By Jay Adams, Denver Water

The state has legalized marijuana for medicinal and recreational use and those plants need water to grow. The plants are part of Colorado - there is no denying it. 

With the legalization of recreational marijuana, Jeff Tejral, Manager of Conservation, and Michael Thomas, Conservation Office Technician, want to know how much water growers in the blossoming industry are using. 

In an effort to start gathering data on the cannabis industry’s water use, the conservation team reviewed 16 grow facilities in Denver Water’s service area that were registered with the state in 2014. Thomas traced consumption at the addresses back to 2005. 

While the research was not able to determine how long the grow operations were in business at each address, it did reveal a steady increase in water consumption during key periods when laws changed in Colorado.  Although the amount of water the growers use is only a small portion of Denver Water’s overall supply, Tejral wants to have a good understanding of the industry and where it’s heading. "They are our customers and the people who use their product are also our customers," he said. 

Tejral is reaching out to growers, including Denver Relief in northeast Denver. He found that Denver Water and cannabis growers have a common goal — use only what you need. For Denver Water, conservation is a long-held practice. At Denver Relief, using the right amount of water is important because it builds healthy plants, and healthy plants lead to good sales and good business. 

“We want to know if we are over-feeding these plants," said Nick Hice, Denver Relief co-owner. Denver Relief is constantly experimenting with the amount of water, light and nutrients plants receive. Some of the experiments have resulted in reduced water consumption. "Two years ago we used 80 gallons of water per week for a table of 21 plants. Today we use only 60 gallons a week," Hice said. Denver Relief will continue experimenting with water use to see if it can keep plants just as healthy or even healthier with less water. 

Another benefit of reduced consumption is that it requires less labor. "If we don't have to water as much, our staff can spend more time monitoring the plants for disease and overall health," Hice said. 

Denver Relief and Denver Water have another common goal: both would like to see the marijuana industry develop a list of best practices for the water-related aspects of growing cannabis. The list would include promoting the use of charcoal water filters instead of reverse osmosis to remove chemicals from tap water that plants do not need, such as fluoride and chlorine. Charcoal filtration not only removes the chemicals, but also uses less water.