Researchers shed light on river resiliency to flooding

Researchers at the University of Nevada, Reno have completed an extensive study of river resilience, examining how river ecosystems recover after floods. They developed a new modeling approach that used data from oxygen sensors placed in rivers to estimate daily growth in aquatic plants and algae. The researchers then sampled algal and plant biomass in 143 rivers in the contiguous United States to determine the extent to which biomass is disturbed by flood intensity and how quickly rivers recover from floods. It takes time.

An increased understanding of river resilience is essential to maintaining healthy rivers, as human actions can affect flood regimes and alter river conditions for other aquatic life that depend on algae and vegetation. can do Source of food.

Joanna Blaszczyk, assistant professor in the university’s College of Agriculture, Biotechnology and Natural Resources and Global Water Center, and Hayley Lowman, a postdoctoral scholar, led the research, which was published in two separate journal articles.

Early work, led by Blaszczak and published I Environment Letters Last June, the first six rivers were studied and the groundwork and methodology for the second study, to be conducted by Blaszak, was hired by Lowman to evaluate 143 rivers. Results of this research Published on January 24. Proceedings of the National Academy of Sciences.

This research is unique because it estimated changes in biomass in rivers more frequently than ever before without the need to directly sample rivers. This is done using both data. Oxygen sensor A population model of algal and plant biomass in rivers by the U.S. Geological Survey—similar to a human population model that models population changes over time, but instead of algae and plants Model the change in quantity.

Oxygen Sensors began collecting data in 2007, and the latest study of 143 rivers led by Nevada includes some data spanning nine years, the longest such records on file for rivers worldwide. is of me

“Previously, you had to go to a river and sweep rocks to measure algae, and do this over a long period of time to estimate changes in biomass growth and loss. Blaszek said. “It’s very time-consuming, so the data is extremely limited compared to how extensive our sensor networks are.”

Blaszczak said that with oxygen sensors that took data as often as every five minutes, the team found that they could use statistical models to infer the amount of photosynthesis that occurs daily and in the river over time. I can estimate daily changes in the amount of biomass.

“Dissolved oxygen sensors show peaks during the day and lows at night, and from those patterns, you can estimate how much new algae and other biomass grew that day,” he said. “With sensors measuring data continuously for years in hundreds of rivers, we can get a much bigger, clearer picture. The data is there, and we use it to model the size of the flood needed to disturb the biomass in a river. can be used to create, as well as the rate at which a river recovers from flood damage, which can help us manage rivers more effectively.”

getting started

In the first study, Blaszak used two years of data from oxygen sensors placed in six rivers. She found that she could use this data to successfully model the extent of river-specific flooding that disturbed primary biomass, and that, in general, biomass disturbance and ecological The flood intensity required to reduce system productivity was less than the disturbance flow threshold required for activation. Stream bed sediment, a metric of obstruction commonly used by those studying rivers.

In other words, instead of estimating river disturbance from the movement of rocks on the river bed, this study used changes in organisms—algae and plant growth—to quantify river disturbance and found that biological Disturbance was minimal.

“The amount of biomass is the water quality and the food source for everything that lives in the river,” Blaszak explained, “so it’s more important than rock movement, in terms of how the river ecosystem works. affected by disorder.”

Blaszak, a freshwater ecologist, began the work with Robert O. Hall Jr. of the University of Montana’s Flathead Lake Biological Station and enlisted the help of fellow assistant professor Robert Shriver, a plant ecologist, to complete both research projects. of the. Modeling biomass growth. Blaszczak, Shriver, and Lowman all conduct research as part of the College’s Department of Natural Resources and Environmental Sciences, as well as the College’s Experimental Station Research Unit. Blaszczak said the college’s faculty often take an interdisciplinary approach to tackling research challenges.

Spreading on a continental scale.

Blaszczak wanted to apply this approach to more rivers over a longer period of time to shed light on how different factors are affecting both the thresholds of a river. the flood Its resilience to disturbance and flooding. Thus, he recruited Lowman to begin a second, more extensive study. Lowman’s research examined landscape and river characteristics that affected rivers’ resilience to flooding.

“We’ve never seen such great insight into the resilience of rivers, and because of the amount of data and our modelling, we now understand the natural variation in resilience, and that rivers above dams are all “recover faster,” Lowman said.

The fact that wide rivers without dams recover more quickly than wide rivers with dams upstream, he said, was not immediately obvious, and is an example of How our actions can affect and/or manage rivers. Most of the rivers Lowman studied had three to four years of data, with some having up to nine years, and some having less than a year.

“Having three to four years of data is more than we’ve ever been able to use before,” Lowman said. “And, we used rivers of different sizes with different climates and terrain characteristics.”

In addition to wide rivers without dams being more resilient, Lowman said rivers that flood frequently also recover more quickly.

“It may be that they have had a long history of frequent flooding, so their algae and plant communities have developed the ability to adapt to more frequent disturbances,” he said.

Overall, Lowman said the new model’s results are consistent with other previous methods. But, he said, some sites took a month or longer to recover from flooding than other sites, regardless of river size.

“It could be the composition of algal and plant communities, the structure of the river bed, or other factors,” he said. “Dells and recovery times are highly likely to depend in part on slope, sediment grain size, and possibly other factors that are not well documented. These are some next steps for future research.”