Matt Gentry | The Roanoke Times

A Mountain Lake guest walks on a dirt path leading to a temporary boat dock at the lake in Giles County on Wednesday.

Visitors at Mountain Lake Resort are still having the time of their life, even though the lake is only about 50 percent full.

This emptying of one of Virginia's two natural lakes -- and also the highest east of the Mississippi River -- is just part of the cyclic nature of the attraction.

Mountain Lake continually loses water through cracks and holes in the bedrock below the surface, and studies have shown that water also enters through these openings.

Under normal conditions, snowfall and rain contribute enough precipitation for the amount of water entering the lake to equal about the same amount draining from the basin.

However, the lake began draining below normal levels in 2005 and has remained low, said H.M. "Buzz" Scanland, general manager at Mountain Lake Resort.

The current loss of water is not uncommon to what happened in 2002, and the lake was full again by the fall of 2003. Scanland said the loss is caused by a lack of precipitation. The here-today, gone-tomorrow character of the lake adds to its uniqueness, he said.

Matt Gentry | The Roanoke Times

Guests in one of the Mountain Lake resort cabins canoe and fish in the Giles County lake on Wednesday. Mountain Lake is one of only two natural lakes in Virginia, and its water levels fluctuate periodically.

"We just haven't had any precipitation," he said. "This lake depends on rain and snowfall, with snow being the best thing because it will seep into the ground."

According to the most recent report of the National Drought Mitigation Center, Virginia is in a moderate drought. And the National Weather Service reports that Blacksburg has received 20.98 inches of rain since Jan. 1, 2.59 inches below the average.

Low water levels in the past caused resort officials to extend boat docks, which have been moved to the opposite side of the lake where it is somewhat deeper.

And as for the once-lakeside gazebo, about 200 yards of vegetation now separate it from the lake.

"There's no solution to it except nature," Scanland said. "If we don't get rain, I don't know what we're going to do, and now the temperature is higher than normal and will cause some evaporation."

When water levels first decreased, the shores were barren, but the level has been down so long, resort workers have planted wildflowers. Other greenery has also sprouted, so visitors who are new to the lake often do not realize the water level has gone down, Scanland said.

Business is down at the resort, but Scanland said he thinks it can only partly be attributed to the lake's water level.

He said more people are taking close-to-home weekend trips this summer because of high gas prices, which contributes to Mountain Lake Hotel's rooms being full on weekends but virtually empty during the week.

Matt Gentry | The Roanoke Times

A dirt path leads past the Mountain Lake resort boat house (right) to a temporary boat dock at the lake in Giles County.

The lower water levels have produced some minor extra costs, Scanland said. Frisbee golf and other extra courses have been installed to add more activities around the lake, and the relocation of the boat docks has led to the need for extra employees to help patrons to the docks.

"We have a few more employees probably, but we haven't had people really complain about the lake being down," Scanland said. "People talk about the holes in the lake and the water coming and going, but hopefully we'll get through this cycle and this time it'll be back for years to come."

Skip Watts, a professor of geology at Radford University and former science and technology adviser to U.S. Sen. Joe Lieberman, was part of a team of scientists in the early '90s who studied the area of Giles County around Mountain Lake for the Nuclear Regulatory Commission. The commission was interested in ancient landslides in the area, hoping to be able to predict earthquake recurrence levels.

"We came up with some fascinating conclusions about what's going on at Mountain Lake," Watts said. "It is a complex hydrologic system there -- you've got several things going on."

Watts said the lake is mostly a result of a landslide that could have happened as many as 10,000 years ago.

"You've got a combination of a landslide -- which dammed the natural flow of the stream there -- and a limestone bottom, which causes the leaky floor," he said.

"The water level of the lake depends on the balance of water leaking out of the bed and new water flowing into the lake, most of which is captured in groundwater by the surrounding watershed.

"It's a water economy."

Researchers once thought it would be possible to drill wells and pump lost water back into the lake, but exploratory drilling was unsuccessful at finding water.

Watts is aware of these attempts, which he called an active system.

However, he said another way to help keep the water levels up that might be interesting to consider is what he called a passive system.

"These might look at ways to enhance the amount of water that is getting to the lake by using gravity and other natural processes, and the other option would be to reduce the amount of water flowing out of the lake," Watts said.

Engineers may be able to pinpoint locations in the lakebed where the most water is lost and even use concrete to stem the loss of water, he said.

Scanland said surveyors in the 1700s reported the lake to be as large as 50 acres, while surveyors in the 1800s reported it as only a pond (the former name of Mountain Lake was Salt Pond).

This proves that the lake is a natural oddity that will have its ups and downs, Scanland said.

Though the lake is half-empty, Scanland prefers to look at it as half-full. He said he is confident the water will return again: "You just have to look back and say, 'Nature is the one that's in control of Mountain Lake.' "