Rains Ease California Drought--Slightly
NAPA, CALIF.—More than 10 inches of rain fell in some areas Feb. 5-9, helping to ease the severe drought facing California grapegrowers. The rain fell mainly in the North Coast counties of Sonoma, Napa and Mendocino as well as the central Sierra Nevada, source of most of the water used by Central Valley growers.
The central Sierra Nevada snowpack tripled during the first two weeks of February, reaching 36% of average, according to the California Department of Water Resources. The northern Sierra snowpack, the largest part of the state’s water supply, has risen to only 19%, while the southern part of the range sits at 26%.
The state remained in a drought emergency at press time.
Paul Verdegaal, the University of California farm advisor for viticulture, almonds and berries in San Joaquin County, which includes most of Lodi, said Feb. 11, “Until the past weekend, we were at 10% to 15% of normal. The 2 inches that fell raised us to maybe one-third.”
Lodi averages 17-18 inches per rainfall year (July 1-June 30), with 7-8 inches falling before Jan. 1. “Dry-farmed vines can get by with 18-24 inches, but the growers normally supplement by the equivalent of 6 to 12 inches.”
Rhonda J. Smith, the UC viticulture farm advisor for Sonoma County, said that parts of the county received more than 15 inches during the five-day period of Feb. 5-9. In spite of that drenching, rainfall totals this year are the lowest recorded in 120 years of data collection.
In an average year, the Sonoma County city of Santa Rosa would have received nearly two-thirds of its annual rainfall by now. So far, the city has received less than a third of its 32-inch average.
At a meeting Feb. 4 in the northern Sonoma County city of Cloverdale, Pamela Jeane, an engineer with the Sonoma County Water Agency, said that the current drought is worse than that of 1977, which older growers and winemakers recall.
Jeane said that the upper Russian River Valley watershed will need a foot of rain during the next three months to return to levels recorded in the previous record-drought year of 1977. All measures rose with the rain, but they did little to raise levels to average. “Before this rain, vineyard ponds that are filled by only sheet flow were nearly dry.”
In Mendocino County, UC farm advisor (and Wines & Vines columnist) Glenn McGourty noted that parts of Mendocino County received 6-12 inches, with high rainfall mostly on coastal ridges. “At the moment, we have about 25% of our normal rainfall, which is normally around 24 inches in Ukiah Valley. This wets the soil in the root zone for many vineyards, a good thing, so growers most likely won’t have to pre-irrigate before bud break, which is something we were facing during our ‘perennial November’ or ‘June-uary.’”
McGourty added, “We are still in a scary place regarding having adequate water to irrigate and frost protect. If we don’t get substantially more rainfall, we will probably be unable to frost protect most of the vineyards that depend on surface water.”
Jon Ruel, president of Trefethen Family Vineyards and immediate past president of the Napa Valley Grapegrowers, said that Napa Valley received more rain Feb. 5-9 than in all of calendar year 2013. The storm brought around 6 inches in Carneros and up to 14 inches on Mt. Veeder.
“On our ranch in the Oak Knoll District, we had 7.5 inches, which was probably typical for valley-floor locations. That 7.5 inches is about one-fourth of our average annual total, so it was definitely helpful, but obviously we are still well shy of ‘normal.’”
He continued, “From a viticultural perspective, the timing of this rain is quite helpful, as it comes just before bud break, when vines will use the native soil moisture to push out healthy shoots. In fact, from the vine’s perspective, this will be a wetter start than we had in 2013.”
He cautioned, “Of course, many growers need water to irrigate throughout the summer as well. Fortunately, in much of Napa Valley, we have access to a stable aquifer via wells and, usually, rains that fill our reservoirs, even in the occasional dry year.”
Mark Battany, the UC farm advisor in San Luis Obispo and Santa Barbara counties, noted that the recent rains were welcome, but they did not make a huge dent in the deficit this year. “Most of the rain fell in Northern California. We are still far, far behind a ‘normal’ year on the Central Coast.”
Michael D. Cahn, the UC farm advisor in Monterey and Santa Cruz counties, said that the precipitation near his region primarily fell in the Santa Cruz Mountains. Not much made it to Monterey County. The major reservoirs in south county are at about 20% of capacity, and the large aquifer under the Salinas Valley is 8 feet below normal on the east side near the Salinas River. The area is totally dependent on local water. It doesn’t get any from the Sierra.
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