Relocated beaver can increase water storage and decrease stream temperature in headwater streams

Abstract

Many areas are experiencing increasing stream temperatures due to climate change, and some are experiencing reduced summer stream flows and water availability. Because dam building and pond formation by beaver can increase water storage, stream cooling, and riparian ecosystem resilience, beaver have been proposed as a potential climate adaption tool. Despite the large number of studies that have evaluated how beaver activity may affect hydrology and water temperature, few experimental studies have quantified these outcomes following beaver relocation. We evaluated changes in temperature and water storage following the relocation of 69 beaver into 13 headwater stream reaches of the Skykomish River watershed within the Snohomish River basin, Washington, USA. We evaluated how beaver dams affected surface and groundwater storage and stream temperature. Successful relocations created 243 m3 of surface water storage per 100 m of stream in the first year following relocation. Dams raised water table elevations by up to 0.33 m and stored approximately 2.4 times as much groundwater as surface water per relocation reach. Stream reaches downstream of dams exhibited an average decrease of 2.3°C during summer base‐flow conditions. We also assessed how dam age, condition, maintenance frequency, and pond morphology influenced stream temperature at naturally colonized wetland complexes. Our findings demonstrate that dam building can increase water storage and reduce stream temperatures in the first year following successful beaver relocation. Fluvial and floodplain morphology of candidate reaches for relocation is an important consideration because it determines the type and magnitude of response. Relocation to reaches with existing small, abandoned ponds may address thermal criteria by conversion from warming to cooling reaches, whereas relocation within large, abandoned complexes or vacant habitat may result in greater water storage. Although beaver relocation can be an effective climate adaptation strategy to retain more stable hydrologic regimes and water quality in our study area, there appear to be regionally specific environmental and geomorphic factors that influence how beaver affect water storage and temperature. More research is needed to investigate how and why these regional differences affect water storage and stream temperature response in beaver‐influenced systems.

Population dynamics of the threatened Oregon spotted frog before and after drought mitigation

“…Historical beaver activity and shrub vegetation is more evident in our Middle Jack study reach compared to our other reaches, and legacy dams also likely contribute to greater water retention. For example, at a beaver reintroduction site along the Skykomish River in Washington, USA, the local water table rose by 30 cm within a single year (Dittbrenner et al 2022). Regardless of the mechanism driving greater late summer moisture at Middle Jack, Oregon spotted frogs in this reach are more likely to persist under drought conditions compared to frogs in our other study reaches.…”

Smarter ways with water

“…Environmental scientist Benjamin Dittbrenner, at Northeastern University in Boston, Massachusetts, studied the work of beavers that were relocated from human-settled areas into wilder locations in Washington state. In the first year after relocation, beaver ponds created an average of 75 times more surface and groundwater storage per 100 metres of stream than did the control site 9 . As snowfall decreases with climate change, such beaver-enabled water storage will become more important.…”

Resetting the Baseline: Using Machine Learning to Find Lost Meadows

“…Many meadows historically supported or were created by beavers (Castor canadensis in North America and C. ber in Europe) through their damming of uncon ned, low-gradient channels (McComb et al 1990, Pollock et al 2003, Polvi and Wohl 2012. New evidence shows that beaver-supported wetlands in forested landscapes can signi cantly increase groundwater and surface water storage and decrease water temperature (Dittbrenner et al 2022). These changes can in uence wild re dynamics and provide important re breaks in otherwise burned landscapes (Fairfax and Whittle 2020).…”

“…These changes can in uence wild re dynamics and provide important re breaks in otherwise burned landscapes (Fairfax and Whittle 2020). Since beavers were much more common prior to the 19th century fur rush (Naiman et al 1988), restoration of beavers and beaver habitats would likely increase these hydrologically resistant landscapes (Wohl 2021, Dittbrenner et al 2022, Jordan and Fairfax 2022. Similarly, meadows were likely larger, wetter, and more common in the mountainous western United States and Canada prior to Euro-American settlement and subsequent meadow degradation (Loheide and Booth 2011;Celis et al 2017;Lubetkin et al 2017).…”