The effects of beaver damming on groundwater flow through a wetland, Beaver Meadow, NY
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The North American beaver is considered to be an ecosystem engineer due to the large impact it can have on both the biotic and abiotic conditions of its surrounding ecosystem. Beavers will often build a dam in a low gradient system, such as a wetland, in order to create a suitable living environment. An increase in hydraulic head behind a beaver dam can cause shifts in the capture zone of the wetland and potentially a reversal in groundwater flow. This study utilized water level data collected before, during, and after the construction of a beaver dam in the Beaver Meadow wetland, located in Western New York. With this information, a groundwater flow model was created with MODFLOW to examine the hydrologic changes that occurred in a beaver modified wetland system. Specifically, this model allowed for the quantification of changes in groundwater flux and changes in the extent of both the capture and discharge zones of this wetland. The emplacement of a beaver dam resulted in minimal change in groundwater flux at this site, which is attributed to a clay unit that underlies the peat, disconnecting this wetland from regional groundwater flow. Adjusting this numerical model to simulate a scenario where the wetland is connected to regional groundwater flow, by removing the underlying clay unit, results in a much larger impact on flow paths. In the absence of the clay layer, the beaver dam causes a 70% increase in discharge through the wetland pond and increases the surface area of both the capture zone and the discharge zone by 30% and 80%, respectively. Some restoration projects are utilizing beavers as a low cost technique to restore wetlands. This research demonstrates that it is important to properly investigate the connectivity of flow paths in a wetland to fully evaluate the effects of a beaver dam on the wetland hydrology.