Preliminary Reconstructions of Streamflow for Three Rivers in the Southern and Central Wasatch Front, Utah

Abstract

The management of water resources is important to nearly all aspects of life, particularly in a region as susceptible to drought as the Intermountain West. In order for water management plans to be effective and reliable, they must be created with an understanding of climate variability throughout the past. This study presents reconstructions of streamflow along the Wasatch Front in Utah, with a particular focus on the frequency of high-magnitude, long- duration periods of drought. These reconstructions were created through the well-established methods of dendroclimatology — the study of determining past climates from the width of tree rings3. Current water management plans in Utah County and the surrounding area are based on no more than 100 years of streamflow measurements. Climate reconstruction through the study of tree rings allows for an understanding of the climate patterns of this region hundreds of years beyond the extent of current records. To collect tree-ring samples, pencil- sized pieces of wood were extracted from the trunks by a mechanical hand drill, doing no harm to the trees. Samples were collected from six moisture-sensitive sites in northern Utah and principal components analysis was performed to extract the major modes of variability in ring width, which were then used as predictors of streamflow in linear regression models from the Provo and Weber Rivers and Big Cottonwood Creek, all important contributors to water resources along the urbanized Wasatch Front. Models for all three rivers were statistically significant, and the preliminary reconstructions suggest that periods of drought higher in magnitude and longer in duration than in the historical record have occurred in the past 300 years.