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 Identify the specific water quality concern and objectives. For example, the water quality
parameter, such as dissolved oxygen (DO), must be quantified in the reservoir and the release. The
existing release characteristics must be determined, including discharge volume and withdrawal
characteristics in the pool.
Determine the various release options for a given project. This will involve examination
of release options that typically are not made, such as low-flow (minimum) releases from a flood control
gate. The improvement of release quality with a modification of the release schedule to include releases
from this optional structure must then be evaluated (Figure 4.4.3). In the case of selective withdrawal,
the SELECT model (Davis et al. 1987) can be used to predict release quality for most high-head
release structure options. If reaeration through the structure is a desired outcome, computational
methods to predict the amount of reaeration through a gated conduit, which have been developed by
Wilhelms and Smith (1981), may be used. Once the release options have been identified, determine
the volume of water required to achieve the stated water quality goal. In most cases, this can be
determined using a mass balance approach, where the existing release quantity is diluted with the water
quality release.
Figure 4.4.3 Example of improved dissolved oxygen with supplemental releases
4.4-9
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