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Colorado River

Reconstructed Naturalized Colorado River Flow at Lees Ferry Near Page, Arizona

Time series plot of past Colorado River flows created by analyzing tree-rings. The plot displays the 25-year running average of the reconstructed flows. Flows are plotted as a percentage of the 1906–2004 average of observed natural flows (18.5 billion cubic meters or 15.0 million acre-feet). The red horizontal line is the lowest 25-year running mean of observed flows (1953-1977).

Instrumental Record of 'Naturalized' Colorado River Flow at Lees Ferry Near Page, Arizona

Instrumental record of Colorado River streamflows. The naturalized flow of the Colorado River has varied between 5.3 and 24.0 million acre-feet per year at Lees Ferry near Page, Arizona. Naturalized flow is an estimate of the River's flow that would occur in absence of human diversions or withdrawals. One acre-foot is equal to approximately 326,000 gallons.

Turning a New Leaf: When Tree-Rings Meet Water Policy

By Michelli Murphy | The University of Arizona | October 15, 2008
Researchers are using tree-rings to reconstruct past Colorado River streamflow to see how common, and extreme, southwestern drought can be—information that is vital to water managers.

Streamflow: Natural Variability and Human-Caused Changes

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Current observations suggest that climate change is altering streamflows in ways that negatively impact water supply for southwestern populations. Many climate models suggest that these changes will worsen as the climate warms, accentuating the natural variability inherent in river flows.