While much of the focus during the current drought has been on public water agencies, experts say it remains to be seen how much of an effect the dry weather will have on private well systems.

Thousands of residents in Tuolumne and Calaveras counties get their water from private wells. If the drought continues, the number of wells that run dry will depend on a number of factors, said Calaveras County Environmental Health Director Brian Moss.

"Right now, we're not seeing any variation in deepenings or new well construction," Moss said. "Do we expect that to change? We don't know. It depends on the conditions over the rest of winter, where the wells are located and how deep they are."

When a well runs dry, the owner has two options - deepen the well or build a new one in a different location. They must first obtain a permit for the construction from the county's environmental health department.

Moss said most well owners choose to go the generally less-expensive route by deepening the existing well.

Marvin Tanko, owner of Tanko Water Well Drilling, which has locations in Sonora and Angels Camp, said he hasn't experienced an unusual increase in calls for deepenings or new wells yet this year, though a lot of calls have been from customers concerned about the situation and what they should do.

"There's not a huge panic yet," he said. "Everybody's kind of waiting to see before they pull the trigger on adding an extra well to supplement TUD (Tuolumne Utilities District) water."

The TUD board implemented mandatory restrictions on customers this week and is eyeing emergency water-rate increases to offset the costs of operating under heavy water conservation. The district is the largest provider of water in the county, with 14,000 connections serving roughly more than 40,000 residents.

Many other agencies in the state have called for similar or even stricter measures in response to the growing water crisis.

The California Department of Water Resources conducted a snow survey Thursday that found the average snowpack in the Sierra Nevada was about 88 percent less than normal - the lowest reading to date since the DWR started keeping records in 1960.

If conditions don't change soon, it could be the third straight year with below normal precipitation.

Some farmers and growers in Tuolumne County started seeing their wells dry up as early as last summer, according County Agriculture Commissioner Vicki Helmar.

Helmar said she's received recent calls from growers with wells who are concerned about the current situation, and others who believe their water supply is secure despite the weather.

"I think we are going to find out as time goes on, that we will see a good number of wells go dry for agricultural folks," she said. "It is a big concern for our ag community."

A local well-owner who watched his fail during the drought of the late 1980s and early 1990s warned about being "overconfident" in a well's production capacity.

"Wells can give a lot of people comfort if they haven't been through a prolonged drought, but they might want to rethink that attitude and start conserving water indoors and outside," said Al Dahlstrand, a retired mining engineer and master gardener.

Dahlstrand lives on a five-acre property on the east side of Jamestown and owns a well that he uses to irrigate 11 trees that produce peaches, pears, apricots, almonds and cherries.

During the earlier drought, Dahlstrand used the well for both irrigation and household water. He was forced to tie into the public water system in 1989 for his home because a number of wells in his area were failing or having water quality problems.

In Dahlstrand's case, he and his neighbor were both on the same system.

"We were on the same limestone fracture system, so I could see our well go down as he was pumping," Dahlstrand explained.

Most of the well systems in Tuolumne County are drilled into hard rock where water is pooled into fractures.

One fractured-rock system can typically produce enough groundwater to support a couple of households, but it's not uncommon for next-door neighbors to have wells that draw water from separate fractures.

"You get all these little canyons and valleys in the foothills … because the rock was fractured (by water) over hundreds of millions of years," he said. "It's pretty rough terrain, and that's typically the host for wells we tap up here."

The fractures usually "recharge" as the snowpack melts and water runs off into the rock. However, with what's shaping up to be a historically low snow pack, the concern is that many wells won't recharge and could dry up over summer.

"I would caution anyone with a well - don't be overconfident," Dahlstrand said. "Start conserving before you have a problem, because it could get very expensive."

Dahlstrand said the cost to tie into a public water system could vary greatly depending on how far from the infrastructure the property is located, but 25 years ago it cost him about $3,500.

Tanko said his average starting price for a new well is typically between $8,000 and $12,000, while deepening costs about $15 per foot depending on the type of rock and conditions.

Tuolumne County Environmental Health Director Rob Kostlivy said he expects to see an uptick in new well construction in the county this year.

"We're anticipating a busy year," he said. "Since TUD is putting restrictions on the amount of water people can use and people have landscaped properties, it's possible they are going to be punching new wells to meet their water demands."

One county residence on a natural spring well had to drill a new one after running dry about a week ago, Kostlivy said.

Because of the nature of the county's mostly fractured-rock systems, Kostlivy expects many more will be running dry if the area doesn't receive a "substantial amount of rain" over the next two to three months.

"It's not like the valley where we have these deep aquifers under several hundred homes," he explained. "Your water in Tuolumne County is inside those cracks and fissures (in the rock). So if there's nothing to charge that, it will go dry."

Kostlivy is encouraging well owners to report any issues or failures to the county as it looks to secure any available assistance for well drilling or water deliveries.

"We're really trying to mitigate this before something severe happens," he said.

To report well problems, call the Tuolumne County Environmental Health Department at 533-5633, or the Calaveras County Environmental Health Department at 754-6399.