Title page for ETD etd-04262011-154246


Type of Document Master's Thesis
Author Roningen, Jeanne Marie
URN etd-04262011-154246
Title Hydrogeologic Controls on Lake Level at Mountain Lake, Virginia
Degree Master of Science
Department Geosciences
Advisory Committee
Advisor Name Title
Burbey, Thomas J. Committee Chair
Henika, William S. Committee Member
Mauldon, Matthew Committee Member
Parker, Bruce C. Committee Member
Keywords
  • electrical resistivity
  • karst
  • hydrogeology
  • baseflow
  • evapotranspiration
Date of Defense 2011-04-22
Availability unrestricted
Abstract
Mountain Lake in Giles County, Virginia, has a documented history of severe natural lake-level changes involving groundwater seepage [Jansons, 2004] that extend over the past 4200 years [Cawley, 1999], and as of December 2010 the lake was about 2% full by volume. Situated in the Valley and Ridge physiographic province on the axis of a plunging anticline and straddling contacts between three upper Ordovician and lower Silurian formations, the lake is one of two natural lakes in Virginia.

A daily water balance, geophysical surveying with dipole-dipole electrical resistivity, and chemical sampling have shed light on the nature of flow to and from the lake, including: 1) the steady nature of net groundwater outflow, 2) the seasonal response to precipitation of a forested first-order drainage system in fractured rock, 3) the influence of a fault not previously discussed in literature regarding the lake, and 4) the possibility of flow pathways through karst features.

Results from a water balance indicate steady lake drainage and significant recharge when vegetation is dormant, particularly during rain-on-snow melt events. The resistivity profiles display a highly heterogeneous subsurface and reveal low-resistivity areas that suggest flow pathways to and from the lake. Well logs, satellite images, and outcrop observations appear to confirm the presence of a fault to the east of the lake. Chemical evidence suggests that karst features may be present in the upper Reedsville-Trenton formation underlying the lakebed.

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