REAERATION THROUGH LOW DAMS
IN THE OHIO RIVER
HERBERT C. PREUL, Associate Professor
ALBERT G. HOLLER, Research Fellow
Division of Water Resources and Hydraulics
Department of Civil Engineering
University of Cincinnati
Cincinnati, Ohio
INTRODUCTION
With increasing minimum requirements for concentrations of dissolved oxygen
in our streams, practical information is needed on the most efficient methods of
stream reaeration. Mechanical methods have been most popular and have been
applied for this purpose in a number of cases. However, aeration through the proper
design and operation of hydraulic structures has been largely overlooked.
Usually energy dissipation has been of main concern, and the aeration potential
has not been considered. The time has now come when this latter aspect must be
included in design and operation. Such consideration usually will not cause a significant increase in the original cost of the structure, and essentially no operation cost is
incurred for this benefit.
This paper presents results from field prototype studies and laboratory model
studies conducted over a several year period. The prototype measurements have been
carried out at Meldahl Dam and at Markland Dam, located for navigation purposes in
the Ohio River near Cincinnati, Ohio. Both of these dams are low head structures
with tainter gates provided for discharge control. The hydraulic parameters that
influence reaeration through structures of this type have been identified. It was
found that proper control of these parameters can increase the reaeration of flow
through these structures.
In the laboratory, basic studies have been carried out with flows through a
model tainter gate in a test channel. It is believed that the results from this work may
be generally applicable to other hydraulic structures for the improvement of reaeration in a stream.
THEORETICAL CONSIDERATIONS
A generalized section through a navigation dam, of the type constructed on the
Ohio River, is shown in Figure 1. Various pertinent dimensions have been noted on
the drawing.
The conditions which affect oxygen transfer resulting from flow through a dam
may be grouped into four categories: 1) Upstream conditions; 2) Structural configuration and discharge control; 3) Water quality and water-air relationship; and 4)
Downstream conditions.
In the operation of a particular installation, only the structural configuration is
fixed while the other conditions may be variable. The operational factors which can
be controlled are the upstream and downstream conditions. Factors involved in these
conditions are discussed below.
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