Challenges with Water Temperature
Water temperature has significant and systematic effects on biological processes at all levels of organization, from phytoplankton to whole ecosystems. In addition to its own effects, temperature influences several other parameters and can alter the physical and chemical properties of water such as dissolved oxygen and photosynthesis production. Some organisms, particularly aquatic plants, flourish in warmer temperatures, while some fishes such as trout and salmon prefer colder streams.
Solutions Provided by EEMS
EFDC+ provides a multitude of sub-models for temperature simulation. This includes a robust heat model allowing accurate temperature transport simulation, fully accounting for surface heat exchange and solar radiation impact. A bed thermal model and heat coupled ice sub-module are available. When working on colder regions where ice formation and ice melt impact the hydrodynamics, surface processes such as oxygen reaeration, or contaminant fate and transport, EFDC+ provides the ability to represent the ice with a robust ice sub-model linked to the heat sub-model.
When dealing with thermal power plant cooling water, the EE Modeling System provides the means to simulate the impacts of once-through cooling with a range of forced evaporation options.
Examples of Studies Done with EEMS
Manatee Thermal Habitat Analysis
Southwest Florida Water Management District (SWFWMD) built a 3D hydrodynamic model (salinity and temperature) of the Chassahowitzka River/Estuary System using EEMS. This model was used to determine the minimum baseline refuge areas/volumes and determine the changes in salinity regimes due to reductions in spring discharges. Under the direction of SWFWMD a data assessment and statistic regression for missing data periods, calculated the joint probability analysis to establish the baseline critical condition of MFL for providing adequate protection to the manatee refuge. The areas that meet the manatee habitat criteria in the Chassahowitzka system during critical conditions were identified.
Hydrothermal Study, Lay Dam, Coosa River, AL, USA
Electricity production accounts for one of the largest water usages in the United States and worldwide. Water for thermoelectric power is used in generating electricity with steam-driven turbine generators. Surface water was the source for more than 99 percent of total thermoelectric-power withdrawals, according to United States Geological Survey (USGS). Forced evaporation (FE) in a receiving water body due to added heat from once-through cooling for thermal electric generating plants has been studied by Electric Power Research Institute (EPRI) and the USGS. However, these approaches are for screening level analyses and/or analytical solution. In contrast, EEMS is equipped with the tools to address site specific FE such as this study carried out on the Coosa River, Alabama.
Real-time Thermal Hydrodynamic Model Decision Support Tool, AL, USA
DSI developed a real-time three dimensional hydrothermal model for Coosa River, AL, between Logan Martin Dam and Lay Dam using EEMS. The model’s external forcing factors include flow releases from Logan Martin and Lay Dam, flows from tributaries, power plant withdrawal and temperature rise, and atmospheric conditions. The real-time model was calibrated against the field measurements of flows, water level, and water temperature. The model was developed to serve as a decision-making tool for Alabama Power Company (APC) electricity generation and assist in efficient operation of Logan Martin, Lay and Plant Gaston in order to meet generation needs while staying in thermal compliance at the monitoring buoy below Gaston.
Download Example EE Models
Download an example model and run with the free EEMS Demo Version.
This example model uses the heat coupled ice model with frazil transport option (ISICE=4) in a 3D lake. The user can run this and make comparison with other options such no ice (ISICE=0) and the normal heat coupled ice model (ISICE=3).
Use EEMS to simulate hydrodynamics in Lake Washington. The model uses temperature modules with the Sigma-Zed vertical layering option to simulate thermal stratification in Lake Washington, Seattle, USA. The Sigma Zed model is unique to EFDC+ and is designed to reduce pressure gradient errors with an approach that is computationally efficient.
