General studies : November, 1967 / by John C. Ayers, Joseph C. K. Huang.

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The available studies of natural river effluents are for
rivers of about 4000 cfs flow, and the studies are not sufficiently
advanced to enable us to scale down to the 1200 cfs flow of the
initial one-unit plant. The discussion in this section is, then,
for the possible ultimate 4-unit plant, and is over-pessimistic
for the case of the one-unit plant. The discussion is also conservative in that lack of data force us to treat of plume length
at the vanishing point, rather than to a point of a few degrees
of residual heat that would pass unnoticed.
From mid-spring until the height of summer, river effluents
are commonly warmer than the receiving lake water. River effluents
emerging through river mouths become immediately subjected to the
directional and dispersive actions of wind and alongshore currents.
The river-effluent model contains the basic desiderata of the plant
effluent problem, except that temperature differences between river
and lake are usually not so gross as will be those between plant
effluent and lake.
For nearly a year we have required our ships to log wind
direction and direction of turn of river effluent each time they
enter or leave a river mouth. In all the cases yet seen, the
river effluent has turned downwind immediately after leaving the
river mouth.
On several occasions we have tried to follow the effluent of
the Grand River whose mean summer flow is about 4000 cfs (Horton
and Grunsky 1927). In every case we have lost visual (color),
thermal, and turbidity or conductivity evidence of river water
within three miles of the river mouth. Similar, but fewer, attempts