Sacramento, California - Environmental scientists with the California Department of Fish and Wildlife (CDFW) recently published a first-of-its-kind study that clearly shows that water used for growing marijuana has a devastating effect on fish in the state.

The study showed that during drought conditions, water demand for marijuana cultivation exceeded stream flow in three of four study watersheds. The resulting paper, entitled “Impacts of Surface Water Diversions for Marijuana Cultivation on Aquatic Habitat in Four Northwestern California Watersheds,” concludes that diminished stream flow from this water-intensive activity is likely to have lethal to sub-lethal effects on state and federally listed salmon and steelhead trout and will cause further decline of sensitive amphibian species.

The study was published online in the scientific journal PLOS One and can be found here.

By using online tools to count marijuana plants and measure greenhouses, and conducting inspections of marijuana cultivation sites with state wildlife officers and local law enforcement, CDFW scientists quantified plant numbers and water use. Utilizing stream flow data provided by staff at the National Oceanic and Atmospheric Administration (NOAA), CDFW determined water demand for cultivation could use more than 100 percent of stream flow during the summer dry season in three of four study watersheds. Stream flow monitoring conducted by CDFW in the summer of 2014 appeared to verify these results.

“All the streams we monitored in watersheds with large scale marijuana cultivation went dry,” said CDFW Senior Environmental Scientist Scott Bauer, lead author of the research paper. “The only stream we monitored that didn’t go dry contained no observed marijuana cultivation.”

CDFW’s Law Enforcement Division works closely with dozens of other state and federal agencies to eradicate illegal marijuana grows on public, tribal and private lands as well as protect the state’s natural resources.

“This research paper demonstrates the importance of greater regulatory efforts by state agencies to prevent the extinction of imperiled fisheries resources,” said CDFW Assistant Chief Brian Naslund. “CDFW’s new Watershed Enforcement Team (WET) was created with just that in mind.”

The WET program works with agency partners to protect public trust resources from the negative effects of marijuana cultivation, which include both excessive water use and pollution.

CDFW will continue to monitor the effects of water diversion for marijuana cultivation on stream flow through the summer of 2015.

Marijuana cultivation is legal in California if growers have the proper CDFW lake and streambed alteration permits. Responsible growers help conserve the state’s natural resources and are less likely to be subject to enforcement action.