American Viticulture Areas
American Viticultural Areas, or AVAs, are geographical wine grape growing regions in the United States. Their boundaries are defined by the Alcohol and Tobacco Tax and Trade Bureau (TTB) and established at the request of wineries or other petitioners. Washington State currently has 13 AVAs.
Washington’s premium wine industry began in the 1960s. The majority of the state’s wine grapes are planted east of the Cascade Range in the Columbia Valley appellation, which encompasses the Yakima Valley and Walla Walla appellations. The climate and soils produce grapes with intense fruit flavors and high natural acidity.
Washington's vineyards straddle the 46th and 47th parallels, at approximately the same latitude as Bordeaux and Burgundy.
Because of its northerly location, Washington receives up to two more hours of sunlight per day during the growing season than California's North Coast. More sun means more flavor development in the grapes.
It can pour in Seattle, which has an average rainfall of 46“ per year, but east of the Cascades annual rainfall averages less than 10 inches. The Cascade Range creates a rain shadow that protects Eastern Washington from Pacific storms and allows for warm, dry days during the growing season. Low precipitation and low humidity minimize rot, mildew, disease and pest problems in the vineyards.
Growers control the amount of moisture the vines receive during the growing season. This provides for better canopy management and controls berry size to produce concentrated flavorful grapes. Growers irrigates only when necessary to dial in and concentrate the flavor balance in the grapes. The Columbia, Yakima and Snake rivers provide plenty of water via an extensive aqueduct system.
Daily temperatures can fluctuate as much as 40-50 degrees during the growing season. This swing allows the retention of the grape's natural acidity and fresh fruit flavors which produce lively and fresh wines. Chilly nights (40-45 degrees F) lock in the acids and flavors; warm (but not-too-hot) days (85-90 degrees F) ensure that the grapes ripen slowly without excessive sugar development.
The Columbia Valley's cold winters force grapevines into dormancy. Once or twice a decade, sub-zero temperatures can damage some vines in the coolest parts of the valley. However, careful and on-going matching of grape varieties to vineyard sites lessens the impact. Vines are planted on their own roots rather than on rootstock, so in the event of severe winter damage, the vine can be trained up from the root system and produce a crop the next year. At this time the root louse, Phylloxera is not a problem in Washington, probably because the cold winters and sandy soils slow its spread.
About 15,000 years ago a series of cataclysmic geologic flooding events occurred that allowed the formation of present day soils in eastern Washington. The floods converged on the Pasco Basin and were slowed by constriction of the Wallula Gap before draining into the Columbia River. The constriction caused back flooding of local rivers and valley basins and deposited fine grain slack water sediments (silt/sand) over the surrounding area. The floods deposited immense gravel bars and ice-rafted huge granite boulders (erratics) to higher elevations.
The resultant slack water deposited sediments and the subsequent wind-blown loess sediments make up the majority of the present day soils and are the backbone of agriculture in all of eastern Washington. These sandy loam soils are very well drained—and a perfect medium for grapevines.
The Columbia Valley covers 18,000 square miles and provides a huge range of geographical and climatic conditions for grape growing. This diversity creates distinctive fruit characteristics from individual sites and offers a myriad of stylistic options to winemakers.
Because of the diverse growing conditions in Eastern Washington, a large number of grape varieties do well here. When planted in the right locations, Chardonnay, Sauvignon Blanc, Riesling, Gewurztraminer, Semillon, Pinot Grigio, Viognier, Cabernet Sauvignon, Merlot, Syrah, Malbec, Petit Verdot, Barbera, and many others thrive.