Thursday, 13 February 2003: 11:45 AM
Using dendrohydrologic data in Colorado water resource planning and management
Colorado, along with much of the intermountain western United States, has experienced severe drought conditions across the state in 2002. The drought, preceded by several years of near to below average snowpack, has resulted in statewide projected water-year streamflows that range from 58% to less than 10% of average, lower than any other year in the instrumental record. Until now, drought planning in much of Colorado has prepared for 1950s-like drought conditions, but planners are now questioning whether that drought is an adequate "worst-case scenario." If the 2002 drought continues, it may exceed the overall severity of the 1950s drought and the recurrence interval of this 2002 extreme drought will need to be established. The instrumental record is too short for this task, but extended records of streamflow, reconstructed from tree rings, will allow an assessment of the reccurrence of this extreme drought in the context of 300 to 700 years of hydroclimatic variability. In this study, we have partnered with five major Colorado water utilities and management agencies to determine the most useful applications of dendrohydrologic data in management and planning. Drought is the foremost concern and we are exploring ways to use tree-ring reconstructions of streamflow, drought, and precipitation to place the current drought in a long-term perspective. We are also investigating other types of extremes in natural hydroclimatic variability over past centuries. Differences in drought conditions among basins are of particular interest because several large water utilities draw from water resources in basins both east and west of the Continental Divide. Reconstructions of hydroclimatic variability at the basin level will help determine the spatial and temporal variability of past hydrologic extremes and identify possible climatic controls on drought.