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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DISSOLVED OXYGEN-PPM DISSOLVED OXYGEN-PPM
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PILOT STUDY OF DYNAMICS OP
RESERVOIR DESTRATIFICATION
AVERAGE ANTECEDEN
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T OP
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U.S. DEPARTMENT OF THE INTERIOR
CEC£RAL WATER POLLUTION CONTROL ADMINISTRATION
KOPENT S. KER* »n* ttaAWOMA
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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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JULY 25,1967




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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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                                                                19




                         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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                                                                  20
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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                                                                21




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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                                                                22




                      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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1.   Irwin, W. H.,  J.  M.  Symons, and G.  G. Robeck.  1967.  Water




     quality in impoundments and modifications from destratifi-




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     Cincinnati, Ohio.




2.   Symons, J. M«, W. H. Irwin, E. L. Robinson, and G. G. Robeck.




     1967.  Impoundment destratification for raw water quality




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3.   Symons, J. M., W. H. Irwin, and G.  G. Robeck.  1967.  Reservoir




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     Vol. I.  New York, John Wiley & Sons, Inc.

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 9.    Welch, Paul S.   1952.   Limnology.   2nd edition.  New York,




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