Climate and Streamflow Variability Related to Surface Water Supply in the WesternUnited States

摘要

Interrelated hydroclimatic elements were investigated to determinecharacteristics of the spatial and temporal climate varibility in a five-state region in the Northern Rocky Mountains, covering the 1951-1985 period. The three primary hydroclimatic elements analyzed included total water-year streamflow (ST), winter (October 1-March 31) accumulated precipitation (PR), and April 1 snowpack (SN). Analysis of SN and PR data sets, from about 270 sites across the five-state study area, revealed that the 0.55 measure of variability isoline separated stable regions from unstable regions. Three basic and persistent patterns of annual SN values surfaced: years with a consistent anomaly over the entire region (wet or dry); years with a distinct north-to-south gradient; and average years. The long-term wet and dry periods experienced in the northern and southern regions of the five-state region are due to north-to-south gradient patterns.