Dendrohydrologic reconstructions: Applications to water resource management

Water resource planning is primarily based on 20th century instrumental records of climate and streamflow. Unfortunately, even the longest gage records capture only a limited portion of the range of natural hydrologic variability that is possible. Tree-ring reconstructions of streamflow (i.e. dendrohydrologic reconstructions) have proven to be useful for augmenting existing instrumental streamflow records. These proxy records of streamflow have provided an expanded temporal context from which to evaluate the 20th century instrumental record and have provided scenarios for events such as severe sustained drought impacting the Colorado River basin. Tree-ring reconstructions of hydrologic variability may provide more than an extended record of seasonal or annual variability. In this study, we are working with the City of Westminster (Colorado) water planners to tailor reconstructions and information from reconstruction to better meet water resource planning and management needs. Dendrochronological techniques have yielded a high quality reconstruction of total annual flow for Clear Creek, the sole source of water for Westminster. However, planners' needs would be better met with other products. Our efforts have been concentrated on methods to generate more accurate reconstructions of low flow and probability estimates for flow values for specified thresholds. Ultimately, we hope to provide estimates that are suitable as input for hydrologic forecasting models.