In the arid western US, groundwater-surface water interactions have been historically shaped by the presence of beavers, with beaver dams storing and redirecting water into the floodplain. As populations of beavers have declined, local municipalities, state agencies, and private landowners have been installing beaver dam analogues (BDAs), a stream restoration structure that mimics the form of natural beaver dams, in beaver-less stream reaches. Due to their simplicity and expected benefits, BDAs are gaining extensive attention and implementation across the western US, in spite of the absence of clear scientific data to assess their impacts on reach scale hydrology. The proposed project aims to address this gap in knowledge in order to determine the extent to which BDAs alter groundwater and surface water levels, groundwater- surface water exchange, and evapotranspiration by monitoring a research site containing several BDAs located in Wyoming, USA. The project will be performed in close collaboration with The Nature Conservancy of Wyoming (TNC-WY), who owns and manages the research site. While the proposed work aims to improve understanding of hydrological processes in the context of BDA deployment, observations will also inform several management goals associated with BDAs (including reducing stream velocity, reconnecting the stream channel to the floodplain, and supporting riparian vegetation for wildlife habitat and forage for cattle). Investigators will work in close collaboration with TNC-WY to evaluate these management goals, to share findings with local and regional practitioners and stakeholders, and to leverage the research site as a demonstration site for BDAs.
The primary objective of this project is to disentangle the complex feedbacks between the stream, atmosphere (via evapotranspiration), and aquifer (via hyporheic exchange and water table dynamics) associated with BDA implementation at the watershed scale. To address this objective, field and in situ observations as well as high resolution imagery via unoccupied aerial vehicle (UAV) will be collected annually at research sites and used in combination with integrated modeling of stream-aquifer-atmosphere responses to constrain behavior during the length of the project and beyond. Observations and numerical modeling will be leveraged to determine the hydrological mechanisms governing interactions between BDAs and evapotranspiration, streamflow, and groundwater levels to achieve a full understanding of how BDA structures shape the physical hydrology of stream reaches. Empirical analyses and model-based approaches employed in this study will directly assess the responses of the research site to BDA installation. In addition, both empirical and model-based analysis will yield transferrable insight regarding the impacts of BDAs on hydrological processes and how this compares with reference reaches. As the body of literature assessing the mechanisms and impacts of BDAs is virtually nonexistent, this work will provide much-needed context for western US watersheds where changes due to climate and humans are colliding. Finally, this work will significantly advance the field of data collection via UAV for hydrological and ecological sciences by providing the broader scientific community with a template to use UAVs for environmental data collection.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
