WATSONVILLE — With winter rains filling California rivers and reservoirs in a dramatic display of drought-ending bluster, the rush is on to capture the overflow before the bounty is squandered, washed forever to sea.

Numerous water agencies from the Central Valley to the Central Coast are busy stashing surplus water underground, a practice known as groundwater recharge in which excess from lakes and creeks is steered onto barren fields, where it soaks into the aquifer below.

But as well-meaning as these efforts are, they often lack the land to bank as much water as they could, experts say. Committing property to the low-payoff endeavor doesn’t usually pencil out. And even when the investment is made, there’s typically no assurance that those putting water in the ground will benefit — instead of a neighbor with a well.

Here in the rural Pajaro Valley, however, officials may have found a way to make the practice more enticing: Farmers plying this fertile stretch of strawberries and lettuce can make money offering up their private land.

Just as households with solar panels get credit for selling power back to the electric grid, landowners can offset their water bills by pushing water underground.

The pilot program, being rolled out by the local water agency in partnership with the region’s conservation district and UC Santa Cruz, has just one participant so far — a berry company that’s reducing its water payments by channeling hillside runoff into the ground. But others are signing up.

“The idea here is to remove some of the disincentive that’s preventing landowners from doing” recharge, said Andy Fisher, a UC Santa Cruz hydrogeologist who pioneered the project. “No one has tried a program like this before, but we think it’s something that could be replicated in other places.”

With California’s first set of groundwater regulations about to kick in, water managers across the state are looking for ways to boost underground reserves. About 40 percent of the state’s water typically comes from the ground, and after decades of overpumping, most places have plenty of room for replenishment.

The new law requires communities statewide, within the next five years, to develop plans for getting their aquifers in balance.

On a recent morning, Dennis Lebow steered his Ford Explorer down a dirt road east of Watsonville to where he’s doing his part to put water in the basin beneath the Pajaro Valley.

His employer, berry producer Reiter Affiliated Cos., is capturing runoff that spills from the tall, green hills above the Monterey Bay in a 4-acre percolation site between a raspberry field and an apple orchard.

“Normally, a lot of the water would run parallel to Silliman Road through a surface ditch to the Pajaro River,” said Lebow, a hydrologist, pointing out how the precious liquid would be lost if the recharge system wasn’t in place.

Instead, drainage from 170 acres of privately owned fields is routed — by gravity — into an intake chamber at a low-lying spot, where it’s filtered before flowing to a muddy pond. There, the water percolates naturally into the aquifer.

“In a wet year like this, I’m excited to see what we can put in the ground,” Lebow said. “It may be two, three, four or 10 times as much as what we’ve done.”

The researchers from UC Santa Cruz have set up gauges to measure inflow after the rainy season. Last year, they counted 108 acre-feet of infiltration at the site, a relatively small amount but a good start, they say. An acre-foot of water can supply up to two households for a year.

With each acre-foot of water dropped into the ground, Lebow’s company is credited $101.50 by the Pajaro Valley Water Management Agency. It’s half of what the grower pays to pump water but helps make the effort worthwhile, Lebow says.

Land expenses aside, a small and relatively low-tech recharge site can cost from tens of thousands of dollars to a few hundred thousand dollars, with larger ones running several million or more. Grant money is sometimes available.

Brian Lockwood, interim general manager for the water agency, said that without reimbursement there would be little reason for landowners to get in the recharge business.

“Alternatively, the whole ranch has strawberries on it,” he said. “They make a lot of money that way. What’s the incentive for them to take 1 to 5 acres out of production to do recharge? There are costs involved to build these projects and, after they’re built, there are maintenance costs.”

The program is scheduled to expand to at least 10 sites over the next few years. That’s enough to offset about 10 percent of the deficit caused by overpumping in the region’s aquifer, organizers say — a significant amount when added to natural seepage from rain and irrigation as well as other recharge efforts initiated by the water agency.

Most recharge programs in California aren’t in private hands, like a 15-acre percolation basin operated by the Pajaro Valley water department miles from Reiter’s pond.

The Central Valley’s big irrigation agencies are diverting flood releases from Sierra Nevada reservoirs to dirt plots they purchased exclusively for water infiltration. Consolidated Irrigation District, which serves parts of Fresno, Tulare and Kings counties, operates more than 50 such sites.

In the Bay Area, the Santa Clara Valley Water District runs nearly 100 small recharge ponds, which are, in part, being filled with piped-in excess from the Sierra.

But the real opportunity for getting more water into the ground is on private land, says Helen Dahlke, a hydrologist at UC Davis.

“You can’t buy any more land and put more infiltration basins in,” she said. “The agricultural landscape is really the natural place to do this.”

Dahlke has been testing alfalfa fields and almond orchards across California to see if they can be safely flooded in the offseason and used as recharge basins. So far, she’s found the farmland doesn’t lose its vigor and crops are minimally affected. But her experiments are not yet done.

In the public consciousness, groundwater recharge remains something of a sidelight to proposals to add water storage through the more traditional method of building reservoirs.

While Proposition 1, the $7.5 billion water bond passed by voters in 2014, might provide some funding, damming rivers comes with its own set of problems — including not only the high cost, but also the difficulty of finding space on rivers and protecting fish. The leading reservoir bids would run as much as $3 billion apiece.

A Stanford University study found that storing water through groundwater recharge is nearly six times less expensive than reservoir expansion.

“Using aquifers should be the new way we capture water for longer duration,” Dahlke said. “And we don’t know when the next wet year will be, so we have to make use of this water now, while it’s available.”

Kurtis Alexander is a San Francisco Chronicle staff writer. Email: kalexander@sfchronicle.com Twitter: @kurtisalexander