PILOT STUDY
OF
DYNAMICS OF RESERVOIR
DESTRATIFICATION
U.S, DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
ROBERT S. KEftR WATER RESEARCH CENTER
ADA, OKLAHOMA
1968
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PILOT STUDY
OF
DYNAMICS OF RESERVOIR DESTRATIFICATION
by
Lowell E. Leach
William R. Duffer,
and
Curtis C. Harlin, Jr.
Water Quality Control Research Program
Robert S. Kerr Water Research Center
Ada, Oklahoma
U. S. DEPARTMENT OF THE INTERIOR
Federal Water Pollution Control Administration
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PILOT STUDY
OF
DYNAMICS OF RESERVOIR DESTRATIFICATION
by
*
Lowell E. Leach, William R. Duffer, and Curtis C. Harlin, Jr.
INTRODUCTION
There is immediate national interest in the broad, new field
of reservoir water quality research directed toward more beneficial
reservoir operations and management practices. Many people will be
affected directly or indirectly by the future control of impounded
water supplies and their management. The goal of these practices
should be the ultimate control of water quality to insure that the
entire volume of water impounded is available for maximum beneficial
use at all times.
In recent years, the stagnation of water at lower depths in
impoundments, due to the natural processes of thermal stratification,
has become a prime concern and a cause of concentrated effort for
remedial measures. Stratification greatly reduces the potential
beneficial uses of the lower levels in impoundments for municipal
and industrial purposes and causes detrimental downstream effects
below impoundments during summer power releases. Dissolved oxygen
levels decrease in the lower density layers due to stratification.
* Project Leader; Head, Reservoir Control Section; and Chief; Water
Quality Control Research Program, Robert S. Kerr Water Research
Center, South Central Region, Federal Water Pollution Control
Administration, U. S. Department of the Interior, Ada, Oklahoma.
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Fish habitat and production of fish-food organisms are limited in
the oxygen-depleted layers at a critical time when most of their
annual growth occurs.
Many recent papers describe the effects of artificial destrat-
ification devices used to aerate thermally stratified impoundments.
The primary effort directed toward control of thermal stratification
has been artificial destratification using various types and arrange-
ments of mixed-flow pumps (1) or compressed air systems (2-6) to mix
the hypolimnion and epilimnion water. The compressed air system is
believed to be the most efficient and was used for this study. The
present research is unique because the destratification system was
established and evaluated in the central pool of an extremely large
reservoir. Other researchers have been very effective in destrat-
ification of relatively small impoundments where the aeration system
utilizes the confinement of the banks to restrict the limits of the
system causing faster and more homogenous aeration. However, for
more general use, the system must be developed for effective appli-
cation in large reservoirs.
The ultimate goal of destratification research at the Robert S.
Kerr Water Research Center is to develop design criteria to the extent
that the most economical size and arrangement of systems can be de-
signed for reservoirs of different characteristics. The approach
being used is to design systems for application in selected reservoirs.
In each case, the system will be evaluated and design modifications
made to the particular reservoir characteristics. The primary objective
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3
of this project is to develop the technique of destratifying large
reservoirs utilizing one or more air diffusor systems strategically
located to give the most desirable cost-benefit ratio.
The pilot study here reported was conducted to gain knowledge
of kinetics and hydrodynamic effects of an air diffusor system placed
near the bottom of a reservoir. The rate of change of the thermocline
resulting from aeration and the trajectory and limits of the aeration
effects, as well as the degree and rate of change of effects, were
primary considerations in evaluating the dynamics of the aeration
system. Evaluation of a compressor with particular capabilities and
its subsurface air diffusor system, based on its input and resulting
net effects, supplies a base from which a more applicable and efficient
system can be designed.
This report presents the progress and development of the pilot
study of the dynamics of destratification of a large reservoir by
utilizing a compressed air diffusor system. The pilot study research
was conducted by personnel of the Water Quality Control Research Pro-
gram, Robert S. Kerr Water Research Center, during the summer and
early fall of 1967 at Eufuala Reservoir, a U. S. Army Corps of Engineers
reservoir located in eastern Oklahoma.
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THERMAL STRATIFICATION EFFECTS
Reservoirs in the Southwestern United States generally become
density-stratified during mid-May and remain so until mid-October,
the most pronounced stratification occurring from June until mid-
September. The fundamental causes of the development of stratifica-
tion are discussed in detail in most works on limnology (7-9).
Normally, at the end of the winter season, water in a reservoir
is cold and has a relatively high density. As the atmospheric
temperature increases, the temperature of both the surface and in-
flowing waters increases with a corresponding decrease in density.
The difference in density between the top and bottom strata of
water eventually becomes great enough to prevent wind-induced mixing
of the water mass, and stratification occurs.
Between the warm, relatively light surface stratum (epilimnion)
and the colder and denser bottom stratum (hypolimnion), there is a
third stratum (metalimnion or thermocline) where the temperature
gradient declines rapidly with depth. The metalimnion remains in
place throughout the period of summer stratification and acts as a
flexible diaphragm preventing mixing of the epilimnion and hypolimnion.
In the southern portion of the United States, the temperature
of the epilimnion may rise to 30°C or even higher. Wind-induced
mixing usually maintains a rather uniform temperature throughout the
depth of the epilimnion.
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5
A small amount of radiant energy from the sun penetrates to
the bottom of the reservoir and produces a small temperature gradient
from top to bottom in the hypolimnion (10). The hypolimnion often
consists of water that was stored during winter or spring. Since
stratification prevents the warm atmosphere from reaching the hypo-
limnion, warming is slight. Even in southern areas, the summer
temperature of the hypolimnion may remain as low as 7 to 10°C.
In the typical large storage reservoirs, the epilimnion is
generally about 25 to 40 feet deep; the metalimnion is 10 to 20
feet thick; and the hypolimnion occupies the remainder of the depth
to the bottom (10).
The epilimnion is circulated by wind-induced currents during
periods of stratification and becomes aerated to the point where the
dissolved oxygen is near saturation.
The hypolimnion, however, is completely shut off from the at-
mosphere; and sunlight usually does not penetrate deeply enough to
support photosynthesis. Dissolved oxygen is removed from the water
by organic decomposition and cannot be replaced. Detention of water
for several months in the hypolimnion often permits total dissolved
oxygen depletion—even in reservoirs receiving inflows nearly
saturated with dissolved oxygen. Stagnant water of the hypolimnion
requires extensive treatment at very high cost before it can be used
for human consumption or certain industrial purposes. Stratification,
therefore, imposes restrictions on water use from a storage reservoir.
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6
New reservoirs that are allowed to fill without having the
vegetation cleared in the impoundment area may have a layer of
stagnant water above municipal water supply intake lines, thus,
seriously deteriorating the water supply.
At hydroelectric dams, the penstocks normally are located
fairly deep in the reservoir; water passing through the turbine
penstocks comes from the hypolimnion which may contain high
concentrations of hydrogen sulfide and almost no dissolved oxygen.
The discharge has very little energy left as it leaves the tailrace
and therefore is not reaerated properly. This discharge water is
often detrimental to fish and causes serious problems in downstream
water uses.
Many changes occur as a result of reservoir stratification
such as the reduction of iron and manganese compounds. Sufficient
research has not been conducted on many of these parameters to fully
understand or evaluate their influence on water quality and the
biota. Some of the conditions which exist as a result of stratifi-
cation appear to be detrimental to fish within the reservoir and to
be responsible for the accumulation of toxic substances in the
hypolimnion.
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RESERVOIR BACKGROUND STUDY
Eufaula Reservoir was selected as the pilot study area for
two significant reasons. The first of these was the physical char-
acteristics of the body of water. There are several interconnected
bodies of water within the reservoir (Figure 1). The reservoir
has a surface area of 102,500 acres and a storage of approximately
2,800,000 acre-feet at 585 feet, which is the maximum power pool
elevation. The central pool, having a surface area of 10,800 acres
and a volume of approximately 570,000 acre-feet at maximum power pool
elevation, is more than ten times as large as any reservoir in which
destratification has been reported. The separate, almost isolated,
upstream bodies of water at the reservoir are outside the influence
of direct destratification effects in the central pool and serve as
a control to illustrate reservoir changes due to normal seasonal
conditions.
The second reason for selecting Eufuala Reservoir as the pilot
study site was the availability of historical water quality data
from several monitoring stations within the reservoir. Eufaula
Reservoir is one of several in the United States presently being
monitored by the U. S. Army Corps of Engineers as part of a national
program to develop criteria for more efficient water quality conser-
vation practices. The Tulsa District Corps of Engineers has
established continuous recording stations as shown in Figure 1 at
points 1, 2, 3, and 4. Temperature, dissolved oxygen, and con-
ductivity have been monitored at these stations since August 1966.
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EUFAULA RESERVOIR
CHECOTAH
]*****?—|^X> ^T w
OUINTON
Corp* of Engineer
PILOT STUDY OF DYNAMICS OF
R F3 F.RVOi* DESTRATI^ICATION
VICINITY MAP
US DEPARTMENT OF THE INTER'OR
f'-EDERAL WATER POLLUTION CONTROL ADMINISTRATE
' WATE* PKSE*RCK CENTER
FIGURE I
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8
A continuous record of these parameters is made at one level and
vertical profiles are taken by Corps personnel on a weekly basis at
each station. Further, these stations are conveniently located for
monitoring in connection with the destratification project, since
they provide data to establish differences between separate, almost
isolated, bodies of water prior to and during aeration.
In early June, 25 buoy stations were located in the central pool
of Eufaula Reservoir (Figure 2). They were arranged in a cross
pattern and stationed approximately 500 feet apart, with the center
of the cross located about 3,600 feet upstream from the dam. Vertical
temperature and dissolved oxygen profiles were measured at these
stations at 5-foot intervals from the surface to the bottom. Vertical
profiles were measured on four separate occasions prior to artificial
destratification for the purpose of determining the thermal stability
and level of stratification. The thermocline was found to be
approximately 22 feet below the surface,and it remained at that
level for each of the four separate measuring periods.
Since there was very little variation among stations, mean
conditions of temperature and dissolved oxygen are presented for
all measured buoy stations on each of the four separate monitoring
dates (Figure 3). Dissolved oxygen levels in the depth from zero
to 22 feet ranged from 10 to 6 ppm at the surface, decreasing to
about 5 ppm at 22 feet, depending on the weather conditions at the
time of monitoring. Dissolved oxygen levels below 22-foot depths
rapidly decreased to near zero and generally remained constant for
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EUFAULA RESERVOIR
CENTRAL POOL
i U.S. ARMY
ENGINEERS
PROJECT
OFFICE
Radiating Buoy Stations
W-9 Through E-8 and N-4 Through S-6
PILOT STUDY OF DYNAMICS OF
RESERVOIR DESTRATIFICATION
PROJECT LOCATION MAP
US. DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
ADA, OKLAHOMA
RO6ERT S KERR
WATER RESEARCH CENTER
FIGURE 2
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TEMPERATURE - C " TEMPERATURE - C°
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DISSOLVED OXYGEN-PPM DISSOLVED OXYGEN-PPM
. vu
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PILOT STUDY OF DYNAMICS OP
RESERVOIR DESTRATIFICATION
AVERAGE ANTECEDEN
CONDITIONS
T OP
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U.S. DEPARTMENT OF THE INTERIOR
CEC£RAL WATER POLLUTION CONTROL ADMINISTRATION
KOPENT S. KER* »n* ttaAWOMA
W»TH« P£SE<»CH CENTEH
FIGURE 3
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9
the four separate monitoring periods. The higher oxygen concentra-
tion at the 50-foot depth gradually diminished during antecedent
monitoring and immediately disappeared when destratification operations
began. One very interesting feature that appears in the dissolved
oxygen profiles for all four antecedent monitoring periods is the
decreased concentration of oxygen at about the 30- to 40-foot depth
resulting in S-shaped curves. This phenomenon was reported by re-
searchers of the Tennessee Valley Authority (11) as having occurred
in reservoirs in the Tennessee River Basin during early summer
stratification. The TVA researchers suggested that this phenomenon
was caused by a concentration of zooplankton at one level which
depleted the oxygen. This phenomenon is discussed in detail by
Hutchinson (8).
The destratification system was similar to one used in the
1965-1966 research conducted on Boltz and Falmouth Lakes in northern
Kentucky (1-3). The system consisted of two diesel-powered, rota-
screw-type air compressors mounted on a barge which was anchored
near the center of the radiating buoy-monitoring stations (Figure 4).
These machines are rated to deliver 150 cfm free air at 100 psig
with the engine speed at 2400 rpm. Compressed air discharged from
the machines passed through a monitoring panel where the air was
filtered, and volume, pressure, and temperature were gauged. Air
discharged from the monitoring panel passed through 150 feet of
1-inch diameter hose to a cross-shaped diffusor system located near
the bottom of the reservoir at a depth of 73 feet. The cross
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10
assembly consisted of four 20-foot legs, each with four microporous
porcelain-type diffusor stones which were spaced 3 feet apart along
the outermost 9 feet of each leg. Compressed air was carried from
the 1-inch diameter main line by a half-inch diameter lateral line
to each leg. Each diffusor stone was attached to the half-inch
lateral line by quarter-inch diameter hose.
The air diffusor stones were commercially fabricated, micro-
porous porcelain, hollow candles having a length of 8-3/16 inches
and an interior diameter of 1-1/2 inches. The bubble-forming
-4
microporous capillaries had an average radius of 25 x 10 cm re-
sulting in 27 percent porosity for each candle.
The aeration effects were monitored initially by simultaneously
measuring vertical profiles of dissolved oxygen and temperature at
each radiating line of buoys with crews operating four separate
dissolved oxygen meters. Measurements were repeated at 4-hour
intervals starting at the aeration system and proceeding outward
along each radiating line to a station where no change from the
preceding readings could be detected. The frequency of sampling
was reduced to four times daily on the second day and two times
daily on the third and successive days of the first week. Measure-
ments were made every third day following the first week.
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11
DISCUSSION OF RESULTS
Artificial destratification was initiated July 25, 1967, after
it had been determined from antecedent measurements that the reser-
voir was intensely stratified and had become stabilized. Compressors
were run alternately at intervals of three days each for a 25-day
period of continuous operation. The volume and pressure of the
machines were about 140 cfm and 65 psig, respectively, in initial
operation and continually declined for the duration of the project,
reaching a minimum of 95 cfm at 45 psig after 25 days of operation.
Monitoring dissolved oxygen profiles and recording their changes
from a point of injection of a destratification system is a very
effective method of evaluating the radiating effects of aeration.
Concentrations of dissolved oxygen increased rapidly during the
initial period of aeration together with a gradual warming of the
water both in depth and lateral distance from the diffusor system.
For convenience in evaluating aeration effects, changes in the
vertical levels of 6.0, 4.0, and 1.0 ppm dissolved oxygen resulting
from aeration were monitored at each of the radiating buoy stations.
Effects of aeration were first noticed on the second day of
operation when the 4,0-ppm dissolved oxygen level had lowered from
28 feet to a depth of 35 feet at the point of aeration and radiated
to a noneffective limit of 1,000 feet from the center of the
aeration system. After four days of operation, the 4.0-ppm dissolved
oxygen level had moved to a depth of 40 feet at the point of
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12
aeration and varied upward in a radiating cone-shaped trajectory
to no measurable effect at a distance of 6,500 feet. The radiating
cone effect continued for the duration of the aeration period, with
the effects having reached a maximum depth of 50 feet at the point
of aeration, and varied upward reaching a noneffective limit (22-
foot depth) at a distance of 14,200 feet by the end of the 25th
day of operation. The volume of water aerated below the 22-foot
depth during the aeration operation was 65,800 acre-feet in an area
of approximately 3,000 acres.
Radiating vertical dissolved oxygen profiles illustrate coning
effects much better than temperature profiles for the same stations,
since dissolved oxygen changes exhibit much wider ranges than
temperature changes.
Data collected during the aeration operation from the U. S.
Army Corps of Engineers stations located upstream from the central
pool were carefully examined for variations in temperature and
dissolved oxygen and compared to antecedent conditions. It was
found that these control stations were very stable through the
entire period of aeration and did not change from their antecedent
conditions. The antecedent conditions in the central pool and the
upstream control stations were the same at the beginning of destrat-
ification; therefore, comparison of control stations and the stations
in the central pool during destratification shows the net effect
of destratification.
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13
Profiles in Figure 5 illustrate the gradual lowering of the
thermocline and changes in temperature and dissolved oxygen levels
in the reservoir at antecedent aeration conditions and at selected
periods of aeration. The profile in Figure 5 of antecedent con-
ditions represents a mean for all stations, while the other three
profiles represent the maximum effect which occurred at buoy stations
near the center of the aerator.
Water temperature in the top 22 feet varied with the wind
velocity and air temperature while the dissolved oxygen for that
level was stable at approximately 8 ppm. Temperature profiles
indicate a gradual warming below the 22-foot depth as destratifi-
cation progressed, with the most significant increase occurring in
the depth range from 22 to 50 feet and only a slight increase
below 50 feet. Dissolved oxygen levels below the 22-foot depth
show very significant increases down to the 50-foot depth—the effect
gradually lowering as destratification progressed.
Progressive changes in a selected dissolved oxygen level illus-
trate aeration effects (Figure 6). The profile representing the
period prior to the destratification operation shows the depth and
stable conditions of 4.0-ppm dissolved oxygen level. Profiles
representing succeeding periods illustrate progressive lowering of
the 4.0-ppm level of dissolved oxygen as a result of continuous
aeration. Station zero indicates the point of aeration. The
coning effect of the dissolved oxygen levels, previously discussed,
is particularly evident in these sections.
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AUGUST 2, 1967
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AUGUST 18,1967
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PILOT STUDY OF DYNAMICS OF
RESERVOIR DESTRATIFICATION
PROGRESSIVE AERATION CONDITIONS
US. DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
ROBERT *. KERn AOA fwi A^^^UA
WATER RESEARCH CENTER
FIGURE 5
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PAGE NOT
AVAILABLE
DIGITALLY
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14
Restratification was rapid after aeration ceased on August 18,
followed by normal "overturn" due to seasonal changes (Figure 7).
Restratification occurred during a 4-day period immediately after
aeration ceased, but the 4.0-ppm dissolved oxygen level did not
completely return to its initial elevation. After restratification
had reached its greatest intensity, the reservoir began to cool as
a result of lower air temperatures and the dissolved oxygen levels
gradually increased in depth, finally becoming completely isothermal
at 20°C and having a constant dissolved oxygen level of 7.5 ppm by
October 17, 1967. Isothermal reservoir conditions continued through
December 1967. Water temperature decreased steadily to 11°C in
mid-December, while the dissolved oxygen level throughout the
central pool steadily increased to more than 10 ppm during the
same period•
The volume of water affected by the system was computed based
on the volume of the cone of influence below the 22-foot depth.
Radiating trajectories of the 6.0-, 4.0-, and 1.0-ppm dissolved
oxygen levels were plotted for each period in question and ex-
trapolated to their effective limits. The effective limits of
their trajectories were connected, thus outlining the cone of
effect for each day selected. The volume on each selected date
was measured to determine the progressive change in volume with
continued aeration (Table 1).
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PAGE NOT
AVAILABLE
DIGITALLY
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Table 1. SUMMARY OF DESTRATIFICATION EFFECTS
HOURS OF
COMPRESSOR
DATE
July
Aug.
Aug.
Aug.
Aug.
Aug.
28,
2,
7,
9,
16,
18,
1967
1967
1967
1967
1967
1967
OPERATION
70
200
320
365
535
580
VOLUME
OF
AERATED
WATER
AC-FT
30
36
45
59
59
65
,600
,000
,600
,500
,800
,800
ACCUMULATED
POUNDS
AIR PUMPED
184
449
614
722
980
1,109
,400
,500
,100
,900
,700
,600
THERMAL
ENERGY
DIFFERENTIAL
KW-HR X105
1065
1140
2210
2710
I860**
**
2600
**
The volume of effect was considered only below a depth of 22.0 feet.
Cooler temperature gradient than previous dates due to several con-
secutive days of cool, cloudy weather as well as greatly reduced
air pressure and flow from the compressors.
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15
Energy input was determined using destratification efficiency
methods outlined by Symons (12, 13). Differences in stability energy
units for the isolated volume of artificially aerated water were
computed using control temperature conditions and temperature con-
ditions for several separate periods of aeration. However, in
several cases, the difference in computed stability values was
negative or near zero. This technique considers the entire body
of water utilizing temperature gradients for separate periods of
time. During aeration of a large reservoir, however, only an
isolated portion of the total volume may be affected and the iso-
lated volume continues to increase as aeration progresses. Since
the affected volume continually changes with resultant changes in
stability, it does not appear feasible to use this technique for
determining energy added to a large reservoir during aeration.
The method used for evaluation of the pilot study system
takes into account compressed air input, volume of water affected,
and effective thermal energy input. The weight of compressed air
input in pounds based on the gauged input volume, pressure, and
temperature was computed using the basic equation pv=RT where: p
2
is the absolute pressure in Ibs/ft , v is the specific volume in
3
ft /lb of air, T is the absolute temperature in degrees Rankine,
and R is a constant for air (53.3 ft/degree Rankine). The accu-
mulated weight of air pumped into the central pool was compared
to volume of water affected for various periods of time during
the progress of operations. This comparison is made in Table 1.
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16
It should be noted that there was no significant change in water
volume affected from August 9 to August 16. This resulted from
cool weather conditions and compressed air being pumped into the
reservoir at very low pressures. The low air pressures were
partially due to mechanical problems with the compressors. The
pilot system would have been more efficient had larger air dis-
tribution lines and less restrictive connections been used. The
pressure drop from the panel board to the diffusor candles was
from 65 psig to less than 1 psig with only the top half of the
candle discharging air. The bubbling pressure of the candle is
approximately 0.5 psig.
Thermal energy input into the central pool was computed from
the difference in the mean temperature profiles at the upstream
control stations and the mean temperature profiles of stations in
the central pool. These values represent the difference in thermal
energy of the aerated portion of the central pool and that of the
same body of water on a particular date had there been no aeration.
These energy values, expressed in kilowatt-hours, are differences
in energy on particular dates during aeration. The mechanical
energy input is accumulative; however, effective thermal energy
is based on differential temperature gradients of affected and
unaffected areas and is not accumulative energy. As mechanical
input increases and aeration time progresses, the volume of
aerated water increases. There was a sharp drop in thermal
energy on August 16 when the compressors were not producing
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17
sufficient air pressure and volume to maintain circulation in the
central pool.
Further development of the thermal energy relationship versus
mechanical energy input should result in a very effective means of
evaluating the efficiency of this system and other systems being
used for destratification. An efficiency index may serve as a future
guide for spacing of systems for destratification of entire reservoirs.
An interesting observation was made by a professional scuba
diver during destratification operations. The diver noticed, prior
to the destratification operations, that fish were present at
maximum depths of 18 to 25 feet; but when destratification was in
progress, the number of fish increased in the affected area and
fish were also present at maximum depths of 45 to 50 feet, the
greatest concentration occurring in the immediate area of the
aeration cone. These observations were made on several occasions
by the diver and noted to be unusual for Eufaula Reservoir for that
particular time of year.
As a result of the reported change in distribution of fish
and their increased numbers, there has been a great deal of interest
from fisheries biologists to study the influence of the destratifi-
cation effects on fishes and other biological parameters including
plankton, benthic macroinvertebrates, nutrients, and photosynthesis.
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18
SUMMARY
The pilot study of dynamics of reservoir destratification has
advanced development and design of a system to destratify large
reservoirs. Rate of change of the water volume affected and the
magnitude of aeration were determined in the central pool of Eufaula
Reservoir. The pilot system was undersized for circulating the
entire volume of the central pool, yet 65,000 acre-feet of water
below a depth of 22 feet was aerated by the 25th day of operation.
Aeration effects extended as far as 2.5 miles from the point where
the system was installed, covering an area of approximately 3,000
acres at a depth of 22 feet. Rate of change of hydrodynamic
aeration trajectories and thermal effect versus mechanical energy
input are discussed. Pilot system design and operational limita-
tions served as a guide for design of a more effective system for
continued research and development of destratification of large
reservoirs.
Interesting changes in vertical distribution and concentrations
of fish have prompted proposals from other agencies to conduct
parallel research on effects of destratification on fish popu-
lations and other biological parameters.
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FUTURE WORK
The present study was based on projections of studies conducted
by other researchers (1-3) who used similar systems on very small
reservoirs. The results obtained from the 1967 study were ex-
tremely favorable for complete control of stratification in very
large reservoirs.
Plans are being made to continue this work during the summer
of 1968, with modifications of the system being made based on
experience gained during the 1967 study. The type and size of
equipment used, the volume of water aerated, and hydrodynamic
changes in the central pool have served to guide redesigning of
the system requirements for destratification of the entire central
pool of Eufaula Reservoir. The type of system proposed will have
one or more electrically powered rota-screw-type air compressors
capable of producing 1200 cfm of free air at 125 psig. For
practical application, convenience, and safety during continued
study, the compressors will be located either on the dam or an
accessible shore location near the dam.
The air distribution system will be completely redesigned.
Larger diameter piping and a greater number of diffusor candles
to reduce pressure loss in the system will be used.
The destratification operation will be a two-phase study.
The first phase will be started in early June after the central
pool has become intensely stratified and has stabilized. The
central pool will be aerated at the maximum rate for four
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consecutive weeks, stopping for three or four weeks to allow complete
restratification. The system will be modified for the second phase
by changing either the air distribution system or the rate of air
flow. The distribution system may be modified by using a different
number of the same size diffusor candles or the same number of
diffusors of a different size. In addition to measurements of
dissolved oxygen, temperature, and conductivity, samples will be
collected at various depths on a regular basis and analyzed for
chlorides, sulfates, and total dissolved solids. Buoy stations
located in the upper reservoir control area will be monitored for
static control through the entire project.
As a result of the behavior of fishes as noted during the
present study, cooperative research will be conducted by the
Oklahoma Department of Wildlife Conservation and the Oklahoma
Cooperative Fishery Unit of the Bureau of Sport Fisheries and
Wildlife. The project will entail evaluation of the effects of
large-scale artificial aeration and destratification by use of
compressed air on the distribution of fish and fish-food organisms
in a stratified reservoir. Effects of the influence of aeration
and destratification on nutrient distribution and primary pro-
ductivity will also be determined.
The U. S. Fish and Wildlife Service will also conduct a
study to determine both daytime and nighttime distribution of
fish by using echo sounding equipment and a midwater trawl.
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Measurements will be made during destratification in the aerated
portion of the central pool and in a relatively undisturbed control
area for approximately four days.
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ACKNOWLEDGMENTS
The authors gratefully acknowledge the assistance and
cooperation of the staffs of the Operations Division, Hydraulics
Branch, and Eufaula Dam Project Office of the Tulsa District,
U, S. Army Corps of Engineers.
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REFERENCES
1. Irwin, W. H., J. M. Symons, and G. G. Robeck. 1967. Water
quality in impoundments and modifications from destratifi-
cation. Federal Water Pollution Control Administration, USDI,
Cincinnati, Ohio.
2. Symons, J. M«, W. H. Irwin, E. L. Robinson, and G. G. Robeck.
1967. Impoundment destratification for raw water quality
control using either mechanical or diffused air pumping.
Federal Water Pollution Control Administration, USDI,
Cincinnati, Ohio.
3. Symons, J. M., W. H. Irwin, and G. G. Robeck. 1967. Reservoir
water quality control by destratification. Federal Water
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5. Ford, M, E. 1963. Air injection for control of reservoir
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6. Bemhardt, Heinz. 1967. Aeration of Wahnback Reservoir
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8. Hutchinson, G. Evelyn. 1957. A treatise on limnology.
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9. Welch, Paul S. 1952. Limnology. 2nd edition. New York,
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10. Kittrell, W. F. 1959. Effects of impoundments on dissolved
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