17 June 2009
Spotlight on the Colorado River
Following is an excerpt from a June 16 report, Global Climate Change Impacts in the United States. The report, produced by the U.S. Global Change Research Program, a collaboration of 13 U.S. government agencies, is a comprehensive review of how climate change is affecting the country today and what can be done to mitigate the impacts.
This section of the report examines climate-related water shortages of the Colorado River — a vital resource to millions in the United States and Mexico.
The Colorado River system supplies water to more than 30 million people in the Southwest, including Los Angeles, Phoenix, Las Vegas and Denver.
Reservoirs in the system, including the giant lakes Mead and Powell, were nearly full in 1999, with almost four times the annual flow of the river stored. By 2007, the system had lost about half of that storage after enduring the worst drought in 100 years of record keeping. Runoff was reduced due to low winter precipitation, and warm, dry and windy spring seasons that substantially reduced snowpack.
Numerous studies over the past 30 years have indicated that the river is likely to experience reductions in runoff due to climate change, and diversions from the river to meet the needs of cities and agriculture are approaching its average flow. Under current conditions, even without climate change, large year-to-year fluctuations in reservoir storage are possible. If reductions in flow projected to accompany global climate change occur, water managers will be challenged to satisfy all existing demands, let alone the increasing demands of a rapidly growing population.
Efforts are underway to address these challenges. In 2005, the Department of Interior’s Bureau of Reclamation began a process to formalize operating rules for lakes Mead and Powell during times of low flows and to apportion limited water among the states.
Ensuring that all have access to water is a challenge for governments. In the United States, seven states and 10 American Indian tribes share the Colorado River with Mexico. The river is a resource vital to survival. “It is a big balancing act” to try to satisfy the competing users and interests that need Colorado River water, Robert King, chief of interstate streams with the Utah Division of Water Resources, told America.gov. Simply stated, there is not enough water in the river system to satisfy all the demand, he said. For more, see “Water Usage and the Colorado River.”
For more on the Global Climate Change Impacts in the United States report, see “U.S. Regions Experiencing Climate Change Effects Now, Report Says.”
