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~~'!.3~5 LITERATURE REVIEW E.aporatlon .upp.......lon-general Literature on evaporation suppression was reviewed and included in the bibliography of V olume I of this series and will not be repeated here. This literature is addressed almost entirely to the monolayer film concept. The exception to this is a growing number of papers concerned with suppression on very small impoundments, particu- larly for storage related to water harvesting. An important collection of papers dealing with water harvesting was cited in Volume I as a forth- coming Agricultural Research Service publication. This volume is now available and the more complete reference is included herein (ARS, 1975). Evaporation .upp.......lon by destratIDcatlon The literature contains only one paper which . discusses the concept of using destratification as a means of decreasing evaporation. This USGS Water Supply Paper by Koberg and Ford (1965) is addressed primarily to the mechanics of the thermocline itself and to destratification tech- niques for water quality purposes. However, four pages of the paper are devoted to an estimate of changes in the evaporation rate on Lake Wohlford, California, during 1962 due to artifical destratifica- tion. The authors appear to begin with the premise that destratification will decrease evaporation during the summer, but that in order to account for the resulting decrease in heat loss (heat of vaporization), the increased evaporation during later months will balance the amount of water salvaged during the summer. Their measurements, however, indicate a net salvage of 5 percent of the annual evaporation due to thermal mixing, Lake Wohlford has a maximum depth of 48 feet and therefore does not develop a strong thermocline. The authors state that the decreased surface area due to water level draw down during late summer and fall months may explain the unexpected net savings they measured. They appear not to have considered the large amount of additional heat carried from the outlet (a process which is separate from draw down itself) as contributing to the net savings. Limnology The nature of the thermocline structure in water impoundments has been treated in many works on lhe general subject of limnology and only two will be mentioned here. An excellent short treatment of limnology was written by 1. R. Vallentyne (1957). It includes a discussion of how the thermocline developes and describes an intuitively attractive method of quantifying the strength of the thermocline. The approach is to calculate a parameter called relative resistance to mixing at any depth as a function of water temperature gradient. This is a somewhat different approach than the stability calculation widely adopted in later literature. A monograph entitled "Man-Made Lakes: Their Problems and Environmental Effect" (Ackerman et aI., 1973) includes several papers on limnology of reservoirs in a Physical Limnology section. DeslratlDeatlon for quaI1ty obJectl.... There is extensive literature on the results of artificial thermal mixing of reservoirs for various reasons related to water quality improvement. The Public Health Service published a collection of papers resulting from a series of related projects under the title "Water Quality Behavior in Reservoirs" (Symons, 1969). The papers included on destratification are: a. Impoundment Destratification by Me- chanical Pumping. b. Impoundment Water Quality Changes Caused by Mixing. c. Managemeot and Measurement of Dis- solved Oxygen (DO) in Impoundments. d. Calculation Technique for Oestratifica- tion Efficiency. e. Water Quality in Impoundment and Modifications from Destratification. 5