AGU Release No. 06-19

Beavers, long known for their beneficial effects on the environment near their dams, are also critical to maintaining healthy ecosystems downstream. Researchers have found that ponds created by beaver dams raised downstream groundwater levels in the Colorado River valley, keeping soil water levels high and providing moisture to plants in the otherwise dry valley bottom.
Cherie Westbrook of Colorado State University and colleagues there and at the U.S. Geological Survey in Fort Collins, Colorado, conducted a three-year study in Rocky Mountain National Park, examining valley ecosystems downstream in the Colorado River. They noted that water diverted by beaver dams is forced out of the natural stream channel and spreads across and down the valley for hundreds of meters [yards]. In addition, dams built on the river changed the direction of groundwater flow in the valley. The changes caused water to infiltrate the river banks and flow underground toward the sides of the valley, instead of down the center of the valle … more.

Read more here at Science Daily and Denver Post.