Impacts of a beaver dam analogue complex on streambed vertical hydraulic gradients in a 1.2‐km stream reach in Wyoming, USA

Abstract

Beaver dam analogues (BDAs) have seen growing use as restoration structures across the western United States. This study investigates the patterns in streambed upwelling and downwelling along a 1.2-km stream reach in Red Canyon Creek (RCC), Wyoming before and after the installation of 31 new BDAs and the upgrade of four existing BDAs in July 2021. Over 100 mini-piezometers were used to measure upwelling and downwelling in low-flow, summer periods as quantified by vertical hydraulic gradient (VHG). Both before and after BDA installation, the stream reach was dominated by downwelling patterns, suggesting that RCC was a net losing stream during this summer period, with and without BDAs. While there were spatial variations in VHG before BDA installation, this variation was not dependent on stream depth, water surface concavity, sediment characteristics, and position relative to meanders, suggesting that unobservable subsurface properties may be a control on VHG or that there are attributes that were not captured due to the 10-m spacing of mini-piezometers. After BDA installation, VHGs were primarily related to the magnitude of the elevation gradient across the BDA. VHGs were highest near the BDAs and diminished once moving more than a few metres from the BDAs. When VHGs were averaged over the full reach length, BDAs appeared to slightly enhance net stream loss, albeit we could not control for possible seasonal differences in water table gradient during the observtion period.