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<br />50 <br /> <br /> <br />0018"/i <br /> <br />being two additional cetyl alcohols, octadecanol, and dodE'ocanol (Crul1e <br /> <br />and Harbeck, 1960). A number of different methods .for dispensing <br /> <br />the materials to form a film on the water have also been tried and <br /> <br />new ones are currently being developed. <br /> <br />It is well documented that the films suppress evaporation but <br /> <br />great difficu.lty has been experienced in maintaining the film over <br /> <br />bodies of water exposed to the wind. Under lahoratory conditions <br /> <br />. where the film can be maintained continuously, reductions in evapo~- <br /> <br />ation up to 40 percent have been obtained but in open water the re- <br /> <br />ductions are much less. In the Lake Hefner, Oklahoma, experiments.. <br /> <br />as reported by the Senate Select Committee on Water ReBOUrCel1 (1960), <br /> <br />the measured .reduction was 9 percent over an 86-day period with a <br /> <br />m~ximum saving of 14 percent during one weekly period. Although <br /> <br />intensive efforts were made to maintain the film during the experi- <br /> <br />. ment, this was only partly successful due to breakup of the film <br /> <br />caused by wind. The same difficulty has been encountered in other <br /> <br />similar tests and appears to be responsible for the low saving rate <br /> <br />obtained under field conditions. <br /> <br />Koberg (1961) has reported on measurements of evaporation <br /> <br />reduction {rom stock ponds located in southern Texas 'made in coopera- <br /> <br />tion with the Texas Department of Agriculture and .the Southwest Re- <br /> <br />search Institute. Nine tests were conducted .onthe stock ponds using <br />