Pacific Northwest Research Station

The Olympia Aquatic and Land Interactions Team

2008 Science Accomplishments

Riparian forests regulate stream flow through evapotranspiration

Scientists found that riparian forests are the primary location of lost streamflow from evapotranspiration in late summer in small watersheds. A study in the H.J. Andrews Experimental Forest explains how daily fluctuations in discharge were generated and why. Observations of daily fluctuations showed that the time lag between maximum evapotranspiration demand and minimum discharge increased, and the amplitude in daily fluctuations decreased as streamflow decreased.

Recently there has been renewed interest in using land management to "harvest" water, especially to augment streamflow during seasonal droughts. This research indicates that vegetation management on upland portions of watersheds may increase total annual water yield, but efforts specifically designed to enhance low-flow discharge in summer would have to concentrate vegetation management efforts in riparian areas.

Also, water quality in many streams is often limited during the summer when low flows combined with high air temperatures raise water temperature, lower dissolved oxygen, and increase concentration of pollutants. This research highlights naturally occurring signals that could be used to improve understanding of watershed processes and help inform management designed to protect or improve water quality.

Partners: Montana State University, Pennsylvania State University, U.S. Geological Survey

To learn more, contact Steve Wondzell at swondzell@fs.fed.us.

Trout in Spirit Lake have unusual adaptations

As the closest and largest lake adjacent to Mount St. Helens, Spirit Lake underwent extensive changes during the 1980 eruption. It was transformed from a relatively pristine coldwater mountain lake to a larger, shallower lake containing a warm microbial broth in which no air-breathing organisms survived, including fish. The lake gradually returned to conditions that supported flora and fauna more typical of the Cascade Range over the next decade, but the first trout was not captured until 1993. The rainbow trout population has expanded rapidly, and the fish are exhibiting exceptional growth rates and unusual life histories. They grow fast, have unusual spawning characteristics, and die young, in marked contrast to trout in most mountain lakes.

The unusual adaptations of Spirit Lake trout to the volcanic environment have piqued international scientific interest. For example, scientists in Chile are seeking to extend lessons learned at Spirit Lake to lakes near the currently erupting Chaiten Volcano.

Outcome: Chilean scientists look to recovery of Spirit Lake for clues about possible recovery of lakes near currently erupting Chaiten Volcano.

Partners: University of Washington, U.S. Geological Survey, Washington Department of Fish and Wildlife, Wild Fish Conservancy

To learn more, contact Charlie Crisafulli at ccrisafulli@fs.fed.us.