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Diffuser System Modeling and Design For Dissolved Oxygen Enhancement of Reservoirs and Releases (PDF, 1.1MB)

Mark H. Mobley, Gary E. Hauser, Dan F. McGinnis, R. Jim Ruane

In support of the Tennessee Valley Authority’s Lake Improvement Program, a line diffuser system was developed that was applied and proven effective at six TVA hydropower projects. To be effective, the placement of the diffusers and distribution of the oxygen input must be optimized for site-specific water quality and water flow conditions. Most TVA applications were relatively straightforward designs with consistent water flows, deep intakes, and the single objective of release DO enhancement. While line diffuser applications have typically been oriented longitudinally in the old river channel, they can be arranged in any configuration for special purposes. A forebay diffuser system can be designed to continuously aerate a large volume in the reservoir to handle daily volumes associated with peaking hydro turbine flows, or it can be designed with capacity to handle instantaneous peak discharges. Aeration at the proper location in a reservoir can eliminate hydrogen sulfide, iron, and manganese in water supply withdrawals or prevent release of these compounds during hydro generation. Highly intermittent hydropower applications have created a need for a base load oxygen rate combined with intermittent generation load oxygen rate. New applications often require aeration at specific locations in a reservoir to meet fish habitat or oxygen demand requirements. Such increasing complexity in diffuser designs has led to increased use of mathematical modeling to predict diffuser performance in the context of dynamic reservoir conditions. Models are now used to help optimize size, placement, and operation of the line diffuser. New pre- and post-processors are available that reduce the time and cost of using sophisticated models in the design of demanding diffuser applications. This paper describes the line diffuser design and several modeling applications. Results from operational line diffuser systems and model predictions for systems currently under design are presented.



Simulations for Design of Oxygen Systems In Reservoirs (PDF, 0.2MB)

Gary E. Hauser, Dan F. McGinnis, Mark H. Mobley, R. Jim Ruane

Tools for designing aeration systems are improving as reservoir applications become more complex.  TVA is currently using bubble plume models, CE-QUAL-W2 reservoir water quality model, and specialized CE-QUAL-W2 inputs to simulate injection of oxygen into reservoirs with porous hose line diffusers.  Two-dimensional reservoir-wide effects of the oxygen injection are then evaluated to help size, locate, and develop operational plans for oxygen system installation.  This paper will describe design tools and applications at reservoirs in the eastern United States.



Hydropower Tailwaters


Thermal and Bioenergetics Modeling For Balancing Energy and Environment (PDF, 0.2 MB)

Gary E. Hauser, John Stark, George Robbins, Bethel Herrold

Dynamic thermal and bioenergetics models were applied to help define issues, identify alternatives, and quantify effects of various reservoir releases improvement options for Bull Shoals and Norfork Dams in northern Arkansas.