BALBOA PARK – Federal hydrologists yesterday announced the discovery of an aquifer far beneath Balboa Park that San Diego officials may tap to irrigate nearby flowers and lawns.

JOHN R. McCUTCHEN / Union-Tribune Federal hydrologists have spent the past few weeks drilling a monitoring well at Balboa Park near the golf course at Pershing Drive and 26th Street. Anthony Brown (above), a U.S. Geological Survey hydrologic technician, swapped out measuring devices at the well above the newly discovered, 600-foot-thick aquifer.

Fueled by concerns about the region's water inventory, the U.S. Geological Survey and three public water agencies are scouting for groundwater – particularly in areas that have been overlooked. San Diego has very few sources of groundwater, which is a serious problem when water supplies are as tight as they are this year.

“We have a 600-foot-thick aquifer that we didn't know was here. Bingo,” said Wesley Danskin, project chief for the geological survey team.

Danskin and other hydrologists have spent the past few weeks drilling a monitoring well at Balboa Park near the golf course at Pershing Drive and 26th Street. They don't expect the aquifer there, or others in the county, to substantially reduce the region's reliance on the Colorado and Sacramento river systems.

But even small sources of water have become increasingly significant as prices for imported water rise and factors such as drought make out-of-town supplies less reliable.

How much water could be pumped from the Balboa Park site and that water's salinity won't be known for a few months. Danskin's team must first sink five giant straws into the 1,500-foot-deep hole and test the water. If the salt content is too high, the water would have to be treated before it could be used for irrigation.

The uncertainty didn't take the shine off yesterday's announcement for city officials, who have agreed to pay for most of the $300,000 well project.

“We are encouraged that this investment has shown there is water here,” said Bob McCullough, a planning manager for San Diego's water department.

He said a new and local water source would be especially helpful in Balboa Park, where gardens and golf courses are irrigated with drinking water.

Groundwater accounts for about 2 percent of the county's water supply, according to the San Diego County Water Authority. The agency wants to triple the use of local groundwater by 2020. Several of its member water districts, including San Diego and the Sweetwater Authority, are contributing to that goal.

“We can't be asking people for water outside the area if we have not made the most of what we have here,” said Dan Diehr, a senior resource specialist at the County Water Authority.

He was excited about the geological survey's announcement of the new aquifer. “It offers the biggest potential for groundwater production above and beyond what we already are producing,” Diehr said.

Outside Balboa Park, the federal hydrologists are trying to complete what would be the most comprehensive study of San Diego County's groundwater resources. They are mapping aquifers such as the San Diego Formation, a large subsurface field of sand and gravel from which water can be extracted.

Danskin's study area spans a few miles wide along the coast and stretches roughly from La Jolla to Rosarito Beach in Mexico. That swath has the best likelihood of yielding groundwater because most other parts of the county have shallow bedrock that limits water storage.

The federal study involves eight monitoring wells, and hydrologists hope to drill 10 others in the next few years.

“I think of it as something like a jigsaw puzzle,” Danskin said. “We have one very clear piece here in Balboa Park and others around the region. We are trying to fill in the balance so that we can see the picture clearly.”

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Mike Lee: (619) 542-4570; mike.lee@uniontrib.com