It's the first day of fall at Great Basin National Park, and the changing aspens have painted the flanks of Wheeler Peak with veins of yellow and orange and red.

The change of seasons goes mostly unnoticed underground, as two of the park service's resident cave explorers cover about 500 feet in 90 minutes, much of it through tight passages that require them to crawl or scoot along on their bellies.

The purpose of today's trip is to check conditions in the cave and retrieve small devices called dataloggers, which record temperature and moisture levels.

While they're at it, Baker and Roberts discover what might just be a new species of cave critter no one has ever seen before.

It isn't the first time, either.

In the past two years alone, staff members have identified at least seven possible new cave species at Nevada's only national park, about 300 miles northeast of Las Vegas.

So far only two of the tiny animals have been officially described and given scientific names, but Baker and Roberts expect at least one more of their discoveries to become official this year with the publication of a scientific paper on the critter.

Several others are either in the process of being described or are awaiting the collection of additional specimens.

"Every trip you go in you can find something new, which is one of the really interesting things about caving," says Roberts, who is the park's natural resource program manager.

Recent finds include two varieties of tiny shrimp and two new kinds of all-white cave millipedes.

One of the millipedes was discovered in the unlikeliest of places: crawling its way across a concrete walkway frequented by tourists at the park's most-visited attraction, Lehman Caves.

This literal unearthing of new critters at Great Basin could do more than thrill entomologists and amateur bug enthusiasts. It could sharpen anxiety about the Southern Nevada Water Authority's plans to pump billions of gallons of groundwater a year from Snake Valley, just east of the park.

At the very least, the flurry of discoveries provides opponents with one more argument against a project already painted by its critics as a threat to rural residents, native plants and air quality from Ely to Salt Lake City.

Great Basin Superintendent Andy Ferguson voiced some of his concerns during the authority's Aug. 20 meeting on the controversial pipeline.

"I wanted the Southern Nevada Water Authority to be aware that Great Basin National Park is a national treasure, and anything that would impact on this national treasure is something that's going to be felt throughout the country," Ferguson said.

"I'd like them to know that we're extremely concerned -- very concerned -- and we just don't believe that the taking of water out of this little valley will be a good thing for the park."

Snake Valley represents the final leg of the multibillion-dollar pipeline the authority plans to build to tap groundwater across eastern Nevada.

The authority is seeking state permission to pump as much as 16 billion gallons of water a year from the vast and sparsely populated watershed on the Nevada-Utah border.

The valley is home to many of the authority's harshest critics, including ranch families who have lived in the area for generations.

Baker married into one of those families. Her father-in-law is Dean Baker, a longtime Snake Valley rancher who has become the de facto spokesman for pipeline opponents.

For their part, though, Gretchen Baker and other staff members at Great Basin National Park are trying to let science do the talking when it comes to the groundwater project.

The park service is in the process of drilling four monitoring wells just outside the park boundary as part of a research project funded through the sale of federal land in the Las Vegas Valley.

Three more monitoring wells will be drilled inside the park as soon as an environmental review of the work wraps up in the spring, Ferguson said.

In the meantime, Baker, Roberts and their colleagues are drawing up maps, collecting samples and monitoring seasonal changes in the caves in hopes of developing a baseline that can be used to identify any impacts from the groundwater project.

One senior environmental planner for the Southern Nevada Water Authority insists there shouldn't be any impacts.

Lisa Luptowitz said the authority's proposed wells would operate a few thousand feet below and a "substantial distance" away from the caves and their water sources.

As Luptowitz put it, there is a "hydrologic disconnect" between the caves and the areas where the authority eventually plans to drill its production wells.

She added that potential impacts to the caves will be addressed in detail in a federal environmental review of the pipeline project. A draft of that document is scheduled for release in the spring.

Great Basin staff members aren't just discovering new critters; they're finding whole new caves in and around the park.

The total right now stands at 42, including the longest, deepest and highest elevation caves in Nevada.

Baker, who is the park's ecologist, said the caves come in "a whole range of sizes," from ones you can walk through to ones only large enough for "belly crawling."

And then there are some that are "all vertical so you only can go up and down on rope to see the cave," she said.

The deepest cave in Nevada, appropriately named Long Cold, has "permanent ice in the bottom of it year round," Roberts said.

He suspects more caves might be hidden away within the park's 77,000 acres of steep mountain terrain. There might even be one out there as large and intricate as Lehman, which boasts more than 300 rare shield formations.

Lehman is the only cave that is open for guided tours by the general public.

The park service issues permits to experienced spelunkers for a handful of the other caves, but most of Great Basin's caverns are strictly off-limits. A few of them are so dangerous that even park personnel are not allowed inside.

Model Cave is one of the park's most diverse in terms of biology and hydrology. Snowmelt completely floods portions of it during the summer, but there is evidence that the cave also gets moisture from the groundwater table and nearby Baker Creek.

"This cave's been known for fifty years, and yet we're still finding brand new species out of it," Roberts said.

In November, for example, Baker, Roberts and another staff member took a survey trip 2,000 feet into the deepest reaches of Model, and on the way back out Roberts spotted something in a puddle. Drifting in the 55-degree water were tiny white objects that turned out to be freshwater shrimp.

He saw them but they did not see him; the shrimp have no eyes.

Baker said they put a few of the critters in a vial and sent them off to a specialist at the University of Illinois.

"He said, 'Oh, you guys have found something new. Go get more,'" Baker said. "It took several months and many trips to get enough of the adults to send to him."

In the process, they stumbled across another type of shrimp they'd never seen before, something called an ostracod.

As it turns out, finding tiny new species in a pitch-black cave isn't always the hard part. Locating an expert to confirm a discovery can be just as much of a shot in the dark.

"There aren't many people who describe these species. That's one of our biggest problems," Baker said. "There is one person who would describe the ostracods if we can find enough. He did his Ph.D. dissertation on the ostracods of Nevada and then he went back home to Turkey."

To analyze specimens of other possible new species, the park has turned to taxonomists in Brazil and the Czech Republic.

"A lot times there's only one or two people in the entire world who are the experts at these things," Roberts said.

His favorite critter is the Model Cave Harvestman, a spindly, pale-orange spider first identified and described in 1971.

Baker is partial to the Campodeid Dipluran, a primitive-looking insect about half an inch long and all white, with long antennae and tails. She doesn't know whether the bugs are unique to the park because she can't find a qualified specialist who can tell her.

"There's nobody currently describing them, so they go in the deep freezer," Baker said with a sigh.

The first day of fall yields one possible new discovery in Model Cave: a silvery beetle about the length of an eyelash.

Roberts spots it in a small pile of organic debris about 250 feet from the cave entrance, and Baker collects it in a small vial filled with ethyl alcohol.

First, though, Roberts lets it crawl around on his hand so Baker can snap its picture. The beetle scuttles so fast it's hard to photograph.

Such rapid movement suggests it could be a surface dweller that found its way into the cavern somehow. Most cave critters move slowly due to the cold and their own sluggish metabolisms, which help them survive on what meager nutrients they can find in the dark.

The beetle will need to be sent off to Illinois for positive identification, but the two smiling cave explorers say they have never seen anything like it before.

Contact reporter Henry Brean at hbrean @reviewjournal.com or 702-383-0350.