Defining the terroir of the Columbia gorge wine region, Oregon and Washington, USA using geographic information systems (GIS)

The Columbia Gorge Wine Region (CGWR) extends for about 100km along the Columbia River and includes the Columbia Gorge American Viticultural Area (AVA) and the southwest portion of the Columbia Valley AVA. As of September 2013, the region is home to 82 vineyards, 513 hectares (1268 acres), 36 wineries and 41 different varieties of Vitus Vinifera, with Pinot Noir being the most widely planted grape variety in both AVAs. To better understand the physical factors affecting Oregon and Washington wine, this project analyzes the climate, topography, geology and soil at vineyards in the CGWR using Geographic Information Systems and existing earth science databases.

Vineyards range in elevation from 29 to 548 meters (95 to 1799 feet). The microclimates vary within this relatively small wine region, allowing for diversity in grape varieties planted. Three Winkler climate regimes are represented within the CGWR, including Regions Ia, Ib, and II from the Winkler Index (Jones et al., 2010). The average growing season temperatures range from 13.7°C (55.7°F) to 17.7°C (63.9°F) and the average growing degree-days range from 871 for °C (1567 for °F) to 1664 for °C (2994 °F). 58% of the vineyards are characterized within an intermediate climatic regime, 29% are within a cool climatic regime, 9% are within a warm climatic regime and 4% are on the boundaries between a cool, intermediate or warm regime. The growing degrees days calculated for the CGWR are similar to those measured in the Willamette Valley, Oregon, Burgundy, France, Umpqua Valley AVA, Oregon and Bordeaux, France.

All of the soils used to grow grapes are well drained and within a xeric moisture regime. 30 soil types are represented among the vineyard sites, with the Chemawa Series (Underwood Mountain) and Walla Walla Series (eastern portions) being dominant. Majority of the soils contain a silt loam texture, with 46.5% of the total vineyard acreage planted on soils formed in loess from eastern Washington and Oregon. The Missoula Floods influence the texture and age of the soil in this region, with skeletal textures close to the Columbia River and finer textures at higher elevations. Other common geological deposits at vineyards in the CGWR include, Quaternary Basalt (19.6%), Missoula Flood deposits (9.1%), The Dalles Formation (8.0%), Columbia River Basalt Group (7.5%), Pliocene Basalt (3.0%), Quaternary Surficial deposits (3.0%), lahars (2.3%) and Quaternary Basaltic Andesite and Andesite (0.9%).

Common geological deposits, soil series, and climate conditions at vineyard sites vary spatially in the region, making this one of the most diverse wine regions in terms of growing conditions in the Pacific Northwest.

Authors: Hilary Whitney and Scott Burns

Department of Geology, Portland State University

Email: hilaryannwhitney@gmail.com and burns@pdx.edu

Keywords: Columbia Gorge, terroir, geographic information systems (GIS)

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