Final 2015 Museum of Earth Sciences Lecture probes landmark disappearance
Radford University Geology Professor Skip Watts and Geology Lab Coordinator George Stephenson explored the case of the disappearing Mountain Lake for the Museum of the Earth Sciences Lecture on April 7 in the Hurlburt Student Center Auditorium.
Watts set the stage by defining geologic engineering and its application to the Mountain Lake mystery.
“Mountain Lake in Giles County is one of only two naturally formed lakes in Virginia,” said Watts“The other being Lake Drummond in the Great Dismal Swamp in the southeastern portion of the state. Throughout history, the lake has fluctuated in size and has even been known to almost disappear, most recently in the 1600s.”
For most of the 20th Century, the lake was robust and near full pond, prompting the development of a resort community around the property.
“The lake is primarily fed by a stream that enters from the south end near the hotel and it meanders through the bed before exiting at the northern end of the property,” explained Watts. “When the water input is less than the water loss at the northern end, the level of the lake drops and it can become quite small.”
An ancient landslide that is now leaking likely caused the dam that contains the water in the lake.
Watts and Stephenson recapped the research protocols and technology that they, along with RU geology students, are using to explore the geology of the landmark lake.
Their research arsenal includes a remotely operated submarine, dubbed “Flipper,” arrays of side-scan sonar, electric resistivity sensors, quad copters, seismic mapping software and flow monitoring operations. From their efforts, a picture of the lakebed and the forces at work has been developed.
“We also needed to determine where the water was going and to find the places where it was leaking from the lake,” said Stephenson. “We used a dye trace study by injecting fluorescein into some of the drain holes and then placed devices at a number of sites downstream to capture the harmless tracer.”
This discovery of the destination of the leaked water combined with the data collected about the site allowed the geologists to make several recommendations to mitigate the problem presented by a much-loved lake that had leaked away.
A local contractor “nudged” some of the natural rock material into the leaking holes, or pipes, and the lake has begun to refill slowly to a level of about one-third of its full pond status.
The containment of the water is part of an equation that included a dwindling supply of water to fill it.
“While we seem to have successfully found a way to help limit the water that is exiting the lake, it appears that there is less water coming into the stream that feeds the lake than in past decades and that is a new challenge that we are helping the property owners tackle,” said Watts.
Watts, Stephenson and several students are now assessing the watershed above the lake to determine how development has impacted the inflow of the water. Two studies of the watershed were featured at the recent annual conference of the Southeastern Section of the Geological Society of America (GSA):
- Dylan Dwyer and Kent Weidlich on their research titled "Potential water sources for Mountain Lake, Giles County, Virginia."
- David Imburg and Dwyer on their research, titled "Effects of terrain modification on surface water runoff from the Blueberry Cottages Watershed at Mountain Lake, Giles County, Virginia.
The Radford University Museum of the Earth Sciences is part of the department of geology in the College of Science and Technology and an affiliate of the Virginia Museum of Natural History. The museum serves as an educational resource for earth science-related themes for the university, K-12 communities and the general public. It is open from October through November and from January through April while RU is in session. To learn more about the Museum of the Earth Sciences, contact Steve Lenhart at (540) 831-5257 or firstname.lastname@example.org.