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46 , HYDROLOGIC AND HUMAN ASPECTS OF THE 1976-77 DROUGHT River near Bluff, Utah, 50 mi west of the Four Corners, would have been dry in July 1977 if releases from Navajo Reservoir had not been made. Numerous thunderstorms during the latter part of July in Colorado increased the flows significantly, some enough to reach the normal range for a few days during the last week in July. The annual runoff for the 1977 water year at four index gaging stations in Colorado was the lowest of record for periods ranging from 31 to 69 years. Frequency relations of annual flows for these four sites indicate that the drought in 1977 was the most severe since the area was settled. Though the annual runoff of the Yampa River at Stream boat Springs, Colo" for the water year 1977 was only 4 percent less than that in 1934, the timing of the runoff was different. The October to March runoff in 1977 was 66 percent of that in 1934, a difference of 13,550 acre-ft, because the carry-over effect from 1933, an above normal year sustained the flow in 1934; whereas, the flow in 1977 was less because 1976 was a below normal year. The opposite occurred during the months April to September when runoff in 1977 was 8,920 acre-ft more than during the same months in 1934. Storage was reduced to record low amounts in many reservoirs. By the end of June 1977 storage was down to 25 percent of capacity in a reservoir from which Cortez, in south- western Colorado, obtains its water supply. Another reservoir in the area had only 15 percent of capacity and a third was dry-all at a time of year when they are normally nearly full. At the same time, the primary water supply for Price, Utah was exhausted, and the city had to depend upon Schofield Reservoir which was only half full, By September 30, 1977, storage in Flaming Gorge Reservoir on the Green River at the Wyoming-Utah State line was only 76 percent of average. The decrease in storage since September 30, 1975 in Flaming Gorge Reservoir and in Lake Powell on the Colorado River at the Utah-Arizona State line was 5.63 million acre-ft, and 86 percent of this occurred in 1977. The storage reservoirs for the Colorado-Big Thompson Project are near the headwaters of the Colorado River. Runoff into them in 1977 was only 124,000 acre-ft or 52 percent of average, but the transmountain diversions to the South Platte River basin on the eastern side of the Rocky Mountains amounted to 309,000 acre-ft or about 140 percent of the average annual diversion. Contents of Shadow Mountain Lake were held within a narrow range during the 1976 and 1977 water years, but storage in Lake Granby was reduced 269,100 acre-ft in the 2-year period. Ground-water Conditions The direct effect of the drought on ground- water levels with respect to reduced recharge was masked by the effects from increased pumping. There are only five areas in the Upper Colorado Region in Utah where ground-water use is significant, and major development has occurred only in the one near Loa in south- central Utah. The average withdrawal of ground water is 23,000 acre-ft and during the drought years this was increased to 35,000 acre-ft in 1976 and 37,000 acre-ft in 1977. During 1977, about 300 wells were drilled, and of these 50 were large withdrawal wells, The maximum decline in water levels from limited data in Utah was 8.6 ft near Loa, In Colorado, changes in ground-water levels in 1976 and 1977 were within the range exper- ienced in other years. The discharges of springs were noticeably low, but the overall effect of the drought on ground water was minimal, Water Quality Minor changes in dissolved-solids concen- trations were observed in many streams, but these were similar to the changes that occur in nondrought periods. The reduced flows in some streams were not sufficient to flush and dilute contaminants or the return flows from irrigation. The lower peak flows and annual runoff were accompanied by reduced sediment dis- charge on many streams. Activities Resulting from the Drought A large proportion of the water supply for the Denver metropolitan area comes from the upper Colorado River basin via transmountain, inter-basin transfers, Because of the drought