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Napa Valley prepares for future drought

Options include more wastewater treatment, tapping future reservoir

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Lake Berryessa drought

Visitors went to the water’s edge of Lake Berryessa at the Spanish Flat campground in September as the water level on the lake continued to recede amid a historically severe California drought.

Napa County’s drought-easing ideas include using highly treated wastewater for drinking, having communities with extra water help out those in need, and tapping into the planned Sites Reservoir in Colusa County.

There are 22 proposals in all within the recently released Napa Valley Drought Contingency Plan. Those three rose to the top for further exploration.

The plan, done for local agencies along with the U.S. Bureau of Reclamation, might not help much with the current drought, should this winter be dry. Most of the ideas would take time to become reality.

“It’s more long-term,” said Patrick Costello, the city of Napa’s water resources analyst. “It coincided with this drought by happenstance.”

One idea is to turn wastewater from the Napa Sanitation District and the city of American Canyon into drinking water.

NapaSan and American Canyon already clean up wastewater to a degree that it can be used for irrigation. Recycled water-only pipes serve farms, homes and businesses in rural Coombsville and Carneros, the airport industrial area and near Jameson Canyon.

Making treated wastewater meet “purified water” standards for drinking would require a higher degree of treatment. A study would look at ways to meet regulatory requirements while minimizing costs and maximizing the water produced.

“Production of purified water would establish a drought-proof water supply for the region,” the Drought Contingency Plan said.

Another idea is to reserve water at Sites Reservoir, a proposed $3.3 billion reservoir in Colusa and Glenn counties 75 miles away that would store water pumped from the Sacramento River. Its size would rival that of Lake Berryessa.

American Canyon has set its sights on Sites. It has spent about $2 million to be one of the 29 communities and agencies in California that will be take water from the reservoir when it is built, possibly by decade’s end.

It’s the only Napa County community so far to buy into Sites. Costello said other communities will decide in 2023 whether to follow suit. The city of Napa has some interest, but the matter is just beginning to be discussed.

Napa Valley cities could also study how to better integrate existing supplies. The concept is that Napa Valley as a whole might have enough water, but water might not be available to those who need it.

That’s because local cities don’t draw from the same bucket. For example, the city of Napa gets water from local Lake Hennessey, local Milliken Reservoir and the Sacramento-San Joaquin Delta. St. Helena gets water from local Bell Canyon Reservoir and wells, as well as some from Napa.

“If it can be shown that regional distribution of surplus water is plausible both physically and institutionally, rethinking the operations within the Napa Valley could dramatically reduce the vulnerability of individual communities to future droughts,” the contingency plan said.

There are 19 other drought-easing ideas in the Drought Contingency Plan. One that has yet to get much traction is buying Lake Curry reservoir in remote southeast Napa County.

Vallejo created the reservoir a century ago and stopped using it in the early 1990s when the adjacent treatment plant could no longer meet state standards and needed expensive upgrades. The city has tried to sell Lake Curry at times, with no takers.

In a state where water is liquid gold, Lake Curry is unwanted. There are reasons.

Buying Lake Curry could cost $20 to $30 million. Still more money would be needed to build conveyance facilities, the Drought Contingency Plan said.

The plan also looked at possible effects of global warming.

Most climate projections indicate the Bay Area will continue to experience high year-to-year variability. Annual rainfall in Napa Valley from 1960 to 2005 ranged from 10.71 inches to 60.22 inches, the plan said, though it didn’t give the location of the rain gauge.

That variability makes it difficult to detect a strong signal for future rainfall, even though multi-model projections show a small increase, the plan said.

Temperatures are another matter. Here, the Drought Contingency Plan does see a strong signal.

“Rising temperatures in the Napa Valley will make the region more arid,” the plan said. “This temperature trend is fairly consistent across the state. Rising temperatures could result in an increase on water demands, especially within the agricultural and outdoor sectors.”

The Napa Valley Drought Contingency Task Force that spearheaded the plan consists of the city of Napa, American Canyon, St. Helena, Calistoga, Yountville, Napa County and NapaSan. It worked with the Bureau of Reclamation.

This study will prove “invaluable” for the Napa Valley region as it explores how to adapt to drought and what regional projects may be of highest value, Vanessa Emerzian of the Bureau of Reclamation said in a news release.

Having the Drought Contingency Plan will position the projects for potential federal and state funding, according to the bureau.

The receding water level of Lake Berryessa makes enjoying the lake more challenging, but not impossible. There are fewer boat launches available and getting to the water's edge is a longer trek but the cool lake waters make the extra effort worth it.

You can reach Barry Eberling at 707-256-2253 or

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Napa County Reporter

Barry Eberling covers Napa County government, transportation, the environment and general assignments. He has worked for the Napa Valley Register since fall 2014 and previously worked 27 years for the Daily Republic of Fairfield.

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