WSP04999

• File Number: 8054
• Description: Water Salvage
• State: CO
• Basin: Statewide
• Date: 6/1/1975
• Author: Utah Water Research
• Title: Water Salvage Potentials in Utah - Volume II - Evaporation Suppression by Reservoir Destratification
• Water Supply Pro - Doc Type: Report/Study

35

30

25
z
0 20
en
'"
w
'"
0..
0..
:>
'" 15
....
z
w
u 10
'"
W
0..
5

o
30

40 50 60

80 100

RESERVOIR MAXIMUM DEPTH (FEET)

200

700

1000

300

500

FIgure 16. Snppresslon lIlI a function of depth and flow Index.

example. Flaming Gorge has a residual tempera-
ture increase of 1.0oC at the end of October. Lake
Powell has a residual of 3.20C on the same date.
and this caused a subsequent 20 percent reduction
in net suppression estimate for total recovery to
natural condition (or for continuous operation).
The much lower residual at Flaming Gorge could
be expected to cause only a 6 percent decrease (if
the effect is assumed to be linear) for continuous
operation.

The tendency of a high flow index to increase
suppression holds only within a certain range. A
/low so high as to cause a significant velocity in the
reservoir itself will destroy the thermocline. Arai (in

Ackerman, et aI., 1973) places this velocity at 20
em per second (0.6 feet per second). Cutler
Reservoir is an example of a shallow impoundment
which creates what is essentially a slow moving
portion of the Bear River. The seasonal flow index
for Cutler was calculated as 11.0 and the average
velocity toward the outlet as 1.8 ftlsec. No
thermocline exists at Cutler because of this
velocity. A comparison of this velocity and flow
index with the critical velocity of 0.6 suggests that
the critical flow index (above which the velocity
destroys the thermocline) has an order of
magnitude of 3.0. A conservative value of 2.0 was
used in the model as the flow index above which
suppression is forced to zero regardless of other
parameters.

38