What Does Climate Change Mean for Water in the Colorado River Basin?

Sunset over the Rockies, which are soon to get hotter and drier. Photo credit: Rocket Scientist X, Flickr Creative Commons


Secretary of State Hilary Clinton recently celebrated the work of an Israeli scientist whose innovations in water conservation have been applied throughout the Middle East, noting “the importance of getting the most out of every drop of water. In many regions of the world, water is either too scarce or too unpredictable to sustain an American style of agriculture.”

But it’s not clear that the American Southwest can sustain an American style of agriculture, or for that matter an American style of lawn.

Nearly every climate change model puts a red bulls-eye on the Colorado River Basin, suggesting profound temperature increases over the coming decades.  The models don’t speak in unison when it comes to precipitation projections, but most studies that have looked at the effects of both temperature and precipitation agree that the temperature signal will far outweigh the precipitation signal when it comes to water availability in the region.  It’s going to get much hotter and drier.

Last year the Bureau of Reclamation finalized their first assessment of climate change impacts on Colorado River flows, concluding they would most probably decline by 8.7% by 2060.  That’s a loss of 1,300,000 acre-feet, the entire annual capacity of the canal diverting water to Los Angeles, Orange, and San Diego counties.

Now we have confirmation from Reclamation that whatever water is left in the Colorado River won’t go as far.  Hotter temperatures will drive an increase in water demand.  The average projected increase in water use, based solely on temperature increases, is 500,000 acre-feet.

In simple terms, increased temperatures mean that every living thing will need more water to survive.  This includes all the lawns we water and all the crops we grow with Colorado River water.

Reclamation hasn’t put these two numbers together yet in a public document, but the result is profound.  The climate change impact on Colorado River water translates into a decrease in supply and an increase in demand totaling a deficit of  1,800,000 acre-feet.  Keep in mind, this is just the average, not the worst case.  Moreover this is just the deficit created by climate change, and does not account for the inevitable increase in water demand by a growing regional population.

Embedded in all of these projections is tremendous uncertainty.  The future of water – and life – in the West will be very different from anything we’ve come to expect. A willingness to adapt and change to new conditions will be critical to life in the West.  The time to start planning is now.


Jennifer Pitt is the Colorado River Project Director for Environmental Defense Fund.



Meet the Author
Jennifer Pitt is the Colorado River Project Director for Environmental Defense Fund. She works with Colorado River water users throughout the Colorado River basin—including seven states in the United States and two in Mexico—to develop practical programs to restore river habitats and to dedicate water to environmental resources. She has worked as a park ranger and a Congressional aide, and has a Masters degree in Environmental Studies from Yale University.