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II. Hydrologic Description of the Drought <br />The current drought, which began in 2000 and has continued to the present, has been the <br />most severe on record by several measures. Streamflows in Colorado in 2002 have <br />generally been the lowest in over 100 years and the tree ring data suggest that flows are <br />probably the lowest in 300 to 500 years. In terms of multiple year streamflow deficits, <br />the current drought is worse than the historic droughts of the 1950s and 1970s. While <br />this drought has not lasted as long as the drought of the 1930s, it is not yet over and it has <br />been more severe than any three -year period of the 1930s. <br />A. Conditions in the Spring of 2002 <br />1. Snowpack <br />By mid - winter of 2002, Colorado - like most of the interior West - was in its third year of <br />drought. In February snowfall across the state was well below average. It marked the <br />sixth consecutive month with below normal snowfall and resulted in a continued decrease <br />in the state's snowpack. The readings indicated the statewide snowpack was 56% of <br />average, down slightly from January's 58% of average. The lowest percentages (less <br />than 50% of average), occurred in the San Juan, Animas, and Rio Grande basins of <br />southwestern Colorado, and the South Platte headwaters and Saint Vrain basins in <br />northern Colorado. The highest snowpack percentages were measured in two Colorado <br />River tributaries, the Williams Fork and the Blue River, both at 73% of average. <br />Elsewhere across the state, readings ranged from 50% to 70% of average. In 2002 <br />Colorado was in its fifth consecutive year with below average conditions on March 1. In <br />the San Juan, the hardest hit basin, snowpack had dipped to only 28% of the previous <br />year's. <br />The statewide snowpack percentages continued their steady decline during March. On <br />April 1 readings were only 53% of average, statewide. Not since the drought year of <br />1977, when the state had only a 46% of average snowpack, had conditions been this poor. <br />(Figure 11. 1.) Again, the lowest percentages were found across southern Colorado. The <br />combined San Juan, Animas, Dolores, and San Miguel basins reported the lowest <br />readings, at only 34% of average. The Rio Grande Basin, at only 38% of average closely <br />followed. Also, the Arkansas Basin saw its percentage decrease sharply to 48% of <br />average. Conditions were somewhat better in the north, but remained low. The state's <br />best snowpack occurred across the Colorado and North Platte basins, both reporting 63% <br />of average readings. During late March, warm temperatures induced rapid snowmelt at a <br />number of measuring sites. <br />Snowfall across Colorado during April, normally the second snowiest month, was <br />unusually low and temperatures unusually high. As a result, snowpack steadily declined <br />throughout the month leaving the state with only 19% of its average on May 1, a record <br />low, dipping 2 percentage points below the previous record measured on May 1, 1981. <br />The lowest percentages in individual basins were again found in southern Colorado, with <br />the Rio Grande and combined San Juan, Animas, Dolores, and San Miguel basins both <br />�1 <br />