The historical potential of snowfall as a water resource in Arizona

Abstract

Central Arizona depends on spring snowmelt for a major portion of its annual surface water resource. Surface reservoirs supply an important part of the water used by a large, recently developed (in the last 30 years) and still expanding urban and agricultural community. Knowledge of the variability of the snowfall water resource is limited to U.S. Weather Bureau precipitation records from about 1900 and Soil Conservation Service snow course data from 1934, brief records when the variability of precipitation and the investment dependent upon them are considered. Tree-ring chronologies from the San Francisco Mountains and White Mountains region of central Arizona were used to reconstruct past annual snowfall water equivalents for up to the last 500 years. Long term means and variances of annual snowfall were calculated from the reconstructions and short and long term trends of snowfall were identified. To develop snowfall reconstructions, response functions were developed for the tree-ring chronologies to isolate those which were responding to snowfall. Chronologies responding to snowfall were calibrated with modern snowfall records and snowfall reconstructions were generated for the length of the chronologies with the calibration equations. Verification with independent data assured the validity of the snowfall reconstructions.