Science Source

On the causes of declining Colorado River streamflows

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