RESERVOIR RELEASE IMPROVEMENT
Charles E. Bohac, Environmental Engineer
E. Dean Harshbarger, Supervisor, Research and Testing Section
Jack L. Davis, Program Manager, Reservoir Release Improvements
Richard J. Ruane, Program Manager, Special Projects and Research
Svein Vigander, Head, Fluid Systems Physical Analysis Group
Division of Water Resources
Tennessee Valley Authority
Chattanooga, Tennessee 37401
BACKGROUND
Reservoir releases are sometimes deficient in dissolved oxygen (DO) and streamflow
needed to provide for assimilation of oxygen-demanding wastes. In addition, DO, flow
and temperature might not be optimum for tailwater sport fisheries and other recreational
activities. This chapter addresses the Tennessee Valley Authority's (TVA) investigations
to improve the releases from a number of its reservoirs where such inadequacies exist.
Results are presented on a feasibility analysis of alternatives and an experimental hydro-
turbine aeration program.
DO TRENDS
The DO trend of the Tennessee River was evaluated by determining the average rate of
change of DO over the time periods 1960-1979 and 1975-1979 [1]. Over the period 1960-
1979, all main stem reservoir releases showed decreases in DO except Fort Loudoun, Nicka-
jack, Watts Bar and Chickamauga. These last four reservoirs actually had improved DO
trends, possibly due to extensive pollution control efforts along the main stem and headwaters of the Tennessee River. For the 20-yr period 1960-1979, the mean DO concentrations in reservoir releases decreased by about 1.1-1.2 mg/1 at Kentucky and Pickwick, which
are near the mouth of the Tennessee River, and increased about 0.3-0.4 mg/1 at Watts Bar
and Fort Loudoun, near the headwaters.
From 1975 to 1979, all main stem reservoirs but Chickamauga showed decreases in
DO, indicating that perhaps the beneficial effects of wastewater cleanup programs have
already peaked, and water quality may now be again on the decline. If the trend of the
last five years prevails, DO levels in the main stem releases could decrease as much as 1.4-
1.7 mg/1 at Kentucky and Pickwick and 0.7-1.0 mg/1 at Watts Bar and Fort Loudoun in
the next five years. Not all of the potentially significant variables were analyzed, and the
results from trend analyses, especially for a short period such as five years, should be viewed
with caution. Regardless of the trends, however, there are stream reaches within the TVA
region which have periodic low DO at the present, and they are shown on Figure 1.
POTENTIAL FOR DO IMPROVEMENT
TVA reservoirs where the need for improved DO is most critical were identified and the
potential improvement in DO was estimated assuming the use of several aeration methods
currently under development by TVA and others. DO data for releases for the years 1970-
1979 were evaluated to determine:
1. the minimum observed dissolved oxygen concentration;
2. the average annual minimum DO;
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