Water underneath the Bay may save the day

A pocket of groundwater underneath San Francisco Bay could provide water to irrigate local parks and landscapes — a possibility crews are exploring by digging test wells.

In recent years, Redwood City has exceeded its water allotment from the Hetch Hetchy Reservoir, prompting city leaders to explore ways to conserve water and maximize the use of potable water. The city had been using approximately 326 million more gallons per year that it is allotted.

A city task force then recommended a recycled-water pipeline, which is currently pumping water to Redwood Shores and will eventually bring the water to other parts of the city.

The task force also suggested exploring under the city for aquifers, subterranean layers of rock and sand that contain water.

“There really isn’t an aquifer right under Redwood City, but there is one under the Bay that the Seaport area touches,” said Community Development Director Peter Ingram, who also oversees the city’s water program.

The first drilling took place roughly more than a month ago, but the water turned out to be too salty for watering plants, Ingram said. However, they’ll continue to drill deeper in search of fresh water that could be used to water Red Morton Park and similar sites.

Redwood City has used less than its Hetch Hetchy allotment this year for the first time in roughly a decade, but as the city expands, more drinking water will be needed.

The U.S. Geological Survey recently released a study that water levels in the nation’s aquifers are declining due to overuse.

“We’re using groundwater more and more in this country,” USGS hydrologist William Cunningham said. “Our population is increasing. Groundwater in general is a renewable resource.”

But supply varies, Cunningham said, and it depends on the amount of rainwater a region gets and how heavily aquifers are being tapped.

As yet, nobody has done a comprehensive study of how much groundwater might be available in the Bay Area, said Jim Nickles, a USGS spokesman.

While some residents in San Francisco and on the Peninsula have private wells for watering and even drinking water, it’s impossible to know how many, said Tony Winnicker, San Francisco Public Utilities Commission spokesman. San Francisco uses some underground wells to water areas of Golden Gate Park.

“We know that in a lot of the backyards in the creek basins, there are wells for irrigation, but we have no inventory or regulatory control over them,” Ingram said.

San Bruno has utilized wells since 1940s

While Redwood City explores groundwater for irrigation, other Peninsula cities have been tapping into their aquifers for generations.

San Bruno began digging wells in the 1940s, and now gets roughly 50 percent of its water — roughly 2.1 million gallons per day — from underground supplies, Deputy Public Works Director Robert Howard said. That water flows to residents and businesses, for drinking and irrigation.

The other 50 percent of the city’s water supply comes from the San Francisco Public Utilities Commission’s reservoir at Hetch Hetchy in the Sierras. For 50 years, the groundwater supply has remained steady.

“We’ve seen [the aquifer] as a smart way to approach the use of water because it’s a flexible system,” San Bruno City Attorney Pamela Thompson said. “The aquifer has declined somewhat from what it was originally, but it’s recharging to approximately the same degree that it’s being used.”

bwinegarner@examiner.com

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