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practicalwinerylibrary.com Access Practical Winery & Vineyard article archives online. TECHNICAL RESOURCE FOR GROWERS & WINERIES 64 Minimum resale price policy, price-cutters By Suzanne DeGalan 68 Intellectual property: What's trending and how to capture it By Katja Loeffelholz grapegrowing Surface-renewal measurements of actual evapotranspiration BY Tom Shapland, Ph.D., W Tule Technologies, Oakland, Calif. ater conservation is critical to California viticulture as population and environmental pressu res ma ke f resh water resources less reliable. Irrigation management impacts grape quality, but reducing water applications to meet quality objectives can put the crop at risk. A new technology from the University of California, Davis, provides viticulturists with a tool to quantify the amount of water that evaporates from a broad area of a vineyard. Surface-renewal technology has recently been improved to perform well in vineyards. Grapegrowers use the measurements of actual evapotranspiration (ET) to help them decide how much water to replace in a vineyard when they irrigate. ET is a combination of water transpired through the vines and other vegetation along with water evaporating from the soil and other surfaces in the field. Surface-renewal technology provides viticulturists with remote monitoring of vine-water status by tracking changes in actual vineyard ET between irrigation events. The new technology assists growers in maintaining yield and quality objectives while increasing water-use efficiency by more accurately assessing crop water use. In order to measure how much water the vines are using, surface renewal quantifies how much heat and water vapor the wind carries away from a 2- to 5-acre vineyard block.1 A surface-renewal station looks like a basic weather station installed at one location within a vineyard block. Each morning, the surface-renewal station sends data to the Internet via a cellular connection. The viticulturist receives an automatically generated email at customized intervals that reports: 1) How much water evaporated from a hypothetical well-watered grass field (i.e., Reference ET) for both the previous week and forecast for the following week. The California Irrigation Management Information System (CIMIS) provides growers with Reference ET values. By estimating the ET of a well-watered grass field, Reference ET describes the evaporative demand of the atmosphere. With the past and forecasted Reference ET, the grapegrower can anticipate how evapo- 60 p racti c al w i ne ry & v i n e yard FE BRUARY 20 14 A surface-renewal tower measures the actual evapotranspiration from a vineyard. The net radiometer at the upper right portion of the tower measures the amount of light energy absorbed by the vineyard. The airtemperature sensor on the middle left portion of the tower measures how much heat the wind has carried away from a broad area (approximately 2 to 5 acres) of the vineyard. Ground heat-flux sensors (buried 2 inches) measure the energy conducting into or out of the ground. The gray box houses the data logger and cellular modem, protecting the electronics from spray deposition. rative demand is expected to change during the next week. 2) How much water has evaporated from the vineyard during the past week. Actual vineyard ET is different from Reference ET, because it is the water loss from a vineyard itself and not the water loss from a hypothetical well-watered grass crop somewhere else. The actual