To return to the Midwest Fish & Wildlife Conference website, go to http://www.midwestfw.org/ The following schedule and room names are subject to change (as of February 1, 2017). Please check back for updates.
Presenters: Presenters for technical presentations are either the primary author (the first name listed in the abstract), or are indicated with an asterisk next to their name. Please note: the conference schedule is hosted by Sched.org which allows you to search within the schedule, and filter the schedule to show sessions only occurring on a certain date or within a track. You can also build your own schedule by creating a free account with Sched.org by selecting "SIGN UP" in the top right corner.
AUTHORS: Carol A Johnston, South Dakota State University
ABSTRACT: Streams are the accumulation of flow from precipitation, and beavers rely on stream flow to build their ponds. A first step toward understanding the sustainability of beaver ponds under future climate change is to determine the catchment area required to supply water to beaver ponds under current climate conditions. I investigated this question within a 300 km2 area of Voyageurs National Park for which I had previously mapped 1,065 beaver ponds using aerial imagery. I applied two approaches to determine minimum beaver pond catchment area: 1) calculating a flow accumulation threshold, and 2) computing the average area of headwater watersheds containing created beaver ponds. In the first approach, I used a Digital Elevation Model (DEM) with 3 x 3 meter pixels and a vertical accuracy of < 15 cm to compute land surface flow direction, and then used the hydrology tools in ArcGIS to compute flow accumulation, which counts the number of upslope cells that flow into any given cell. Superimposing this back on the original aerial photo, I identified a flow accumulation threshold (i.e., minimum number of contributing cells) that matched the location of streams flowing out of headwater beaver ponds: 6390 cells, or about 5.75 ha. The second approach used beaver dams visible on the aerial imagery to define pour points, which were then used with ArcGIS hydrology tools to define watershed boundaries. The median area of headwater watersheds using this second approach was larger (19.1 ha) because some of the watersheds encompassed wetlands that lacked channelized flow. Both approaches identified flowing water at much higher elevations than streams depicted by the National Hydrography Dataset. Future changes in the amount, intensity, and timing of precipitation under climate change may affect beavers’ ability to create and sustain their ponds.
