Environmental Fluid Dynamics Code Research Articles

Three-dimensional hydrodynamic modeling of the Chicago River, Illinois

We present and describe results from a three-dimensional model applied to the Chicago River under a wet weather condition. Chicago River is an integral part of Chicago, the third largest city in United States, for recreational, commercial and industrial purposes. Although the flow in the Chicago River is supposed to be from north to south, the flow acquires a three-dimensional nature at various points in the river. The reasons for the three dimensionality of the flow can be attributed to the dynamic boundary conditions generated by combined sewer overflow (CSO) events during wet weather conditions, as well as the presence of confluences of various branches of the river with creeks and slips. This work presents the hydrodynamic application and validation of a three dimensional numerical model, which was used to simulate the flow in the Chicago River for a period of 8 days in September of 2008, during which the torrential rains in the city of Chicago led to intense CSO events. The numerical model used for the aforementioned exercise is the Environmental Fluid Dynamics Code (EFDC) which solves the three dimensional vertically hydrostatic, free surface, turbulence averaged equations of motions for a variable density fluid. The results obtained by the numerical model were validated with the help of stage values obtained from the USGS gauging station [Station No. 05536123] present inside the domain of interest. It was estimated that during the storm September 2008, several billion gallons of water were discharged into Lake Michigan from the Chicago River Controlling Works to prevent city flooding. The 3D model also provides a tool for the management of the waterways, in particular for future analysis of different alternatives being considered to reverse the Chicago River once again with the goal of preventing the passage of invasive species (e.g. Asian carp) towards the Great Lakes.

WASP_SEDDEER: Incorporation of SEDDEER into WASP

In this study, SEDDEER (Sediment Deposition and Erosion), a stand-alone sediment and contaminant model which simulates one water box and the underlying multiple sediment bed layers, was incorporated into Water Quality Analysis Simulation Program (WASP7.4). WASP7.4 toxic module (TOXI7) was modified to include SEDDEER to develop WASP_SEDDEER model. Tests were designed to ensure that the coupling of the WASP7.4 and SEDDEER bed models is correct. The tests compared WASP_SEDDEER one-box simulations against SEDDEER results to verify fluxes across the sediment-water interface. Also, two-vertical-boxes water-column model tests were performed to compare WASP_SEDDEER output against Environmental Fluid Dynamic Code (EFDC) solutions. The comparisons revealed a good fitting between WASP_SEDDEER and EFDC results (R2 values above 0.95) verifying a successful incorporation. Exploratory applications of EFDC, WASP7.4, and WASP_SEDDEER to Mobile Bay for simulating sediment and contaminant transport showed the capabilities of WASP_SEDDEER for estimating suspended sediment and contaminant concentrations throughout the computational domain.

Investigation of saltwater intrusion and salinity stratification in winter of 2007/2008 in the Zhujiang River Estuary in China

Saltwater intrusion is a serious environmental problem in the Zhujiang River Estuary (ZRE), which threatens the water supply of fifteen million people. The hydrological observations as well as meteorological and tidal forcing in the winter of 2007/2008 were analyzed to examine the saltwater intrusion in the ZRE. The observational results suggest that the maximum vertical difference of salinity can reach 10 in the Humen Channel during neap tide, but is very small in the Hengmen Channel. The vertically averaged salinity from time series stations during spring tide is higher than that during neap tide. A three-dimensional finite difference model was developed based on the environmental fluid dynamic code (EFDC) to study the mechanism of saltwater intrusion and salinity stratification in the ZRE. By analyzing the salt transport and the temporal variation of saltwater intrusion, the authors found that the net salt transport due to the estuarine circulation during neap tide was more than that during spring tide. This caused salt to advance more into the estuary during neap tide. However, saltwater intrusion was stronger during spring tide than that during neap tide because the spring-neap variation in salt transport was small relative to the total length of the saltwater intrusion. The physical mechanism causing this saltwater intrusion was investigated by a series of sensitivity experiments, in order to examine saltwater intrusion in response to river discharge and winds. The freshwater source was a dominant influencing factor to the saltwater intrusion and controlled salinity structure, vertical stratification and length of the saltwater intrusion. The prevailing northeast monsoon during winter could increase the saltwater intrusion in the ZRE. Though the southwest wind was unfavorable to saltwater intrusion during spring tide, it could increase stratification and saltwater intrusion during neap tide.

Analysis of agricultural pollution by flood flow impact on water quality in a reservoir using a three-dimensional water quality model

This study presents the Yuqiao Reservoir Water Quality Model (YRWQM), a three-dimensional hydrodynamic and water quality model of the Yuqiao reservoir, China. The YRWQM was developed under the environmental fluid dynamics code (EFDC) model and was calibrated and verified to hydrodynamic and water quality data, using two sets of observed data from January 1 to December 31, 2006 and from May 1 to October 31, 2007, respectively. The primary hydrodynamic and transport driving forces are inflows/outflows and surface wind stresses. Considering effects of water transfer and wind on the advection-dispersion processes, the model results showed better agreements with observed data in the reservoir. The YRWQM predicted the variations of water quality resulting from agricultural pollution which flowed into the reservoir with floods lasting for 12 days in 2009. The results indicated that the concentrations of chemical oxygen demand and total nitrogen were increased 225 and 314%, respectively. Considering the interactions between chlorophyll-a and nitrogen in the model, the results indicated the reservoir was not a nitrogen-limited environment. We suggest the management should focus on agricultural pollution strategies for the reservoir during the flood period. The YRWQM could be a useful tool for water sources management in the reservoir.

거문도 바다숲 조성해역의 해수유동 특성

To arrange effectively artificial reefs for marine afforestation, tidal currents were analyzed by numerical experiments. The numerical experiments were carried out by EFDC(Environmental Fluid Dynamics Code), and water column was vertically divided 5 layers. Tidal current patterns showed to be affected by main current at outside of study area, and circle currents of two were observed from analysis of residual currents. The calculated harmonic constants of tide and tidal current agreed well with those of observations at two stations for tide and two stations for tidal current. The model successfully reproduced the tidal current around the Geomoondo marine afforestation. It suggest that artificial reefs for marine afforestation should be installed belt zone at study area.

바다숲 조성해역의 해조류 포자 확산모델링

전남 거문도 바다숲 조성용 시설물의 효율적인 배치를 위하여 수치실험을 통하여 바다숲 조성해역의 조석류에 의한 해수유동을 분석하였으며, 분석된 해수유동을 바탕으로 하여 바다숲 조성해역 인근에 위치한 자연적인 해중림에서 발생한 해조류 포자의 거동을 파악하기 위하여 입자추적실험 및 부유사 농도변화 실험을 수행하였다. 수치실험에 사용된 수치모형은 EFDC(Environmental Fluid Dynamics Code)를 사용하였으며, 연직방향으로 총 10개층으로 나누어 실험을 수행하였다. 실험결과, 바다숲 조성해역의 해수유동패턴은 대상해역 바깥쪽의 주류에 비해 방파제의 역할을 하는 밖노루섬으로 인해 흐름이 약하고, 잔차류를 분석한 결과 주로 북서방향의 흐름이 형성되나 크기는 미약하였다. 인근에 위치한 자연 해중림은 크게 2곳으로, 이들 해역에 투하한 해조류 포자는 투하한 후 30시간이 경과하면 대부분 해저면에 안착하였다. 포자는 대상 해역의 미약한 흐름에 의해 발생지역에 대부분 안착하였다. 바람조건을 적용한 경우에는 적용하지 않은 경우에 비해 포자가 남동쪽으로 좀 더 이동하여 안착하나 그 차이는 미미하였다. 부유사 실험결과 부유사 농도는 조시별로 흐름에 따라 농도가 변화하며 표층보다 저층에서 높게 나타났다. 이러한 결과를 토대로 바다숲 조성용 시설물을 효율적으로 배치할 수 있을 것으로 사료된다.

Three-dimensional modeling of sediment transport in the Wuhan catchments of the Yangtze River

Abstract A three-dimensional flow-sediment model of the Wuhan portion of the Yangtze River was developed using the EFDC (Environmental Fluid Dynamic Code) in order to study the changing riverbed. The model was also calibrated and validated by daily measuring of the water surface elevation and using suspended sediment concentration data secured from June 1 to September 30, 2004. Based on this model, the mobile sediment on the riverbed was simulated for the high water period of the Yangtze River. The results indicate that erosion is the main issue, with maximum erosion (0.27m) occurring at the banks of Tian Xingzhou. In addition, according to a suspended sediment concentration analysis for the Han Kou Hydrologic Station section of the river, the concentration there increased from left bank to right bank.

The impact of the operation of Eastern Route Project of the South-to-North Water Diversion Project on water quality in Lake Nansi

Lake Nansi consists of four lakes: the Nanyang,Dushan,Zhaoyang and Weishan Lake.It is a lake in the line of the Eastern Route Project(ERP) of the South-to-North Water Diversion Project(NSBD).After the project supply water in 2013,the water quality of Lake Nansi will be affected significantly.Based on the existing theories and methods,a three-dimensional hydraulic control and water quality model of the lake is presented.The model is developed under the Environmental Fluid Dynamics Code(EFDC) model.It was calibrated and verified to hydrodynamic and water quality data,using two sets of observed data from October 1 to December 31,2006 and January 1 to June 30,2007,respectively.The observed data including water surface elevation,water temperature,chemical oxygen demand,dissolved oxygen and ammonia nitrogen from five stations is used as forcing for simulations.The model results show that temporal and spatial patterns for hydrodynamic and water quality components are consistent with observed data in the reservoir.Because the direction of the water supply and natural flow is converse,the Lake Nansi is divided into the upper-lake and the lower-lake by Erji dam in the Lake Zhaoyang.Two scenarios of whole supplying water term of the lake were simulated using the model.By the analysis of the variations of the hydraulic control and water quality of the upper-lake and lower-lake,This paper proposed three advices of the ERP operation,which can help the project to give full benefits and improve the water quality.

Saltwater intrusion in the Pearl River Estuary during winter

An intensive observation and a three-dimensional finite-difference model of Environmental Fluid Dynamic Code were used to study saltwater intrusion in the Pearl River Estuary. The model simulation was carried out for December 2007 to February 2008, which covered the in situ observation. The model was forced by observed winds, tidal elevation at open boundaries, and river discharges from eight inlets in the Pearl River Estuary. The agreements with observation were verified in terms of current, salinity and tide elevation. Using the computed tidal current, the residual current was also calculated to estimate material transport. In addition, the Lagrangian method was used to track the trajectory of particles from the mouth of Humen and Modaomen inlets. By computing the flushing time of these two channels, the authors find that there exists close relationship between flushing time and saltwater intrusion. Potential impact of sea-level rise on saltwater intrusion was also studied. Sensitivity experiments indicate that sea-level rise can impact on the saltwater intrusion in the Pearl River Estuary, such as increasing salinity concentration and intrusion distance, especially during neap tide in winter (dry season).

Prediction of water temperature in stratified reservoir and effects on downstream irrigation area: A case study of Xiahushan reservoir

With increasing concern in environmental and ecological protection, more studies have focused on solving the problems caused by dam. Large reservoirs often release low-temperature water in spring and summer, which have adverse effects on downstream ecosystem. The 3-D Environmental Fluid Dynamics Code (EFDC) and 1-D longitudinal stream temperature model were used in this paper, to predict the water temperature in reservoir and canal and analyze the effects on irrigation area. The results indicate that the affected area is within a 55km distance mainly in the period between April and June. Some management and engineering measures should be adopted to reduce the impact.

Application of EFDC and WASP7 in Series for Water Quality Modeling of the Yongdam Lake, Korea

This study aims to test the feasibility of combined use of EFDC (Environmental Fluid Dynamics Code) hydrodynamic model and WASP7.3 (Water Quality Analysis Program) model to improve accuracy of water quality predictions of the Yongdam Lake, Korea. The orthogonal curvilinear grid system was used for EFDC model to represent riverine shape of the study area. Relationship between volume, surface and elevation results were checked to verify if the grid system represents morphology of the lake properly. Monthly average boundary water quality conditions were estimated using the monthly monitored water quality data from Korean Ministry of Environment DB system. Monthly tributary flow rates were back-routed using dam discharge data and allocated in proportion to each basin area as direct measurements were not available. The optimum number of grid system was determined to be 372 horizontal cells and 10 vertical layers of the site for 1 year simulation of hydrodynamics and water quality out of iterative trials. Monthly observed BOD, TN, TP and Chl-a concentrations inside the lake were used for calibration of WASP7.3 model. This study shows that EFDC and WASP can be used in series successfully to improve accuracy in water quality modeling. However, it was observed that the amount of data to develop inflow water quality and flow rate boundary conditions and water quality data inside lake for calibration were not enough for accurate modeling. It is suggested that object-oriented data collection systems would be necessary to ensure accuracy of EFDC-WASP model application and thus for efficient lake water quality management strategy development.

Integration of Environmental Fluid Dynamics Code (EFDC) Model with Geographical Information System (GIS) Platform and Its Applications

Data management and analysis are important for the application of water quality modeling in water environmental protection. The integration of the Environmental Fluid Dynamics Code (EFDC) model with Geographical Information Systems (GIS) is discussed in this paper. The data management and analysis ability of this widely used water quality model was enhanced by the integration. Database methods are used to integrate the different types of modeling data into a GIS platform. The spatial data modeling and analysis capacity of GIS is used in the pre-processing and post-processing of EFDC. The integration application is demonstrated by a case study of the Lower Charles River Basin water quality model, which was built with EFDC and has 56 varying-size curvilinear horizontal grids and 8 vertical layers. The case study shows that the integrated system significantly improved the application of EFDC with more efficient data processing, organization and analysis, and can be used as a powerful tool for water environmental management and decision making.

Application of a three-dimensional eutrophication model for the Beijing Guanting Reservoir, China

The Beijing Guanting Reservoir (BGR) is located northwest of Beijing and has been an important water supply reservoir ever since the construction of a dam near the town of Guanting in 1954. As a result of excessive nutrients and organic carbon loadings from the drainage basin over the last several decades, the BGR suffers from eutrophication as well as other contamination problems and has not been used as a drinking water supply reservoir since 1997. As a management step to restore the reservoir's water quality, a numerical model was developed based on the environmental fluid dynamics code (EFDC) framework. The model simulated three phytoplankton species based on the observed cyanobacteria, green algae, and diatom concentrations in 2004 for the Yongding arm of the reservoir, which is separated from the rest of the reservoir by a sand bar. The model was calibrated with vertical temperature profiles as well as the observed chlorophyll a and nutrients concentrations in the water column. The calibrated model was further applied to investigate management scenarios, which include reduction in external loadings of nutrients with constructed wetlands, biomanipulation, and transferring water from CeTian Reservoir. All three scenarios can reduce the peak chlorophyll a levels in the reservoir. The background nutrients were high, and reducing the external nutrients was effective only after a reduction in background nutrients after phytoplankton growth. The biomanipulation and water transfer scenarios could also delay the occurrence of the peak chlorophyll a. Because the model was developed based on one year of data, the model can only reveal the short-term effects of applying the management scenarios. Future studies will consider the long-term processes, such as diagenesis, when data are available to predict the long-term effects of the scenarios.

Prediction of algal blooming using EFDC model: Case study in the Daoxiang Lake

Algal blooming has become one of the key fields of study on eutrophication of water body recently. The mechanism of algal blooming is still not understood well. However, it is obvious to understand that algal blooming has close relationship with chlorophyll-a. Therefore, if the trends of chlorophyll-a concentration can be simulated accurately, it will be helpful for the prediction of algal bloom events. In this study, a model named Environmental Fluid Dynamics Code (EFDC), which was developed by U.S. Environmental Protection Agency, was described and used to simulate the eutrophication process in the Daoxiang Lake, Beijing. To run the eutrophication model for the Lake, a field sampling was conducted in March–October of 2008 with interval of 10–20 days. Meanwhile, the algal bloom assessment criteria were investigated and the indicator of chlorophyll-a concentration was selected as input for the prediction of algal bloom in the Daoxiang Lake. After model calibration and validation, traditional statistics has been done between modeled results and observed values. The modeled results show that the simulated chlorophyll-a concentration basically agrees with the observed concentration except the later period of station 2# and the average algal bloom prediction accuracy is 63.43%. It was verified that the EFDC model can be used for chlorophyll-a concentration simulation and algal blooming prediction in the Daoxiang Lake.

Scenario analysis of water pollution control in the typical peri-urban river using a coupled hydrodynamic-water quality model

The water quality pollution and ecological deterioration in peri-urban rivers are usually serious under rapid urbanization and economic growth. In the study, a typical peri-urban river, Nansha River, was selected as a case study to discuss the scheme of peri-urban river rehabilitation. Located in the north part of the Beijing central region, the Nansha River watershed has been designated as an ecologically friendly garden-style area with high-tech industry parks and upscale residential zones. However, the Nansha River is currently seriously contaminated by urban and rural pollutants from both nonpoint sources (NPS) and point sources (PS). In this study, the pollutant loads from point sources and nonpoint sources in the Nansha River watershed were first assessed. A coupled model, derived from the Environmental Fluid Dynamics Code and Water Quality Analysis Simulation Program, was developed to simulate the hydrodynamics and water quality in the Nansha River. According to the characteristics of the typical peri-urban river, three different PS and NPS control scenarios were designed and examined by modeling analyses. Based on the results of the scenario analysis, a river rehabilitation scheme was recommended for implementation.

Anthropogenic Influences on the Tidal Prism and Water Exchanges in Jiaozhou Bay, Qingdao, China

The tidal-driven flow field and average residence time for water in Jiaozhou Bay in the years 1966, 1988, 2000, and 2008 were investigated using the EFDC (Environmental Fluid Dynamics Code) with a coupled dye module. Jiaozhou Bay (JZB) in northeastern China is a semi-enclosed shallow bay that has undergone large-scale land reclamation over the last four decades, especially over the extensive intertidal flats. Data from field observations were used to calibrate and verify the EFDC model for JZB. The verified JZB model was used to study spatial variations of flow field and water exchanges from 1966 to 2008. The overwhelming influence of human activities, especially land reclamation, is the main cause of the significant changes in hydrodynamic conditions and water exchange in JZB. The human-induced changes of the coastline position-configuration and nearshore bathymetry have resulted in substantial changes in the residual current patterns, especially in Qianwan Bay, Haixi Bay, and northeastern Jiaozhou Bay. The overall tidal prim of JZB has been reduced by 26% as compared to that in 1928. This is considerably less than the 35% reduction obtained by other studies. The decreasing water-exchange ability corresponds to an increasing average residence time (ART) over the past several decades, particularly after the 1980s. In addition, the influences of the return flow of the bay water from the open sea back into the estuary were quantified by determining the return flow factor for each year. An existing tidal prism model was revised by introducing a mixing factor κ, and a simplified formula was developed for JZB. The revised tidal prism model suggests continued deterioration in water quality and exchange ability of Jiaozhou Bay in the near future.

Numerical Simulation of Salinity and Dissolved Oxygen at Perdido Bay and Adjacent Coastal Ocean

Abstract Environmental fluid dynamic code (EFDC), a numerical estuarine and coastal ocean circulation hydrodynamic model, was used to simulate the distribution of the salinity, temperature, nutrients, and dissolved oxygen (DO) in Perdido Bay and adjacent Gulf of Mexico. External forcing factors included the coupled effects of the astronomical tides, river discharge, and atmospheric winds on the spatial and temporal distributions of salinity and DO. Modeled time series were in good agreement with field observations of water level, nutrients, temperature, salinity, and DO. Perdido Bay and adjacent northern Gulf of Mexico coasts can be divided into two areas according to salinity, water level, and DO concentrations. The first area was lower Perdido Bay and the associated Gulf of Mexico coasts, acting primarily under the influence of tidal forcing, which increases the vertical stratification. The second division was upper Perdido Bay, which was influenced by both tidal forcing and freshwater inflow. Simulatio...

Modeling impacts of Yangtze River water transfer on water ages in Lake Taihu, China

To improve water quality and alleviate eutrophication in Lake Taihu, the third largest freshwater lake in China, a Yangtze River water transfer project was initiated in 2002 to bring water from the Yangtze River to Lake Taihu to dilute and divert pollutants out of the lake. We used a three-dimensional numerical model, Environmental Fluid Dynamics Code, to study the impacts of water transfer on the transport of dissolved substances in the lake by using the concept of water age. In particular, the influences of inflow tributaries and wind forcing on water age were investigated. Model results showed that the effect of water transfer on transport processes in the lake is strongly influenced by hydrodynamic conditions induced by wind and inflow/outflow tributaries. During the simulation year (2005), the water ages in Lake Taihu were highly variable both spatially and temporally, with a mean of approximately 130 days in summer and 230 days in the other seasons. Southeasterly winds—dominant in the summer—could improve the quality of water by reducing the water age in the eastern areas of the lake, which are used as a drinking water source, and in Meiliang Bay, the most polluted bay. In terms of dilution, the most efficient flow rate for transferred water was predicted to be approximately 100m3/s. The spatial distribution of water ages showed that water transfer may preferentially enhance exchanges in some areas of the lake unless nutrient concentrations in the transferred water are reduced to a reasonable level. This study provides useful information for a better understanding of the complex hydrodynamic and mass transport processes in the lake, which is important for developing and implementing effective ecological restoration strategies in the region.

Integration of USEPA WASP model in a GIS platform

The integration of water quality analysis simulation program (WASP) with a geographical information system (GIS) is presented. This integration was undertaken to enhance the data analysis and management ability of the widely used water quality model. Different types of data involved in WASP modeling were converted and integrated into GIS using a database method. The spatial data modeling and analysis capability of GIS were used in the operation of the model. The WASP water quality model was coupled with the environmental fluid dynamics code (EFDC) hydrodynamic model. A case study of the Lower Charles River Basin (Massachusetts, USA) water quality model system was conducted to demonstrate the integration process. The results showed that high efficiency of the data process and powerful function of data analysis could be achieved in the integrated model, which would significantly improve the application of WASP model in water quality management.

Fine silt particle pathline of dredging sediment in the Yangtze River deepwater navigation channel based on EFDC model

Based on the Environmental Fluid Dynamics Code (EFDC), a three-dimensional baroclinic model for lower reaches of the Yangtze River, Yangtze River Estuary, Hangzhou Bay and the adjacent sea areas was established with the sigma-coordinate in the vertical direction and the orthogonal curvilinear coordinates in the horizontal direction. The fine silt particle tracers were injected during different tides with the calibrated three-dimensional numerical model in the Yangtze River Estuary to simulate the migration tracks of the tracers in the following three days, and thereby study the migration behavior of the fine silt particles of dredged sediment after dumping at different locations in the navigation channel in the Yangtze River Estuary. The study shows that the particle paths of the tracer particles basically migrate to the open sea along the middle axis of river course in the form of reciprocating oscillation, the migration and diffusion directions of tracer particles are basically parallel to the navigation channel in guide levee, similar to long belt distribution, and the tracer particles migrate to the southeast out of the guide levee. The particle which is on the southern and northern sides enter groin and cross the navigation channel in the process of movement, and is easy to deposit in the navigation channel. The migration tracks of the particles released at different layers are basically similar at the same release station, but specifically different, varying at different cross sections. The result can be used for the choice and evaluation of dredging schemes in the Yangtze River Deepwater Navigation Channel.