Feb 17, 2017

The 21st century Colorado River hot drought and implications for the future

by
Udall, Bradley, Overpeck, Jonathan
,
Water Resources Research

This paper is the first to show the large role that warming temperatures are playing in reducing the flows of the Colorado River.

Jonathan Overpeck, study co-author and Regents’ Professor of Geosciences and of Hydrology and Atmospheric Sciences and director of the University of Arizona Institute of the Environment


  • States that the period between 2000 and 2014 was the worst 15-year drought in the Colorado River Basin on record, with annual flows that were 19% below the 1906-1999 average
  • Finds that unprecedented temperatures (0.9°C above the 1906-99 average) were responsible for at least one-sixth to one-half (average of one-third) of flow reduction
  • Finds that, while warming is expected to continue due to ongoing greenhouse gas emissions, neither observations nor climate models suggest a trend towards greater precipitation in the Colorado Basin
  • Highlights significant risk of decade-long and decades-long droughts in the next 100 years that will likely offset any increase in mean precipitation
  • Finds that unabated warming will spur temperature-induced flow declines ranging from -20% to more than -30% by mid-century and from -35% to more than -55% by end-century
  • Concludes that, though precipitation increases may mitigate these losses to some extent, such increases are not evident at this time and models do not agree on future precipitation changes
  • Concludes that Colorado River flows will be more severely affected by climate change than currently assumed, particularly if greenhouse gas emissions are not significantly reduced