Does California Wine Use Too Much Water?

Making wine requires water. But how much?

Water is a precious resource in drought-prone California, and its use in agriculture is rightfully a contentious topic. Recently, I’ve heard from readers — and from listeners who tuned in to a recent episode of KQED Forum where I was a guest — who are concerned about the sustainability of viticulture in this state. While a wine glut is compelling some grape growers to remove their vineyards, some readers are suggesting that this might be a good thing from a water use perspective.

So I wanted to understand: Just how big of a water suck are California grapevines, really?

The TL;DR here is that California wine grapes don’t gulp nearly as much water as crops like almonds, pistachios and alfalfa. But the real story here is much more complex — so wine and water geeks, read on!

“Let’s say everything is equal and you have wine grapes growing exactly next to almonds. The almonds are going to use more water,” said Mallika Necco, an assistant adjunct professor in UC Davis’ Dept. of Land, Air and Water Resources and an assistant professor at the University of Wisconsin-Madison.

Generally, a grapevine might use 25-35 inches of water per year, while it might require 41-54 inches to irrigate almonds, according to Megan Bartlett, an assistant professor in UC Davis’ Dept. of Viticulture and Enology.

Grapes are unusual among California crops for a few reasons. First, they can command a much higher price than many other fruits or vegetables — especially in places like Napa and Sonoma counties — which means that growers are willing to spend more in order to ensure high quality.

Second, they’re one of several crops whose quality can actually improve under water stress. Many grape growers employ what’s called deficit irrigation, giving the vines just enough water to get by, which some believe can lead to more concentrated flavors. It’s counterintuitive, but sometimes drought years coincide with excellent wine vintages.

A not-insignificant number of California growers even employ dry farming, eschewing irrigation altogether and leaving the vines to rely only on precipitation and whatever groundwater their roots can access. In fact, the French government long prohibited irrigating grapevines, and still strictly limits it — proof that dry farming is not only possible for vineyards, but commonplace.

Tomatoes are another crop that can taste better with less water; perhaps, like me, you’ve shelled out for those pricey, delectable, dry-farmed Early Girls. But “I don’t think we see as nuanced irrigation management in any other crop as we do with wine grapes,” Necco said.

Although irrigation accounts for most of the water used by grapevines, growers also apply water for other reasons, like frost protection. So while a vineyard in a hotter, inland area like the Central Valley could require more irrigation than a vineyard in cooler, coastal Mendocino County, Necco said, the Central Valley grower might never need to apply any water to keep frost at bay in the winter. Frost protection could account for as much as 20% of a Mendocino County vineyard’s overall annual water use, she added.

Then there’s the matter of the water source. When an irrigation hose drips water onto a vine’s roots, where is that water coming from? If it’s coming from a pond filled with rainwater capture, great. If it’s coming from an aquifer that’s not being replenished, or diverting from a stream, that may not be so great.

“There’s a lot of questions about water use and the sustainability of viticulture in Paso Robles,” Necco said, “because they don’t get very much rain, and it’s primarily groundwater-irrigated.”

Agriculture overall uses about 80% of California’s developed water supply, according to the Pacific Institute. So as the state attempts to combat the effects of climate change, it’s essential that farmers find ways to get by with less, Necco said. Dry farming may not be a feasible option for every farm or vineyard, but she’s currently researching how regenerative farming practices — which are becoming increasingly popular in the wine industry — may make crops more water-efficient.

“There needs to be a reduction in the amount of water that’s used for agriculture,” said Necco. “It’s going to happen in the next two decades. That will dramatically shift what we grow in California.”