UC Berkeley researchers released a study suggesting that marijuana farms in California, relative to other crops, consume less water than previously believed.
Researchers looked into farms in Northern California, including those in Humboldt, Trinity, Mendocino and Sonoma counties. Their findings found that earlier assumptions about marijuana production and water use had been misinformed by incomplete data. Earlier studies did not take into account differences in growing conditions, temporal variation and water storage.
“There is growing concern over the impacts of cannabis farms on the environment and water resources in particular, yet data on cultivation practices and water use patterns have been limited,” the study reads.
According to the study, the assumption that marijuana production uses more water than other crops may have been exacerbated by the close proximity of marijuana farms to one another and increased “temporal clustering” due to the plants requiring more water in late summer months.
Steven Beissinger, campus professor of ecology and conservation biology, said the inaccuracies may be due to the largely covert nature of marijuana farming in the years prior to its legalization in California.
“I’m not sure whether it was because the marijuana itself demanded more water,” Beissinger said. “I suspect it was a combination of the expected water demands and the large number of illegal growing operations.”
The study also examined the claim that irrigation for cannabis agriculture was a threat to streamflow. Researchers found that many marijuana farms lack sufficient water storage, forcing farmers to draw water from streams instead.
According to Van Butsic, campus assistant cooperative extension specialist and one of the study’s researchers, legal marijuana production is generally sustainable, given that stored water is used.
“The main problem is that most cannabis farmers are not yet permitted in California, and these farms might not be following the law,” Butsic said in an email. “Most cannabis grown legally in California is sustainable.”
Ultimately, Butsic added, it was found that cannabis plants use a similar amount of water as tomatoes. He noted that, like tomatoes, there is often high variability in water usage in marijuana farming.
The study also highlights the difference between mixed-light and outdoor marijuana farms. While outdoor farms kept to the traditional growing season of April to October, mixed-light farms extended outside of it. It was also found that mixed-light farms used more water than outdoor farms.
As a relative newcomer to California’s agricultural landscape, marijuana farms have had less say in the demand for water, according to Beissinger.
“Agriculture is our biggest demand for water in the state,” Beissinger said. “Maybe this might mitigate some of the concerns, or at least put them in perspective relative to other demands by agriculture for water.”