2007 Drought in Review
By Brian Fuchs, Climatologist, National Drought Mitigation Center
Drought of unprecedented intensity enveloped the Southeastern United States in 2007, while record-breaking rains ended drought’s grip on Texas. California got worse, while conditions improved in the High Plains and other parts of the West. Roughly the same proportion of the contiguous U.S. was abnormally dry or in drought at the beginning and end of 2007 – 50 percent in January, compared with 54.6 percent in December – but there were huge changes in the affected areas.
In January, upper Minnesota, the High Plains, the Southern Plains and Arizona had patches of extreme (D3) drought, with exceptional drought (D4) in an area of southwest Texas. At the start of the year, 5.9 percent of the country was in extreme or exceptional drought, compared with 5.8 percent at the end of the year. But at the end, the main areas affected were states in the Southeast and Mid-Atlantic, California, Nevada and Nebraska. The amount of exceptional drought increased significantly from just 0.3 percent of the United States in January to 2.4 percent in December.
The shift in drought areas is highlighted by the fact that the D3 and D4 regions in January were almost completely relieved of drought by the end of 2007. Minnesota had 40.9 percent of the state in D3 last January, with 96 percent of the state abnormally dry or worse. In December, just 39 percent of the state was abnormally dry (D0), with only 3.8 percent in moderate drought (D1). There was no severe (D2) or extreme status in the state. Texas was another state that recovered nicely from the drought of 2006-07, with record rainfall throughout the state. Texas had its wettest January to August period on record, with Dallas-Ft. Worth measuring 16.52 inches of rain in June and July. It was the wettest there since 1973, with 28 of the 61 days receiving measurable precipitation. In January, 75.9 percent of Texas was abnormally dry or in drought, compared to 48 percent in December. In January, 37.7 percent of Texas had D2-D4 drought conditions. No part of the state showed D2 or worse in December. Outside of a dry fall and early winter, Texas had one of its wettest years on record.
The High Plains saw a reduction in drought in 2007, though parts of the region were still in drought for the eighth consecutive year. In January, 73.1 percent of the High Plains was abnormally dry or in drought, compared to 53.2 percent in December. Areas of D3 drought shrunk from 14.3 percent of the region to just 0.3 percent during the year, with the last remaining pocket of D3 in western Nebraska. With the longevity of drought in this region, many long-term effects such as low reservoir levels will not improve without significant precipitation.
The 2006-2007 water year (October 1-September 30) was very dry in the western United States, with record low snowpack in many locations. California, coming off a very wet and bountiful 2005-2006 water year, experienced one of the driest years on record with the state having its driest November-April. Los Angeles ended up with the driest “rainy season” (July 1 to June 30) on record with just 3.21 inches of rain. This tally was the lowest since record keeping began in 1877. In January, 59.3 percent of California was abnormally dry or in drought, compared to 91.1 percent in December. California ended 2007 with 58 percent of the state in D2 or D3 drought, compared to none in January.
Heat was also a major factor in the expansion of drought in the West during 2007. Many locations set all-time record temperatures beginning in July. Boise, Idaho, set a record for the highest average monthly temperature at 83.1 degrees Fahrenheit in July, which was also its warmest month ever. Utah had its warmest August on record, while Reno, Nevada had its hottest August following a July that was the hottest of any month ever in Reno. The heat and dryness sparked numerous fires throughout the West during the summer months, and by late July, active fires were burning in northern Nevada, eastern Oregon, eastern Washington, Idaho, western Montana, and Utah. The largest fire ever in Utah burned 363,000 acres in the south-central part of the state, which started on July 6 and was not contained until the 16th.
The southeastern United States became the drought epicenter in 2007. January saw the Southeast with 47.8 percent of the region in D0-D2 status, with the majority of that just abnormally dry. At the end of December, 90.4 percent of the region was abnormally dry or in drought status with a high proportion in extreme and exceptional drought -- 19 percent was in D3 and 22 percent in D4. Many locations had record low precipitation for the year and annual deficits of 20 or more inches were common. Significant rains the last week of December brought welcome relief. Along with the dryness, heat was also a problem, with several months of above normal temperatures and extended heat waves. Long-term improvement in the region is not expected while La Niña is in place. It is expected to last through the first half of 2008.
Thanks to Doug Lecomte, Climate Prediction Center, who generated some of the statistical information used in this report.
© 2008 National Drought Mitigation Center