Characteristics and Spatial Variability of Droughts in Idaho

Abstract

An application of run theory to annual streamflow sequences in Idaho permits the assignment of return periods to historical drought events, based on the statistical characteristics of the streamflow record. For 63 stations with historical record lengths exceeding 30 years, several major periods of streamflow deficit have occurred, with return periods significantly greater than might be expected from a random sample of the long‐term stochastic process. Since drought severity is shown to be a function of spatially‐dependent statistics, a regional pattern to this severity is defined in terms of a drought potential index (DPI) which indicates the 100‐year return period deficit for flow periods less than the mean annual flow. The mapped DPI values vary significantly throughout the state, with several regions showing a much greater potential for persistent, severe streamflow deficits.