Abstract
Abstract. Beaver ponds are surface-water features that are transient through space and time. Such qualities complicate the inclusion of beaver ponds in local and regional water balances, and in hydrological models, as reliable estimates of surface-water storage are difficult to acquire without time- and labour-intensive topographic surveys. A simpler approach to overcome this challenge is needed, given the abundance of the beaver ponds in North America, Eurasia, and southern South America. We investigated whether simple morphometric characteristics derived from readily available aerial imagery or quickly measured field attributes of beaver ponds can be used to approximate surface-water storage among the range of environmental settings in which beaver ponds are found. Studied were a total of 40 beaver ponds from four different sites in North and South America. The simplified volume–area–depth (V–A–h) approach, originally developed for prairie potholes, was tested. With only two measurements of pond depth and corresponding surface area, this method estimated surface-water storage in beaver ponds within 5 % on average. Beaver pond morphometry was characterized by a median basin coefficient of 0.91, and dam length and pond surface area were strongly correlated with beaver pond storage capacity, regardless of geographic setting. These attributes provide a means for coarsely estimating surface-water storage capacity in beaver ponds. Overall, this research demonstrates that reliable estimates of surface-water storage in beaver ponds only requires simple measurements derived from aerial imagery and/or brief visits to the field. Future research efforts should be directed at incorporating these simple methods into both broader beaver-related tools and catchment-scale hydrological models.
Highlights
The volume of water stored at the surface of wetlands, ponds, and lakes is of great concern to those responsible for assessing risks and balancing water supplies to societal demands
The simplified V–A–h method is based on a simple power equation (Hayashi and van der Kamp, 2000), where the area of a pond (A), at a given height above the pond bottom (h), is described as h 2/p h0 where h0 is the unit height of the water surface (e.g. 1 m for shape index (SI) units), s is a scaling coefficient that represents the area of a circle (m2) with a radius that corresponds to h0, and p is a dimensionless morphometry coefficient that represents the shape of the bathymetric curve
The 40 ponds well represented the various types of beaver ponds that are created in riverine and wetland habitats (Baker and Hill, 2003), with maximum dam heights ranging from 0.25 to 2 m and dam lengths (Dlen) spanning 3–308 m, with medians of 0.83 and 40 m, respectively
Summary
The volume of water stored at the surface of wetlands, ponds, and lakes (as a function of stage) is of great concern to those responsible for assessing risks and balancing water supplies to societal demands. Arriving at reliable estimates of such storage is difficult without some knowledge of the feature’s morphometry, i.e. information that is often time consuming and impractical to acquire, especially when the features are numerous and transient through space and time (Milly et al, 2008) This is true for beaver ponds owing to their cyclic creation and abandonment. Beaver dams increase the openwater area within watersheds (Hood and Bayley, 2008) and ponds bring numerous ecosystem benefits (Johnston, 2012), but beaver ponds can be viewed as burdensome or even dangerous from an anthropomorphic perspective (Butler and Malanson, 2005; Green and Westbrook, 2009) Such concerns, whether positive or negative, generally centre around the pond’s capacity to store water and sediment, highlighting the need for quick and accurate surface-water storage estimation methods
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