KELSEYVILLE >> Throughout the county, winegrape growers are using specialized technology to water crops as the drought continues into its third year.
“Lake County grape growers and growers throughout the state have known for decades that water is a precious resource and it must be used judiciously,” said Bryan Rahn, owner of Coastal Viticultural Consultants, one of several firms that provide water management services to grape growers in Lake County and the North Coast. “A large part of my consulting practice is water conservation and improving wine grape quality.”
Lake County”s agricultural mix includes approximately 8,718 acres of vineyards. While a handful of vineyards near Kelseyville and Upper Lake use surface water drawn from Clear Lake, the majority of vineyards use groundwater for irrigation.
“Most growers are keenly aware that without a sound water strategy and sustainable water supply for their vineyards, it is unlikely that those vineyards would survive financially or even physically,” Rahn said.
In fact, nearly all Lake County vineyards use drip irrigation systems to deliver a precise amount of water to the vines at the right time during the vine”s growth cycle. Perhaps a third of these vineyards also use overhead sprinkler systems, mostly to prevent frost damage during the spring.
Lake County grape growers employ a range of technologies and irrigation management strategies for precision irrigation. This technology ranges from high-tech, real-time web-based data to visual observations and shoot-length measurements. For example, growers use weather data, crop evapotranspiration (ETc) measurements, real-time soil moisture, vine water status measurements and hands-on techniques to conserve water.
These technologies, combined with boots in the field, deliver the data that allow growers to precisely and effectively manage their limited water supplies.
The practices are not new to Lake County growers vineyard managers who have worked in water management and stewardship for more than three decades.
“We began converting our old furrow and sprinkler irrigation systems and installing drip irrigation back in the late 1970s after that drought,” long-time grape grower Walt Lyon said. “Drip is a great tool. It saves us water and energy — more crop per drop.”
“Growers don”t want to pump water if it”s not needed,” Rahn, a Certified Professional Soil Scientist, agronomist and vineyard consultant for more than 25 years, said. “Labor and energy are expensive.”
Rahn makes weekly vineyard visits with growers including Bruce Merrilees, vineyard manager for Bella Vista Farming. During these visits, they examine grapevine water status, discuss irrigation water requirements and use several tools to measure the water status of the soil and the grapevines.
“The pressure chamber and infrared thermometer tell us when to irrigate,” Merrilees said. “The neutron probe measures soil water volume and precisely how much irrigation water we should apply without over-irrigating and wasting water. This year, the pressure chamber data showed us that we could delay irrigating for a couple of weeks in some blocks.”
While many of the tools are high-tech, Rahn uses a low-tech method as well.
“Even feeling the grape leaves with your hands is another useful diagnostic tool,” he said. “When leaves are actively transpiring (have sufficient moisture), they are cool to the touch. Not only are the leaves cooler, but so is the fruit. Cooler clusters yield superior fruit quality.”
