tree rings
The climate of the US Southwest
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).
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
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.
Tree Ring 101
How tree rings can lead to estimates of past streamflow is not readily obvious. It's natural to think that trees lined right along a river would act as the best gages. As it turns out, those trees are relatively useless - or complacent, as researchers call them. Even in times of drought, riverside trees draw up plenty of water from the moist soil, packing on wide growth rings year after year.