Geology and wine 8. Modeling viticultural landscapes: a GIS analysis of the terroir potential in the Umpqua Valley of Oregon

Geoscience Canada, Dec, 2004 by Gregory V. Jones, Nicholas Snead, Peder Nelson

Grape Growing in Oregon

Oregon currently ranks as the fourth largest wine producer in the United States, growing grapes in six appellations (Federally designated grape growing and wine making regions, called American Viticultural Areas-AVAs): Applegate Valley, Columbia Valley, Rogue Valley, Umpqua Valley, Walla Walla Valley, and Willamette Valley (Fig. 2). In 2002 there were 582 vineyards and 176 wineries growing more than 25 different varieties on over 10,000 harvestable acres with an economic benefit of over 250 million dollars to the state (Oregon Vineyard and Winery Reports, 2002). While Oregon is widely known for its Pinot Noir, other regions in Oregon are finding that warmer climate varieties can be ripened to produce quality wines (e.g., Merlot, Tempranillo, Syrah, and Malbec).

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Umpqua Valley AVA

The Umpqua Valley American Viticultural Area (AVA) is located entirely within Douglas County (Fig. 3) (Code of Federal Regulations, 2000). Grape growing and wine making started in the Umpqua Valley during the 1880s, but because of the region's distance to a larger market (i.e., Portland, San Francisco) it never established itself as a dominant industry in the region. In 1961 the region became the home for some of the earliest plantings of post-prohibition winegrapes in Oregon and in 1984 the Umpqua Valley AVA was established. Within the region, there is a diverse array of landscapes and climates that offer the various conditions needed to produce both cool and warm climate grape varieties. Today, the Umpqua Valley AVA has over 650,000 acres zoned for agriculture and, as of 2002, was planted with over 1,100 acres of vines on nearly 60 vineyards (Jones, 2003a). Production totaled over 1200 tons of grapes crushed at twelve wineries in 2002 (Oregon Vineyard and Winery Reports, 2002) with the dominant varieties grown being Pinot Noir, Chardonnay, Riesling, Cabernet Sauvignon, Pinot Gris, Merlot, and Gewurztraminer. Although the varieties listed above make up over 80 percent of the crop in the Umpqua Valley, the region is proving to be well suited for other varieties such as Baco Noir, Marechal Foch, Tempranillo, Syrah, Malbec, and Dolcetto.

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In comparison to the other grape growing regions in Oregon, the Umpqua Valley AVA has the most beneficial climate structure in the state, with the longest growing season, the lowest risk of both spring and fall frosts, and low-ripening period rainfall and temperature extremes (Jones, 2003b). The region is warmer than the Willamette Valley to the north, but cooler than the Rogue Valley to the south (Fig. 2). Heat accumulation varies north to south in the AVA with growing degree days averaging 2200-2400 in the north and 2400-2700 in the south. Precipitation is also quite variable from north to south, averaging 30-60 inches annually (Oregon Climate Service, 2002). The growing season averages 200 days across the AVA, varying from 180 to over 215 days depending on elevation, while the median last and first frost (32[degrees]F) occurs on April 10 and October 31, respectively.