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<br />1.0 B A C K G R 0 U N D <br /> <br />1.1 THE W EAT HER <br /> <br />The 1976-77 winter season in Colorado was the driest on record since the <br />drought years of the early 1930's. By the end of January 1977, only isolated <br />portions of the State had received normal precipitation. Dry conditions were <br />most severe west of the Continental Divide (Western Slope) where cumulative <br />winter precipitation levels ranged between 11 and 48 percent of normal. <br />Cumulative precipitation levels were somewhat higher in the Eastern portion of <br />the State, averaging about 65 percent of normal. As time progressed through the <br />late winter months, conditions did not improve. The mountains and Western Slope <br />received some late winter snows while the eastern portion of the State experi- <br />enced drier conditions than it had during the early part of the winter, with the <br />cumulative effect on precipitation levels being negligible. <br /> <br />Under normal conditions, the spring runoff from melting mountain snows <br />provides approximately 75 percent of Colorado's water needs. However, as spring <br />approached in 1977, mountain snowpack stood generally just below 50 percent of <br />normal. (See Figure 1-1). The subsequent runoff was minimal, sustaining <br />average streamflow at-levels which were far below normal and, in many cases, <br />below record lows. Many streams and springs dried up completely. <br /> <br />The low streamflow levels which prevailed thr'oughout the State as a result <br />of the reduced winter snowpack were unfortunately not boosted by early spring <br />rains, prompting some to label the situation a "double whammy." In fact, the <br />most significant precipitation occurrence in the State during March 1977 was a <br />blizzard on the Eastern plains which must be considered more of a disaster than <br />a boon to moisture levels. Nine people were killed in the blizzard which <br />brought with it 60 to 80 mph winds which caused snow drifts of up to 25 feet, <br />extens ive power outages, severe wi nd eros i on to crops, and thousands of <br />livestock deaths. Ironically, precipitation levels were measured as high as 375 <br />percent of normal for the month of March in some of the areas most heavily <br />impacted by the blizzard. Nevertheless, March was a disaster for many Eastern <br />high plains farmers and ranchers; for others it was a near disaster. Dryland <br />farmers were on the brink of plowing under a winter wheat crop which had first <br />been thrashed by blizzard winds and was about to succumb to the lack of moisture <br />when, finally, the rains came. <br /> <br />April and May were good months for precipitation in the eastern portion of <br />the State. In fact, relatively wet conditions persisted in the east for the <br />duration of the summer. By the end of August, precipitation levels in most <br />eastern areas had reached or surpassed annual norms. <br /> <br />The changes in Western Slope conditions were not nearly as pronounced as <br />those in eastern portions of the State. Although most areas of the Western <br />Slope received substantial rainfall in July and August, the spring and early <br />summer had remained extremely dry. The net result was that Western Slope annual <br />precipitation levels remained significantly below normal, ranging between 44 <br />and 81 percent of the annual norm. <br /> <br />14 <br />