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4.4.4.4 Summary
Concentration of flow through a small number of spillbays is a technique that can improve DO
in releases from low-head navigation dam spillways. While it could be used at almost any facility that
operates a number of gates across the face of the structure, it is especially useful at gated-sill types of
projects. The method relies on increasing the turbulence and air entrainment of the flow plunging into
the stilling basin of the spillway.
Although reported applications of this technique are limited, it holds much potential for
increased flow aeration with little or no structural modification. Information concerning this technique is
summarized in Table 4.4.4.
Table 4.4.4
Summary of Concentration of Flow Through One Gate
Characteristics
Description
Low dissolved oxygen levels (and associated
Targets
concerns)
Reaeration of flow through increased turbulence
Mode of action
as a result of concentrating the flow through a
minimum number of release gates
Effectiveness
Moderate
Possible increased scour and erosion of stilling
Negative features
basin and downstream
Change in the flow conditions and patterns for
ship traffic
Costs
Minimal
Most applicable to lock and dam projects but can
Applicability to reservoirs
be used at other projects where thp flow is usually
spread out over multiple outlets
4.4.5 OPERATIONAL OPTIMIZATION FOR WATER QUALITY
4.4.5.1 Description
Reservoirs are operated for many purposes, most commonly flood control, hydropower,
navigation, recreation, and water quality. At times, conflicting results may occur, when operating a
4.4-14

 


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