High and dry: How legalisation of cannabis is impacting local water security

Indoor cannabis cultivation uses six times as much energy as the pharmaceutical industry and generates 15 million tons of carbon, equivalent to the emissions from 3 million cars © Jessica Hyde | Dreamstime.com

Beyond the arguments over medical benefits, cash crops, and cross-border ‘drug wars’, Montgomery Simus explains how the global footprint of cannabis trafficking is rapidly diversifying, complicating the lives of water, carbon and energy managers

On the desert edge of Las Vegas, Nevada, an organic farmer harnesses ample sun and soil–and water siphoned from the distant Colorado River–to offer his customers yearround access to local produce. They may come for fresh asparagus, eggplant or sweet peppers. But what they come running back for, he concedes, is his locally grown aromatic flowering herb: Cannabis sativa, otherwise known as marijuana.

His cash crop is facing competition, across the western US and abroad. The cultural fears and political bans that once forced cannabis growers quite literally into the closet are giving way to acceptance. Increasingly, marijuana is becoming just another taxable substance, like tobacco or beer.

Officials who haven’t legalised both its consumption and production often simply look the other way. Based on price signals from Europe and North Africa to the Americas and Oceania, import substitution in the cannabis market has been noticed in almost every developed country. Ted Leggett, an analyst at UN Office of Drugs and Crime, warns: “Cannabis is the dominant illicit drug in every region of the world, and its use is growing almost everywhere.”

Marijuana global seizures map 2008 (Volume in metric tonnes, Trend 2007-2008)
Marijuana global seizures map 2008
(Volume in metric tonnes, Trend 2007-2008)

In the US, the industry has exploded, with recent sales up 74 percent, to US$2.7 billion following liberalisation, according to ArcView Group. As markets open up, business plans proliferate. Even Microsoft now helps track legalised marijuana “from seed to sale”.

Yet amidst all this growth arises a new fear: the impact of global trafficking on local water.

“Cannabis is a very much a weed that can grow in tough environments around the world and it can tolerate stresses much better than produce like broccoli,” says the Nevada grower, who asked not to be named as his license is up for renewal. “There may be windows of opportunity not to water as extensively as usual if we go back to a more organic approach to cultivation.”

Water goes up in smoke

Perhaps. But there’s little indication that water security has crossed growers minds. Indigenous to the rainy river valleys of Central Asia and the Indian subcontinent, marijuana is now grown worldwide in nearly every ecosystem and climate–even those, like Nevada, that lack rain. As reported by 420Intel, global patterns of cannabis cultivation have atomised from highly concentrated production in a few developing countries to decentralised production in almost every country, including those already suffering from depleted aquifers and desiccated river beds.

Dr Zach Burt, Institute of International Studies, Berkeley, University of California © University of California
Dr Zach Burt, Institute of International Studies, Berkeley, University of California © University of California

This complicates life for water professionals. Marijuana, it turns out, is one thirsty plant. While there is no universally accepted figure due to differences in species and cultivation methods, one recent peer-reviewed study estimates that a marijuana plant requires 22 litres of water a day–the same amount of water needed to sustain a head of broccoli for an entire growing season.

Sound mild? It adds up to a heavy footprint. In Northern California’s famed “Emerald Triangle” with an average outdoor marijuana planting density of 130,000 plants per square kilometre, that adds up to 430,000 cubic metres of water per square kilometre. That makes cannabis plants twice as thirsty as grape vines, on a par with almonds, and less than corn, potatoes or alfalfa.

Excessive water use in marijuana production may have become a more controversial and a volatile issue than the cultivation of the plant itself. Today, California Department of Fish and Wildlife helicopters circle high over steep timberland in Humboldt County’s coastal mountains, prowling for potential water diversions and environmental damage caused by the lucrative cash crop.

But excessive water demand isn’t the only vice of cannabis growers. Many degrade land and build dams which speeds erosion and clogs streams. Neighbours and downstream anglers complain of overuse of fertilisers and pesticides which pollute salmon habitat, as well as complaining about the “discarding of trash and haphazard management of human waste”. The US Forest Service estimates that it costs up to US$15,000 per acre to clean up polluted watersheds from illegal marijuana growing operations.

Comparing crops

Water professionals and marijuana growers alike find it unfair to look at raw resource use and polluted runoff in isolation. All life requires water, and no use can be judged in a vacuum. As cannabis becomes legal, advocates argue that it’s better to compare productivity, measured by retail units (it takes seven litres to produce an eighth of a pound of cannabis) per cubic metre compared with say, almonds (400 litres per can), wine (1,300 litres per bottle), avocados (300 litres per pound) or a quarter pound of beef (1,500 litres).

There’s also the economic argument for maximising revenues per drop. Marijuana is a cash crop like no other–if you have the water to grow it. A report by the University of Denver’s Water Law Review gives a detailed economic breakdown of growing marijuana vs. growing potatoes on the same amount of land. All of the cost is built into water and the return for cultivating marijuana is much higher, says Nicholas Rising. “Growers can expect a return of about US$0.22 to US$6.67 per gallon of water “invested” in each plant of marijuana grown outdoors [assuming an eighth of marijuana harvested per plant]. Compare those figures with the return of about US$0.02 to US$0.03 per gallon of water to grow one square foot, yielding about eleven to fourteen ounces, of potatoes.”

Complicating matters, cannabis puts pressure on another water resource: electricity. Indoor growers make huge energy demands on the grid. One study estimates that it takes as much energy to produce 18 pints of beer as it does just one marijuana joint.

Xcel Energy, which serves most of urban Colorado, annually sells some 300 gigawatt hours of electricity to cannabis growers alone, or enough to power some 35,000 homes. The US marijuana growing industry may soak up at least 1 percent of the country’s electricity and, if all states legalised cannabis, the industry could buy as much as US$11 billion per year in electricity.

More research needed

Despite all the potential profit and peril, the water-energy impact of marijuana cultivation remains little understood. Energy and environmental systems analyst, Evan Mills, published a paper quantifying the carbon footprint of cannabis. It turned out to be huge. Among his findings: indoor cannabis cultivation uses six times as much energy as the pharmaceutical industry and generates 15 million tonnes of carbon, equivalent to emissions from 3 million cars.

Cannabis puts pressure on another water resource: electricity, with indoor growers making huge energy demands on the grid © Bob Doran
Cannabis puts pressure on another water resource: electricity, with indoor growers making huge energy demands on the grid © Bob Doran

Yet Mills focused only on indoor cultivation, where excessive waste comes from illicit activity. Covert growers, for example, use diesel generators to avoid suspicious electric bills, and install extremely bright and energy intensive UV lighting. Moving out into the sunlight will reduce the energy and carbon footprint.

But these traditional energy measures don’t include the power related to the water consumed in the growing process or the energy required to lift / move the water to where the plants are located.

“The embedded energy in the water used for illegal operations will also most likely decrease as pot cultivation is legalised and moves outdoors,” says Dr Zach Burt, a water expert in California. “Transporting and treating water increases both the embedded energy and the per-unit cost of water, so it is likely that both will decrease under legalisation. By legitimising the trade, the cannabis energy and carbon footprint is likely to decline.”

The price of energy is a constraint on water and lighting. And the Northwest Power and Conservation Council found that huge savings could be realised if farmers switched to efficient greenhouses and to LED lighting, and their yields would increase. But not everyone agrees, and the old traditional ways die hard.

According to energy efficiency consultant John Morris, one cannabis grower in the West is converting a 90,000-square-foot warehouse. Despite installing energy efficient lighting and US$2 million in rooftop solar panels, he still expects to pay around US$1 million a month for electricity.

The grower in Las Vegas maintains that potency of outdoor plants is far lower than marijuana cultivated indoors. “While there are significant benefits to growing plants and produce in receptive natural settings like northern California and Oregon, there are bigger benefits in growing produce locally and avoiding the energy costs in transportation & distribution,” says Morris.

In short, it all comes back to the customer. At farmers’ markets, people like to know how and where and by whom their food is grown. The same ‘locavore’ impulse drives buying decisions over how a drug of choice is cultivated. After legalisation, sustainable certification may not be far behind.