What's Up with the Lake?
Mountain Lake is one of only two, naturally-formed, freshwater lakes in the state of VA. The other is Lake Drummond, in the Dismal Swamp of the Hampton Roads area. Mountain Lake is also the highest naturally-formed lake in elevation east of the Mississippi River (approx. 3800’ above sea level).
The lake was formed approximately 6,000 years ago; two theories of formation are supported:
1. PARTIAL DAM … Recent studies suggest a small “gorge”-like waterway on the North end of the lake where Pond Drain is now located. Over time, soil and rock have eroded and dammed up this flow. What exists now is a “partial dam” on the northern-most slope of the lake bed – essentially it’s a leaky lake!
2. COLLAPSED BASIN … Layers of softer limestone rock exist underneath the harder, more resistant sandstone formations of rock. Overtime, water finding its way down in to the rock underneath the soil has eroded the limestone, causing the surface stone to slowly collapse and sink in to the “bowl” or basin-like structure we see on the north end.
LIKELY- the lake’s formation many thousands of years ago is a combination of these phenomena.
It is a known and documented fact that the lake level has dropped several times since its formation. Some of these low periods have existed for just a small number of years or for as many as 30+ years. However, it is unknown if the lake has ever emptied to the literal mud puddle level that we have witnessed in the past several years.
The first recorded historical account of Mountain Lake was made by Christopher Gist on May 11, 1751. Gist was an explorer with the Ohio Land Surveying Company-
The last time the lake was low was for a minimum period of 36 years dated to the late 1700s in to the 1800s. Trees grew in the lakebed and stumps and old logs are still seen in the lake today (so we know that the lake was at least as low as we are seeing it currently).
Historical account by Rogers, 1884:
“This beautiful sheet of water is situated at the intersection of the Salt Pond Mountain and several of its spurs, and not as it is commonly supposed, on the top of the mountain. Its height above the base of the mountain, is probably from 900-1000 feet, but it is surrounded by steep and lofty hills on every side, excepting that by which it is approached, and that through which its water finds a small outlet, falling in a picturesque cascade of great height, and then flowing rapidly into the creek below. Rock and earth gradually accumulated at the passage, having dammed the waters up, and hence the trees and shrubs which grew upon its margin, may now be seen sometimes standing erect at a considerable depth beneath its surface.”
- The “cascade” was located at the North end of the lake, flowing in to Pond Drain stream.
- The road that traverses the mountain, rt. 613 today, was originally located on the East side of the lake, along today’s Old Turnpike Tr. The road was re-located to the West side of the lake in the early 1900s; a levy was built to direct overflow of the full lake under the road and down in to Pond Drain.
- “Trees and shrubs” seen “at considerable depth” attest to the dramatic fluctuations in the lake levels.
There is a constant outflow of water through the bottom of the lake in addition to water evaporating from the water’s surface (caused by temperature and low humidity in the air). Inflow of water occurs in the form of springs and precipitation. When there is more water flowing out than there is coming in, the lake is low. Years prior, there has always been more water coming in to the lake than leaking out through the bottom, allowing the lake to be full.
Water flows out of the bottom of the lakebed disappearing through many “piping holes” located within the four major “depressions”. These piping holes vary in size from just an inch to over 12 inches. Outflow of water within the piping holes varies and depends on several factors: amount of debris or soil within or near the holes; perhaps the water level of the aquifer beneath the mountain; water pressure from the amount of water within the pond.
Where does the water go when it disappears through the bottom? The exact answer to this is unknown! A dye trace study was conducted in 2012 by VT graduate student Luke Joyce. Coal-traps were placed in surface streams of the major drainages surrounding Salt Pond Mtn. to survey for the harmless dye. The dye is detectable for up to three months; however, only one very faint, trace amount of the dye was observed – down Pond Drain stream.
What does this tell us? The water could be held under the mountain in a reservoir and surfacing after a longer period of time; or, the water could be flowing elsewhere underneath the mountain.
Operation: Lake Restoration—January, 2013
Historically, Mountain Lake has been a significant natural asset that was a draw for people seeking respite from more developed areas along the east coast. The lake has been an important recreational feature of the Mountain Lake property for decades. The lake also contributes to the scenic and aesthetic value of the property, setting the Mountain Lake Lodge apart from other competing facilities.
Research conducted by qualified scientists has developed a picture about how water moves around the lake. In an effort to restore the natural lake levels of Mountain Lake for recreation and to enhance the scenic value of the property, land managers determined that it is economically and environmentally feasible to recreate a natural process to slow water outflow from the lake by moving larger and varied particles into the depressions and piping holes. Rock and soil were moved from the upper slopes of the lake bed in to the piping holes and depressions. A small amount of bentonite clay was also mixed in to the substrate.
Radford University research suggested that the most natural plan for mitigating the loss of water was to simulate natural landslide processes by nudging existing graded colluviums & lake sediments into the depressions. The U.S. Army Corps of Engineers agreed and issued a permit through Bill Newcomb of Draper Aden Associates, Blacksburg, VA.
Click "Read More" to see the current state of the lake.+ Read more - Read less