Projects by Discipline / Water Resources Engineering

City of Boulder Tree-ring Study

The City of Boulder’s water supply largely depends on streamflows in Boulder Creek, which have been recorded since about 1910.  These records show that annual streamflow volumes varied greatly and that droughts of various severity occurred during this period.  Until recently, Boulder’s ability to assess the vulnerability of its water supply system to droughts was limited to this 90-year period of record.  

Tree-ring records have proven to be useful in extending our knowledge of streamflows back in time and providing valuable insights to the long-term variability of streamflows. This is possible because the widths of individual growth rings of properly selected trees generally mimic the variation of annual flow volumes in nearby streams.

Scientists at Hydrosphere and the National Oceanic and Atmospheric Administration (NOAA) collaborated to identify several tree-ring records that are well correlated to natural flows in Boulder Creek and then generated estimates of streamflows in Boulder Creek that extend back as far as 1703.   These data have provided us with an enhanced perspective on the current drought. They show that this year’s (2002) streamflows are probably the lowest that have occurred during the last 250 to 300 years.  They also suggest that droughts lasting more than 15 years have occurred several times within the past 300 years.

The City of Boulder is using this information to better assess the adequacy of its water supply system and to improve its drought response strategies.  Taking advantage of the knowledge gained from tree-rings will undoubtedly benefit other communities throughout the West in their water supply planning efforts. 

Other Tree-ring web sites:

NOAA Paleoclimatology Program Tree-Ring Home Page

Henri D. Grissino-Mayer's Science of Dendrochronology Web Pages

Listen to the KUNC Radio Interview with Hydrosphere's Lee Rozaklis (mp3 file-2.9M)

Read the Associated Press news story dated September 23, 2002 as published in the Boulder Daily Camera.