NOAA's National Geophysical Data Center is studying tree ring data from the past 300 years to gather information on Clear Creek, the main source of water for the City of Westminster, Colo., Connie Woodhouse, of the center's paleoclimatology program, told scientists at the annual meeting of the American Meteorological Society in Albuquerque, N.M., today.

The information, which provides insight into the duration, severity, and magnitude of drought, is useful in water resource management. NOAA hopes to provide estimates suitable as input for hydrologic forecasting models.

In the study, total annual streamflow was reconstructed from tree ring chronologies over a 300-year period. The tree ring data were compared with data from the instrumental record for the period 1912-1980.

Woodhouse found that in the 20th century, the most extreme low flow periods coincided with the droughts of the 1930s and 1950s. In the 1930s event, annual flow was below average for eight consecutive years. In contrast, the 1950s low flow event lasted only four years, 1953-1956, but the cumulative negative effect was similar to the 1930s event.

NOAA's paleoclimatology program uses data from sources such as tree rings, corals, ice cores and sediments, to provide climate scientists and resource managers with records of past climatic variability and change extending back centuries and millennia. These paleoclimatic data are a valuable complement to the much shorter time series derived from instruments and satellites. Paleoclimatic data are used to describe the full range of climate variability, to identify and understand the causes of this climatic variability, to evaluate and improve predictive climate models, and to improve the ability to separate human-induced climate change from natural climate variability.

For more information on NGDC, see: http://www.ngdc.noaa.gov