(Fort Collins-AP) -- This year's drought has been called the worst in a century. But officials really don't know when the state has been this dry because weather data only goes back a hundred years.
But an engineer with a water consulting company in Boulder says his study of tree rings suggest the northern Front Range is having its driest year since 1725.
Lee Rozaklis studied the Boulder Creek basin and was able to piece together a 297-year history of the area's water.
Trees typically grow little in dry years, leaving different degrees of thin ringlets.
Rozaklis pinpointed 1725 as the driest year by comparing the ringlet patterns from the various trees and matching those results against the available historical record.
He also found other periods of drought that lasted years.