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. . . nDJ~08 CHAPTER V WATER Irn30URCES confluence with the Colorado River at a point about 15 miles northeast of Moab, Utah. When the creek was flowing 55 gallons per minute in June 1966, its salt concentration was 9,120 p.p.m. Onion Creek waters are not used for irrigation because of high salinity. Salt-laden water seeps into a 200-yard-long section of Castle Creek about 2 miles abave the creek's junction with the Colorado River about 10 miles northeast of Moab. About 2.9 tons of dissolved solids daily are estimated to enter the river from this source. While most of the irrigation from Castle Creek is above the point of salt entry, a small area located downstream near the Colorado River is successfully irri- gated from the creek. McElmo Creek, which JOlns the San Juan River near Aneth, Utah, con- sists mainly of return flows from irrigated lands in Montezuma Valley, Colo. Although containing relatively high concentrations of soluble salts, the creek water is used successfully for irrigation on lands that have ex- cellent internal drainage characteristics. Present Water Uses Waters of the San Juan Area are used primarily for irrigation, munici- pal, and industrial purposes. Recreation and fish and wildlife uses are also important but as a rule do not consume appreciable quantities of wa- ter and are generally incidental to other uses. Stock watering likewise is important. If water for livestock is not otherwise available, it is developed by various means on grazing ranges and other places of need, but quantities are not great. Irrigation Approximately 17,500 acres are irrigated in the study area, includ- ing 13,300 acres in Utah and 4,200 acres in Colorado. Not all of these lands are irrigated every year. In 1967, for instance, a year of below- normal spring runoff, only about 13,100 acres were irrigated. There has been essentially no expansion of irrigation in the past 30 years. Surface water is used at times on about 16,350 acres of irrigated land, ground water on 700 acres, and both surface and ground water on 450 acres. Ground water is used on land in West Paradox, Castle, and Spanish Valleys and along Montezuma Creek. Only about 450 acres are irrigated from rivers of the area--Dolores, San Juan, and Colorado. These lands experience no water shortages. About 10,000 acres are irrigated from streams heading in the La Sal Mountains and 6,350 from streams heading in the Abajo Mountains. Data on irrigated lands in the study area are tabulated on the fol- lowing page. The location is designated by area descriptions used in 53