Streamflow and Groundwater Response to Stream Restoration Using Beaver Dam Analogues in a Semi-Arid Perennial Stream

Degradation of stream and riparian environments across the western United States has damaged critical ecosystems, water quality, and increased sedimentation of reservoirs. Low tech, process-based restoration methods such as beaver dam analogues (BDAs) have been adopted by practitioners because they restore ecosystem function, improve habitat, and reduce downstream sediment delivery at a low cost. However, few studies have examined the potential impacts of beaver dam analogues on the quantity and timing of streamflow, which is of primary concern for water stakeholders. We address this gap with 2 years of streamflow and riparian groundwater observations before and after installing a series of 17 BDAs on Fish Creek, a first-order stream in semi-arid northern Utah. Within 8 weeks of BDA installation, and 1 year later, we found no significant change in streamflow compared with control and Regional Reference sites. Shallow groundwater table elevations within 7 m of the stream edge increased significantly, up to 14 cm, relative to the control reach. Our results suggest that the small, local hydrological changes from BDA installation are superimposed on much larger-scale snowmelt and alluvial groundwater controls on streamflow, suggesting BDA installation can restore ecosystem function without deleterious impacts on streamflow. These findings are especially relevant to restoration and water stakeholders with concerns about impacts of BDAs on downstream flows.