Colorado State University Geosciences Professor Ellen Wohl is so at home in rivers and streams that if you manage to catch her in her office on campus, she might be listening to stream sounds while she works.
The prolific field scientist and University Distinguished Professor has studied rivers and watersheds from ephemeral desert channels to torrents in the tropics on every continent except Antarctica. Today, the National Academy of Sciences announced that it will honor Wohl with the G.K. Warren Prize for her expansive research and advancements in river and watershed sciences.
“Her work has dramatically influenced and guided river management and restoration worldwide,” the academy said in its announcement. “Wohl is the author of an extensive number of publications and books, introducing broad audiences to river science, and is an extraordinary mentor and role model for women in science.”
Wohl is what’s known as a fluvial geomorphologist, or a scientist who studies river processes and physical characteristics. She was drawn to CSU by its legacy of water research and its location, where she would have quick access to mountain streams.
“We have such a great community of people to work with at CSU who are focused on all different aspects of water,” Wohl said. “If I have a question about water chemistry, fish, macro-invertebrates, riparian plants, whatever, there’s somebody I can talk to on campus.”
Respect for rivers
Wohl said that she couldn’t resist studying rivers and called them a delightful environment in which to work. They are also critically important, she added.
“Our survival absolutely depends on them. Particularly in Colorado,” Wohl said. “All our drinking water in the West, certainly in Fort Collins, comes from surface water. That’s not going to change.”
Her recent research examines how rivers respond to wildfire. After a fire, excess water and sediment rush down denuded slopes, causing flash floods, debris flows and sedimentation in drinking water reservoirs. Wohl’s goal is to improve river resilience for all the living things that rely on the water.
“What can we do that will make these systems better able to recover after fire and that will have downstream impacts on the communities that drink that water?”
Wohl said the answer lies in understanding the complexities, or as she calls it “messiness,” of river networks. Many U.S. rivers have been simplified to single channels that flush everything downstream very effectively. Her work has found that restoring some of the historic messiness, including floodplains, branching channels, fallen trees in the water and beaver activity, enhances river resilience.
Slowing downstream transport also gives microbes that live in the floodplain and underneath streams time to clean the water. Microbes and plants can break down excess nitrate, which is a serious issue along the Front Range, Wohl said.
Nitrate from agricultural fertilizer, feedlots and burning fossil fuels is transported in the atmosphere and falls as rain, snow or dry deposition on the eastern side of the Continental Divide, ending up in surface water. Consuming excess nitrate in drinking water is detrimental to human health. Excess nitrate in reservoirs also can lead to algae blooms that can be toxic to people and other organisms. Additionally, algae blooms can deplete oxygen in the water, causing fish kills.
“It’s a great concern for water quality managers to try and do what we can to reduce nitrate levels,” Wohl said.
Dry outlook
Wohl said Colorado’s future holds “more rainfall, but generally less water” due to continued warming and drying of the climate and human consumption. Snowpack, which supplies water to communities and feeds river ecosystems, will decline, along with river flows throughout the state.
“The good news is we have some wiggle room because we waste an awful lot of water, so we can conserve a lot more than we use,” she said. “But there’s a limit to how much you can conserve.”
The 1922 Colorado River Compact, which was renegotiated 100 years later to account for declining flow and a rapidly growing population, was based on a limited record of stream measurements taken during anomalously wet years, Wohl said, so the river’s water was overallocated from the start. Fluvial geomorphologists can extend the streamflow record and estimate long-term water supply by looking at geologic indicators – information that could help with future allocations.
Benefiting those downstream
Across the diverse environments in which Wohl has worked, the common thread is that they were all shaped by flowing water, the same force that has shaped a career she thoroughly enjoys.
“In addition to going to all the amazing natural places, by far one of the highlights of my career is working with really motivated, enthusiastic, capable people,” Wohl said.
The National Academy of Sciences will present Wohl with the G.K. Warren Prize April 28 during the NAS 161st Annual Meeting. The prize is awarded once every five years.
Wohl plans to use the $20,000 prize to establish a graduate student research fellowship through the Geological Society of America, in honor of her Ph.D. advisor Victor R. Baker.
Wohl’s award was among 20 announced today by the National Academy of Sciences that recognize extraordinary scientific achievements. View the full list of recipients in the NAS press release.
