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f. Impoundment Destratification for Raw Water Quality Control Using Either Me- chanical or Diffused-Air Pumping. g. Influence of Artificial Destratification on Plankton Populations in Impoundments. h. Control of Reservoir Water Quality by Engineering Methods. An extensive bibliography on "Artificial Destratification" is given following lhese papers. Another publication which is related to the Public Health Service project is a state of the art paper by Symons and others (I 969) which summarizes and adds. to the previously cited information. This paper discusses destratification results on a few lakes and describes a suggested methodology for estimating the capacity of equipment required for destratification. The second method discussed (the DE method), is based upon calculating the theoretical minimum amount of energy required to destroy a thermocline (the stability) and multiplying this by a factor which was required on previous field trials. This method appears to be suitable for destratification for evaporation studies. The results reported indi- cate a DE (destratification efficiency = theoretical minimum/ actual energy) varying from 0.2 to 1.5 percent by diffused air, depending on the season. The authors recommend a design DE of 0.5 percent for the diffused air method and 0.1 percent for mechanical pumping of water. This indicates a much better efficiency for the diffused air method than for mechanical pumping of water on the reser- voirs studied (which were only 40 to 60 feet deep). Figure 4 shows the pattern of circulation which is achieved during a destratification operation. An American Water Works Association Committee. also chaired by Symons, has gathered and summarized the results of a survey of 33 water suppliers who have destratified their reservoirs. The responses from 29 of these reservoir operators have been reproduced by the committee (A WW A, 1971) and summarized as a Committee Report (Symons. Committee Report, 1971). This report was particularly useful in this research because of its cost and energy requirement data which will be discussed later. The agencies responding to this survey were mostly in the U.S. but included two foreign reservoirs. The purposes of destratification included taste and order control (45 percent), increasing dissolved oxygen (37 percent) and various other mineral and algal control purposes. The methods of destratification included six different categories but all involved pumping of either air or water and the predominant method was air (55 percent Diffused Air and 33 percent Commercial Air-Aqua System). Most of the energy sources were electrical (83 percent) with various fossil fuels making up the balance. '1 PUMP DISCHARGE~AFT , , ~ ,"-- '-~';/ ~rno/~" ....>+L~;II "~"";:'){" .," ."Y\""'-_~'" ~,:....:': -0.'.-.,',., -.'-,' . . , - . . CUR!:l~T 9.F'.CI~~ ." " ". ,,' " .to. ',"', ',-" ".:> ", ,\ -r "_. '," :::; "c. . :t: ':~j~;~l '". "-"; '~'. , . :.~.\.i>,} ~':h ':.i'~, .-.,' Figure 4. General deotratIflcaUon ocbeme (after Symons, 1969). 6