Between the lines: Tree rings hold clues about a river's past

January 10, 2018, Utah State University
By analyzing centuries-old growth rings from trees in the Intermountain West, researchers at USU are extracting data about monthly streamflow trends from periods long before the early 1900s when recorded observations began. Credit: Matt Jensen/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 at Utah State University are extracting data about monthly streamflow trends from periods long before the early 1900s when recorded observations began.

Their findings were published Jan. 6 in the Journal of Hydrology and, for the first time, show that monthly streamflow data can be reconstructed from annual tree-ring chronologies—some of which date back to the 1400s.

"By linking tree rings and flow during the past 100 years when we have recorded observations, we can use as a tool for measuring flow long before there were gauges on the rivers," said USU's Dr. James Stagge, a hydrologist and civil engineer who led the research. "Our study takes this one step further and uses different tree species and locations to reconstruct monthly flow, rather than annual flow."

Knowing monthly streamflow, the authors explain, is key to making better-informed decisions about 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.

Credit: Matt Jensen/USU
"One data point per year gives a very limited picture," said co-author Dr. David Rosenberg, an associate professor of civil and environmental engineering at USU. "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, Stagge and co-authors built a model that reconstructs monthly streamflow for three rivers in Northern Utah. The reconstructions are available to the public at www.paleoflow.org and show monthly streamflows dating back to 1605 for the Logan River and as far back as 1400 for the Bear and Weber rivers.

The team used tree-ring chronologies from seven species selected from a range of locations and elevations. Stagge says different tree species at different elevations respond to the changing seasons at different times of the year and in slightly different ways, recording unique parts of the seasonal flow. The model overlaps the tree-ring chronologies and combines annual streamflow information and climate data to arrive at a monthly streamflow estimate.

"Now we can get down into a monthly scale and pick up seasonal patterns within the streamflow," said Stagge. "It's the seasonality that determines drought, how reservoirs fill, and when there are shortages. Now that we have this method, we can start looking at what major droughts over the past 600 years would mean for today's water supply."

Hydrologists at USU have demonstrated that monthly streamflow data can be reconstructed from annual tree-ring chronologies. Credit: Matt Jensen/USU

Explore further: River streamflow reconstructed to 1490

More information: J.H. Stagge et al, Monthly paleostreamflow reconstruction from annual tree-ring chronologies, Journal of Hydrology (2017). DOI: 10.1016/j.jhydrol.2017.12.057

Related Stories

River streamflow reconstructed to 1490

May 26, 2006

A tree-ring-based study of 508 years of the U.S. Colorado River streamflow confirms droughts have occurred that were more severe than those of 2000-04.

Tree rings reveal nightmare droughts in the West

May 1, 2014

If you think the 1930s drought that caused The Dust Bowl was rough, new research looking at tree rings in the Rocky Mountains has news for you: Things can get much worse in the West.

How to stop human-made droughts and floods before they start

November 16, 2016

Alberta's rivers are the main source of water for agriculture in Canada's Prairie provinces. But climate change and increased human interference mean that the flow of these headwaters is under threat. This could have major ...

When trees die, water slows

December 16, 2015

Mountain pine beetle populations have exploded over the past decade due to warmer temperatures and drier summers, and these insects have infected and killed thousands of acres of western pine forests. Researchers have predicted ...

Recommended for you

The long dry: global water supplies are shrinking

December 13, 2018

A global study has found a paradox: our water supplies are shrinking at the same time as climate change is generating more intense rain. And the culprit is the drying of soils, say researchers, pointing to a world where drought-like ...

Death near the shoreline, not life on land

December 13, 2018

Our understanding of when the very first animals started living on land is helped by identifying trace fossils—the tracks and trails left by ancient animals—in sedimentary rocks that were deposited on the continents.

New climate model to be built from the ground up

December 13, 2018

Facing the certainty of a changing climate coupled with the uncertainty that remains in predictions of how it will change, scientists and engineers from across the country are teaming up to build a new type of climate model ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.