Sonoma County's Russian River Valley AVA, one of California's most prestigious wine regions, strikes an impressive balance between quantity and quality. It covers roughly one fifth of Sonoma County as a whole, and yet retains a worldwide reputation for the quality of its wines.
Typically it is the world’s smaller appellations and AVAs that are famed for the quality of their terroir. Russian River Valley, then, is a happy exception to the rule; not only is it arguably Sonoma County’s most prestigious AVA, it is also one of its largest, accounting for almost 15% of the county’s total vineyard area. From north to south, Sonoma County measures roughly 60 miles (100km); almost one-third of this is occupied by the Russian River Valley AVA. Since it was extended in 2005, the AVA now covers more than half of the over-arching Northern Sonoma AVA and entirely encompasses the Chalk Hill and Green Valley sub-regional AVAs.
© Sonoma County Vintners
The river after which the AVA is named is the second-largest (after the Sacramento) within the nine-county Greater San Francisco Bay Area. It rises in the Laughlin Ranges at the centre of Mendocino County, and flows southwards for 110 miles (180km), falling almost 2000ft (610m) along its course. Only the final tenth of the river's course is covered by the Russian River Valley AVA, as it snakes between Healdsburg and its mouth at the Pacific coast 20 miles (30km) due west of Santa Rosa.
The finest Russian River Valley vineyard sites are planted on either Goldridge Series or Franciscan Assemblage soils. The Goldridge Series is highly characteristic of Sonoma Valley and consists of deep, moderately well-drained soils formed in material weathered from weakly consolidated sandstone. The Franciscan Assemblage, named after the San Francisco area, is a chaotically distributed mix of greywacke sandstones, limestones, deep-sea radiolarian cherts, altered mafic volcanic rocks (greenstones), serpentinites, shales and high-pressure metamorphic rocks. There are also alluvial soils of various make-ups here, concentrated close to the river itself; these are the 'benchland' regions.
Many millions of years ago, the area that roughly equates to the modern-day Russian River Valley was a shallow inland sea, not too dissimilar from the San Francisco, San Pablo and Grizzly bays today. After a prolonged period of seismic and volcanic activity, the valley took on the form that we know today. As confirmed by the area's susceptibility to earthquakes, however, the tectonic activity is clearly far from over.
A number of tributaries feed into the Russian River within the confines of the AVA, namely the Green Valley, Franz, Santa Rosa, Mark West and Dutch Bill creeks. Some of these flow westwards, down from the Mayacamas Mountains (which separate Sonoma Valley from Napa Valley), while others flow eastwards from the very southern tip of the North Coast Ranges. With all this water around, the valley benefits from a certain level of climatic cooling, particularly as the river broadens as it approaches the cool waters of the Pacific.
The westernmost Russian River Valley vineyards lie just eight miles (13km) from the coast and enjoy some of the coolest terroir in the county. These tend to be planted with the cooler-climate varieties Pinot Noir and Chardonnay, while further inland (particularly in Chalk Hill) the preference is for Cabernet Sauvignon and Zinfandel. The rest of the AVA happily makes do with the cooling effect of the morning fog that rolls inland from the Pacific, sneaking its way through the Petaluma Gap before burning off as temperatures rise towards midday. The fog is also responsible for the wide diurnal temperature variation here; night-time temperatures in summer drop as much as 35 to 40 degrees Fahrenheit from their daytime high. Relative to California's warmer AVAs, then, Russian River Valley has a cool growing season and therefore a long, slow, ripening period. This helps to limit the risk of over-ripe fruit, which would otherwise translate to baked, stewed aromas in the area's wines.
As the decades have rolled by, Russian River's winemakers have become increasingly aware of the advantages their cool climate brings. It was this realisation (and the corresponding quality of Russian River Valley's Pinot Noir and Chardonnay) that has led to the international fame the AVA and its wines have achieved.