Analysis of water temperatures in Conowingo Pond as influenced by the Peach Bottom atomic power plant thermal discharge

Water quality safety is of critical importance in environmental improvement, particularly with respect to drinking water resources worldwide. As the main drinking water sources in Shenzhen, China, the cascade reservoirs comprising the Shiyan, Tiegang, and Xili Reservoirs are highly regulated and have experienced water quality deterioration in recent years. In this study, a three-dimensional hydrodynamic and water quality model was established using the Environmental Fluid Dynamics Code (EFDC) for the cascade reservoirs. The relationships between water quality and improvement measures were quantified and the main pollution sources for individual reservoirs were identified. Results showed that the hydrodynamic and water quality model well captured the spatial and temporal variations of water level, the permanganate concentration index (COD Mn ), and total nitrogen (TN), with high resolution in the cascade reservoirs. The correlation coefficients between simulations and observations were close to 1.00 for water levels, and over 0.50 for COD Mn and TN concentrations. The most effective methods for water quality improvement were the reduction of the runoff load for TN and transferred water load for COD Mn in the Shiyan Reservoir, reduction of the transferred water load in the Tiegang Reservoir, and an increase in transfer water volume, especially in the flood season, in the Xili Reservoir. Internal pollution sources also played an important role in water pollution, and thus sedimentation should be cleaned up regularly. This study is expected to provide scientific support for drinking water source protection and promote the application of hydrodynamic model in water quality management.

Section: Model Descriptionmentioning

confidence: 99%

Assessment of Water Quality Improvements Using the Hydrodynamic Simulation Approach in Regulated Cascade Reservoirs: A Case Study of Drinking Water Sources of Shenzhen, China

Hua

Zhang

2017

“…EFDC uses orthogonal curvilinear or Cartesian horizontal coordinates and a stretched sigma vertical coordinate. EFDC uses an internal-external mode splitting to numerically solve the momentum equations and solves internal and external modes at the same time step, but it solves the external mode semi-implicitly with respect to barotropic pressure gradient term in depth-averaged momentum equations [28][29][30]. The Mellor and Yamada level 2.5 turbulence closure scheme is implemented in the model [31,32].…”

Section: Hydrodynamic Modelmentioning

confidence: 99%

Quantification of Water and Salt Exchanges in a Tidal Estuary

Devkota

Fang

2015

A calibrated three-dimensional hydrodynamic model was applied to study subtidal water and salt exchanges at various cross sections of the Perdido Bay and Wolf Bay system using the Eulerian decomposition method from 6 September 2008 to 13 July 2009. Salinity, velocity, and water levels at each cross section were extracted from the model output to compute flow rates and salt fluxes. Eulerian analysis concluded that salt fluxes (exchanges) at the Perdido Pass and Dolphin Pass cross sections were dominated by tidal oscillatory transport FT, whereas shear dispersive transport FE (shear dispersion due to vertical and lateral shear transport) was dominant at the Perdido Pass complex, the Wolf-Perdido canal, and the lower Perdido Bay cross sections. The flow rate QF and total salt transport rate FS showed distinct variation in response to complex interactions between discharges from upstream rivers and tidal boundaries. QF and FS ranged from −619 m

“…In the last several decades, 3D Environmental Fluid Dynamics Code (EFDC) (Hamrick 1992) has been widely used in modeling river, estuarine, and coastal hydrodynamics and transport processes. Hamrick and Mills [29] developed and used the EFDC model to simulate thermal transport and water temperature distributions in Conowingo Pond that were influenced by thermal discharges from the Peach Bottom atomic power plant. In order to quantify numerical and modeled entrainment, Kulis and Hodges [30] explored the grid resolution required in EFDC to capture gravity current motions in an idealized basin with and without a turbulence closure.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity Analysis of Flow and Temperature Distributions of Density Currents in a River-Reservoir System under Upstream Releases with Different Durations

Chen

Fang

2015

Abstract:A calibrated three-dimensional Environmental Fluid Dynamics Code model was applied to simulate unsteady flow patterns and temperature distributions in the Bankhead river-reservoir system in Alabama, USA. A series of sensitivity model runs were performed under daily repeated large releases (DRLRs) with different durations (2, 4 and 6 h) from Smith Dam Tailrace (SDT) when other model input variables were kept unchanged. The density currents in the river-reservoir system form at different reaches, are destroyed at upstream locations due to the flow momentum of the releases, and form again due to solar heating. DRLRs (140 m 3 /s) with longer durations push the bottom cold water further downstream and maintain a cooler bottom water temperature. For the 6-h DRLR, the momentum effect definitely reaches Cordova (~43.7 km from SDT). Positive bottom velocity (density currents moving downstream) is achieved 48.4%, 69.0% and 91.1% of the time with an average velocity of 0.017, 0.042 and 0.053 m/s at Cordova for the 2-h, 4-h and 6-h DRLR, respectively. Results show that DRLRs lasting for at least 4 h maintain lower water temperatures at Cordova. When the 4-h and 6-h DRLRs repeat for more than 6 and 10 days, respectively, bottom temperatures at Cordova become lower than those for the constant small release (2.83 m 3 /s). These large releases overwhelm the mixing effects due to inflow momentum and maintain temperature stratification at Cordova.