Christian Moueix is the kind of man who has annual rainfall statistics memorized. "In Bordeaux, the average is 38 inches, with much less variation than Napa," he detailed. "The past 25 years in Napa range from 8 to 63 inches." It’s important for vintners—and not just Moueix, whose 134-acre Napa Valley property Napanook Vineyard is dry farmed—to keep track of rain because early precipitation can set the stage for an excellent vintage. At the same time, too much rain can have negative consequences. "Vintages with heavy rain, above 50 inches, were 2011, 2017 and 2019," Moueix said. "What does that mean? Vegetation is so strong that even if we reach full ripeness, there is still some herbal character."
California's three weeks of storms dumped a tremendous amount of rain on the state. While the weather led to at least 22 deaths and scores of washed-out roads, mudslides and flooded neighborhoods, many farmers couldn't help but welcome the wet weather after years of being strapped for water resources. Many areas have already attained their average rainfall for the entire year. As a result, aquifers are recharged and reservoirs are full.
And for the state as a whole, according to the California Department of Water Resources, the snowpack in the Sierra Nevada mountain range currently holds more than twice the water content than in an average year. Melt from the snowpack provides approximately 30 percent of the water supply to the state each year.
The series of atmospheric rivers that carried warm moisture from the Pacific to the West Coast shifted with each storm, ensuring that almost every part of the state saw heavy rainfall at some point. Most parts of Napa and Sonoma experienced more than 25 inches of rain. Paso Robles rainfall estimates were around 20 inches. But rainfall also varied within each appellation—the western part of Sonoma's Russian River Valley usually gets more rain than the Alexander Valley, and that was the case during these storms.
The season's rain has brought much of the state out of severe drought risk but, as a whole, California remains moderately or abnormally dry. "We'll take all the rain we can get," said Hanzell president and director of winemaking Jason Jardine. "A rainy day is never a disappointing day!"
Harnessing the rain
Of course, rain has to fall at the right time for vintners. Winter months are the best time for rain in the vineyard. The grapevines are dormant up until budbreak. And a big drink, thanks to Mother Nature, helps fill reservoirs and ponds, allowing vintners to use water at will for frost protection or irrigation throughout the season. On the other hand, too much rain, in rare cases where vineyards become flooded for extended periods, can waterlog vines and prevent oxygen from reaching the roots, impeding the vines from gathering water and nutrients.
How vintners use the rain depends a lot on their specific approach in the vineyards. At Hanzell in Sonoma, Jardine farms biodynamically, and early rains in October and November helped establish cover crops, which are now flourishing thanks to the rain in December and January. Moisture also activates microorganisms, which help break down organic matter and liberate minerals for the vines.
Erosion is a big concern for Jardine because of Hanzell's hillside vineyards. Erosion can wash away those key minerals and nutrients. Many growers combat the problem with hay bales, but cover crops, grasses and herbs planted between the rows, can also prevent soil from washing away. They also help vintners control moisture levels year round.
Jardine uses cover crops and a no-till strategy to create a sponge layer to soak up the rain. Later in the season, he crimps cover crops to avoid disrupting topsoil. That layer then acts as a buffer against the sun, aiding in retaining moisture in the soil for extended periods. This also keeps the soil temperatures cooler, which can, depending on the subsequent weather conditions, translate to later budbreak than usual, ideally reducing the threat of frost damage.
"Getting moisture around roots, at a depth many vines haven't seen in a long time, is advantageous," said Jardine. However, he noted that this strategy isn't for everyone. "Farming should be about adapting to local conditions and terroir rather than being dogmatic."
A refill and cleanse
Over in Napa, Moueix's dry-farmed Napanook vines rely upon groundwater and underwater springs to provide water. As a result, the vines have become better at self-regulating over the years, adapting to seasonal conditions and reaching deeper for water in some years, and thus more resistant to drought conditions.
Flooding is a different challenge. Moueix and winemaker Tod Mostero mitigate excess groundwater via underground drains. "We want to see the saturation [in the soil] drop, so that vines aren't swimming and have to go deeper to find water," explained Mostero, noting that when vineyards irrigate, they're correcting for natural conditions. "Dry farming allows the vine to adapt naturally and conserve in cases where there isn't as much water."
To the south, growers in Santa Barbara County, which typically doesn't see as much rainfall as Northern California, are rejoicing. "We exist on somewhat of a feast or famine cycle," said Dragonette co-founder and winemaker Brandon Sparks-Gillis. "On the heels of essentially five years of drought conditions, the county is at 112 percent of normal. So being significantly ahead of the curve is money in the bank."
One of the region's biggest problems, which drought conditions have exacerbated, is sodium levels in the soils. The region's proximity to the Pacific Ocean and breezy conditions bring salty air off the coast, which builds up in the soil, causing sodium toxicity that can lead to poor canopy growth and reduced yields over time. Sparks-Gillis said these heavy rains have cleansed the soils.
He joked that farmers are nervous about everything, and that they'll sleep easier knowing there are some water reserves this year. But, of course, there are still many months left, and both Jardine and Moueix were quick to point out that untimely spring rains could impact the flowering and fruit set or bring unwanted vegetative growth. "For us, the rain was very welcomed," said Moueix. "Average rain on the ranch for the past 25 years is 30.7 inches per season. As we speak today, we're at 31.4 inches. We wish to have more, as long as it falls early in the season."
But Mostero amended Moueix's thoughts: "If it doesn't rain again, the spring will be dry. The game has only just begun."