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Between the Lines: Tree Rings Hold Clues About a River’s Past

Published in Utah State Engineer – Oct. 2, 2017 – USU hydrologists are looking centuries into the past to better understand an increasingly uncertain water future.

By analyzing centuries-old growth rings from trees in the Intermountain West, researchers in the civil and environmental engineering department are extracting data about monthly streamflow trends from periods long before the early 1900s when recorded observations began.

Their findings show, for the first time, that monthly streamflow data can be reconstructed from annual tree-ring chronologies –some of which date back to the 1400s.

tree rings

By analyzing centuries-old growth rings from trees in the Intermountain West, researchers in the civil and environmental engineering department are extracting data about monthly streamflow trends from periods long before the early 1900s when recorded observations began.

“Trees grow one ring per year and the ring width gives an annual snapshotof hydrologic conditions,” said USU’s Dr. Jim Stagge, a hydrologist and civil engineer who’s leading the study. “By linking tree ring chronologies from multiple locations and tree species with observed streamflow data, we can statistically reconstruct monthly streamflows.”

Knowing monthly streamflow, the authors explain, is key to making better-informed decisions about water use and management. In Utah and around the world, populations in arid climates depend on seasonal and often inconsistent water supplies for agriculture and urban use.

“One data point per year gives a very limited picture,” said collaborator Dr. David Rosenberg, an associate professor of civil and environmental engineering. “Decisions about water management happen much more frequently than just once per year. Water managers have to make decisions every month, every week, sometimes every day.”

To fill in the missing monthly data, researchers built a model that reconstructs monthly streamflow averages for three rivers in Northern Utah. The reconstructions are available to the public at www.paleoflow.org and show monthly streamflows dating back to 1661 for the Logan and Bear rivers and as far back as 1430 for the Weber River.

Collaborators include Justin DeRose with the U.S. Forest Service and Dr. Tammy Rittenour, an associate professor in USU’s department of geology.


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Media Contact: Matt Jensen – Utah State University, College of Engineering | matthew.jensen@usu.edu | office: 435-797-8170 | cell: 801-362-0830 | engineering.usu.edu | @engineeringUSU