Aug 30, 2018

On the causes of declining Colorado River streamflows

by
Mu Xiao, Bradley Udall, Dennis P. Lettenmaier
,
Water Resources Research
  • States that over the period 1916-2014, the Upper Colorado River Basin (UCRB) naturalized streamflow declined by 16.5%, despite the fact that annual precipitation in the UCRB over that period increased slightly
  • Performs a set of experiments with the Variable Infiltration Capacity (VIC) hydrology model to examine the causes of the runoff declines
  • Results show that:
    • The pervasive warming has reduced snowpacks and enhanced evapotranspiration (ET) over the last 100 years
    • Over half of the long‐term decreasing runoff trend is associated with the general warming
  • Finds that:
    • Whereas a mid-century drought was caused primarily by pervasive low precipitation anomalies across UCRB, higher temperatures have played a large role in the ongoing post‐Millennium Drought
    • The post‐Millennium Drought has also been exacerbated by negative precipitation anomalies in several of the most productive headwater basins