Development of a model to identify the effects of beaver ponds on stream hydrology
NOTE: This research is ongoing and results are preliminary
With shifting precipiation and streamflow regimes in the western United States, and given projections of future climate change, there is likelihood for continued hydrologic alterations and potential water scarcity. Additionally, projected, rapid population growth in the western U.S. may increase future water demand beyond the capacity of current water resources infrastructure. The majority of proposed projects aimed at mitigating future water scarcity seek to develop additional, expensive, man-made reservoirs. However, we believe North American Beaver may provide a low cost, viable alternative to mitigate changing hydrologic regimes without the massive ecological consequences of large reservoir construction.
Previous studies have suggested the ability of beaver to positively alter hydrologic patterns with their dam building activity. Ponds resulting from beaver dams store water on the land surface and facilitate groundwater recharge by reducing stream velocities and increasing ground water elevations. It is believed this additional water storage may supplement streamflow during annual summer droughts, increasing baseflows and providing more water for downstream use. However, these hypotesized effects have only been observed at small-scales (e.g. 1km stream reaches with 5-10 beaver dams), therefore, we do not adequately understand the effect of beaver dams on hydrology at scales meaningful to water management. The purpose of this study is to quantify the potential effects of beaver dams on water storage and water delivery at watershed scales.
Figure 1. Potential increases to water storage above and below ground resulting from beaver dam construciton.
Using the Beaver Restoration Assessment Tool (BRAT) to determine dam density and location on a drainage network, we are developing a spatially explicit model to determine the inundation extent and volume of a beaver ponds. With estimates of inundation extents and water surface elevations we can then use MODFLOW to determine the change in groundwater levels associated with beaver pond construction. Ideally, we will use 10 meter DEMs as inputs as they are nationally available. For development of the model we are also using 1m LiDAR DEMs in certain locations.
Figure 2. Preliminary modeling workflow.
Figure 2. Modeled depth of beaver ponds and increase in ground water (GW) levels using a 1m LiDAR DEM.
Hafen, K., and W. W. Macfarlane. 2016. Can beaver dams mitigate water scarcity caused by climate change and population growth? StreamNotes November:1-5.