Water Woes: Drought Hits the Wine Industry. Again.

Tony Crabb, co-owner of Puma Springs Vineyard, surveys his nearly empty reservoir as of early May.

A 2015 study by the Pacific Institute highlighted that California agriculture uses an estimated 80% of the state’s developed water supply.

Although California is not unfamiliar with drought, 2021 is somehow different. It is likely to go down as one of the driest in the state’s recorded history. In response to the crisis, Tom Vilsack, secretary of the U. S. Department of Agriculture, designated 50 counties in California—including Napa, Marin, Sonoma and Mendocino—as natural disaster areas on March 5. California only has 58 counties.

In April, Gov. Gavin Newsom announced a drought emergency in Sonoma and Mendocino counties, emphasizing the dire situation thereby holding a press conference, while standing on a dry and cracked section of the Mendocino Lake’s bed. In normal years, the stage would have been nearly 40 feet underwater.

“Oftentimes we overstate the word historic, but this is indeed a historic moment, certainly historic for this particular lake, Mendocino, which is currently at 43% of its capacity, said Newsom, acknowledging this as the second year in a row of tough drought conditions.

State Sen. Mike McGuire, D-Healdsburg, told the Sacramento Bee in late April that “Lake Mendocino is the canary in the coal mine when it comes to California’s drought.”

A few weeks later—according to the Department of Water Resources data exchange center website—Lake Mendocino had dropped to 30% capacity; Lake Sonoma was at 39% capacity and Lake Berryessa in Napa County was at 69% capacity. As a result of the worsening conditions, by early May Newsom had added 39 additional counties to the list, including Napa.

Although Marin County remains outside of Newsom’s proclamation, for now, about 25% of Marin’s, and the majority of Sonoma’s, water comes from the Russian River watershed (RRW). The RRW is different from most large water systems in the state—such as the Klamath and the Sacramento—in that it relies primarily on rainfall more than other large water systems in the state because it is isolated from snowmelt and large natural lakes.

Agriculture uses 80% of the water

The state’s Mediterranean climate—dry, hot summers with most precipitation falling only during the winter—makes it a near-perfect place for growing a variety of crops, including wine grapes. However, even a modest drought puts pressure on the delicate balance between water, animals, plants and people.

A 2015 study by the Pacific Institute highlighted that California agriculture uses an estimated 80% of the state’s developed water supply. And whereas vineyards require much less water than almond trees or the biggest guzzler of all, alfalfa, they still need far more water than such crops like beans or potatoes. That said—and if you talk with vineyard owners you’ll hear this early and often when discussing water—the most common type of irrigation in a vineyard is a drip system which is exceptionally efficient, whereas sprinklers or furrow “flood” irrigation used in other farming practices tend to overwater and evaporate into the air, where it is lost.

This argument is true to a certain extent. However, flood irrigation is more efficient at refilling underground aquifers, and drip irrigation allow for farming in areas that would otherwise be inaccessible using more traditional methods.

High temperatures and yearly challenges

Exacerbating the drought, California had its hottest year on record in 2020. According to the Public Policy Institute of California’s Water Policy Center, the excessive heat makes for a “thirstier” atmosphere, which increases evaporation and reduces water availability for ecosystems and humans. Warming also decreases the proportion of precipitation that falls as snow. Snowpack is an important part of the state’s water storage system and accounts for about 30% of the water supply. California’s snowpack has hovered around 50% of normal for the last two years, and “snow droughts” make it difficult to fill reservoirs, replenish underground aquifers and generate hydropower.

In addition, yearly challenges are stacking up on the wine industry. For Northern California wine-grape farmers—and the entire West Coast wine industry more broadly—the current drought could not have come at a worse time. Hoping to recover from years of consecutive wildfires, a general softening of consumer demand for wine and the ravages of the pandemic, those in the industry had hoped 2021 might prove uneventful, allowing time to stabilize their businesses and rebuild inventories. However, now, with a looming historic drought, it looks like the volume of grapes harvested will be much less than in normal years as growers reduce crop loads, limit irrigation, and allow vineyards to go fallow or remove them altogether.

“We just don’t have the water to irrigate this year,” says Tony Crabb, co-owner of Puma Springs Vineyard, which is located between Alexander and Dry Creek valleys in northern Sonoma County. “Normally our reservoir would be filled this time of year, but it’s basically empty.”

A farmer’s perspective

It was early May when Crabb and I stood atop his near-empty reservoir. Nearby goats chomped on dry weeds while standing on the pond’s parched banks. To the east, separated by the serpentine Russian River flowing eastward, Mount St. Helena loomed in the distance, its bluish-beige slopes shimmering in the scorching afternoon sun. To the west of us lay rolling hills covered with a sight normally only witnessed in late summer — the corduroy texture of vineyards covered in alternating ridges of verdant grapevines against the sharp contrast of the already bone-dry earthen rows that appeared like beige strips of carpet.

For grape farmers and the wine industry, the drought is just another part of the job. “The drought conditions are very worrisome for our entire community and especially our local grape-growers and farmers who rely on crops for their livelihood,” says Karissa Kruse, president of the Sonoma County Winegrowers and executive director of the Sonoma County Grape Growers Foundation. “As we think about the impact to agriculture in general, fortunately, grapes are very efficient crops and do not need much water. In fact, grape irrigation uses only 3 to 6 inches per year in Sonoma County, so that remaining water accumulated in the rainy season goes back into the ground and recharges the aquifer.”

Although long-term droughts that damage grapevines are harmful, short-term droughts may actually have positive impacts on wine quality, according to Mark Greenspan, president and viticulturist at Advanced Viticulture Inc. “Drought will not detrimentally affect wine quality necessarily,” says Greenspan. “If anything, some vineyards that tend to start with too much moisture stored in the soil may benefit by having less water available in the soil, so they can control vegetative growth and induce mild stress in the vines, which can often benefit wine quality.”

Jennifer Williams, co-owner and winemaker of Napa Valley’s Zeitgeist Cellars is seeing effective changes in vineyard management practices but worries that the high heat and dry weather will shrivel the grapes before they become completely ripe. “We are seeing slightly fewer canes or buds left on the vines to prevent high water demand later in the season,” she says. “We are seeing growers, who still have water, irrigating early in the season to mimic rain events. My biggest concern in hot, dry years is getting to the finish line with fruit condition intact.”

The local impact of distant droughts

Even distant droughts are having a local impact on drought response. As the global population continues to expand and extreme weather events cause instability, agricultural practices are not the only activities affected by droughts. This year Taiwan—typically one of the rainiest places on earth—is gripped in a crippling drought that has its reservoirs at less than 20% capacity. This impact in the small island nation is being felt beyond farming. Because water is used to cool the machinery that makes semiconductors—computer chips—the lack of water is one of the leading causes of a slowdown within Taiwan’s $100 billion semiconductor industry. The result is long lag times for mobile phones, laptops and TVs and delays in shipments for the very technology that might help local farmers monitor their crops.

Companies such as Fruition Science are using technology within vineyards, including sap-flow monitoring, to better understand the need for water on a per-vine basis.

“We use a systematic approach to irrigation, incorporating plant-based metrics,” says Thibaut Scholasch, co-founder and vice president of research and development. “Our customers report up to a 60% reduction in water and energy use along with increases in both quality and yield.” Scholasch and his team are not the only ones employing technology to monitor irrigation. Dozens of companies have sprung up in the last few years, each looking to deploy technology to increase the efficiency of irrigating.

“[Our grape farmers have] invested in new innovations to better monitor water needs on a vine-by-vine, minute-by-minute basis, including pressure bomb testing and evapotranspiration sensors,” says Kruse.

Many farmers now use sap-flow sensors and/or track evaporation rates, often by using hand-held “pressure bomb” testing devices or by fixing evapotranspiration monitors directly onto the plants themselves. Beyond these tools, aerial infrared images, often captured by drones, model normalized difference vegetation indexes (NDVI) to quickly determine those areas of the vineyard that require watering. A few vineyardists are deploying electronic soil-moister sensors, and nearly all have weather stations that provide real-time data on temperature, rain, wind and humidity. Regardless of which technology is used, it is the rare grape farmer who does not now have the ability to check in on his or her vineyard using a smartphone app.

“We make extensive use of soil moisture profile probes,” says Greenspan. “While not exactly new technology, they give us a clear idea of where roots are active, where water is and isn’t in the soil profile and guide us for precise and efficient irrigation. Other technologies exist, but we feel that the soil moisture probes are the most valuable and indispensable.” In subsequent conversations, Greenspan shared that they’ve had weeks to month-long delays in receiving their technology, possibly due to complications from Taiwan’s drought and compounded by COVID-19.

Beyond high-tech options, some farmers are experimenting with sunscreen-like sprays to reduce sunburn and evaporation, whereas others are deploying shade.

“Here at the Oakville Station in Napa County we are exploring the benefits of using overhead optically-selective shade films to help reduce sun damage and extreme temperatures,” says Kaan Kurtural, cooperative extension specialist, in viticulture with the UC Davis Department of viticulture and enology. Kurtural is headquartered at the department’s Oakville Station, a 40-acre research vineyard in Napa Valley. Much of the station’s recent work has been focused on understanding the impacts of extreme weather events such as drought on wine grapes.

“We have also developed molecular markers to test for water stress and another one to test for solar radiation damage,” says Kurtural. “Beyond looking at these tools, our team is testing different trellis systems, pruning alternatives, improved irrigation practices, rootstock-cultivar combinations and cover-crop management in an attempt to collect data that may help our understanding of the current situation but also to provide the industry tools they need to manage the current and future environments.”

The depletion of groundwater

Groundwater depletion is a growing concern. NASA Gravity Recovery and Climate Experiment (GRACE) satellites became active in 2002 and have since documented a sobering trend: Underground aquifers throughout California, including Northern California’s Wine Country, are on the decline. When water is pulled from deep wells or kept in water-sealed ponds, water stores that normally reside underground contract. Typically, this is fine as long as rainfall and standing floodwater eventually percolate down and replenish the stores. However, in a process called subsidence, if through overuse or lack of rain these underground ancient aquifers contract long enough, they are lost forever. GRACE tracks the amount of water available on the surface and within the earth’s crust, using gravitational pull as a measuring stick.

Subsidence is nothing new in California. In the 1970s, geologist J.F. Poland posed for a photo standing next to a towering telephone pole near Fresno. Near the top of the pole, 30 feet up, was a sign with the year 1925. Farther down another sign read 1955, and at the bottom, propped at the base of the pole next to Poland’s feet, sat a sign with the year 1977. Because the process is slow and seemingly benign, Poland was attempting to highlight the sizable subsidence in the area that had resulted from compaction caused by groundwater abstraction. The pole would need to be a lot higher today.

Beyond looking at changes in elevation due to excessive groundwater extraction, in 2018 the state of California’s Department of Water Resources “reprioritized” four additional groundwater basins within Napa, Sonoma and Marin counties. Shifting them from “low” to “high” priority under the Sustainable Groundwater Management Act (SGMA) means that each of these basins is now subject to increase scrutiny and monitoring. Data from SGMA’s website map indicates that many areas within all three counties witnessed a greater than a 10-foot decline in groundwater levels between 2010 and 2020. (For more information, visit sgma.water.ca.gov/webgis.) Although subsidence is not a major concern for these counties at present, that could change if groundwater levels continue to contract.

A recent “Annual Report—Water Year 2020” presented by the Napa County Groundwater Sustainability Agency suggests that although groundwater does fluctuate from month to month, it appears relatively stable from year to year. Perhaps, but a disturbing graph in the report shows that 2020 had a net change of nearly 25,000-acre-feet of groundwater. (That’s enough water to serve 50,000 families for a year.) The change was the biggest since data began being collected in 1988.

A history of droughts and floods

California has a long history of droughts and floods. The perplexing, frustrating and ongoing challenges associated with the use of agricultural water are nothing new in Wine Country, or the entire state of California, for that matter. Water has been a consistent source of consternation, with those who have it wanting to keep it and those who need it with a seemingly unquenchable thirst.

In Mark Arax’s recent book, The Dreamt Land: Chasing Water and Dust Across California, he documents the history and the role of water—both droughts and floods—in defining California’s particular obsession with the “liquid gold” that is water, highlighting the great lengths to which people have gone to obtain and even plunder the life-sustaining natural resource that falls freely from the sky.

Quoting a story he’d read about a member of the Wintu tribe who lived at the base of Mount Shasta, where the great flow of northern waters begins, Arax wrote: “[They] watched in bewilderment in the 1850s as the white man started to erect his system of moving the rain. The natives could not fathom the pressure the strangers were putting on the land. Demands of this sort would stretch the earth too thin, the Indians warned. Cracks would open up in the ground and swallow up mankind. The spirit would strike back first as drought and then more devastatingly as a flood.”

Many local farmers attempting to get through another tough year are looking for cracks—perhaps not as ominous as those depicted by the Wintu Native American, but concerning nonetheless.

Without water, what can you do?

Crabb and I stood quietly as we surveyed his nearly empty pond. At its bottom a few feet of turbid, muddy water remained, just enough for a family of geese that had found refuge as their goslings grew strong enough to fly. “We can weather this year,” says Crabb, his voice sounding resolute. After a long pause, he added, “But if this happens again next year we may have to remove part of the vineyard. Without water, what can you do?”

The history of potassium

Beyond the basic ingredients essential for photosynthesis—carbon dioxide, water and sunlight—grapevines require a collection of nutrients to thrive. One of the most important is potassium, which makes up roughly 3% of the dry weight of a grapevine. In vines, potassium plays a key role in the regulation of water movement within the plant; is involved in the transportation of sugars, nutrients and amino acids; influences color development in red grape varieties; and is critical to proper pH balance within the berries and the resulting wine.

Although potassium makes up only about 2% of the earth’s crust, it is the eighth-most abundant element on earth and is indispensable for both plant and animal life.

Metallic potassium was first isolated by Sir Humphry Davy in 1807 when he concentrated wood ash in large iron pots in a process that created “potash.” The English word for potassium comes from potash; however, the chemical symbol K comes from the Latin word for alkali, kalium. In the periodic table of elements, potassium is listed as one of the alkali metals. Pure potassium is a soft, waxy metal that is easily cut with a knife. To prevent it from reacting with oxygen and water, samples of metallic potassium are usually stored submerged in mineral oil. For living organisms, however, the pure form of potassium is not very useful. Instead, the usable form of potassium is its positively charge ion, normally referred to as a K with a plus sign (K+).

Such positively charged elements (cations) are attracted to negatively charged elements, called anions. For example, chloride (the atomic symbol of which is CL) is a negatively charged anion CL- and can therefore interact with the K+ cation to form a stable compound. The most common potassium compound, KCL, or potassium chloride, is a substance often found in fertilizers.

Managing potassium levels

Managing proper potassium levels within plants such as grapevines during a drought is critical. Within the vine itself potassium, unlike many other nutrients, remains highly mobile, flowing freely within the vine’s vasculature and being distributed throughout the plants as needed. Within leaves potassium influences the opening and closing of stomata, small pores on the surface of leaves that regulate the plant’s gas exchange. When potassium is present within the stoma’s cells the pores open, and when it is absent, they close. Therefore, when water is scarce, a stoma releases potassium, closing the pore and thereby retaining more water and protecting the plant from the stress associated with drought.

Beyond regulating water within the plant, the stoma also allows for carbon dioxide exchange, which is an integral component of photosynthesis. Potassium’s positive-charged cation also energizes ATP (adenosine triphosphate), a molecule that provides the necessary energy to catalyze the process of photosynthesis.

Given all this, it might seem that encouraging high levels of potassium within a grapevine would make sense, especially during a drought. But although critical to normal function, having too much potassium will result in the plant moving and storing the element within the berries, which can cause color instability in red grapes and result in high pH wines. That said, too little potassium in the plant is equally as devastating. As stated above, beyond greatly increasing the risk of drought stress, causing color instability and inhibiting photosynthesis, too little potassium also hinders shoot, root and fruit growth and causes sucrose (sugar) sequestration in leaves, reducing yield and hindering fruit ripening.

A vineyard that has a low level of potassium during a drought is easy to spot: The oldest leaves die off as the plant attempts to shift any remaining potassium to younger leaves and to the berries. As the year progresses, leaf tips curl and turn brown and insufficient chlorophyll between leaf veins results in a condition called “chlorosis.”

Testing for optimal levels of potassium is best accomplished through a combination of taking soil samples at the vineyard and also sending leaf petiole samples to the lab — once during bloom and then again in late summer (70 to 100 days after bloom). The target range of potassium within petioles is typically anywhere from 1.5 percent to 2.5 percent, although a lot depends on a host of factors, including time of year, varietal and site. Given the possible negative effects of potassium on winemaking, most winemakers prefer that supplemental potassium be only added prior to veraison.

Best Vineyard Management Practices

“Our commitment to sustainability includes many water conservation best practices— almost 30 different practices that focus on water management and quality—including water reduction, water quality, soil moisture monitoring, deficit irrigation and more,” says Karissa Kruse, president of the Sonoma County Winegrowers and executive director of the Sonoma County Grape Growers Foundation. “Our grape-growers have been focused on water conservation for years and have specifically adjusted farming practices in order to conserve water.” Here’s a list of the best management practices for vineyards from the Sonoma County Winegrowers.

1. Use a low-flow sprinkler irrigation system in the vineyard.
2. Test the distribution uniformity of the irrigation system (at least every five years) and use visual monitoring across the blocks to make necessary corrections and protect from overwatering.
3. Inspect and clean water filters in the irrigation system when pressure differences are found.
4. Use soil and/or plant moisture monitoring devices to determine irrigation needs.
5. Initiate irrigation as late as possible in the season on a block-by-block basis.
6. Limit irrigation to between 8 p.m. and 6 a.m.
7. Use evapotranspiration data from CIMIS (California Irrigation Management Information System) stations to approximate vine water demand over a given time period.
8. Apply irrigation water at 50% to 65% of evapotranspiration (ET) or less on red grapes and 70% to 80% of ET or less on white grapes.
9. Coordinate the application of water among adjacent blocks or neighboring landowners so that instantaneous usage rates are spread out by withdrawing water at different times.
10. Utilize information from the National Weather Service Enhanced Frost/Heat Forecast Information System to improve and coordinate water management in advance of heatwave events.

For optimal vineyard “cultural” practices during a drought, Mark Greenspan, president and viticulturist at Advanced Viticulture Inc., recommends the following: “Prolonged drought can weaken vines where water is not available for irrigation,” he said “Extremes of precipitation, temperature and wind are [often] more detrimental than the drought itself. Fortunately for us, grapevines can grow with only a little water, which isn’t true for most other crops.” He offers these additional tips:

1. Mow cover crops instead of disking to keep weeds under control and lessen competition for water but retain soil structure.
2. Apply early irrigation only if needed to get the vines’ foliage to fill their trellis, but don’t necessarily continue to irrigate after.
3. Delay irrigation for as long as possible, waiting for shoot elongation to slow down and stop before irrigating.
4. Conduct early suckering and shoot-thinning to encourage shoot elongation with less water input and to reduce water consumption.
5. Perform crop thinning prior to veraison (the onset of the ripening of grapes) to encourage earlier ripening.
6. Conduct less leaf removal than in normal years to keep fruit shaded and protected from weather extremes.
7. Minimize the use of nitrogen fertilizers to limit vegetative growth but encourage potassium fertilization for better water use efficiency.