The Ohio River Valley is one of the most heavily industrialized basins in the
United States. As a result, the Ohio River, Monogahela, MusldngUln, Kanawha, and
other tributaries often experience poor water quality. One measure of poor water quality
is low dissolved oxygen concentrations during low flow periods.
Most of the rivers in the Ohio River Valley have been transformed into navigable
waterways through a series of locks and dams. The free flowing river is now a series of
pools. Quiescent pools do not promote the transfer of oxygen into the water due to low
turbulence levels. Fortunately, the hydraulic structures themselves may actually be a key
componen~ in improving the water quality because of the high turbulence levels generated
at these structures. The purpose of this study is to investigate the use of dam gates and
hydropower installations for the addition of oxygen to the water.
The amount of oxygen added to the water varies with the structural
characteristics, gate opening, and hydraulic conditions. Analysis of the most recent data
taken in 1998, along with data taleen in previous years, shows trends for oxygen transfer
at gate sill structures.
Gate tests indicate that a high tailwater submergence of the sill allows minimal
oxygen transfer to occur until an unsubmerged hydraulic jUlUP forms. The transfer
efficiency will increase until a maximUlU transfer is reached. Beyond this critical gate
opening, the transfer efficiency will level out or may even decline. If the submergence on
the sill is low, a hydraulic jUlnp can form at very low gate settings. In this case, the
transfer efficiencies will increase to a maximUlU at the critical gate opening. After this
gate setting is reached, the transfer efficiencies will level out or decline.
Te:;ts were also perfonned on hydropower installations with the draft tube air vent
opened. Analysis of all sites indicates that oxygen transfer is negligible due to
insufficient suction head. The minimal retrofit scheme is not suitable for raising oxygen
levels. A more detailed study of retrofit options is needed to raise oxygen levels through
In conclusion, the gated sill structures show promise as a tool for improving water
quality within the river system by raising oxygen levels, if operated under close-tooptimum
hydraulic conditions for gate aeration.
Urban, Alicia L.; Gulliver, John S.; Miller, Kimberly F.; Kincaid, George P..
Gas Transfer at Gated Sill Structures In the Ohio River Valley.
St. Anthony Falls Laboratory.
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