A DENDROHYDROLOGICAL RECONSTRUCTION FOR THE WALKER RIVER WATERSHED (EASTERN SIERRA NEVADA/WESTERN GREAT BASIN, USA) USING NEW MODELING TECHNIQUES

High-resolution models that address the data needs of wildlife and water resource managers include reconstructions of hydroclimatic variability with seasonal to annual resolution over several centuries, since these long-term records are ideal to determine the historical range of variability of moisture conditions in specific habitats and of surface water resources in specific watersheds. Tree-ring records recently obtained from single-needle pinyon (Pinus monophylla) stands were used to extend the instrumental record of hydroclimatic variability in the Walker River basin, at the boundary between Nevada and California. Two different ring-width standardization methods, one based on cambial age (the “C-method”) and one based on a cubic smoothing spline with a known frequency response, were used to produce two sets of tree-ring chronologies from the increment core samples. The C-method has been found to provide a theory-based alternative to the empirical “conservative” standardization option, and to perform equally well as the well-known Regional Curve standardization method. Available tree-ring series for the Walker River basin span the past 4-5 centuries at annual resolution, and the record extension model REXTN, which includes both a noise term and an autoregressive term, was used to perform the reconstruction. The dendrohydrological time series is presented, and its features are discussed and interpreted in terms of dry/wet episode duration, magnitude, and peak. This approach allows for a quantitative representation of the likelihood of droughts or pluvials that can be expected in this region.