mu}m$ does not affect propagation velocity but the buoyancy flux affects clearly. Finally, it is found that the numerical model computes the bed elevation change due to turbidity currents properly. Specifically, a discontinuity in the bed elevation, arisen from the hydraulic jumps and resulting difference in sediment entrainment, is observed.

• Journal of Korean Society on Water Environment
• /
• v.29 no.3
• /
• pp.365-376
• /
• 2013

The purpose of this study was to evaluate effects of spatio-temporal changes in land uses and rainfall magnitude using the Soil and Water Assessment Tool (SWAT). Prior of application of the model to real-world problem, the model should be calibrated and validated properly. In most modeling approaches, the validation process is done assuming no significant changes occurring at the study watershed between calibration and validation periods, which is not proper assumption for agricultural watersheds. If simulated results obtained with calibrated parameters match observed data with higher accuracy for validation period, this does not always mean the simulated result represents rainfall-runoff, pollutant generation and transport mechanism for validation period because temporal and spatial variables and rainfall magnitude are often not the same. In this study SWAT was applied to Mandae study watershed in Korea to evaluate effects of spatio-temporal changes in landuses using 2009 and 2010 crop data for each field at the watershed. The Nash-Sutcliffe model efficiency (NSE) values for calibration and validation with either 2009 or 2010 was evaluated and the NSE value for calibration with 2009 and calibration with 2010 were compared. It was found that if there is substantial change in land use and rainfall, model calibration period should be determined to reflect those changes. Through these approaches, inherent limitation of the SWAT, which does not consider changes in land uses over the simulation period, was investigated. Also, Effects of changes in rainfall magnitude during calibration process were analyzed.

• Journal of Korea Water Resources Association
• /
• v.37 no.11
• /
• pp.897-913
• /
• 2004

There has been continuous efforts to manage the water resources for the required water quality criterion at river channel in Korea. However, we could not obtain the partial improvement only for the point source pollutant such as, wastewater from urban and industrial site through the water quality management. Therefore, it is strongly needed that the Best Management Practice(BMP) throughout the river basin for water quality management including non-point source pollutant loads. This problem should be resolved by recognizing the non-point source pollutant loads from upstream river basin to the outlet depends on the land use and soil type characteristic of the river basin using the computer simulation by distributed parameter model based on the detailed investigation and the application of Geographic Information System(GIS). Used in this study, Annualized Agricultural Non-Point Source Pollution (AnnAGNPS) model is a tool suitable for long term evaluation of the effects of BMPs and can be used for un gauged watershed simulation of runoff and sediment yield. Now applications of model are in progress. So we just describe the limited result. However If well have done modeling and have investigated of propriety of model, well achieve our final goal of this study.

• Proceedings of the KSRS Conference
• /
• 2000.04a
• /
• pp.166-171
• /
• 2000

밀티빔 음향 측심기 (Multibeam Echo Sounder)는 탐사선에 수직방향으로 해저면을 주사(Swath)하여, 한번의 송수신(Ping)으로 다중의 빔자료를 얻을 수 있는 측심기로, 해저면에 반사되어 되돌아오는 음파의 음압을 기록하고, 사이드 스캔 소나 자료도 동시에 취득하는 기능을 가지고 있으므로, 측심된 해저 지형(Bathymetry)과 해저 지형을 덮고 있는 해저면의 퇴적 상황(Sediment Environment)도 동시에 얻을 수 있는 다목적 측심기이다. 본 논문에서는 L3사의 Sea Beam 2100 멀티빔 음향 측심기를 통해 얻은 자료를 처리하여, 3차원 공간 데이터인 DEM(Digital Elevation Model)을 생성하고, VRML을 이용한 웹상에서의 해저 지형 가시화를 통해, 세계 어느 곳에서나 웹을 통하여 쉽게 정보를 공유할 수 있는 3차원 해저 지리 정보 시스템의 구현을 목적으로 한다. 멀티빔 음향 측심기를 통해 얻어진 자료는 항해 자료 보정, 음속 보정, 빔 좌표 계산과 분리, 오측심 자료 제거, 조석 보정 등의 단계를 거쳐 측심자료의 정확도 및 신뢰도를 높이는 과정을 거치게 된다. 보정된 멀티빔 음향 측심자료는 무작위 점 사상(Point Topology)으로 산재 되어 있는 빔 자료를 임의의 단위영역으로 변환하는 과정을 거쳐야 하는데, 이 과정을 격자화라고 한다. 자료의 격자화를 통해 3차원 공강 데이터인 DEM 파일을 제작하고, 이 DEM 파일과 음압 영상을 이용해 웹상에서의 3차원 해저 지형의 가시화를 실현한다. 웹상에서의 3차원 지형 가시화에서 방대한 양의 지형 데이터는 데이터 전송 시간과 렌더링 시간에 치명적인 문제이다. 따라서, 렌더링 시간과 데이터 전송 시간을 단축시키기 위한, 지형 자료의 LOD(Level of Detail)를 통해, VRML을 이용한 보다 효과적인 웹상에서의 3차원 해저 지형의 가시화를 실현한다.면 기업은 고객으로 공간적인 제약으로 인한 불신을 불식시키는 신뢰감을 주게 된다. 이러한 고객서비스 향상과 물류비용 절감은 사이버 쇼핑몰이 전국 어디서나 우리의 안방에서 자연스럽게 점할 수 있는 상황을 만들 것이다.SP가 도입되어, 설계업무를 지원하기위한 기본적인 시스템 구조를 구상하게 된다. 이와 함께 IT Model을 구성하게 되는데, 객체지향적 접근 방법으로 Model을 생성하고 UML(Unified Modeling Language)을 Tool로 사용한다. 단계 4)는 Software Engineering 관점으로 접근한다. 이는 최종산물이라고 볼 수 있는 설계업무 지원 시스템을 Design하는 과정으로, 시스템에 사용될 데이터를 Design하는 과정과, 데이터를 기반으로 한 기능을 Design하는 과정으로 나눈다. 이를 통해 생성된 Model에 따라 최종적으로 Coding을 통하여 실제 시스템을 구축하게 된다.the making. program and policy decision making, The objectives of the study are to develop the methodology of modeling the socioeconomic evaluation, and build up the practical socioeconomic evaluation model of the HAN projects including scientific and technological effects. Since the HAN projects consists of 18 subprograms, it is difficult In evaluate all the subprograms simultaneously. Despite, each program is being performed under the category of HAN projects, so the common soci

• Journal of Korea Water Resources Association
• /
• v.37 no.10
• /
• pp.857-868
• /
• 2004

Since the self-purification capacity of rivers in Korea is significantly controlled by environmental maintenance flow supplied by upstream reservoirs during drought season, it is obviously important to operate the river and reservoir systems considering not only water quantity aspect but also conservation of downstream water quality and ecosystem. In this study, an unsteady river water quality model KORIVl- WIN was developed as a tool for evaluating the impact. of reservoir operations on the downstream water quality. The model parameters were calibrated and verified using field data obtained in Geum River on September and October of 2002, respectively. Intensive data sampling was performed on November 22, 2003 to investigate the effect of a short-term flushing discharge of Daecheong Reservoir, which increased outflow from 30 $m^3$/s to 200 $m^3$/s for 6 hours, on downstream water quality. The model performance was evaluated by comparing simulated results with observed data including hydraulics, biochemical oxygen demand(BOD$_{5}$), nitrogen and phosphorus species during the flushing event. It showed very good performance in predicting the travel time of flushing flow and water quality variations of dissolved forms of nitrogen and phosphorus species, while revealed large deviations for BOD$_{5}$ possibly due to missing the effect of organic matters resuspension from river bottom sediment during the wave front passage.

• Journal of Korea Water Resources Association
• /
• v.56 no.1
• /
• pp.23-34
• /
• 2023

This study analyzed the bed load transport and channel change on the vegetation zone through laboratory experiments and numerical simulations. To examine the effect of vegetation zone in the laboratory experiment, artificial vegetation zones made of acrylic sticks were installed in the experimental channel, and discharge conditions were adjusted to examine the bed load transport and channel change in the vegetation zone. Next, numerical simulations were performed by applying the same conditions as those of the laboratory experiment to the Nays2D model, a two-dimensional numerical model, and the applicability of the numerical model was examined by comparing the results with the results of the laboratory experiment. Finally, by applying a numerical model, the bed load transport and channel change according to the change in vegetation density were examined. As a result of examining the bed load transport and channel change in the vegetation zone according to the discharge condition change by applying the laboratory experiment and the numerical model, the results of the two application methods were similar. As the discharge increased, bed load from the upper stream was deposited inside the vegetation zone. On the other hand, on the other side of the vegetation zone, the flow was concentrated and erosion occurred. Also, the range of erosion increased in the downstream direction. As a result of examining the bed load transport and channel change according to the change in vegetation density, as the vegetation density increased, the bed load from the upper stream was deposited inside the vegetation zone. On the other hand, due to the increase in vegetation density, the flow was concentrated to the opposite side of the vegetation zone, erosion occurred.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.9 no.2
• /
• pp.64-72
• /
• 2004

We measured the vertical profiles of $O_2$, H$_2$S, and pH in sediment pore water beneath marine cage fish farms using a microsensor with a 25 ${\mu}{\textrm}{m}$ sensor tip size. The sediments are characterized by high organic material load. The oxygen consumption, hydrogen sulfide oxidation, and sulfate reduction rates in the microzonations (derived from the vertical distribution of chemical species concentration) were estimated by adapting a simple one-dimensional diffusion-reaction model. The oxygen penetration depth was 0.75 mm. The oxic microzonations were divided into upper and lower layers. Due to hydrogen sulfide oxidation within the oxic zone, the oxygen consumption rate was higher in the lower layer. The total oxygen consumption rate integrated with reaction zone depth was estimated to be 0.092 $\mu$mol $O_2$cm$^{-2}$ hr$^{-1}$ . The total hydrogen sulfide oxidation rate occurring within 0.7 mm thickness was estimated to be 0.030 $\mu$mo1 H$_2$S cm$^{-2}$ hr$^{-1}$ , and its turnover time in the oxic sediment layer was estimated to be about 2 minutes. This suggests that hydrogen sulfide was oxidized by both chemical and microbial processes in this zone. The molar consumption ratio, calculated to be 0.84, indicates that either other electron accepters exit on hydrogen sulfide oxidation, or elemental sulfur precipitation occurs near the $O_2$- H$_2$S interface. Total sulfate reduction flux was estimated to be 0.029 $\mu$mol cm$^{-2}$ hr$^{-1}$ , which accounted for more than 60% of total $O_2$ consumption flux. This result implied that the degradation of organic matter in the anoxic layer was larger than in the oxic layer.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.8 no.4
• /
• pp.392-400
• /
• 2003

We used an oxygen microelectrode to measure the vertical profiles of oxygen concentration in sediments located near point sources of organic matter. The measurements were carried out between 13th and 17th May, 2003, in semi-closed bay and coastal sediments in the central part of the South Sea. The measured oxygen penetration depths were extremely shallow and ranged from 1.30 to 3.80 mm. This suggested that the oxidation and reduction reactions in the early diagenesis should be studied at the mm depth scale. In order to estimate the oxygen consumption rate, we applied the one-dimension diffusion-reaction model to vertical profiles of oxygen near the sediment/water interface. Oxygen consumption rates were estimated to be between 10.8 and 27.6 mmol O$_2$ m$\^$-2/ day$\^$-1/(average: 19.1 mmol O$_2$ m$\^$-2/ day$\^$-1/). These rates showed a positive correlation with the organic carbon of the sediments. The corresponding benthic organic carbon oxidation rates calculated using an modified Redfield ratio (170/110) at the sediment/water interface were in the range of 89.5-228.1 mg C m$\^$-2/ day$\^$-1/(average: 158.0 mg C m$\^$-2/ day$\^$-1/). We suggest that these results are maximum values at the presents situation in the bay because the sampling sites were located near point sources of organic materials. This study will need to be carried out at many coastal sites and throughout the seasons to allow an understanding of the mechanisms of eutrophication e.g. the spatial distribution of oxygen consumption within the oxic zone and hypoxic conditions in the coastal sea.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2015.05a
• /
• pp.237-237
• /
• 2015

The district of Marlborough has had more than its share of river management projects over the past 150 years, each one uniquely affecting the geomorphology and flood hazard of the Wairau Plains. A major early project was to block the Opawa distributary channel at Conders Bend. The Opawa distributary channel took a third and more of Wairau River floodwaters and was a major increasing threat to Blenheim. The blocking of the Opawa required the Wairau and Lower Wairau rivers to carry greater flood flows more often. Consequently the Lower Wairau River was breaking out of its stopbanks approximately every seven years. The idea of diverting flood waters at Tuamarina by providing a direct diversion to the sea through the beach ridges was conceptualised back around the 1920s however, limits on resources and machinery meant the mission of excavating this diversion didn't become feasible until the 1960s. In 1964 a 10 m wide pilot channel was cut from the sea to Tuamarina with an initial capacity of $700m^3/s$. It was expected that floods would eventually scour this 'Wairau Diversion' to its design channel width of 150 m. This did take many more years than initially thought but after approximately 50 years with a little mechanical assistance the Wairau Diversion reached an adequate capacity. Using the power of the river to erode the channel out to its design width and depth was a brilliant idea that saved many thousands of dollars in construction costs and it is somewhat ironic that it is that very same concept that is now being used to deal with the aggradation problem that the Wairau Diversion has caused. The introduction of the Wairau Diversion did provide some flood relief to the lower reaches of the river but unfortunately as the Diversion channel was eroding and enlarging the Lower Wairau River was aggrading and reducing in capacity due to its inability to pass its sediment load with reduced flood flows. It is estimated that approximately $2,000,000m^3$ of sediment was deposited on the bed of the Lower Wairau River in the time between the Diversion's introduction in 1964 and 2010, raising the Lower Wairau's bed upwards of 1.5m in some locations. A numerical morphological model (MIKE-11 ST) was used to assess a number of options which led to the decision and resource consent to construct an erodible (fuse plug) bank at the head of the Wairau Diversion to divert more frequent scouring-flows ($+400m^3/s$)down the Lower Wairau River. Full control gates were ruled out on the grounds of expense. The initial construction of the erodible bank followed in late 2009 with the bank's level at the fuse location set to overtop and begin washing out at a combined Wairau flow of $1,400m^3/s$ which avoids berm flooding in the Lower Wairau. In the three years since the erodible bank was first constructed the Wairau River has sustained 14 events with recorded flows at Tuamarina above $1,000m^3/s$ and three of events in excess of $2,500m^3/s$. These freshes and floods have resulted in washout and rebuild of the erodible bank eight times with a combined rebuild expenditure of $80,000. Marlborough District Council's Rivers & Drainage Department maintains a regular monitoring program for the bed of the Lower Wairau River, which consists of recurrently surveying a series of standard cross sections and estimating the mean bed level (MBL) at each section as well as an overall MBL change over time. A survey was carried out just prior to the installation of the erodible bank and another survey was carried out earlier this year. The results from this latest survey show for the first time since construction of the Wairau Diversion the Lower Wairau River is enlarging. It is estimated that the entire bed of the Lower Wairau has eroded down by an overall average of 60 mm since the introduction of the erodible bank which equates to a total volume of $260,000m^3$. At a cost of $$0.30/m^3$ this represents excellent value compared to mechanical dredging which would likely be in excess of $$10/m^3$. This confirms that the idea of using the river to enlarge the channel is again working for the Wairau River system and that in time nature's "excavator" will provide a channel capacity that will continue to meet design requirements.