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Show PART IX PRESENT WATER USE Incidental use on water-consuming, noncropped areas was charged on those areas which consume water incidental to the cropped lands as a result of the practice of irrigation. Incidental consumptive use was estimated at 315,600 acre-feet or 18,6 percent of the consumptive use by irrigated crops. Incidental water use values for New Mexico and Utah are the figures in the 1948 Upper Colorado River Compact Commission's Advisory Committee Report. Recent survey data from the Wyoming State Water Plan was used for Wyoming. Colorado data are from recent Type IV River Basin Cooperative Studies by the Colorado Water Conservation Board and the U. S. Department of Agriculture. Incidental water use in Arizona was estimated at 10 percent of consumptive irri- gation requirement. Reservoir Evaporation Evaporation from 309 irrigation reservoirs for 1965 normalized conditions was 138,600 acre-feet. These reservoirs provide 2.77 million acre-feet of usable capacity for regulation of streamflow. The 1965 normalized evaporation on reservoirs is based on operation studies under normal operating conditions. Data have been adjusted where available to reflect average conditions that may not have existed during 1965. On many reservoirs operational data are not available and estimates were made using general relations of supply and demand. Of the amounts shown above, evaporation from regulating and exchange reservoirs used in connection with export was 23,700 acre- feet. Storage in the 8 1/3 reservoirs used for this purpose was 1,182,200 acre-feet. The fraction shown allows for one-third of the storage of Green Mountain Reservoir for export purposes, the balance of storage is for irrigation. Evaporation loss from main stem regulating reservoirs (Flaming Gorge, 67,000 acre-feet, and Lake Powell, 576,000 acre-feet) for 1965 normalized conditions was 643,000 acre-feet. It should be noted, however, that these evaporation losses will be charged against the separate States only if curtailment of use is required in the Upper Colorado River Basin to make delivery required by the compact at Lee Ferry. The 1965 normalized evaporation on the reservoirs is based on Bureau of Reclamation operation studies under normal operating conditions . Imports Inflow to the region through a transmountain diversion from Sevier River in the Great Basin to Paria River averages 2,600 acre- feet. This represents a credit against local use within this region. 44 |