A lack of rain and snow has depleted streams throughout Pennsylvania's Susquehanna River Basin, and as of yesterday, at least half a dozen companies involved in hydraulic fracturing are suspended from tapping those waters to produce shale gas.

Hydraulic fracturing, or fracking, uses millions of gallons of water and chemicals to release pockets of natural gas that are trapped inside underground rock formations. Many of these drilling operations get their water from "withdrawal sites" at nearby streams and import it using trucks and pipelines.

But low water levels have blocked companies from accessing 19 sites across six northern Pennsylvania counties, and they can only resume taking water when the streams have recovered to normal levels for at least 48 hours.

"It's a stream protection measure we've had in place before," said Susan Obleski, director of communications for the Susquehanna River Basin Commission, which issued the suspensions. "What's unique to this year is how early in the season we're seeing suspended withdrawals."

In 2010 and 2011, the commission issued most of its water restrictions during the summer months. But an abnormally warm spring and winter, coupled with a lack of rain and snowfall, are causing water levels to drop much sooner than usual.

Weather reports say there could be some light rain in the state over the weekend, but overall precipitation is expected to be at least 50 percent below normal over the next five to 13 days, according to the National Weather Service's Climate Prediction Center.

"We were all very hopeful for a substantial rainfall event this weekend, and forecasts are already scaling that back," said Obleski. "It certainly could be a bad year for suspensions."

Despite the dry forecast, she said, natural gas companies are unlikely to start panicking because they diversify their water resources in anticipation of such suspensions. They often bring in water from a number of streams -- some of which are not yet off-limits -- or use public water to supplement their supplies. So, for Pennsylvania's frackers, it's likely to be business as usual.

"Our water department said it's nothing," said Diane Gross, a communications specialist for the natural gas production company Talisman Energy USA Inc., which owns more than 350 natural gas wells in Pennsylvania and had at least five of its water withdrawal sites suspended this week.

"It's something that happens every year," said Gross, who explained that water demand is already low due to decreased drilling.

Thanks to the falling price of natural gas, "we're down to one rig, anyway."