Drought, Tree Rings, and Water Resource Management in Colorado

Bridging the gap between scientific knowledge and the application of this knowledge to resource management is a challenging task. Recently, a major drought in the western United States provided a “window of opportunity” to address the application of paleohydrologic data to water resource management. This drought played an important role in reminding water providers and resource managers that droughts are a natural part of the climate and that understanding the range of natural drought variability is critical for long-term planning. In Colorado, the water year 2002 was of particular concern to water providers as flows were the lowest on record at many gauges. The frequency of occurrence of this extreme event could not be assessed with the length-limited gauge records. This motivated water managers to examine the longer records of hydroclimatic variability provided by proxy data from tree rings. The interest in the information derived from tree-ring records provided an impetus for collaborations with a number of water providers, both municipal and rural. The partnerships with two of these providers are described. At Denver Water, tree-ring reconstructions are being used directly as input to a water system model to assess the reliability of water supply under a broader range of conditions than afforded by the gauge record alone. For the Rio Grande Water Conservation District, the extended record of streamflow variability has provided more qualitative information relevant for placing 20th century hydroclimatic variability into a multi-century context.