WEITCHPEC, Calif. — The California National Guard on Monday joined more than a dozen other agencies to help the Yurok tribe combat rampant marijuana grows that have threatened the reservation’s water supply, harmed its salmon and interfered with cultural ceremonies.

Law-enforcement officers began serving search warrants at about 9 a.m. in the operation, which came at the request of Yurok officials and targeted properties in and near the reservation along the Klamath River.

The Humboldt County Sheriff’s Drug Enforcement Unit coordinated the raid and was joined by, among others, the Bureau of Indian Affairs, Bureau of Land Management, California Department of Justice’s North State Marijuana Investigation Team, and Yurok police.

State environmental scientists were standing by to enter the properties and survey for damage once the sites were secured.

Yurok Tribal Chairman Thomas O’Rourke joined officers as they staged at a hillside fire station Monday morning and thanked them for assisting in what was dubbed “Operation Yurok.”

“They’re stealing millions and millions of gallons of water and it’s impacting our ecosystem,” he told the officers. “We can no longer make it into our dance places, our women and children can’t leave the road to gather. We can’t hunt. We can’t live the life we’ve lived for thousands of years.”

California’s largest tribe has sought help combating marijuana grows in the past but until now never received such a vigorous response. Then the drought hit.

The strains on dual water systems that serve 200 households and rely entirely on surface water became apparent last summer, when residents began complaining of plummeting pressure.

When tribal staff surveyed the land from a U.S. Coast Guard helicopter, they were startled at the number of grows. By this summer they had tripled, officials estimated. And when the marijuana crop was planted in late spring, community water gauges once again swung low.

This time, creeks ran dry.

“Streams I’ve seen in prior years with more severe droughts where water ran, there’s no water now,” said O’Rourke.

To strengthen its enforcement abilities, the tribal council last fall approved a new controlled-substance ordinance that allow for civil forfeiture in circumstances where cultivation has harmed the environment.

(All growing on the reservation is illegal, as the Yurok tribe does not honor state medical-marijuana law.)

The breakthrough came in April when staffers from the governor’s office were discussing the drought with tribal officials. Gov. Jerry Brown, tribal officials were told, had pressed for California National Guard assistance with marijuana eradication and specifically urged the Office of the Adjutant General to assist in the Yurok operation, said Capt. Pat Bagley, operations officer in charge at the scene.

He was expecting to haul out two miles of irrigation hose at one grow alone.

For the Yurok, the damage is broad. Sediment and chemical runoff have suffocated juvenile fish, and warmer, shallower water has triggered an increase in the parasite Ceratomyxa shasta, which targets salmon.

Rodenticide has poisoned the Humboldt marten and weasel-like fisher, which the Yurok consider sacred. The danger of encroaching on a guarded grow site has made it unwise to gather medicine, acorns and materials for baskets, or to prepare sites for ceremonial dances.