Oct 22, 2009

Declining annual streamflow distributions in the Pacific Northwest United States, 1948–2006

C. H. Luce and Z. A. Holden
Geophysical Research Letters
  • States that although increasing variability in annual flows has been noted, the nature of those changes is largely unexplored
  • Tests for trends in the distribution of annual runoff using quantile regression at 43 gages in the Pacific Northwest
  • Finds that 72% of the stations showed significant (a = 0.10) declines in the 25th percentile annual flow, with half of the stations exceeding a 29% decline and a maximum decline of 47% between 1948 and 2006
  • Finds that fewer stations showed statistically significant declines in either median or mean annual flow, and only five had a significant change in the 75th percentile, demonstrating that increases in variance result primarily from a trend of increasing dryness in dry years