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Bridging climate science, citizens, and policy

Colorado River System Could Be Severely Threatened By Climate Change

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One of the well-documented effects of climate change in the future is increased probability of widespread and long-term drought.  Related to those effects will be the accessibility of fresh water to meet the needs of ecosystems and human societies.

The Colorado River system is in the midst of a 10-year drought.  Abundant geologic evidence shows that the region, without climate forcing by humans, is susceptible to decadal- to century-scale droughts.  Post-2007 IPCC Report studies have dug further into the question of what future climates would be like under different CO2 emission scenarios.  A related study that examined what different stream flows and projected changes in water demand would mean for the Colorado River System has been accepted to a peer-review journal, Water Resources Research.  Keep in mind that the Colorado River System delivers water to 30 million people and a large number of ecosystems.  Key components of the system for human use includes reservoirs.  If stream flow is reduced for consecutive years, it will have far-ranging impacts that are not yet fully defined or explored. What is known is this: those reservoirs can’t capture what doesn’t flow through the System.

The researchers found that through 2026, the risk of fully depleting reservoir storage in any given year remains below 10% under any scenario of climate fluctuation or management alternative.  That is certainly good news.  During this same period, the reservoir storage could even recover from its current low level, which is currently at 59% of capacity.  But if climate change results in a 10% reduction in the Colorado River’s average stream flow as some recent studies predict, the chances of fully depleting reservoir storage will exceed 25% by 2057, a much more worrisome outcome.  Even more disturbing, if climate change results in a 20% flow reduction, the chances of fully depleting reservoir storage will exceed 50% by 2057.  Exceeding a 50% probability is indicative of a critical danger to human societies and warns of unacceptable ecosystem collapse across a large region.

This is the future we could saddle future generations with.  Or we can take action now, when the costs are still well within reach, and stop forcing the climate system as hard as we’re doing.  Rep. John Salazar (D, CO-03) voted for the more dangerous future by joining with the two Colorado Republican Representatives and voting against H.R. 2454, the American Clean Energy and Security Act of 2009.  The remainder of the Colorado delegation, all Democrats, voted for the less risky future.  The Senate should take up their version of the legislation this fall.  Will Sens. Udall and Bennet vote for a better future?  When (if?) a compromise bill comes up for a final vote, will legislators do the morally right thing?  They’d better.  30 million+ people are at risk of becoming mighty thirsty.

Cross-posted at SquareState.

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