September Drought Update: Rain and Snow Bring Some Statewide Relief: However, Drought Unlikely to Subside by Spring

The last few weeks have brought the closest thing to statewide drought relief that Coloradoans have seen this year as rain fell throughout the state accompanied by cool temperatures, high humidity’s and the first high elevation snow of the season. However, even with a wet fall and above average snowfall this winter, experts at Colorado State University’s Colorado Climate Center warn that the resources for most water users will not likely recover from the drought by next spring.

"It is, of course, possible that we will have heavy snows this winter and there is a reasonable chance for widespread precipitation as we move into autumn," said Roger Pielke Sr., state climatologist and professor of atmospheric science at Colorado State. "But if we receive just an average or below average snowpack, with respect to municipal and irrigation water needs, we are not going to come out of this drought within the next year."

According to Pielke, for Colorado to truly catch up would require the state to receive well above average precipitation over the next several years. More than 100 year’s worth of historic data show that it usually takes several seasons to recover from an extreme drought of the magnitude of the current year. Additionally, even with heavy winter snowpack, some parts of the state would likely recover more quickly than others, but it would be rare for the entire state to recover at the same time.

"The bottom line is that making up the current water supply deficit in the next 1-2 years is unlikely. Colorado should begin preparing now for a second year of severe drought in 2003," said

Pielke. "If we do receive copious precipitation, we will be fortunate, but it is prudent to prepare for the worst case drought situation that is possible based on the past climate history of the state. Agriculture and water resource specialists should already be starting their contingency planning."

NOAA’s U.S. Seasonal Drought Outlook report, updated Sept. 19, reiterates this point by stating that areas with serious water shortages may not be out of danger even with average snowfall amounts this winter. The report further shows that Colorado’s current drought conditions are split horizontally through the middle of the state, with most of southern Colorado reported as in an ongoing drought with some expected improvement, and the majority of northern Colorado experiencing drought conditions that are expected to persist or intensify.

Experts at the Colorado Climate Center Current Colorado state that statewide precipitation deficits are about 60-100 percent of a full year’s average precipitation, depending on the precise location in the state. Over the course of the last three years, many areas of Colorado have only received two years worth of precipitation, based on long-term averages. Of the eight climate divisions used in Climate Center analysis, several had their driest 12 month period from Sept 1 to Aug. 31 in more than 100 years of record.

"Fortunately, for several water needs across the state, making up the entire deficit to recover from the drought is not necessary," said Nolan Doesken, research associate at the Colorado Climate Center. "For example, dry land agriculture can come close to full recovery with only slightly above average precipitation, especially if those excesses come in the fall and the spring. Some areas of Colorado have greened up noticeably in response to recent rains and it has definitely lifted the spirits of some residents of eastern Colorado."

Doesken added, however, that large river and reservoir systems recover from drought much more slowly, and that late summer and fall rains also contribute little to stream flow or reservoir levels. According to a Colorado Division of Water Resources September update, streams continue to flow at record low levels, some being completely dry in spots. Many reservoirs, especially those used for irrigation, are empty and the statewide average reservoir content is approximately 48 percent of average.

Much of the precipitation that falls this winter will first recharge soil moisture and shallow aquifers instead of reservoirs. Therefore, with average snowpack, Coloradoans should still expect below average runoff and surface water supplies for next year.

"It could take two or more years of average or above average precipitation to restore some of Colorado’s large reservoirs to being close to near average storage levels, given that the precipitation comes in winter and spring," Doesken said.