(CBS SF) — An increasing number of marijuana operations is making California’s drought worse, according to a new study.

A research team in the August issue of the journal BioScience estimates 60-70 percent of the marijuana consumed in the United States comes from California — with the majority centered in sensitive watersheds with high biodiversity.

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The team said aside from the negative environmental impacts such as land clearing and the pollution from pesticides, large-scale marijuana cultivation is diverting precious surface water away from streams and wetlands.

Commentary coauthor Scott Bauer says the impact of unregulated pot growing on water availability, especially while water districts across the state are asked to conserve, is a top concern.

The marijuana growing season runs from June to October, when rain is typically scare. Bauer adds marijuana is a water-intensive crop that uses uses 5-10 gallons of water everyday during their growing season — twice the amount of water than wine grapes when grown outside.

In their own study, Marijuana advocacy group Cal NORML said the average number of gallons used on plants daily was 2.3, adding that overall cannabis cultivation uses .04 percent or less of all water used for agriculture in California.

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A voluntary certification program, known as Clean Green Certified, supports environmentally responsible marijuana cultivation, but demand is low.

“There isn’t as much economic incentive to participate in this program as there is in organics,” says Dr. Short Gianotti, another coauthor on the BioSciences commentary.

The authors are ultimately urging lawmakers to ramp up enforcement and bring marijuana plots under tighter environmental control.

Nicole Jones is a digital producer for CBS San Francisco. Follow her musings @nicjonestweets

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