Without global warming in the picture, the scientists estimate that the Bureau of Reclamation would be unable to meet delivery schedules 40 percent of the time by 2050, although the shortfalls would be manageable.
Toss global warming into the mix, however, and the situation worsens.
Other rivers face long-term declines
Nor is the Colorado alone. The Columbia River, China's Yellow River, India's Ganges, and the Niger in Africa all have seen long-term declines in flow, according to a new analysis by scientists at the National Center for Atmospheric Research, in Boulder, Colo., and the College of William and Mary in Virginia. You can download a PDF of the research paper here. A plain-English description is available here.
The analysis, set for publication in the Journal of Climate next month, looks at flow records from 925 of the world's largest rivers, covering a period from 1948 to 2004. It represents the most comprehensive data base yet assembled to track river flows. Where gaps appear in a river's records, the team used climate and hydrological models to estimate runoff.
Roughly one-third of the rivers experienced significant changes in flow rates – some up, some down. But the rivers with reduced flow rates outnumbered the ones with higher flow rates by 2.5 to 1.
