Cannabis Cultivators’ Report on Water Usage

IMG_0216Drought concerns loom large over industry, but cannabis should not be the scapegoat

By Swami Chaitanya

The biggest concern for all farmers in California right now is, of course, water. It seems that everyone is looking for someone else to blame. Clearly each of us in the exploding human population shares the responsibility. Since 1970, the population of California has doubled; since 1900, when there were 1.45 million California residents, population has increased by 26 times. Today there are 38 million people in this beautiful state. More people simply use more water.

Nonetheless, many want to point the finger at cannabis growers. There have been many estimates about the amount of water cannabis cultivation requires, but the growers never get asked. Who would know better than the growers themselves?

The Mendocino Cannabis Policy Council, along with the Emerald Growers Association, has polled numerous cannabis cultivators about their water usage. From these results, with great help from Casey O’Neil, we derived a formula which is: one gallon per day to produce one pound of cured cannabis flower buds (1:1:1).

So how much water does cannabis really use?

Our canvassing indicates that most cannabis farmers grow plants that average between two and four pounds. One-eighth of an acre (50 feet by 100 feet with 50 cannabis plants) would use 24,000 gallons per season (about eight months or 240 days). This would result in producing 50 two-pound plants and using 480 gallons per plant. A two-pound plant divided into eighths of an ounce yields 256 eighths. Thus, the whole garden with 50 plants would produce 12,800 eighths of an ounce. (For the purpose of this article, an eighth of an ounce is being used as a standard retail unit comparable to one pound of beef, one bottle of wine or one can of almonds.)

Each eighth then requires 1.875 gallons of water (24,000 gallons divided by 12,800). It has been widely reported that producing a pound of beef requires at least 1,500 gallons of water. Wine uses between 180 and 400 gallons per bottle*. Almonds need one gallon per nut or about 100 gallons per can, broccoli takes about five gallons per head and avocados about 75 gallons per pound.

But, wait! The same plant that produces two pounds of cured, finished flower buds also produces at least half a pound of “smalls” which farmers and dispensaries often donate to needy patients, sell at a steep discount or consume themselves. It will also produce at least half a pound of trim shake. The leftover smalls and shake can then be processed to make concentrates, edibles, tinctures, salves, oils, etc. All that additional product, all that value added, with no additional water required.

The California Department of Fish and Wildlife published a report on cannabis growing in Mendocino and Humboldt counties, highlighting three typical valleys. The department concluded that there were about 26,000 plants in Outlet Creek Valley. The implied conclusion, based on an assumption of six gallons of water per day per plant, was that cannabis was drying up the creeks.

A closer analysis points to a different result. Using Fish and Wildlife numbers, which most farmers consider too high, six gallons a day for the peak growing season of 150 days of summer means 900 gallons per plant, which is the same as a 3.75-pound plant for 240 days in our 1:1:1 formula, which would require about two gallons per eighth-ounce. If there were 400 sun-grown plants in an acre, 26,000 plants need 65 acres.

At 900 gallons per plant per season, 26,000 plants use 23,400,000 gallons per season (3.1 million cubic feet of water). Twenty-three million gallons would mean 12 inches of water falling on 71 acres would provide enough water for the entire 65-acre cannabis crop of Outlet Creek Valley, as long as it is properly captured and stored in the rainy season to be used in the dry months. Even in dry years, Mendocino receives about 40 inches of rain, and Outlet Creek Valley covers 103,616 acres, according to Fish and Wildlife.

A questionable assumption in the Fish and Wildlife report is that greenhouse plants, with a canopy of five square-foot canopy (compared to a 10 square-foot canopy for sun-grown plants) would use the same amount of water as their sun-grown counterparts. Nor does the report address the possibility that some greenhouse crops are light-dep grows, which would be harvested in August and so use no water at all in the driest months. Missing entirely in the report is any identification of an individual garden’s actual source of water. There is no mention of storage tanks, ponds, springs, wells or the possibility that water was captured in the rainy months and stored for use in July and August. The unsubstantiated assumption is that all the water came only from Outlet Creek, but the report does not mention the discharge flow of Outlet Creek at all. To demonstrate the effect of increased cannabis acreage, the department would have to show tables of water discharge at Outlet Creek over a period of 10 to 15 years. I doubt such data exists.

The Fish and Wildlife report references only the monthly discharge of the Van Duzen River at Bridgeton in Humboldt County. Nevertheless, using those numbers, the flow at Bridgeton at the lowest rate in September (when most growers are actually cutting back on watering, as harvest begins for some strains in September), is 4.5 million gallons per day. The 26,000 plants at Outlet Creek only use about 4.6 million gallons for an entire month. At the driest time, one day’s flow would water all the plants for 30 days — a discharge rate of 3%, not 20%. Smart farmers know the creeks always have low flow in August and accordingly capture and store water for the dry season.

If there are 100 valleys in Mendocino County growing 30,000 plants, there would be a total of 3 million plants in the county on 7,500 acres needing 2.5 billion gallons per season. In March, Van Duzen Creek discharges nearly 1.3 billion gallons per day; in June, it puts out 321 million gallons per day. Thus, in March, two days of flow would water Outlet Creek Valley for the season. In June it would take eight days of flow for the whole crop.

If one were allowed to grow 400 plants per acre using 900 gal per plant it would need 360,000 gal per acre per season or 1.1 acre feet water.

Mendocino County has approximately 16,500 acres of vineyards, using 25,000 gallons of water per acre per week over a 24-week season. This equals 9.9 billion gallons of water per season.

The Mendocino Cannabis Policy Council and Emerald Growers Association promote responsible organic cultivation in harmony with the environment and work to educate farmers about best practices. The Mendocino Cannabis Policy Council has written a ballot initiative for the 2015 county election to have cannabis cultivation classified as agriculture and regulated as such and to establish an advisory board of cannabis issues to be selected by the board of supervisors.


Swami Chaitanya is a renowned grower from California, and a member of both the Mendocino Cannabis Policy Council and the Emerald Growers Association.




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