EFDC Model Research Articles

Using the EFDC model to evaluate the risks of eutrophication in an urban constructed pond from different water supply strategies

Managers of urban lakes are faced with the challenge of finding a balance between saving water resources and preventing eutrophication. One way to address both of these issues is to use the unconventional water source s such as stormwater and reclaimed water to maintain the water supply in urban constructed ponds. We validated and calibrated the Environmental Fluid Dynamics Code and then evaluated the risks of eutrophication from various water supply scenarios, such as different proportions of stormwater (SW), reclaimed water (RW), and tap water (TW). We found that the different types of water influenced the nutrient or Chla levels in the constructed ponds, but that there was little difference between different hydrological years. The range of the trophic state index in the study pond increased from 5.55% to 68.17% in the urban ponds as the proportion of RW increased from 0% to 100%. Stormwater collection strategies had a clear effect on the trophic state of TW-fed ponds but not of RW-fed ponds. Using an index that integrated the eutrophication risks, eutrophication state, and economic costs, we found that the optimal water supply strategy was to collect treated SW and use TW to replenish the water supply.

Eutrophication control decision making using EFDC model for Shenzhen Reservoir, China

The three-dimensional hydrodynamic and eutrophication model was implemented based on EFDC to help eutrophication control decision making of Shenzhen Reservoir. Model calibration and validation were conducted with two set of independent observed data in 2009 and 2010–2011. The model represented the hydrodynamic process and the spatial and temporal distribution of water quality well. Subsequently, three eutrophication control scenarios were configured, included removing 100% nutrients from all tributaries, increasing by 50% of water flows, and removing 50% nutrients from Dongjiang. As results shown, the maximum chlorophyll-a concentrations were decreased by 1, 16.4 and 46.3%, the average chlorophyll-a concentrations were decreased by 1.3, 29.8 and 29.9%. Increasing water flows and removing nutrients from Dongjiang can significantly improve water quality and effectively reduce risk of water bloom.

Simulation of impacts of Poyang Lake Hydraulic Project on the flow of the Yangtze River using an EFDC model

Simulation of impacts of Poyang Lake Hydraulic Project on the flow of the Yangtze River using an EFDC model

EFDC 모형을 이용한 댐 붕괴류 수치모의 및 매개변수 민감도 분석

In this study, a series of numerical simulation of dam break flow was conducted using EFDC model, and input conditions including cell size, time step, and turbulent eddy viscosity were considered to analyze parameter sensitivity. In case of coarse mesh layout, the propagated length of the shock wave front was <TEX>${\Delta}_x$</TEX> longer than that of other mesh layouts, and the velocity results showed jagged edge, which can be cured by applying fine grid mesh. Turbulent eddy viscosity influenced magnitude of the maximum velocity passing through gate up to 20% and the cell Peclet number less than 2.0 ensured no numerical oscillations.

Modeling the impacts of water transfer on water transport pattern in Lake Chao, China

Water transport pattern plays an important role in determining water and pollution transport, and is worth our investigation. In this study, a hydrological model (Xinanjiang) and a hydrodynamic model (Environmental Fluid Dynamics Code, EFDC) were coupled to investigate the impacts of a water transfer project on the water transport pattern of Lake Chao, China. The Xinanjiang model simulated the inflow discharges for the EFDC model. The validation results were acceptable with a Nash–Sutcliffe coefficient of 0.74 and 0.84 for the Xinanjiang and EFDC models. Based on the calibrated models, four simulations were implemented and compared to evaluate the impacts of the water transfer project on the water transport pattern, described by water age and residence time. The simulation results revealed that the water transfer project had the potential to shorten water age and residence time of the lake, however, should be carried out by considering the influences of wind conditions and water transfer route. This study demonstrated a successful adaption of water age and residence time for describing water transport pattern, and highlighted the importance of model coupling approach in addressing multidisciplinary questions from the complex natural ecosystem.

Water Quality Modeling for a Typical Urban Lake Based on the EFDC Model

Urban lakes are typically characterized by fragile ecological capacities and complex management of their hydrospheric ecosystems. The aims of this study are to establish a reliable hydrodynamic-water quality model for an urban lake, to investigate the responses of water quality to different extreme hydrological conditions associated with rainstorms, and to explore the results from different modeled scenarios surrounding the pollution threats associated with a sewage leak. A three-dimensional hydrodynamic water quality model was developed in this study. The model was calibrated and validated using observed data. The model results agreed well with the observed data, and the averaged relative root mean-squared error (RRMSE) for all of the compared variables was 33.3 %. The validated model was applied to analyze water quality responses for different extreme historical rainfall scenarios from January 1, 2012 to December 31, 2012. The model results indicate that for Lake Tianyinhu, rainstorms adversely affect water quality due to larger nutrient loads, generated by larger rainfall events, and the limited water storage capacity of the lake. Moreover, the responses of water quality to sewage leak events were studied through four scenarios with different leak intensities and durations. The model results indicate that sewage leaks have measureable negative effects on water quality and that it is vital to inspect and promptly eliminate any possible leaks within pipes surrounding the lake. This study may provide a useful tool for hydrological ecosystem protection and management techniques for similar urban lakes.

Assessing the eutrophication risk of the Danjiangkou Reservoir based on the EFDC model

As the source reservoir of the middle route of China's South-to-North Water Diversion Project, the Danjiangkou Reservoir suffers from eutrophication threatens. Thus, it is necessary to develop an eutrophication model for local water resource management. In this study, a three-dimensional (3-D) eutrophication model for the Danjiangkou Reservoir was constructed. The model is different from the existing models for its embedded sediment diagenesis model with fine grids, and it was calibrated and verified by DO, NH4–N, TN,TP and Chl a. The calibrated model was applied to 9 scenarios regarding the variations of a number of key factors, such as water diversions, the increases in TN and the decreases in inflows. The spatial–temporal patterns of trophic status were analyzed and the potential areas of algae bloom were identified. The results will be helpful for local water quality management and provide a valuable example for other similar research.

수치모델을 이용한 진해만 내 소규모 내만의 해수교환율 비교

진해만의 소규모 내만인 당항포만, 당동만, 원문만, 고현성만, 마산만에서의 해수교환율 평가를 위하여 EFDC 모델을 이용해 진해만 전체의 해수유동을 재현하고, 라그랑지(입자추적) 및 오일러(염료확산) 모델기법을 병행하여 해수교환율을 각각 산정하였다. 그 결과 입자추적 방법으로 산정한 해수교환율은 당항포만에서 60.84%로 가장 높고, 마산만에서 30.50%로 가장 낮게 평가되었고, 염료확산 방법으로 산정한 해수교환율은 당항포만에서 45.40%로 가장 높고, 마산만에서 34.65%로 가장 낮게 평가되었다. 당항포만에서 해수교환율이 가장 좋은 이유는 좁은 만 입구로 인한 유속의 가속화 때문이며, 입자추적 방법의 경우 입자가 빠져나갔다가 다시 들어오기 힘든 형태적 특성 때문으로 판단되었다. 한편, 라그랑지 입자의 경우 낙조류에 의해 만을 빠져나갔다가 창조류에 의해 다시 유입될 때 온전한 입자가 그대로 유입하지만, 염료의 경우에는 만을 빠져나간 후 다시 유입하더라도 외해수에 의해 희석되어 유입하기 때문에 염료확산 방법으로 산정한 해수교환율이 전반적으로 더 높게 나타나는 경향을 보였고, 두 가지 방법에 의해 산정된 해수교환율은 같은 조건에서 비교하더라도 상대적으로 전혀 다르게 나타났다. 따라서, 해수교환율을 평가할 때에는 이 두 가지 방법을 병행하거나, 연구의 목적 및 해역의 특성을 충분히 고려하여 모델링 기법을 선정해야만 보다 합리적인 결과를 얻을 수 있을 것으로 판단된다. 한편, 폐쇄도 지수와 라그랑지 및 오일러 방법으로 산정한 해수교환율을 비교한 결과, 폐쇄도 지수가 높을수록 수치모형 기법에 상관없이 해수교환율이 높게 나타났다. 따라서, 폐쇄도 지수가 만의 폐쇄성을 지시하는 지수로 사용하기에 적합하지 않고 수정 및 보완이 필요하다고 판단되었다.

Response of algae growth to pollution reduction of drainage basin based on EFDC model for channel reservoirs: A case of Changtan Reservoir, Guangdong Province

The EFDC model has been used to study response of water quality to varying degrees of pollution reduction in Changtan Reservoir. After verification of the model,a water quality model of Changtan Reservoir was built. Algae growth was simulated under the present situation of pollution load. Pollution reduction scenarios based on two hydrologic years were simulated using the water quality model. The results indicated that overmuch nutrient could lead to eutrophication even in wet years. Under 10% reduction of pollution load,average chlorophyll-a concentrations in three areas( reservoir tail,middle and head areas) decreased by13. 99%,12. 00% and 10. 35% in wet year and by 8. 42%,5. 63% and 2. 10% in dry year,respectively. Under the condition of pollution reduced by 20%,chlorophyll-a concentrations in three areas decreased by 26. 78%,19. 25% and 17. 04% in wet year and by 11. 72%,7. 97% and 5. 12% in dry year,respectively. The water in the reservoir tail area behaved flowing-water similar to rivers,while the water in the reservoir head area also behaved still-water similar to lakes,which has been more dramatic in dry year and the average chlorophyll-a concentration decreased by 5. 12%.

성층강도 산정을 통한 내만의 Hypoxia 산정

Goal of this study is estimating of validity of calculated vertical diffusion coefficient for Masan bay is semi-enclosed bay by using eco-hydrodynamic model that is used to analysis of physical structure of coastal waters and calculates the vertical diffusion coefficient. physical structure of coastal waters is calculated by EFDC model, vertical diffusion coefficient calculated as the density gradient is bigger, the vertical diffusion coefficient as density gradient is increases, the vertical diffusion coefficient is decreased. Validity of vertical diffusion coefficient estimated by reproducibility of concentration of dissolved oxygen that calculated in ecosystem model is constructed by Stella program. The Results of model in 2008~2009 were value of 2008 is 0.529~0.700 and value is 0.542~0.791. This results were similar to observed data and simulated to hypoxia at that time. The `vertical diffusion coefficient` represents stratification and physical stable of a water body, and will be useful for prediction of Hypoxia outbreak.

Development and applicability assessment of 1-D water quality model in nakdong river

Nakdong River passes through many urbanized cities, industrial complex areas, and water intake stations. Recently eight multipurpose weirs are constructed in the middle of the river. therefore the proper water quality management is crucial in this region. Reviewing existing model for hydraulic and water quality analysis, none was found able to reflect the features of the Nakdong River accurately. This study developed 1 dimensional hydraulic and water quality analysis model, where a stable hydraulic analysis is achieved by considering fixed and movable weirs as internal boundary conditions to reflect low flow conditions and irregular channel cross-sections, and the results are then used to construct a water quality analysis model. A sensitivity analysis is performed to review the proper range of parameters for the proposed model, while the applicability and reproducibility are reviewed in comparison to the EFDC model. As a result, the proposed model showed better results than the EFDC model for the hydraulic analysis, while the predicted water quality results were comparable to the two models, although the proposed model showed a high applicability due to its short simulation time.

The Discharge Outlets Layout Optimization of Typical River Section in the Three Gorges Reservoir Area

To improve water quality and alleviate pollution in Changshou-Fuling section of the Three Gorges Reservoir Area, an analysis methodology of regional key discharge outlet based on hydrodynamic-water quality model was developed. The EFDC model was used to study the impact of different discharge outlets on the transport of contamination in the study area by using the concept of pollutant mixing zone and pollutant mixing zone per unit load. Model calibration was conducted using observed data in 2008. Results indicated that EFDC could perfectly simulate hydrodynamics characteristics and contaminant transport process. Calculated results of pollutant mixing zone per unit load showed that the discharge outlet location in Fuling is more reasonable than that in Changshou. This study provides useful information for optimization of discharge outlets location and prediction of pollutant mixing zone in the study area, which is important for the government to make water pollution control measures.

Simulation of eutrophication in Shenzhen Reservoir based on EFDC model

基于EFDC模型构建了深圳水库三维水动力和富营养化定量模拟模型.分别用2009年和2010 2011年流量、水位和水质等观测数据对模型进行了校正和验证,准确地反映了深圳水库的水动力和水质变化过程.在此基础上,假定支流污染截排、水库调度和降低东江引水污染负荷3种情景进行深圳水库富营养化数值模拟,3种情景下库中Chl.a峰值浓度分别降低1.0%、16.4%和46.3%,平均浓度分别降低1.3%、29.8%和29.9%.深圳水库具有良好的交换能力,尚未出现水华暴发,但入库营养盐负荷高,存在较大的富营养化风险;在目前沙湾河污水已经截排的基础上再实施支流污染控制,对水质改善和藻类控制作用已不明显;水库调度和削减东江引水污染负荷对深圳水库水质和富营养化改善明显,能够有效降低水华发生的风险.;The three-dimensional hydrodynamic and eutrophication model of Shenzhen Reservoir was developed based on EFDC framework. Model calibration and validation were conducted with two sets of independent observed data of water flows, water levels, and water quality in 2009 and 2010 2011. The model represented the hydrodynamic processes and the spatial and temporal distributions of water quality satisfactory. Subsequently, three scenarios were configured to provide decision makings for eutrophication control, included removing 100% nutrients from all tributaries, increasing by 50% of water flows, and removing 50% nutrients from Dongjiang. As shown by the modeling results, the maximum chlorophyll-a concentrations were decreased by 1.0%, 16.4% and 46.3%, respectively, the average chlorophyll-a concentrations were decreased by 1.3%, 29.8% and 29.9%, respectively. Therefore, there is no water bloom in Shenzhen Reservoir so far because water has been exchanged quickly, although there has been eutrophication threats because of the large numbers of nutrients entering into the reservoir from Dongjiang. Increasing water flows and removing nutrients from Dongjiang can significantly improve water quality and effectively reduce the risk of water bloom in the reservoir.

Simulation of Pollutant Transportation in Yinluan Open Channel under the Effects of Wind

The water diversion project from Luanhe River to Tianjin is a large-scale project eliminating the water shortage of Tianjin city. Because the long water supply open channel along highroads, the traffic emergent incidents bring great potential dangers to the water supply of Tianjin. In this paper, the prediction model of traffic emergent incidents was built and the transportation of pollutants in Yinluan open channel with the effects of wind was simulated by EFDC model. The evolution and affective area of pollutant in Yinluan open channel was obtained. The results showed that the effects of wind on the transportation of pollutant in Yinluan open channel are strong when the wind direction is along the channel.

새만금호 내 방수제 공사 및 준설에 의한 수리동역학적 특성 변화 수치 모델링

The study area is located on the western coast, and the inner development construction has been ongoing since 2011. The purposes of current study are to effectively simulate and quantitatively predict a temporal and spatial distributions of water temperature and salinity due to the stages of inner development construction in saemangeum reclaimed area. The transient-state numerical modeling using EFDC model is done, and the numerical simulation results are validated reasonably by repetitive numerical model calibration procedures with respect to field measurements of water temperature and salinity. The spatial distributions of water temperature and salinity show similar trends before and after construction of the dikes. In spring season, the salinity has maximum value of 21 psu, while, in summer season, the salinity shows 7 psu in a whole modeling domain. Thus, it is clearly observed that salt water is replaced by freshwater. However, the salinity and temperature reach their initial conditions at the end of the year. The salinity after construction of the dikes is lower than that before construction of them at Mankyeong area. On the other hands, after construction of the dikes, the salinity after dredging operations is higher than that before dredging. Because drastical increasing of water volume in Saemangeum Lake leads to increasing of stagnation time at bottom layer, and salt water is easily intruded to the two estuaries. Therefore, it may be concluded that hydrodynamic characteristics on Saemangeum are dominated by either Mankyeong and Dongjin discharge or sluice gates in/out-flow amounts, and thus they must be properly considered when rigorous and reasonable predictions of water temperature and salinity according to the stages of inner development construction.

Transferring Simulation of Pollutants in YinLuan River Open Channel under Traffic Accidents

The water diversion project from Luanhe River to Tianjin is a large-scale project, which solved the water shortage of Tianjin city. Because the long water supply open channel along highroads, the traffic emergent incidents bring great potential dangers to the water supply of Tianjin. In this paper, the prediction model of traffic emergent incidents in YinLuan River Open Channel was built and the transferring of pollutants under typical scenes was simulated by EFDC model. The evolution and affective area of pollutant in open channel was obtained. The results provide a scientific basis for the decision makers to take effective measures.

한강하구 수로별 순 수송량과 대.소조기 변화에 따른 염하수로의 순 수송량 변동에 관한 수치해석적 연구

The EFDC model with find grid resolution system connecting the Gyeong-Gi bay and Han River estuary was constructed to study on spring-neap variability of net volume transport at each channel of the Han River estuary. The simulation time of numerical model is 124 days from May to August, 2009 with freshwater discharge at Han, Imjin and Yeseong River. The calibration and verification of model results was confirmed using harmonic components of water level and tidal current. The net volume transport was calculated during 30 days with normal freshwater conditions at Seokmo channel and Yeomha channel around Ganghwado. The ebbing net volume transport of 44% and 56% is drained into Gyeong-Gi bay through Yeomha and Seokmo channel, respectively. The ebbing net volume transport nearby Seodo at Yeomha channel convergence flooding net volume transport at Incheon harbor, and drain (westward direction) through channel of tidal flat between Ganghwado and Yeongjongdo to the Gyeong-Gi bay. The averaged net volume transport during 4 tidal cycles was compared to variation of spring-neap periods of the Yeomha channel. The convergence position is moved up- and down-ward according to spring-neap variability. The movement of the convergence zone is appeared because 1) increasing of discharged rate tidal flat channel between Ganghwado and Yeongjongdo at the spring period, 2) The growth of barotropic forcing with downward direction at the spring tide, and 3) The strength of the baroclinic pressure gradient is greater than spring with mixing processes.

목포해역의 점착성 퇴적물 이동에 관한 2차원 수치모의

연안 해역은 해안구조물 건설과 간척 등의 연안 개발로 인해 해안의 퇴적환경이 크게 변화하고 있으며, 이로 인하여 많은 환경변화가 발생하였다. 특히 점착성 퇴적물은 오염물질을 흡착하고 이동하여 환경적으로 큰 변화를 야기한다. 목포해역은 최근에 많은 해안구조물의 건설로 인해 낙조우세가 점점 심해지는 등의 환경변화가 발생하고 있는 지역이다. 이 지역의 점착성 퇴적물을 채취하여 수리실험하고 얻은 침식률 및 침식한계전단응력의 퇴적물 이동모의 활용가능성에 대해 검토하였다. 부유사 농도에 대한 모의 결과는 관측자료와 일치하는 양호한 결과를 보였다. 따라서 수리실험을 통해 결정된 침식률을 사용하는 것이 수치모의에서 정확성을 개선하는 데 기여함을 확인할 수 있었다. 모의과정에서 침식률, 침식한계응력, 침강속도, 활성층 두께 등의 민감도를 분석하였다. Sedimentary environment in coastal zone has been changing due to a large number of coastal structures and continuous coastal development. As a result, the environment has been changing. In particular, the economic and environmental damage can occur due to cohesive sediment transport closely related with the fate of pollutants. Due to large sea wall construction the ebb dominance in the Mokpo coastal waters has been clearer. Cohesive sediment transport was simulated by the EFDC model. The simulated SS showed good agreements with the observed SS. From the sensitivity analysis of sediment parameters, we found out that the erosion rate, the critical shear stresses for erosion and deposition, and the settling velocity are important factors in cohesive sediment transport modeling.

EFDC 모형의 낙동강 수질해석 적용성 평가

최근 많은 연구에서 수리해석과 수질해석을 다루고 있는 EFDC 모형을 낙동강에 적용하여 수질해석의 적용성을 평가하고자 하였다. 낙동강 중하류에 해당하는 낙본 GH 구간과 HI 구간을 대상으로 2008년과 2009년의 수리해석과 수질해석을 수행하였다. 수질해석의 결과는 수온, COD, TOC, DO, TN, TP에 대해 실측자료와 비교하였으며, BOD의 경우 EFDC 모형에서 직접적으로 계산되지 않아 COD와 BOD의 환산식을 유도하여 환산된 BOD를 실측자료와 비교하였다. 금번 연구결과를 실측자료와 비교하였을 때 EFDC 모형이 하천수리해석 뿐만 아니라 수질해석에서도 높은 재현성을 가지고 있는 것으로 판단되나 향후 국내 수질해석에 활용성을 높이기 위해서는 COD나 TOC와 관련된 BOD의 정확한 환산에 관한연구가 수행되어야 할 것으로 사료된다. EFDC model, which is capable of handling both hydrodynamic and water quality analysis has come to use for many recent studies. In order to assess the applicability of the EFDC model, it was applied to Nakdong river. Hydrodynamic and water quality analysis were carried out for Nakbon GH and HI sections chosen as the area of study with gaged data from 2008 to 2009. The comparison was made between water quality simulation results and observed data over water temperature, COD, TOC, DO, TN and TP. On the contrary, a conversion formula was derived to calculate BOD which the EFDC model cannot directly calculates and it was compared to measured data. In this study, it was determined that the EFDC model well represents the behavior of both hydrodynamics and water quality. However, further research on COD, TOC and accurate conversion of BOD needs to be conducted for efficient application to domestic water quality analysis.

물순환장치 가동에 따른 농업용저수지의 3차원 이송확산모의에 관한 연구

본 논문은 국내 농업용저수지의 성층현상을 방지하고자 물순환장치를 설치하였을 때, 3차원 수리해석모델인 EFDC를 이용하여 부유물질 이송확산모의를 하였다. 이를 통해 물순환장치의 이송확산범위를 예측하고, 다양한 운전인자를 조절함으로써 최적의 운전인자를 도출하여 물순환으로 인한 내부변화의 영향을 최소화하고자 하였다. 3차원 이송확산모의 결과에 의하면, 30일 이후에 전 수층에 걸쳐 물순환이 시작되며, 100일 이후 저수지의 전체순환이 가능한 것으로 모의되었다. 또한, 연속운전보다 간헐운전이 저수지 전 구간에서 이송확산농도가 낮게 나타났으며, 안정적으로 전체순환이 일어났다. 물순환장치의 표층과 저층 혼합비율은 표층 혼합율이 높을수록 저수지 영향을 감소시킬 수 있으며, 3:1 동일조건일 경우, Case 8(50일운전:50일정지) 조건이 저수지의 내부영향을 최소화할 수 있을 것으로 나타났다. This study analyzed a 3D hydrodynamic advection diffusion using the EFDC model (Environmental Fluid Dynamics Code) in the agriculture lake to prevent stratification when we install a water circulator. EFDC model was predicted the range of the water circulator and various operational parameters ware derived for minimize the impact of the internal lake. Through EFDC simulation, water circulation is started overall circulation after 30days and a lake overall circulation showed that it was possible operated the water circulator after about 100days. Also, advection diffusion concentration was low in a lake when water circulator operate intermittent condition than continuous condition. And the entire circulation was stable in this condition. The S/B (Surface/Bottom) ratio can reduce the impact of lake as the surface water mixing a lot of. When the same condition (S/B ratio(3:1)), Case 8 (50days operation: 50days stop) of condition were able to minimize the impact of lake.