How Are Beavers Helping Improve Water Quality?
American beavers are proliferating throughout the western United States. According to a recent study, their extensive dam construction improves river water quality so much that it overcomes the negative effects of droughts brought on by climate change.
A Stanford study suggests that beaver dams can have a considerably higher impact on water quality in mountain watersheds than climate-driven precipitations that seasonally fluctuate. The wooden barriers cause an upstream water diversion that raises water levels in the riparian zone (soils and supplementary river areas). Before water joins the main channel downstream, these zones function as filters, filtering out extra nutrients and impurities. The team, after closely monitoring the flow and chemical makeup of the steam, learned that the beavers kept up the dam for around two months until the river washed the mud and branches away. They discovered that the structure flooded the surrounding soil, enabling microbes to neutralize excess nitrogen. While snowmelt and rain indicated a similar impact to that of beavers, the dam significantly enhanced denitrification over the river's typical seasonal fluctuations by 44%. This is because beaver dams produce an unexpectedly sharp drop in water levels between the water levels above and below it, which significantly boosts the removal of nitrates.
The discovery of beaver dams’ effect on water quality was not intentional. It was an accidental discovery during a research project to monitor the hydrology of the seasons and the effects of riparian zones on pollutants and nutrients in a hilly watershed. A PhD student in 2017, Christian Dewey, began conducting field research along the East River, a significant tributary of the Colorado River close to Crested Butte in central Colorado.
Dewey, who is currently a postdoctoral scholar at Oregon State University, explained that a beaver opted to construct a dam at their study location entirely by happenstance. “The construction of this beaver dam afforded us the opportunity to run a great natural experiment.”
The research team detected that the gradient in the East River increased at least ten times more in both the high-water (2019) and drought (2018) years with the dam than it did during high-point summer without the dam. The dam's influence was vastly greater than the climatic hydro-meteorological fluctuations of either drought or copious snowmelt.
Fendorf, a senior member at the Stanford Woods Institute for the Environment and the Terry Huffington Professor of Stanford Doerr School of Sustainability, opined that by simulating hydrological extremes that are greater than those caused by the climate, beavers are preventing the deterioration of water quality and improving it. According to Christian Dewey, beavers won't stop global warming or relieve humanity of the critical need to cut emissions, but they could help mitigate certain issues.
Researchers think more locations would become friendlier for the dam-builders as the western United States becomes drier and warmer, possibly preventing waterways from becoming more contaminated over time.
The research article titled “Beaver dams overshadow climate extremes in controlling riparian hydrology and water quality” was published on 8th November 2022.
