Although widespread snowfall in Colorado’s high country recently has added significant amounts of moisture across the state, researchers from Colorado State University’s Colorado Climate Center warn that the effects from one of the hottest, driest years in state history are far from over.
"The 2002 drought is behind us and we have started on a wetter than average beginning of the water year," said Colorado State atmospheric science professor and State Climatologist Roger Pielke Sr. "However, the reality is that many of the effects of this drought, just like many of Colorado’s past extreme droughts, will likely last several years, even if precipitation returns to average or even above average. Making up the current water supply deficit in the next one to two years is unlikely and Colorado should be prepared for at least one more year of drought effects even with abundant precipitation. With a dry winter and spring, serious drought can quickly return."
Climate Center researchers are quick to emphasize that, even with the recent snowfall, the drought remains ongoing, especially in terms of reservoir storage supplies and deep soil moisture. More than one hundred year’s worth of historic data at the Climate Center show that it usually takes several seasons to recover from an extreme drought of the magnitude of the current year.
Following a dry and mild winter, the 2002 drought hit all areas of Colorado, destroying wheat crops and devastating cattle herds, triggering numerous, large wildfires and draining municipal water supplies. For certain water needs across the state, such as Colorado’s dryland wheat industry, recovery from the drought can occur quickly with regular and well-timed storms in the fall, winter and spring.
However, complete statewide recovery is much more difficult because the state would need to receive average or above average precipitation over the next several years. Additionally, some parts of the state likely will recover more quickly than others – it would be rare for the entire state to recover at once.
"No one predicted the 2002 drought. This drought year also demonstrates that we have not given enough thought to coping with a multi-year drought," said Pielke. "Our experience this past year demonstrates that the state’s water managers and communities need to work together to develop more effective plans for long-term irrigation and municipal water use. For the near future, water conservation and water use efficiency measures should be continued throughout the winter months to help ensure, as much as possible, adequate water supplies next spring."
Part of the problem is that Colorado’s reservoirs are so depleted that an average snowpack and precipitation year will not replenish the water supply. Much of the precipitation that falls this winter will be absorbed by the extremely dry soils and replenish shallow aquifers instead of running into already low reservoirs. The Natural Resources Conservation Service shows Colorado’s reservoir storage at approximately 48 percent of average.
According to Nolan Doesken, climate researcher at the Colorado Climate Center, it could take three or more years of average or above average precipitation to restore some of Colorado’s largest reservoirs to being close to average storage levels, given that the precipitation comes in winter and spring.
"It is only November, Colorado remains in a serious drought and fall weather patterns rarely persist throughout the coming winter and spring," said Doesken. "At this point, we need a lot more moisture, both at low elevations and in the high country, to interrupt this drought. But, the current trend is certainly in the right direction."
The Colorado Division of Water Resources agrees, stating that exceptional snowpack in the upcoming winter would be required to bring the state’s Surface Water Supply Index numbers back to a normal range due to very low soil moisture which will cause reduced river flows next spring. The index, an indicator of mountain-based water supply conditions in the major river basins of the state, is based on stream flow, reservoir storage and precipitation from May through October. The current index shows all of Colorado remaining in drought conditions.
NOAA’s U.S. Seasonal Drought Outlook, released Oct. 31, concurs showing the entire state remaining in drought, severe drought or extreme drought conditions. The drought outlook through January 2003 calls for ongoing drought conditions with some ongoing improvement expected.
The 12-month period of September 2001-August 2002 was determined to be the driest on record for Colorado back to 1895, based on preliminary data from the National Climatic Data Center. Of the eight climate divisions used in a separate Climate Center analysis, several also had their driest 12-month period from Sept. 1, 2001-Aug. 31, 2002 in more than a hundred years of record-keeping. For many Colorado cities and towns, the past year was the driest in more than a century.
"It was a very severe one-year drought and an exceptionally dry and warm one-year period that Colorado fortunately does not witness very often," said Pielke, who recently led a study that showed the past year was even drier for many locations in Colorado than any one year of the 1930s Dust Bowl period.
To determine how the 2002 drought compares to other drought years, Pielke and a team of Colorado researchers analyzed precipitation records from 15 Colorado cities and towns across the state, comparing data back to the 1890s. In all cities and towns studied, the September-August period was among the top 10 driest periods on record. In nine of the 15, it was the absolute driest.
As a result of this year’s drought and hot temperatures, 101 Colorado cities ended up on water-quality watch lists at the Department of Health, as low stream flows intensified contaminant levels normally diluted by snowy mountain runoff. More than half the dry land wheat crop was lost and one-third of the state’s cattle were sold due to low-water conditions. Some estimates state the drought will cost Colorado more than $1 billion, with tourism and agriculture the hardest-hit industries.
The Colorado Climate Center is compiling a comprehensive year-end summary of the 2002 drought, which will be posted by Dec. 6 on the organization’s Web site at climate.atmos.colostate.edu/.
The site also provides access to current drought data and other weather-related information. Through its threefold program of climate monitoring, climate research and climate services, the Colorado Climate Center, housed in Colorado State’s Department of Atmospheric Science, provides information and expertise on weather and climate patterns for the state of Colorado.