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The Orchard Mesa Division: The Orchard Mesa Irrigation District (OMID) operates and maintains the irrigation facilities in the Orchard Mesa Division delivering water to approximately 4,800 water users. The irrigated acreage of the OMID is approximately 6,900 acres (ac) (2790 hectares (ha)). The Orchard Mesa Division is located on the south side of the Colorado River. Water for the Orchard Mesa Division is diverted through the Grand Valley Diversion Dam and is conveyed through the Government Highline Canal up to the bifurcation at the inlets of Tunnel No. 3 and the Colorado River siphon. At the bifurcation, the water destined for the Orchard Mesa Division goes through the Colorado River siphon to the OMID Power Canal. About 17 cubic feet per second (ft3/s) (0.5 cubic meters per second (m3/s)) is delivered directly from the canal to irrigated lands. At the end of the power canal, the water is delivered to the OMID Pumping Plant and the Grand Valley Power Plant. The pumping plant consists of four hydraulically driven pumps which pump water into two different canals. The canals, totalling about 34 mi. (55 km) deliver water to 37 mi. (59 lam) of privately owned and operated laterals. The four hydraulically driven pumps use about 272 ft3/s (7.7 m3/s) to pump 171 ft3/s (4.8 m3/s) onto irrigated lands. The 272 ft/s (7.7 m3/s) used to power the pumps normally returns through the pumping plant/power plant tailrace to the upstream end of the 15-Mile Reach. The power plant consists of two units with one or both units operated depend- ing on the available supply of water. After going through the power plant, the water is normally returned to the 15-Mile Reach. At maximum irrigation-season diversion and usage levels, OMID can demand up to 460 ft /s (13 m3/s) for irrigation/pumping. The sum of all the water rights which could be diverted at the Grand Valley Diversion Dam is approxi- mately 1,720 ft3/s (48.7 m3/s), but due to a canal capacity constraint between the diversion dam and Tunnel No. 3, only about 1,620 ft3/s (45.9 M3 /s) can be diverted. This restriction limits the Grand Valley Power Plant to 310 ft3/s (8.8 in 3/s) during periods of peak irrigation demand. At less than full irrigation demand, up to 400 fees (11.3 m3/s) can be used to generate hydroelectric power. The 90 ft3/s (2.6 m3/s) shortage (400 - 310) is due to the capacity con- straint. Without this constraint, the Grand Valley Power Plant would receive 400 ft3/s (11.3 m3/s) throughout the irrigation season assuming water supplies were available. Consequently, if irrigation demand in the Garfield Gravity Division is reduced, up to 90 ft3/s (2.6 m3/s) of conserved water could be used for power generation. The Orchard Mesa Division facilities also include a check structure and by- pass channel located in the tailrace of the pumping and power plants and a supplemental pumping plant downstream on the Colorado River.