For decades, federal water leaders have flirted with a larger version of Millerton Lake, northeast of Fresno, but money and politics always kept them apart. Suddenly, this affair is getting serious.
A federal study this year shows that a $2.6 billion reservoir, called Temperance Flat, pencils out. Now for the first time, there's a draft environmental impact statement, citing options to make this work.
In November, California voters will be asked to approve a $7.5 billion water bond. There could be public money for nearly half the cost of Temperance Flat, which would double the size of Millerton and answer a generation of prayers for more farm water.
After one of the worst dry spells on record and mounting worry for future water supply, this would easily be the brightest spot of a dismal 2014 for San Joaquin Valley farming.
But Temperance Flat is not locked down. Voters still must approve the bond measure, Proposition 1. Even if the bond passes, Temperance Flat would have to compete with other projects for money.
Naysayers -- environmentalists and an economist -- question whether there will be enough additional water each year to justify billions of dollars in expense.
Still, this could be a key moment in the Valley's history. The last large, new reservoir along the western Sierra Nevada slope was New Melones on the Stanislaus River. It was finished in the late 1970s.
"If we miss this opportunity, (the project) might just go on the shelf," said Ron Jacobsma, general manager of the Friant Water Authority, representing 15,000 farmers along the Valley's east side.
Temperance Flat opponent Ron Stork, senior policy staffer for the advocacy group Friends of the River, based in Sacramento, said he doubts the public will ever go for this idea.
"My guess is that the dam will remain an object of desire and local civic boosterism for many years," he said. "But it will eventually die a quiet and unlamented death."
Many groups are expected to weigh in over the next several weeks as the U.S. Bureau of Reclamation gathers comments on the draft environmental study released earlier this month. The deadline for comment is Oct. 21.
The draft environmental review says Temperance Flat Reservoir would be built 6.8 miles upstream of Friant Dam near Fine Gold Creek, partially inside the back end of 520,000 acre-foot Millerton Lake.
It would be a reservoir within a reservoir, adding a net 1.26 million acre-feet of additional storage. Each 326,000-gallon acre-foot would supply an average San Joaquin Valley family for a year to 18 months.
The new reservoir would flood two Pacific Gas & Electric Co. powerhouses. Among the fixes is installation of another hydro unit at Temperance Flat to replace some of the production as well as provide flexibility to produce electricity later in the warm season.
The Bureau of Reclamation's most notable change from past approaches to Temperance Flat is the emphasis on many benefits, not just water supply or flood control.
The reservoir could help another massive project -- the hard-fought restoration of the river and the re-start of long-dead salmon runs.
It also would provide emergency water storage in the center of the state in the event of a catastrophic event, such as an earthquake.
"We could use this reservoir to help a large part of California in a time of emergency," said Mary Johannis, bureau deputy regional planning officer, based in Sacramento.
But Jeffrey Michael, University of Pacific economist and professor, said the figures just don't add up. He said he supports salmon restoration, but it looks like too much value has been attached to only a few dozen fish annually.
He added that the investment is too high for emergency storage in the event of a catastrophic earthquake at the Sacramento-San Joaquin River Delta, where the state's two great rivers meet with much of California's water. Michael said authorities should be more concerned with the flood risks to people in the delta in the event of a big quake.
He also said federal officials appear to be placing too much value on only a modest amount of additional water each year. He cited the bureau's environmental document, which shows the average additional yield at about 75,000 acre-feet.
"More than $2.5 billion is a lot of money for a project that adds only 75,000 acre-feet more each year for the area," he said.
Valley farm water leaders see a different scenario than the bureau, and they disagree with Michael's assessment.
The bureau looks back at San Joaquin runoff over the past century to estimate the annual yield with the new reservoir. Farm water leaders say the picture changes when the analysis focuses just on later decades, because it has been wetter.
The average yield from 1974 through 2003 for a reservoir the size of Temperance Flat would have been 115,000 acre-feet per year. Instead, federal leaders have been forced to release a lot of water from Friant Dam to the ocean, farm water officials said
"In those years, we lost 14 million acre-feet of water," said Mario Santoyo of the California Latino Water Coalition, which lobbies for Temperance Flat. "You also have to consider climate change. In the future, the snowmelt will come earlier and more precipitation will come in the form of rain. A larger reservoir makes even more sense in the future."
The draft environmental study from the bureau also does not take into account the operation of Temperance Flat in coordination with other reservoirs and canals to the north, water leaders said.
Jacobsma of the Friant Water Authority said: "Through exchanges with delta partners in wet years, we could increase the yield by another 100,000 acre-feet."
Temperance Flat is not the only reservoir proposal on the map. Sites Reservoir in Sacramento Valley could hold more than 1 million acre-feet, too.
The California Water Commission will decide where the bond funding goes if the November measure passes. No more than 50% of costs can come from the bond. The commission also can choose to fund groundwater projects.
Metropolitan Water District of Southern California, among the state's most powerful political forces in water policy, supports more reservoir storage, period.
"It could be Temperance Flat," said Jeffrey Kightlinger, general manager of Metropolitan, which provides water to 19 million Southern Californians. "A lot of study needs to be done, but generally we need the storage in this state."
Stork of Friends of the River said he has seen enough to know the bigger reservoir on the San Joaquin wouldn't work.
"Temperance Flat dam is a political dam," he said. "It's not a dam that would ever make economic sense."
Public meetings to comment on the Temperance Flat draft environmental statement are planned in Fresno and Sacramento:
-- Fresno: 6 to 8 p.m. Oct. 16 at the Piccadilly Inn, 2305 W. Shaw Ave.
-- Sacramento: 1 to 3 p.m. Oct. 14 at 2800 Cottage Way, Cafeteria Conference Rooms 1001-1002