Marijuana Cultivation and Water Conservation

Feb 4, 2016

Colorado Harvest Company CEO Tim Cullen says the plants use a relatively small amount of water.
Credit Maeve Conran


With the legalization of marijuana in various states and forms, conservation groups and others are asking how much legal grow operations affect water consumption.  In Colorado, water managers and researchers are working together to answer that question.


Tim Cullen is CEO of the Colorado Harvest Company, one of the state's largest marijuana businesses.  It employs more than 75 people at their three retail outlets in Denver and their grow facility.  The 10,000 square foot facility houses around 3000 plants.

"The plants that we're looking at right now are all about 8-10 inches tall," says Cullen.  "They're juveniles."

In about five months, Cullen says these plants will mature with golf ball sized flower buds that retail for up to $300 an ounce. 

Marijuana plants at the Colorado Harvest Company's Denver grow facility are grown in coco fiber instead of soil. CEO Tim Cullen says they use coco fiber because it is pH neutral and because there are no nutrients in it.
Credit Maeve Conran

Plants here are grown in coco fiber rather than soil, a substance with no nutrient value.  Cullen says that allows them to closely monitor all the nutrients going to the plant, all delivered through that water.

"We never let water run out of these plants, and if you look in these trays, they're designed to hold water in them," says Cullen.  "We don't want any water to run out of the bottoms of the plants because that's just wasted nutrient."

Practically every drop of water is accounted for in this grow facility, a practice that Jeff Tejral, Manager of Conservation for Denver Water says he's observed in other grow operations.

Jeff Tejral, Manager of Conservation for Denver Water. Tejral says he's been impressed with the attitudes towards water that he's seen in Denver marijuana grow facilities.
Credit Courtesy Jeff Tejral

"I've been in a lot of commercial and industrial sites for audits and I've never seen a place that's actually written down how much water has been used in an area before," he says.  "That was new to me, that was a best practice I'd like to see a lot of people using."

In the early days of legal marijuana cultivation in Colorado, Tejral and other water managers started to pay attention to how much water was being used. 

"We also saw the articles coming out… Mother Jones: 6 gallons per plant per day… that piqued our interest."

In 2014, California Fish and Wildlife officials started clamping down on illegal marijuana operations, which they said were using 6-8 gallons of water per plant per day, stressing drought stricken watersheds.  But in Denver, Tejral says he did not see growers using anywhere near that amount.

"That was way more than what I ever saw," Tejral says. "I would have really noticed that in some of these grow operations with several thousand plants in them."

However, due to the nascent nature of the industry, and the ongoing federal prohibition of marijuana, little official research has been done into exactly how much water cannabis plants use.  That limits options for shared best practices across the industry.

James Zazanis is President of ZJ analytics LLC, an agricultural research company in Maryland.  He's partnering with another marijuana grow facility in Denver to monitor water use, with a goal of creating guidelines for the industry.  Using soil moisture sensors they monitor in real time how much water the plants are using.  While no results are available yet, Zazanis says what he's seen at different grow facilities in Denver is encouraging. 

"These guys are the leaders in using the newest technology," says Zazanis. "They want to understand how plants work on a scientific level and they're really championing conservation."

Back at Colorado Harvest Company, Tim Cullen says he too is eager to see research into conservation techniques. 

"When you're talking about the number of plants we're dealing with, this isn't like filling a pitcher up at your sink and watering your house plants," Cullen says, adding that his nutrient bills are close to $10-12,000 a month.  "So we're not wasting that water once it has nutrient in it.  It really needs to stay in the plant."

And, as the marijuana industry continues to grow and evolve, Denver Water says they'll be looking to Zazanis' findings to help inform them of best practices.

Connecting the Drops is a collaboration between Rocky Mountain Community Radio stations and the Colorado Foundation for Water Education.  Find out more at