Issue link: http://winesandvines.uberflip.com/i/131907
cover story Topography and Temperature Research in Columbia Valley links land and growing degree days By Peter Mitham kevin pogue Highlights A monitor installed at Spring Valley Vineyard records data about the Walla Walla Valley AVA. R ivers and mountains define many of the world's great wine regions, and the West Coast of North America is no different. The Columbia River winds its way south from British Columbia through Washington state; the Willamette River carves a home for Pinot Noir through Oregon, and the Russian River flows through Mendocino and Sonoma vineyards in California on its way to the Pacific Ocean. But understanding how those rivers— and the topography of the valleys they've shaped—influence vineyards is a question with few obvious answers. While the moderating influence major watercourses play on temperature is well-known, as is the potential for valleys to draw in cold air, generating fog banks above the waters, Kevin Pogue of Whitman College in Walla Walla, Wash., has spent the past two years gathering data that could improve grow- 30 W in e s & V i ne s J U NE 2 0 13 • opography influences growing T degree day accumulation. • esearch in the Columbia Basin R pinpoints trends using data loggers in 55 vineyard locations. • eologist Kevin Pogue found that G the daily minimum temperature matters more than the daily high. • ong growing seasons allow GDD L accumulation even in relatively cool areas. ers' understanding of local topography— leading to more knowledgeable site selection and better vineyard management. What the research is Pogue, a geologist, has a long-standing interest in the terroir of the Columbia Basin. He presented a paper to the VIII International Terroir Congress in Soave, Italy, in June 2010, focusing on the influence of the region's basalt-rich landscape on vines, specifically soil temperature, cluster temperature, vine chemistry and other attributes. That same summer, Pogue covered 1,400 miles deploying data loggers at approximately 55 vineyard sites across the Columbia Basin with the intention of gathering data related to vineyard temperatures. Pogue wanted to see if there were links between topography and the accumulation of growing degree days (GDD), an indicator growers use to predict the key stages of fruit development including bloom, véraison and crop maturity. The number of growing degrees for any particular day is the day's average temperature in Fahrenheit minus 50. (For example, a day with an average temperature of 70ºF would log 20 GDD.) The data loggers, the Hobo model produced by Onset Computer Corp., cost approximately $125 apiece. The units record data, which Pogue then had to download (systems that transmit data wirelessly cost closer to $1,500 apiece). Pogue tested the data loggers for consistency prior to placing them in vineyards at a height of approximately 6 feet. All locations were in vineyards to secure relevant readings; locations were away from overhead sprinklers, asphalt and anything else that could distort the readings. The units stayed in place from August 2010 through the end of 2012, giving Pogue data about one of the coolest growing seasons on record—2011, which racked up just 2,312 growing degree days—as well as 2012, which at 2,643 growing degree days was about par with the long-term average of 2,628 growing degree days. What the research found Pogue is just starting to work through the numbers, but the preliminary findings are providing a clearer picture of how growing degree days accumulate, and a better understanding of why vineyards respond differently to weather systems. "People tend to look at daytime high temperatures (and say), 'Oh yeah, it's