Beavers are among nature's best helpers because the dams they build create wetlands, help control flooding, increase biodiversity, reduce erosion, and more. Researchers at the University of Connecticut have found that beavers' activities also benefit underground ecosystems.
UConn Department of Earth Sciences researcher Lijing Wang and her colleagues conducted a study published in Water Resources Research on how water flows through soils, bedrock and other sediments beneath the Earth's surface in a region of the Rocky Mountains, according to a university press release. Their results showed that beaver ponds play a larger role in groundwater recharge than most people realize.
Wang said that during the dry summer season, groundwater is usually one of the only sources of water to recharge streams. She and her team wanted to know whether beaver ponds could also help restore groundwater to healthy levels.
For the research, the team took measurements that included hydrological data and models, geophysical surveys and a machine learning technique to improve estimates of the changes that beavers had made to the landscape.
The team explored various areas in the Rocky Mountains, including floodplains, rivers with gravel bed systems, and rivers with larger rocks, to gain a comprehensive understanding of the influence of beavers on groundwater recharge.
Wang pointed out that beaver ponds could have a greater impact on how groundwater recharges in underground structures, which include shallow soil layers and gravel beds. The researchers also examined “the movement of water available for evaporation into the atmosphere, or evapotranspiration,” according to the press release.
Wang pointed out that evapotranspiration is critical in the arid western United States because it is a key driver of water use and helps offset limited supplies.
She explained that when soil is thick in this region, beaver ponds can result in less groundwater recharge because the ponds increase the amount of surface water available for evapotranspiration. In this case, there would be less groundwater recharge than without the influence of beaver ponds, which ultimately has a positive impact on agricultural needs and water security.
Overall, the team found that beaver activity led to ten times more groundwater recharge compared to periods without precipitation. They then wondered what happened to the water after it flowed underground, and realized that the gravel bed acted as a kind of underground river, pushing the water downstream.
“More water is being washed downstream into the subsoil than we thought. It doesn't stay there and doesn't help maintain the local water table,” Wang said.
These findings inspired the team to shift their focus to New England, which has a very different and more complex river network than Colorado. Wang explained that the rivers include more canals, tributaries and beaver dams, allowing floodplains and wetlands to thrive.
Gaining more insight into how beaver ponds impact the environment in the Northwest would help improve water and land use management.
“Beaver ponds can increase ecological benefits, but we lack a comprehensive understanding of water balance and water quality. We need to understand the trade-offs and benefits,” Wang concluded, noting the need for “further field measurements of floodplain structure, hydraulic properties and evapotranspiration changes” in the study.
Beavers are among the most prolific ecosystem engineers, helping to improve biodiversity, reduce water pollution and protect landscapes from drought and wildfires. Apparently they now deserve thanks for ensuring that important groundwater reserves are replenished for the benefit of animals and people.
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