The potential for California’s growing cannabis cultivation industry to harm streams, creeks and groundwater is the focus of emerging State Water Resources Control Board regulations slated for adoption next year.

The timing of the rules is critical; voters could be on the cusp of making California the fifth state to legalize cannabis for recreational use when they go to the polls Nov. 8 and cast ballots for or against Prop. 64. The state authorized medical use through Prop. 215 in 1996.

In the meantime, efforts are geared toward regulating the use of irrigation water for the cultivation of cannabis for medical use. In signing the 2016-2017 budget, Gov. Jerry Brown ordered the State Water Board to develop “principles and guidelines” overseeing cannabis cultivation, including instream flow objectives, limits on diversions, screening of diversions and oversight of groundwater pumping. The rules would only apply to direct surface water diversions.

The idea is to curb years of abuse in which some cannabis farmers illegally diverted water, causing environmental harm.

“If you are diverting water and have not filed with the Division of Water Rights, you should do immediately,” Dan Schultz, senior environmental scientist with the State Water Board, said at an Oct. 4 workshop on the topic in Rancho Cordova. “It’s very easy for a small number of diverters to have an impact.”

The proposed principles and guidelines will be released between March and May 2017, with an expected adoption by the board in August. A key part of the plan is a small irrigation registration use permit being formulated that will enable growers to develop off-stream storage capacity. Prior to that, it’s expected that growers will not be able to divert water during dry parts of the year.

The State Water Board rules seek a balance between the need by growers to divert water and the need to ensure sufficient flows exist for things such as rejuvenating fish spawning grounds, Schultz said. That applies to groundwater as well should a number of pumps affect nearby surface flows, he said. Regulators want to know which management practices work best.

“This is a new effort for the Board,” Schultz said. “We are looking for a lot of feedback from cultivators.”

Hezekiah Allen, executive director of the California Growers Association, a statewide trade organization for marijuana growers, called for regulations “that make sense and are easy to understand,” including easier storage of water during peak storm events, off-stream storage, which he called a “major focus,” and the recognition that one size doesn’t fit all.

In his July 24 post on the association’s website, Allen wrote that long-term, the Association seeks a cannabis industry “that is completely dependent on rainwater storage and does not divert ground or surface water.”