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After an early Feb. 27 start, the South San Joaquin Irrigation District wrapped up its water delivery season in late October. While October and most of November produced little rain, Northern California has received significant rain since Thanksgiving. Photo by Vicky Boyd

By Vicky Boyd

Thanks to recent rains, the water year is off to a slightly wetter-than-normal start for San Joaquin County. However,  water managers are not jumping up and down with excitement quite yet since the historically rainiest months are still ahead. 

Even if normal precipitation doesn’t materialize, above-average carryover reservoir storage will provide a cushion for next season, they say.

But at least a few growers who rely on groundwater or smaller water districts are not quite as optimistic. Dave Simpson, a Lodi-area winegrape grower, is concerned not just about his personal well but also the Northern San Joaquin Water Conservation District, where he is a board member.

“For our little district, it’s do or die,” Simpson said. “If we don’t get any rain, we don’t have any water next year for North San Joaquin.”

The county maintains a test well about 800 feet from his own private well, allowing Simpson to use county reports to gauge groundwater levels.

During the five-year drought, the county reported a 7-foot drop in the test well. Simpson said he had yet to see this year’s data, but “I’m looking for something better than it’s been.”

Based on declining groundwater levels, about three years ago Simpson had a new pump installed and dropped another 20 feet so he could avoid sucking air.

What does El Niño mean?
The water year runs from Oct. 1 through Sept. 30 the following year. Nearly two months in, precipitation is slightly above normal for the county. Stockton has received 2.51 inches of rain, or 111 percent of normal, between Oct. 1 and Nov. 26, according to the National Weather Service. Last year during the same period, Stockton had received only 0.80 inches. During a normal water year, Stockton receives 14.06 inches.Forecasters with the National Oceanic and Atmospheric Administration say there’s an 80 percent chance of a mild to moderate El Niño this winter. But the warming of equatorial waters in the center and eastern Pacific associated with the weather phenomenon has no reliable influence on Northern California, said Jeanine Jones, California Department of Water Resources interstate resources manager.

“The fact that it’s going to be a weak to moderate El Niño doesn’t really tell us anything as far as precipitation,” she said. “But the correlation to warmer temperatures is much stronger than anything they can say about precipitation.”

In its three-month forecast, the National Weather Service said there are equal chances of the season having above-average precipitation as there are for it to have below-average moisture.

About half of the year’s precipitation falls between Dec. 1 and Feb. 28, with about 75 percent falling between Nov. 1 and March 30, Jones said.

With it being so early in the water year, she said she wasn’t overly concerned about current dry conditions. 

“We’re just starting with the season,” she said. “I’d wait until the end of December and see how the season is up to that point.”

Starting with a cushion
As of Nov. 26, New Melones Reservoir stood at 1,757,449 acre-feet, or 130 percent of normal for that date, according to California Department of Water Resources figures. Average storage for the date is 1,352,889. 

The Oakdale and South San Joaquin irrigation districts together hold senior water rights to the first 600,000 acre-feet that flow into the reservoir each year. 

“Considering the 1.7 (million acre-feet) is where we’re at now, New Melones is going to look really good next year assuming we get average rain,” said Steve Knell, OID general manager.

Although snowpack and precipitation were below normal for the 2017-18 water year, runoff still amounted about 1 million acre-feet, he said. And that helped enhance carryover storage.

“We had a lot of long-term run-off into the reservoir,” Knell said. “As we drew the water down, we had good back flows to keep New Melones up.”

The OID irrigation season ended Oct. 26, and Knell said the board will begin looking at snowpack and predicted run off in early February to determine deliveries and start dates for the 2019 irrigation season.

The North San Joaquin Water Conservation District, which serves about 150,000 acres near Lodi, is in a different situation and can’t carry water over from year to year, said Joe Valente, a vineyard manager and president of the conservation district board.

The district receives water from Camanche Reservoir delivered by East Bay Municipal Utility District via the Mokulumne River. 

“Come Nov. 5, if we have water and we only used half, we don’t have a carry over,” said Valente, also an SJFB board member. “So the challenge we have is to use that allotment in the time frame.”

Because the district has junior water rights, it receives water typically only six of 10 years. What it has explored is in wetter years putting any left-over water to beneficial uses, such as groundwater recharge, before the deadline.

“We’re trying to put everything together so we have a lot of different options,” he said.

Taking things in stride
Only a few months into the water year, Valente said he wasn’t overly concerned.
“I’ve learned over the years there’s not a whole lot I can do about it,” he said. “You just learn to deal with what you’ve got.”

Phil Brumley, who grows walnuts and almonds near Escalon, agreed.

“We’ve had a lot of years like this in the past,” said Brumley, also an SJFB board member. “Then when it started raining, the storm door just stayed open and it just kept coming.”

Much of his ground is served by surface water from the Oakdale Irrigation District. One piece receives water from the Central San Joaquin Water Conservation District, and the few remaining blocks rely on groundwater or a mix of surface and groundwater.

Based on carryover storage in New Melones, Brumley said he isn’t worried about OID deliveries for 2019. What has him a bit more concerned is the Central San Joaquin Water Conservation District, which has junior water rights and receives water from New Melones through the Bureau of Reclamation. 

In addition to reducing the need to pump groundwater, having surface water – particularly from Central San Joaquin, which uses dirt-lined ditches – helps recharge groundwater through percolation.

Brumley’s own wells have dropped 10 to 15 feet during the past five years, although they appear to have stabilized lately. “The water table has come down a little but, but it’s not drastically different than it was a year ago,” he said. “But we can certainly use the surface water out here as well.”