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| Large plants of the type grown by Humboldt farmers | The types of plants eradicated on public lands |
UPDATE April 2021 – Legal Cannabis Cultivation’s Footprint Sinks Common Assumptions About Comparative Water Use
A report from New Frontier Data in partnership with Resource Innovation Institute and the University of California, Berkeley concluded that “while the state’s orchards use nearly 7 million acre-feet of water, and rice fields use nearly 5 million acre-feet, the state’s lucrative cannabis industry only uses 3,000 acre-feet, making it the most water-economical crop among the state’s top revenue crops.” Cal NORML has been arguing for using production-based water consumption data for years.
August 3, 2015 – California NORML has written to Scott Bauer of California Fish and Wildlife questioning his often-repeated estimation that marijuana plants use 5-10 gallons of water every day throughout their growing season (June-October). This figure has been extrapolated to cause law enforcement to overestimate the water consumption of gardens they raid, much as they have always overestimated plant yields and prices.
Public officials such as Sacramento County supervisor Roberta MacGlashen have cited the figure as a reason to double fines on marijuana patients, meaning growing even a single outdoor plant in the county can be cause for a fine of up to $1000/day. The Sacramento Bee has editorialized against using water on any outdoor cannabis plants.
From what Cal NORML has been able to uncover, Fish and Wildlife did not measure or calculate their water usage estimate, but rather lifted data from a 2010 paper from the Humboldt Growers Association and other sources, such as a paper from Chris Van Hook of Clean Green Certification that was written in 2013 to encourage cannabis farmers to store water.
Articles co-authored by Bauer in Bioscience and PLOS both cite a 2010 Humboldt Growers Association calculation of six gallons/plant each day, based on commonly used irrigation methods (towards the end of the document).
But while HGA farmers tend to grow extremely large plants, those eradicated in the wild generally receive far less attention, meaning they are much smaller and therefore require only a fraction of the water used on plants that look more like trees (see photos).
The authors averaged an estimate by Mendocino Sheriff Tom Allman that large marijuana plants require one gallon of water per day and Van Hook’s statement that in extremely hot weather, large plants can use up to 15 gallons per day to bolster their figure.
In an email communication, Van Hook told Cal NORML that at the time he collected data (in 2010) for his 2013 paper, “water was not an issue. I have seen some real improvements since then which is a testament to California agriculture. Just like any agriculture when a problem arises responsible farmers work to improve. I would like to see a new study with some of the water saving improvements I have seen out in the field.”
Bauer and his co-authors state:
Water use data for marijuana cultivation are virtually nonexistent in the published literature, and both published and unpublished sources for this information vary greatly, from as low as 3.8 liters up to 56.8 liters per plant per day.
This is quite a wide range. They continue:
The 22.7 liter (6 gallon) figure falls near the middle of this range, and was based on the soaker hose and emitter line watering methods used almost exclusively by the MCSs we have observed.
However, how long or often the crops were watered cannot be known from this information. They continue:
Because these water demand estimates were used to evaluate impacts of surface water diversion from streams, we also excluded plants and greenhouses in areas served by municipal water districts.
Which is exactly what the Sacramento Board of Supervisors oversees. Legal experts say it’s questionable whether or not growers charged criminally can also be subjected to fines under local ordinances, so it’s likely that Sacramento’s ordinance will affect only backyard growers.
COMING UP WITH BETTER DATA
So far, Sacramento NORML and Cal NORML have canvassed growers from 11 outdoor farms in El Dorado, Placer, Humboldt and Mendocino counties. Water usage has ranged from 1 gallon/plant to 3.5 gallons, although plants were not necessarily watered daily, and less water was used while the plants were still immature. Growers also often scale back on watering at the end of the season, to encourage flowering. Six gallons a day is possible for July and August, but not for 150 days, said one farmer from Mendocino county. The average number of gallons used on plants daily was 2.30 in NORML’s study.
The more pertinent way to look at the issue is in gallons of water per gram of marijuana bud produced. A representative from the Mendocino Cannabis Policy Council said his members tend to grow 2-4 pound plants, with the yield directly related to the amount of water used. Roughly, MCPC and Emerald Growers Association estimate that an average of 1 pound (454 grams) is yielded using an average of one gallon per growing day. So a two-pound plant would require an average of two gallons per growing day, and a four-pound plant would use four gallons.
Using the gallon/day/pound ratio means one gallon yields about two grams of processed bud at a growing season of 240 days (a figure which can be reduced down to 90 days with the use of light-depravation techniques). Two growers in Humboldt county said that they reliably grow two-pound plants watering with 2.5 gallons/day (but not necessarily every day). Taken in total, both estimated that it took an average 2/3 of a gallon daily to yield one pound of bud, one saying he multiplied that by 100 growing days. A farmer in Mendocino who uses water conservation techniques estimates using only 0.3 daily gallons per pound of bud. Adding in two farms in the Sacramento area, one that got 1.22 grams/gallon (using Smart Pots that may have lead to evaporation) and a second that yielded 0.87 grams/gallon, Cal NORML calculates an average of 0.72 gallons of water is needed to produce a gram of marijuana, no matter how many plants are grown or how big they are.
Since a “joint” of marijuana is about 1/2 of a gram, this means a dose of medical marijuana requires less than half a gallon of water. A hamburger requires over 100 gallons of water to produce, and a serving of rice takes around 50 gallons. (Source: UNESCO via LA Times).
TURNING WATER INTO WINE VS. WEED
We have also investigated the often-repeated statement that marijuana uses twice as much water as do wine grapes, from the Bioscience article.
Using the author’s figure of 22 L (6 gallons) of water per plant per day from June – October, they state:
…if we assume a planting density of 130,000 plants per km2, water application rates would be approximately 430 million L per km2 of outdoor-grown marijuana per growing season. For comparison, wine grapes on the California north coast are estimated to use a mean of 271 million L of water per km2 of vines per growing season. Marijuana is therefore estimated to be almost two times more “thirsty” than wine grapes, the other major irrigated crop in the region.
But let’s look at the output from those acres planted, and the total acreage.
Estimates say that about 150-160 gallons of wine are produced per ton of grapes. The amount of grapes grown per acre of land can vary from 2-30 tons, with 4 tons seeming to be the most commonly used figure. Using 8 tons of grapes per acre, we calculate that 26 gallons of water are required to produce a 4-ounce glass of wine. This comes close to the 26-29 gallons/serving of wine from UNESCO data. (For some reason the LA Times, citing UNESCO, says it takes 3.48 gallons of water to produce an ounce of wine, which is why we had previously reported it took about 15 gallons of water per glass; calculating directly from UNESCO the figure is 7 gallons per ounce and 28 gallons per glass.)
By contrast, we estimate that between 1-1.5 tons of marijuana are produced per acre. Using Fish & Wildlife’s figure of 430 million L per km2, this means between 0.63-0.95 gallons of water are used per 1/2 gram serving of marijuana, or 27-41 times less than the water it takes to produce a glass of wine.
Now let’s look total acreage. In 2014, the USDA reports that the total acreage of wine grapes grown in California was 615,000. Our estimates for total acreage of marijuana required for California consumption is 800 acres (with no space between plants); 3000 acres would be a ballpark figure. That ups the differential by a factor of 200, meaning overall wine production uses 5000-8000 times more water than does marijuana in California.
Wine production has been extremely damaging to rivers and creeks in critical salmon-spawning streams. For the past several years, Emerald Growers and other groups have been educating farmers about fish-friendly growing practices and the Small Farmers Association drought management plan calls for goals of 1/2 gallon to 1 gallon per plant for daily use.
CULTIVATION BANS IMPEDE WATER REGULATORS
Certainly, Cal NORML is concerned about severe, localized problems regarding large marijuana farms and water use. Bauer’s articles are about local problems that the press has wildly extrapolated on. PLOS study co-author Lori Pottinger said in answer to an email from Cal NORML “I hope we conveyed that this was a localized problem, that was certainly the intent.”
Taking a statewide view, even using Bauer’s figures marijuana uses a tiny portion of the water used yearly in the state on almonds (3.7 million acre-feet); grapes (2.8 million acre-feet) and rice (2.2 million acre-feet). Commercial agriculture in California uses an estimated 25-45 million acre-feet of water. By comparison, the cannabis industry is estimated to use a mere 3000-15,000 acre feet of water per year. That means cannabis cultivation uses 0.04 percent or less of all the water used for agriculture in California.
In fact, at a recent hearing in the Capitol on the drought, all the fisheries experts spoke about the problems in the Delta (e.g. Shasta Dam and the Thermolito) but all the law enforcement panelists focused on the Emerald Triangle. Big Ag, in the form of rice farmer and Congressman Doug LaMalfa and his successor Sen. Jim Nielsen, and billionaire pomegranate and pistachio farmer Stuart Resnick via his contributee Sen. Dianne Feinstein, have been instrumental in keeping water flowing to farms. Coincidentally(?) LaMalfa, Nielsen and Feinstein are all against marijuana legalization.
Ironically, counties like Sacramento, Butte, Shasta, Tehama and Fresno that have cultivation bans will be unable to sign up farmers for the Central Valley Water Board’s pilot program regulating water use and discharge, due to be finalized in October.
Cal NORML has long worked for regulation of commercial marijuana gardens at a state level, and is participating in discussions about AB 266 and AB 243, which would finally provide oversight on the state’s 19-year-old medical marijuana law.
