Normally, Dry Creek, just west of Napa, lives up to its name this time of year. But three days after the South Napa Earthquake, it suddenly sprang to life.
"This was completely dry and right now it's running at the rate that we'd normally see in May or so," said Garrett Buckland, overlooking a stretch of the creek about 2.5 miles above where it empties into the Napa River. Buckland is a vineyard consultant who pays close attention to the hydrology of the Napa Valley. In September, he said, Dry Creek doesn't usually make it as far as the river.
When he started hearing the sound of moving water shortly after the magnitude-6.0 temblor, Buckland said he wasn't entirely surprised; he said the same thing happened after a 4.9 temblor near here in 2000. Based on that experience, Buckland was willing to make a prediction.
"This will continue to flow all the way until it dries up next year," he ventured. "All those changes in cracks and adjustments to the fissures all across this area are really just releasing a ton of really, really cold, crisp, clean groundwater, basically."
The resurgence of Dry Creek is just one of many similar stories that have arisen since the August 24 quake that struck the Napa Valley and damaged buildings in at least three significant North Bay cities. But the underground dynamics that started it all are complicated and not nearly as clear as the crystalline water bubbling up from below.
Just as elusive is the question of how long it will last. Geologists say this is a common occurrence following earthquakes and doesn't often last more than a matter of weeks. But there are some optimists out there.
"These ephemerals are flowing across the entire Mayacama Range (the western Napa Valley slope)," hydrologist Robert Shibatani, who toured the area last week, wrote in an email to KQED. "Nor is it necessarily a temporary event; streams are still running two weeks after the temblor."
Shibatani surmises that on the west side of Napa Valley, the quake didn't create new springs so much as it opened new connections between underground aquifers, creating a fresh supply for existing springs. If so, these new flows could continue into the rainy season -- but there's really no way to know.
"These flows could represent new base flows, which would be a significant enhancement to overall water supply yield to this area of northern California."
One thing that gives Shibatani hope of some permanence is the volume of water he's seen -- up to 10 or 12 cubic feet per second, which, over the course of a year, would be enough to supply thousands of typical households.
"That kind of volume is considerable given the state of our current drought," he says.
There remain some slippery questions, such as whether upstream wells might start running dry, and ultimately, to whom this wet new windfall belongs.
"As a 'natural' stream flow (albeit new), initial indications [from state water regulators] are that they would be considered 'riparian' rights and permissible for diversion," says Shibatani. "I think that someone needs to really get a sense of the overall scale of this."
As for Buckland, who grew up virtually on the banks of Dry Creek, a spawning stream for salmon and steelhead, he's just happy to see it running with such gusto at the driest time of the year.
"Hopefully this is something that'll really help out our fishery," he says, "but it's amazing what nature can do for us."
Get the best of KQED's science coverage in your inbox weekly.