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 This procedure has been implemented in a real time frame at several hydropower projects,
using a downstream monitoring scheme to identify the need for water quality releases. Once real-time
monitoring identifies the need, the water quality release is made.
4.4.3.3 Implementation
This technique has been applied at several projects to improve downstream DO, usually in
conjunction with a hydropower operation. However, it can be used with any project in which the water
quality concern is a result of stratification in the reservoir, such as release temperature or pH.
At Tims Ford Project, a multipurpose hydropower project operated by the Tennessee Valley
Authority (TVA), the need to establish a minimum release from the project during nongeneration
periods to maintain the downstream fisheries resource was identified (Goranflo and Adams 1987). The
study indicated that 80 cfs should be released. Alternatives that were evaluated included an option to
sluice water through the flood control structure. This would provide the required flow and increase the
release DO oxygen without requiring a structural modification to the project. A similar evaluation was
conducted at the Norris Project with similar conclusions.
Walter F. George Lock and Dam on the Chattahoochee River near Fort Gaines, GA, has
experienced problems with low DO in the tailwaters during nongeneration periods in the late summer
and early fall. An operational technique that relies on downstream monitoring to identify the onset of
low DO conditions is used to enhance the downstream water quality. With the identification of low DO
conditions downstream, spillway gates are opened in an ordered manner until downstream DO levels
stabilize (Findley and Day 1986). A similar operation that relies on downstream monitoring to identify
the need for flood control gate releases has been implemented at Lake Texoma (Price 1990).
Table Rock Dam, located on the White River in Missouri, experiences difficulty meeting DO
criteria in the release during the stratification season. Among the alternatives investigated to correct this
situation was the use of supplemental releases from the hypolimnion through Howell-Bunger valves.
This release would be aerated by the aspiration process associated with these types of valves. The
costs associated with loss of generation capacity due to the releases was significantly greater than other
alternatives for this project (US Army Engineer District, Little Rock 1985).
4.4.3.4 Summary
The water quality released from a multi-purpose reservoir may be improved by modifying the
operation of the various release structures at the project. Specific water quality concerns and
enhancement objectives must be identified. For example, release DO may be low and require
improvement to some minimal level. Operation of an alternative outlet may permit the release of high-
DO water with epilimnetic water or by reaeration for mixing with the poor quality release. Simple
4.4-10
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