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Updated: Drought’s Effect on California Vineyards Varies Substantially

The original version of the article said that Corison runs on city water, information I'd received from the winery but not Cathy Corison herself. Cathy has now explained to me that their St. Helena water connection is used only for emergency fire sprinklers and with a special permit. The winery and vineyard actually use well water. See below for more details.

With lack of precipitation being so consistent throughout the state, one might suppose water challenges to be consistent from one vineyard to the next. That isn’t the case. The impact of this year’s low rainfall varies substantially depending on a vineyard’s location, water source, vine age, soil and even whether or not they faced Spring frost risk.

This is shaping up to be one the driest years on record in California1. January through March 2013 was the driest in recorded history for the Sierras, San Francisco, much of the East Bay, Los Angeles and many other parts of the state—including key agricultural areas.2 Without the ridiculously heavy rains last December this year would likely be the driest ever. How is this dry weather affecting California vineyards?

Lange Twins vineyard in the Clarksburg AVA is one place where shortage of water is never an issue. The AVA is essentially a series of low-lying islands in the fresh-water Sacramento River DeltaRandall Lange told me, “Our problem is trying to get water out of the soil, not lack of water.”

karl-wenteThe Livermore Valley AVA isn’t feeling the pinch right now either. They get water from canals built by the Army Corps of Engineers after World War II, part of the controversial Central Valley Project which routed water from the Delta to agricultural areas. Water supply isn't an issue and this year is pretty routine. Karl Wente (right) of Wente Vineyards tells me, “We’ll open the valve earlier this year to give the vines a drink—to effectively make it rain—and get the soil profiles right, but not too much because we had such a wet December.”

Of course many vineyards don’t have access to huge resources like the Delta. They depend on mountain springs, wells, or private reservoirs. That water is used not only for irrigation but also frost-protection and sometimes in the winery (if it's co-located with the vineyard). Fortunately, this Spring was mild.

Well-established vines need less water than young ones. The Corison Kronos Vineyard—43-year old Cabernet Sauvignon on St. George rootstock—is dry-farmed most every year except for the day immediately after harvest. Then, vines are given a drink to encourage the roots to grow deeper. "The vineyard had been badly watered when I bought it," Cathy Corison said. "Even though the rootstock is St. George, the roots were very shallow. Over the years I've been able to train them to go deeper."

The winery and vineyard rely on their own well for water. "If we're not very, very careful, we can run out water before the end of harvest, but there have been only a couple of years when we were really worried," Cathy explains. "We're set up to be very frugal with water. Wineries don't use very much water. It's not intuitive, but they don't."

Cathy isn't sure whether or not she'll be able to dry farm this year. But she was very happy for the unseasonable rain that came this week, possibly an inch or more. That may make the difference.

Mumm Napa head winemaker Ludovic Dervin was hopeful when I asked him about water availability in May. “The [lack of] rainfall isn’t a problem yet,” he told me. “We didn’t have to use any water for frost protection so, even if water was scarce in winter, we’ve kept it all for irrigation."

When I met with a number of growers from Atlas Peak last month, most told me they rely on springs but have seen no sign of decreased flow. Also on Atlas Peak, Antica Napa Valley has a large reservoir, stocked with fish, in the middle of their vineyard. It was nearly full, thanks in part to those big December rains.

The Antica Napa Valley vineyard in the Foss Valley of Napa Valley's Atlas Peak AVA, May 2013
Photo: Fred Swan

I’ve heard concern about the flow from springs in the Diamond Mountain AVA though. And some growers down in the Paso Robles AVA are seeing well water levels 50 to 100 feet lower than normal.

Paso Robles is an interesting case. Annual rainfall there varies tremendously, from up to 45" near the western edge of the AVA to as little as 8" in the eastern. Temperatures are generally higher in east too, leading to more evaporation. Then there are the soil differences. Paso Robles is known for its deep soils of calcareous stone that absorb water and dole it out gradually to vines throughout the year. Not all of Paso's vineyards sit on that type of soil though.

Tablas Creek Vineyard is located on deep calcareous soil in west Paso Robles’ Adelaida District. That soil, combined with the 28 inches of rain the vineyard typically gets allows for dry-farming most all the time. Tablas hasn't irrigated anything except new plantings since 2009.

A portion of Tablas Creek Vineyard at the beginning of harvest, 2011. Photo: Fred Swan

Tablas Creek Vineyard has gotten just half of it's typical rainfall for two years running though. General manager Jason Haas tells me their wells are in good shape so far, in part because there was only one frost scare this year. That’s a good thing because they will have to turn on the water soon. “We will likely choose to give our established vineyards, at least the hillside ones that always struggle a bit late in the summer, a little bit of water sometime in the next month or so (before veraison),” Haas said. Some of his vines will be left to their own devices though, like it or not. They are head-trained and don’t have irrigation lines.

Wineries may not be hurt badly this year but subsequent years will be a different matter if heavy rain and snow don’t come this winter. Melting snowpack supplies 30% of California’s fresh water. According to California Department of Water Resources reports, snowpack was just 17% of normal on May 1 and it was gone entirely by June. Levels at primary reservoirs are a little below average now3 but will be quite a bit worse by October.

Even with a plentiful water supply, Karl Wente is very measured in his reliance on irrigation. He recalls his viticulture professor, Andrew Walker of U.C. Davis, telling him, “In your lifetime water will be restricted and you will have to move in a dry farming direction.” The Department of Water Resources has not yet declared our current situation a drought and the current predicament isn’t unprecedented. California has been here a few times over the past 50 years. But global climate change trends make one wonder if we’ll recover as readily this time.

1 Water years are run from July 1 through June 30, so the current one is nearly over.
2 “Dry weather has firefighters ready for battle,” LA Times, April 19, 2013
3  The significant exception is San Luis Reservoir, 75% empty. This is due to heavy usage from farmers and a restriction on pumping from the Delta intended to protect the Delta smelt population. 

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This article is original to Copyright 2013 NorCal Wine. Photos by Fred Swan. All rights reserved.