On Water and Weed: Is Marijuana Responsible for California's Drought?

Also see: State Hearing Held on Drought and Illegal Marijuana Impacts to Fisheries

Cal NORML Challenges Fish and Wildlife Figures on Marijuana and Water Consumption

The press has been lapping it up like….well, water: the allegation that marijuana cultivation in California is contributing to the state’s drought crisis. The situation has led to local governments passing “urgency” ordinances naming the drought as an emergency, and stepping up enforcement against medical marijuana gardens with the same claim.

Police are issuing press releases tallying up the supposed water usage for eradicated crops (which, like their dollar amounts, seem quite inflated). A recent release from the Tulare county sheriff’s department alleged that a 12,000-plant marijuana grow (raided by, among other agencies, the National Guard) was slurping up 61,555 gallons of water a day.

Let’s look at the numbers:

It’s estimated by the Emerald Growers Association that, based on final yield, growing marijuana requires an average of one gallon of water per pound, per day. With a 150-day outdoor growing cycle, that amounts to 150 gallons per pound. Indoor growers have estimated their water use at 150-450 gallons per pound, including flushing.

With a pound weighing 454 grams, that means cannabis uses, at most, one gallon per gram, and possibly only 1/3 that much. One joint is about a half a gram, so that the water needed to produce one joint is somewhere between 1/6 and ½ gallon.

How does this compare to other crops, or inebriants? A glass of wine takes 15-30 gallons of water per glass to produce; beer slightly less. A tomato requires 3.3 gallons of water, on average, while a handful of almonds takes 5 gallons (one gallon per nut), and a 1/3-pound hamburger requires 330 gallons.

This chart compares the water consumption for single servings of different foods and beverages with that of cannabis, in gallons:

Statewide, what is the water footprint for cannabis versus other crops? Cal NORML estimates that in-state annual consumption for California is about 2 million pounds, or one billion grams. That figure could be multiplied by a factor of four to account for marijuana that is diverted out of state. At the high-end estimate of one gallon per gram, that means the cannabis crop in California, licit and illicit, uses around 12,000 acre-feet of water yearly if grown indoors; one third of that if grown outdoors. That compares favorably to grapes, which use 2.2 million acre-feet, rice at 2.8 million-acre feet, and almonds, which soak up 3.7 million acre-feet of water yearly. Overall 35-45 million acre-feet of water is used for agriculture in California, some 80% of the state's developed water supply. (Sources: http://www.motherjones.com/environment/2014/02/wheres-californias-water-... and http://www.nrdc.org/water/files/ca-water-supply-solutions-ag-efficiency-...)

This chart compares total water consumption by crop in California to cannabis’s consumption (in millions of acre-feet):

The biggest users alfalfa, which requires over 5 million acre-feet of water yearly, 70% of which goes to feed dairy cows. According to an estimate by professor Robert Glennon from Arizona College of Law, California is exporting 100 billion gallons of water a year to China in the form of alfalfa hay.

Fracking uses an estimated 80 billion gallons of water yearly, about the same as strawberries.

Certainly, there are localized problems regarding water and cannabis cultivation in California. Cal NORML and other groups are in favor of sound environmental regulations and licensing of commercial-sized crops. But put into context, we can see that we can’t use the drought as an excuse to further vilify marijuana.

Also see: Is Pot Cultivation Starving Us of Water? Keith Humphreys, July 2, 2015


Image from "The Humorous Hemp Primer," published by the German government in 1942, the same year the US Government published Hemp for Victory.