Many are in the Dark about Importance of Caves to Water Quality

Posted by | September 3, 2013

Please welcome guest author Lara Lutz. Lutz is a staff writer for the Bay Journal, and has worked as an environmental writer and editor in the Chesapeake Bay watershed since 1995. 

Lara Lutz

Lutz is the author of “Watershed Moments” (Chesapeake Bay Trust 2006), featuring eight local-level stewardship initiatives in Maryland, and “Chesapeake’s Western Shore: Vintage Vacationland,” covering the recreational history of the Bay’s Western Shore. The following piece originally appeared in Bay Journal, and is excerpted in part here with permission. 

 

Wil Orndorff was about 18 years old when he first clambered down a secluded ravine in a Virginia hillside and met the black mouth of Ogdens Cave.

“I’d have come a lot sooner if I’d known it was here,” Orndorff said.

Wil Orndorff, karst protection specialist for the Virginia Department of Conservation and Recreation, inspects an underground stream in Ogdens Cave. Caves are a part of karst geology, which provides much of the stream flow and public drinking water in the Chesapeake Bay’s headwater areas. (photo Dave Harp)

Wil Orndorff, karst protection specialist for the Virginia Department of Conservation and Recreation, inspects an underground stream in Ogdens Cave. Caves are a part of karst geology, which provides much of the stream flow and public drinking water in the Chesapeake Bay’s headwater areas. (photo Dave Harp)

Back then, Ogdens Cave was on private farmland. Today, it’s found on a Natural Area Preserve, a designation that protects some of the most significant natural areas in Virginia.

Orndorff works for the Virginia Natural Heritage Program in the Department of Conservation and Recreation. He looks after this cave and the surrounding landscape because they are part of the enormous underground complex of rocks, caves and moving water responsible for much of the stream flow and public water supply in headwater regions of the Chesapeake Bay.

Officially, this geology is called karst. 

As the state’s only karst protection specialist, Orndorff’s territory is a long swath of land that makes a graceful arc along the Shenandoah Valley in western Virginia. Here, the movement of ancient plates on the Earth’s surface pushed, stacked, folded and rose to become the Appalachian Mountains.

Below the surface, pockets of space formed caves, and a subterranean network began storing, moving and releasing water to the world above. Over time, water dissolved the limestone and dolomite bedrock, creating larger tunnels and caverns, etching its movement in stone that today has been dry for thousands if not millions of years.

A drop of water helps to form a stalagmite in Virginia’s Grand Caverns. (photo Dave Harp)

A drop of water helps to form a stalagmite in Virginia’s Grand Caverns. (photo Dave Harp)

Karst formations can be found in the western portions of Pennsylvania, Maryland, Virginia and much of West Virginia.

Virginia has more than 4,300 known caves, and the Shenandoah Valley is riddled with them. Some are tourist attractions, as a barrage of signs on Interstate 81 makes clear, but the vast majority are not.

Orndorff has studied lots of them, and on this day he was visiting an old friend.

Ogdens Cave, in Frederick County, is not a show cave. There are no public facilities or tour guides. No manicured paths with footlights, railings or creative colored lights.

Beyond its craggy mouth, daylight vanishes. The floor is a rock-strewn slope that continues the downward slide of the ravine outside, but Orndorff moved toward the bottom with quick light steps.

Midway, he stopped and smiled. “Listen. You can hear it,” he said.

The sound was distinct, although nothing in the absolute stillness revealed its source: the distant but steady rush of water.

He moved through another chamber, where the ceiling dropped and cave lichen on its surface glinted like a galaxy of gold stars overhead.

In the next room, the water grew louder and the walls were marked with names. “J.W. Hoar 1898″ projected clearly in the stone, next to Wade from 1979.

Thomas Jefferson admired Virginia’s Natural Bridge so much that he purchased the property in 1774 and owned it until his death. The bridge began as a water cave. The land collapsed around it, until the arc was exposed on the surface. (photo Lara Lutz)

Thomas Jefferson admired Virginia’s Natural Bridge so much that he purchased the property in 1774 and owned it until his death. The bridge began as a water cave. The land collapsed around it, until the arc was exposed on the surface. (photo Lara Lutz)

Here, a shelf of rock hung so low that walking was impossible. Orndorff belly-crawled beneath it on a bed of melon-sized rocks and pulled himself into a squat at the far side, where there was slightly more head room — and a fully running stream.

Above ground, this stream is called Buffalo Marsh Run, and its course is mapped across the rolling terrain. Underground, it moves quickly out of sight and the details of its route remain a mystery.

Orndorff and other geologists who study these features use a special dye to understand how the water moves. Placed in the water, the dye becomes a tracer. In this case, the dye emerged in spring water near Cedar Creek, a few miles away.

At Mossy Creek near Harrisonburg, dye solved another puzzle. The creek contained far more water than the dynamics of its watershed could explain. It turned out that a different stream, farther off, sank into the earth and reappeared in Mossy Creek.

Such connections are a curiosity, but they also have practical meaning for anyone interested in the quantity and quality of water in the Shenandoah Valley.

Municipalities, homeowners with well water, and water-dependent businesses and farming operations all rely on karst groundwater. Aquatic life in streams depends on a base flow of water that is overwhelmingly supplied by underground water emerging from springs. So understanding how the geology works — and how water use and land use in one area might affect another — is vital to planners.

Drawing water from a productive spring could affect streamflow in a seemingly unrelated site. Fish and other aquatic creatures, including unique species found in caves, could suffer the effects. Humans might too: the draw could unintentionally take water from a stream or river on which other people depend.

“Most folks think springs and wells are inherently reliable sources of clean water. I disagree,” Orndorff said. “There is probably plenty of water, but it has to be managed the right way to keep it clean and flowing.

Karst features don’t occur in isolation, Orndorff pointed out, noting: “If development disconnects these features, it can cause problems.”

Cave ecology includes a number of rare and endangered species that have adapted to the cool, dark setting, as well as those like this cave salamander that follow surface streams into the ground. (photo Dave Harp)

Cave ecology includes a number of rare and endangered species that have adapted to the cool, dark setting, as well as those like this cave salamander that follow surface streams into the ground. (photo Dave Harp)

Water in karst geology is extremely vulnerable to pollution. It travels the surface in typical, visible ways, like stormwater runoff and stream corridors. But once underground, it can follow unexpected paths very quickly, while carrying contaminants and pathogens from the surface.

Widespread infiltration occurs through countless cracks and fissures. Examples can be seen in many public caves, where the water drips from the walls and helps to build stalactites.

In Natural Bridge Caverns, tour guide Otis Mabe pointed out a fist-sized hole near the footpath that rarely draws attention. This “blue hole” is part of the cave’s drainage system. “It goes all the way down to the water table, like a natural downspout,” Mabe said. “That water there is last week’s rain.”

Karst also includes direct entry points like sink holes, losing streams and sinking streams.

Sink holes are round depressions in the earth, originally caused by the movement of underground water that pulls the soil down. Some are small, and some are enormous. Surface waters pool here and enter the system more easily. Yet sink holes are often used as illegal dump sites.

Losing streams flow through leaky stream beds, decreasing in volume as the water is drawn underground. Buffalo Marsh Run, which detours into Ogdens Cave, is a losing stream. Sometimes nearly the entire stream drains to the cave. Other times, depending on flow and geologic features, connections to the cave stream are “plugged” and there is greater flow along the surface.

A sinking stream can be quite dramatic, disappearing suddenly though a stony sieve-like depression to continue its course underground. It is no surprise that the name “Lost River” is common in places with karst. In the Shenandoah, Dry River takes its name from this feature, too.

Karst geology includes a variety of features that create direct connections between surface water and ground water. (map by U.S. Geological Survey)

Karst geology includes a variety of features that create direct connections between surface water and ground water. (map by U.S. Geological Survey)

The Swiss-cheese nature of karst geology means that water-borne pollutants on the surface move quickly into groundwater and also into deeper areas of the aquifer.

A spill could have immediate localized impacts, depending on the ways in which underground water moves near the site. Orndorff once tested a well at a residence because the family was getting sick. Tracer dye placed in the toilet showed up in the well the next day.

“The underground plumbing in karst is like pipes in your home. Whatever you pour in, there’s no filtration system,” said Daniel Doctor, a karst map-maker for the U.S. Geological Survey. Pollutants that drop deep into the system will be diluted by larger reservoirs of water, but linger for a long time. “Land use over time here will be affecting the ecosystem for decades,” he said.

Orndorff said that water in some areas with intensive agriculture show high levels of nitrates associated with fertilizer and manure. Nearly all of the wells in the Shenandoah Valley have at least trace levels of atrazine, an herbicide used to prepare cornfields for planting.

Many public water systems in the Shenandoah Valley draw water from karst springs and wells. One such spring feeds Silver Lake near Dayton. Dye tracing has shown that the spring receives some of its water from nearby Cooks Creek, which flows across rolling crop and pasture land. Some farmers keep their cattle out of the stream; others do not. Improperly functioning septic systems can also be a significant source of nitrate.

Cave Bacon (photo Dave Harp)

Cave Bacon (photo Dave Harp)

Orndorff and his colleagues are concerned because many springs show elevated levels of nitrate, with some approaching or even exceeding the EPA drinking water standard.”

Drinking water treatment systems are unlikely to address the problem because most are designed to remove pathogens, not contaminants like nitrate. Special systems that do treat water for nitrate are uncommon and expensive. But even if such systems were widely used to meet drinking water standards, they would do nothing to address the impacts of degraded springs as they flow directly into streams and join the surface ecosystem.

The conservation practices promoted throughout the region — nutrient management plans, streamside forest buffers and careful attention to stormwater management — can also give meaningful protection to streams and groundwater in karst territory. To identify sites that most need such projects, scientists need to understand more about the labyrinth of waterworks beneath them.

Its secrets are largely unknown.

State and federal interest in karst research was revived after a 2002 drought raised concerns about public water supplies in the valley. Communities faced more questions than answers.

Orndorff said that many people refer to the overall water source for the area as “the Great Valley aquifer,” but there may be more than one system at work. “It’s like a vast reservoir, but compartmentalized. We don’t really know the degree to which they are all interconnected,” Orndorff said.

“There is no map of groundwater in the valley,” said Joel Maynard, who works with the Virginia Department of Environmental Quality to track and predict the behavior of water supply in wells.

Daniel Doctor of the USGS is part of the effort to create better maps of Virginia’s karst areas and its groundwater resources. (photo Dave Harp)

Daniel Doctor of the USGS is part of the effort to create better maps of Virginia’s karst areas and its groundwater resources. (photo Dave Harp)

Landowners who want to drill a well sometimes call Maynard to learn about the water resources on their land, but his advice is limited.

“I can look at what people around them have gotten. They might fall in that range, but they might not,” Maynard said. “You can make generalities, but there are all sorts of outliers and understanding them is key.

The Karst Groundwater Protection Program run by the Virginia Department of Conservation and Recreation originated in 1994 with federal funds from the Clean Water Act. The program has been scaled back because of budget cuts and is now funded through a combination of state funds, grants and inter-agency contracts.

The USGS has measured springs and sampled for water quality, and Doctor is part of an effort to better map karst features and water flow throughout the region.

One of their most surprising findings is that the region’s rivers draw 80 to 90 percent of their base flow from springs.

“If you don’t protect spring flow you diminish the river flow,” Doctor said. “January through March is the critical period for recharge, and if you don’t have enough snow or rain during those months, it could give you a drought in the summer.”

For the vast majority of Virginia springs, the boundary of the recharge area is unknown.

(Lucidity Information Design, LLC)

(Lucidity Information Design, LLC)

Researchers like Doctor and Orndorff are using modern technology in their work, including seismic data, ground-penetrating radar and satellite imagery. Dye-tracing continues to help with ground-truthing.

“It’s a big tool but you have to use it carefully,” Orndorff said. “You can’t simply say that Stream A feeds Stream B. But you can say that Stream A in some conditions influences Stream B.

Even as researchers work toward understanding these resources, there is no comprehensive understanding of the locations and quantity of groundwater withdrawals.

Virginia’s Groundwater Protection Act allows the Department of Environmental Quality to regulate groundwater withdrawals in specially designated areas. Currently, Virginia has only two Groundwater Protection Areas, both in the Coastal Plain. Orndorff would like to see one or more in Virginia’s karst region.

“Such a designation would shed light on a lot of unreported groundwater use in the valley,” he said.

A number of government agencies, along with universities and nonprofit organizations, are at work on behalf of karst throughout the Chesapeake region, with interests ranging from geologic history and cave ecology to water quality, water quantity and stewardship practices.

The Karst Waters Institute, based in Leesburg, is focused on scientific research. The Mid-Atlantic Karst Conservancy owns more than 5,000 acres of caves and karst lands, while the Cave Conservancy of the Virginias offers a stewardship guide for landowners and educational resources for teachers.

Project Underground is a national environmental education program on caves and karst that originated in Virginia. Project Underground workshops have provided thousands of formal and informal educators with tools for teaching about karst resources.

The Virginia Cave Board, appointed by the governor, has been working for decades to promote research and provide advice on development issues. They are in the early stages of creating a cave and karst trail that will help the public move beyond the narrow view of a show cave to understand the incredible geologic phenomena that waters the valley and feeds the Chesapeake Bay.

Like all water stewardship efforts, public attitude is key. “Stewardship requires forethought,” Orndorff said. “We need to be doing this not just for ourselves and our children, but for folks even further down the line.”

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