Drought focuses attention on cannabis water use

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Cavedale Road is bumpy – steep, narrow, its asphalt broken like a jiggled jigsaw. Perhaps this is as it should be, given that it is the road to the top of the world.

“Welcome to the Top of the World,” says Doug Gardner, the owner of the property high in the Mayacamas just yards away from the Napa County line. There’s a five-bedroom cabin next door called Top of the World, though Gardner’s family sold that part of the property in 1981. But no one wants to live there full time – the road is too bumpy.

Gardner, a sturdy 38-year-old, works by himself inside the fenced cultivation site, which has an acre’s worth of planted cannabis in both fabric “Geopot” barrels and in-ground beds. About a third of this crop is just days away from harvest, and the air is redolent with a fresh tart smell. Gardner’s name is apt – but, as it turns out, this is his first crop. Even so it’s a bumper one, thanks in part to the abundant water supply that the ranch is blessed with.

Hooker Creek bubbles out of a mountain slope just on the other side his driveway, and trickles year-round to a pond on the property. That pond provides the entire water supply for the acre of plants. Gardner has installed a pump at the pond to bring the water back uphill to the cultivation site, and a system of pipes and drip irrigation hoses distribute the water.

Gardner has suffered from epilepsy his whole life, but at some point he found that cannabis – especially CBD-rich cannabis – was of invaluable help in managing the disorder. He labored through the process of getting a permit from Sonoma County starting four years ago, insisting that he was going to grow “medicinal cannabis.”

It’s all about the water

Permit Sonoma didn’t care about that, they just wanted to make sure he kept his water use within the allowances set up for outdoor cannabis farms: 2-acre-feet per year. The Default Water Use Guidelines the county lists are derived from the state Department of Water Resources. Indoor or mixed-light cannabis are allocated 4-acre-feet per acre of plant canopy, and outdoor cannabis grows 2-acre-feet per canopy. (An acre foot is the amount of water that covers one acre a foot deep, or roughly 326,000 gallons; the “canopy” referred to is the plants’ leaf area – Gardner’s single acre of plant canopy occupies a 3-acre fenced garden.)

“We don’t want to underestimate the amount of water use – obviously water is a precious natural resource in Sonoma County, there are lots of demands on your water and our groundwater,” said Permit Sonoma policy manager Bradley Dunn. He explained the default rates are high “consistent with our goal of protecting water in Sonoma County.”

Permit Sonoma’s guidelines not only include cannabis crops, but other agricultural uses as well: vineyard irrigation is set at 0.6-acre-feet per year, irritated orchards at 1.8, and irrigated pasture at 3.6 (though livestock irrigation comes in at only 0.5). These numbers explain why many believe that cannabis is a water-hungry crop and plays a significant role in the region’s water shortage.

There are two reasons why that assumption is misleading: the crop value, and total acreage. In Sonoma County there are almost 60,000 acres of grape cultivation, compared to less than 30 acres of cannabis cultivation.

“There are multiple factors when looking at how much water a crop takes,” says Erich Pearson, Sparc dispensary’s director for both their retail operations and their cultivation site, in Glen Ellen down the hill from Gardner’s garden. “How many jobs does that crop make? How much revenue does it bring in – to the business and to the county – from that acre of crop? How much tax revenue? I can guarantee you there’s no crop in California that produces more tax revenue than cannabis does.”

California collected about $817 million in adult-use marijuana tax revenue during the 2020-21 fiscal year, state officials estimated.

For Sparc’s operation in Glen Ellen, Pearson says they use under 1.5-acre-feet a year, below the county allowance. An elaborate system of drip irrigation distributes water from the on-site well – and unlike every other agriculture in the county, wells are metered for cannabis farmers.

The view from Glentucky

Mike Benziger is another significant cannabis grower in the Sonoma Valley, having started a second career after he sold Benziger Family Winery to the Wine Group in 2015. A brush with cancer got him interested in medicinal herbs of several kinds, including cannabis, all of which grow at his playfully named Glentucky Farms in Glen Ellen.

Few people in cannabis cultivation have as much experience as Benziger does in farming overall, and he’s been able to leverage that experience to help him manage water use wisely. For instance, he uses soil moisture probes in many areas of the farm. “This way we water only when the plant needs it not on a formula. This saves a lot of water,” he said.

Like other cannabis farmers, and most commercial and industrial projects approved through a use permit since 2004, his wells are monitored for water flow, and the county can inspect and monitor his water use at any time. However, he adds, their permit allows only rainwater usage, to avoid tapping into the groundwater resource.

“We have been farming biodynamically for 21 years concentrating on soil health which has a direct effect on moisture holding capacity. This also saves a lot of water,” Benziger said.

“We have 25,000 gallons of rainwater holding ability,” he added. “Which under normal conditions is plenty.”

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