| OCR Text |
Show Evaporation is Major Loss From Reservoirs of Utah Twelve times as much water is lost by evaporation from fresh water reservoirs in Utah as will be developed by the total Bonneville Unit of the Centra Utah Project. The May through October loss on nine reservoirs In Central Utah is over 22,000 acre feet enough to irrigate 7,500 acres of farm ground for a summer season. Saving part of the evaporation loss would mean vast new stores of water for irrigation, hydro power and cooling fossil fuel electrical generators. Past efforts to retard evaporation have not proved to be technically or economically feasible. But a Utah State University engineer says there is a way to do it at low cost. The method, according to Trevor C. Hughes, associate professor at the Utah Water Research Laboratory, is a byproduct of procedures already in use in the United States and Europe to improve water quality. It is called thermal destratification. That simply means mixing the colder bottom layers of water with warmer top layers. The cooled surface water evaporates more slowly so water is saved. "Several municipal water supply agencies in the United States and Iurope have been destratifying their reservoirs in recent years to improve water quality by increasing dissolved oxygen. This results In method will suppress evaporation. They have tested side benefit decreases evaporation," Hughes says. The water is mixed by pumping air to the deepest part of the reservoir. As the air bubbles to the surface it carries with it enough colder, more dense water to start a mixing current. A surprisingly small amount of energy Is required to get the current moving, he explains. The procedure has been followed on Hyrum Reservoir by USU researchers to retard algae growth and that was lowering water quality?" Existing theory convinces Hughes and his co-workers, E. Arlo Richardson, state cllmatologist, and graduate student James A. Fran-ckiewicz, that the mixing method waill suppress evaporation. They have tested it on specially cooled evaporation pans which were compared to a standard pan. They consistently measured less evaporation from the cooled pads. The project team gathered water temperature profile data from 16 Utah reservoirs last summer. This information was used to develop a mathematical model which has estimated the potential of the concept on over 80 other reservoirs in Utah. Results indicate that 20 to 30 percent of the summer evaporation can be eliminated on the deeper reservoirs in Utah. The study shows that the savings on the central Utah impoundments would be more than 10 percent of the anticipated loss, or a total of 2,338 acre feet. That means that nearly 800 acres of ground could be irrigated with the water that could be saved from evaporation by Hughes' mixing procedure. The researches' figures show that the savings on the reservoirs would be as follows: Sevier Bridge Reservoir 9.7 percent of the six; month (May-October) evaporation loss, or 9S1 acre feet; Mona Reservoir 9 6 percent, 404 acre feet; Electric Lake 19.6 percent, 103 acre feet; Huntington 5.2 percent, 15 acre feet; Miller Hat 7.8 percent, 14 acre feet; USU Engineer Trevor Hughes, right, and graduate student James Franckiewicz examine evaporative pans used in a study of water loss from Utah reservoirs through evaporation. Cleveland 3.4 percent, 5 acre feet; Millsite 14 percent, 122 acre feet; Joe's Valley 18.5 percent; 268 acre feet; Fish Lalte 9.1 percent, 456 acre feet. In addition to conservation of irrigation water on Utah reservoirs, the concept has Important potential in terms of water for energy development. "Any means of significantly increasing the quantity and or quality of water in the Colorado River Basin should be of considerable value, not only to the Colorado River region but to the entire nation because of the corresponding increased supply of water available to energy production," Hughes points out. Average annual evaporation on Lakes Mead, Powell and Flaming Gorge totals about 1.6 million acre feet. Destratifying those substantial bodies of water would be a major undertaking, the USU researcher admits. But he's convinced the benefits would easily justify the effort. For emaple, if 22 percent of the annual evaporation on Lake Powell could be prevented as the researchers predict it could, the added hydro power generated would be 3.3 times the energy required to accomplish the water conservation. This means the method could add significantly to the hydro power generating capacity of the lake. Hydro power is economically efficient in terms of dollars per kilowatt hour, but requires consumptive use of water (by evaporation from the lakes backed up behind the hydro power generating dams) that is much higher than other energy sources such as fossil fuel-fired generator, he points out. This is particularly serious in the Southwest, he says, where evaporation is high and water may be the limiting production input to energy development. Not only does the water evaporating from the lakes on the Colorado system represent hydro power loss, but it also limits water availability for fossil fuel energy development. There is another advantage to saving the water. A treaty between the United States and Mexico requires 1.5 million acre feet of annual flow to Mexico. Recently the increasing salt content of the water flowing to Mexico has become a cause of stress between the two nations. If water saved from evaporation were added to the flow to Mexico the salt content would.be deluted. The U.S. recently agreed to construct a desalination plant at Yuma, Ariz., to remove some of the salt. Dilution could eliminate the need for the plant, and simultaneously add to the hydro power supply rather than adding a major new energy demand, Hughes points out. |
