Ecological Monitoring Report Vernal Pools on the Hanford Site
Shallow ephemeral wetlands (also known as vernal pools) in very small to rarely large depressions occur throughout the exposed, volcanic scablands on the Columbia Plateau. These pools are characterized by fresh water inundation for much of the winter and spring, followed by dramatic lowering of the water table at the approach of summer. On the Columbia Plateau, vernal pools are geographically limited but can be locally common (Rocchio and Crawford 2015b). In the state of Washington the Columbia Plateau Vernal Pool ecosystem is considered to be “Imperiled,” that is with a high to moderate risk of extirpation (Rocchio and Crawford 2015a). In 1997, during surveys conducted on the Hanford Site for the U. S. Department of Energy, Richland Operations Office (DOE-RL), The Nature Conservancy (TNC) located three previously undocumented clusters of approximately 20 vernal pools. The Hanford Site pools were located on the east end of Umtanum Ridge, in the central part of Gable Butte, and at the eastern end of Gable Mountain (TNC 1998). The fall and winter of 1996/1997 was unusually wet; 9.7 in. (25 cm) of precipitation fell from October 1996 through March 1997 compared with a normal (30-year average) precipitation of 4.85 in. (12.3 cm) (MSA 2018). The fall and winter of 2016/2017 was also an unusually wet period with 6.86 in. (17.4 cm) of precipitation, which included 28 in. (71 cm) of snow falling between October and the end of February. During the late winter of 2017, the vernal pools documented in 1996/1997 were rediscovered and found to contain significant amounts of water. This report documents the study of roughly 25 vernal pools found on Umtanum Ridge, Gable Butte, and Gable Mountain during 2017.