12 Livermore Valley Vineyard Districts Charted
May 08, 2019
|Wetmore Vineyard, possibly the oldest vineyard site in the Livermore Valley AVA, is owned by Wente Family Estates. Photo credit: Barry Zupan|
The Livermore Valley Winegrowers Association has completed a scientific study that divides the Northern California wine-growing region into 12 sub-districts based on differences in topography, soils and micro climates. The association has not applied for recognition of the districts as American Viticultural Areas, but will begin sharing the district concept with growers, winemakers and the wine trade to emphasize the diversity and potential of the 260,000-acre Livermore Valley AVA.
“For years, growers and vintners have anecdotally talked about the differences between the far western side of the AVA and the eastern side, the differences between the valley floor and the hillsides, the variation in soils and the differences from one vineyard to another," said the association’s executive director, Chris Chandler. "We’ve needed to get beyond anecdotes and general observations."
Patrick Shabram Geographic Consulting of Loveland, Colo., drew the districts based on a study of the Livermore Valley's soil and topography by Coastal Viticultural Consultants of Angwin, Calif., and Shabram's own study of meso-climate patterns of the valley. A grant from the California Department of Food and Agriculture to the winegrowers association funded these studies.
"We didn’t know exactly what the research would yield when you overlay the climate data on top of the soils and slopes information. It turns out that there are 12 identifiable districts,” Chandler said. The districts average 22,000 acres each.
The studies fill gaping holes in what was known about the valley’s conditions for viticulture. They don’t exactly turn the general assumptions of local winemakers and growers upside down but do add thousands of data points and dozens of new insights, including a much better picture of how hot and how cold the Livermore Valley AVA is.
Tesla district is Region III
Shabram’s analysis showed a range of 10-year growing degree day averages within the Livermore Valley AVA from 3,128 degree days at the Lawrence Livermore Valley National Laboratory to 3,766 degree days in the central part of the city of Livermore. Four of the six weather stations in the AVA gave 10-year averages that make the Livermore Valley a warm Region III, not a hot Region IV.
Shabram's “Viticultural Districts of the Livermore Valley AVA” start with the Tesla district, being the area just south and east of the city of Livermore through which Tesla Road (named for electrical engineering pioneer Nikola Tesla decades before Elon Musk created his car company) runs, and where the most commercial viticulture activity is centered.
The area includes the floor of the southern Livermore Valley and some low, rolling hills. Elevations are generally under 700 feet, the soils are mostly alluvial and the climate is cooler than farther north in the AVA. Shabram writes that the coolness is “a result of cool Pacific air flowing in through the Vallecitos pass and air drainage off higher elevations mixing with other airflow onto the Livermore Valley.”
Shabram describes in his climate study how the AVA as a whole has multiple airflow patterns. The Livermore Valley is landlocked but sits directly east of San Francisco Bay. The most direct source of cool maritime air from the bay is over the Dublin Grade on the western side, while air flowing over the Sunol Grade farther south either moves into the Amador Valley and then into Livermore Valley or into the Vallecitos Valley first and then into southern Livermore Valley.
The Tesla district is home to many of the 50-plus wineries in Livermore Valley, including well-known Concannon Vineyard, Wente Vineyards and Murrieta’s Well. Cabernet Sauvignon, a late-ripening variety that benefits from heat, is among the most common varieties planted here, however Shabram’s analysis suggests that the Tesla district is on average in the lower half of Region III. Soils are silty to sandy loams that are deep and well drained.
Ruby Hill and Crane Ridge
Two of the other newly identified grape-growing districts, Ruby Hill and Crane Ridge, also have current commercial viticulture activity. Ruby Hill sits just to the southwest of Tesla above the valley floor at elevations generally stretching from 700 to 1,000 feet, a position that reduces frost risk but is still in the path of cooling Pacific airflow through the Vallecitos pass.
The district takes its name from Ruby Hill Winery, built here in 1887, and also is home to several other current wineries and vineyards. The Crane Ridge district occupies a narrow band to the southeast of Tesla and above the valley floor where the soil parent material is mostly sandstone. Described as similar in elevation and soil to Ruby Hill, Crane Ridge has more west-facing slopes, which are generally greater than 5 percent but can range from 10 to 20 percent. Shabram observes that Tesla, Ruby Hill and Crane Ridge all have later harvest times than other growing regions with similar growing degree days, according to veteran Livermore Valley growers.
The other nine districts continue in a roughly clockwise direction around these three. They are named Altamont, Mendenhall Springs, Vallecitos, Sunol, Palomares, San Ramon Valley, Mt. Diablo Highlands, Valle de Oro and Amador Valley. The districts are defined by a combination of climate, soil, geology and slope, with no attention to existing vineyards, according to the association.
Shabram states, “Climatic, soil and topographic variations are commonly interrelated. Variations in climate are often related to topography. Topography is often related to weathering and bedrock, which, along with slope impact soil development.”
Is Livermore Valley still in infancy?
Two series of maps were prepared by Mike Bobbitt & Associates to accompany the climate study and by Coastal Viticultural Consultants to accompany the soils study. Various maps offer comparisons by degree days, by wind speed, by precipitation, by percent slope, soil texture, water holding capacity and other variables.
Chandler stressed that the Livermore Valley Winegrowers Association does not consider these districts "sub" or "nested" AVAs, like Oakville and Rutherford in Napa Valley. However, the district boundaries and characteristics as described in the third report are dense with information, and inherently argue that the Livermore Valley AVA is not a monolith but a variegated, complex puzzle whose pieces are separated by the nuances of their individual environments.
"Knowing that only 4,000 acres of the AVA are planted to grapevines, and that many of those acres are concentrated in one district, it may be that winemaking in the Livermore Valley AVA is still in its infancy," said Phil Wente, fourth-generation winegrower at Wente Vineyards. "And that's after more than 160 years of history. Many distinct combinations of district, varietal, rootstock, viticultural and enological practices remain to be explored."
|Livermore Valley AVA sub-district map. Courtesy: Livermore Valley Winegrowers Association|
Editor's note: The Livermore Valley Winegrowers Association previously commissioned the author of this news report to write a lengthier summary of the scientific studies referred to here.