PS 42-62 - Can imitating beavers improve water quality and soil health?

Background/Question/Methods

Beaver dam analogs (BDAs) are being built across the Western US to restore stream function. BDAs slow the movement of water, which may increase surface water availability for cattle and wildlife, groundwater recharge, microbial uptake and metabolism of anthropogenically-sourced pollutants and reduce wildfire risk. However, BDAs may also increase surface water temperatures, increasing the risk of eutrophication, and reduce surface water availability to downstream water users. Here, we test how BDAs installed in a first-order, intermittent stream, influence surface water quality, carbon and nutrient cycling, and microbial activity.

Guy Canyon stream flows through the University of Idaho Rinker Rock Creek Ranch (RRCR) Experimental Station in central Idaho. RRCR is an active rangeland site managed using rotational grazing to prevent excessive damage to vegetation and soils. For this study, the upper reach of Guy Canyon stream was divided into four study meadows. A reference control meadow was located upstream of three BDA treatment meadows. In July 2021, 54 BDAs were installed (n = 18 BDAs within each treatment meadow).

Results/Conclusions

Baseline data were collected prior to BDA installation and BDA monitoring will continue through Fall 2022. We are tracking stream temperature and nutrient concentrations (e.g., nitrate, phosphate, carbon) in floodplain and surface water samples. Total Organic Carbon for the water samples taken in 2021 ranged between 15.88 and 118.80 mg/L and the Total Nitrogen was 0.70 to 14.64 mg/L. We are also testing how potential floodplain inundation influences microbial activity and carbon mineralization. This research will help determine the effects and potential risks of BDA installation on water and soil quality, which will directly influence riverine ecosystem function. We are also monitoring the effects of BDAs on annual water supply, bank stability, and forage quality. These data will be used to guide decisions surrounding BDA installation and their utility for restoring stream habitat.