SPOKANE, Wash. (AP) -- Marijuana growers in Washington, Colorado and other states cannot use irrigation water from the U.S. Bureau of Reclamation to grow their crops, the agency said on Tuesday.
Marijuana growing remains illegal under federal law, so irrigation water from its dams cannot be used to grow pot even in states that have legalized recreational or medical use of the drug, the agency said.
The Reclamation Bureau provides irrigation water in 17 states, mostly in the West, and the prohibition against using that water to grow pot applies to all of them.
It's not immediately clear how many growers, if any, had planned to use federal irrigation water to grow marijuana.
Reclamation spokesman Dan DuBray said the growing of marijuana remains illegal under the federal Controlled Substances Act of 1970.
"Using federal water or facilities to that end is not permissible," DuBray said from Washington, D.C.
Local water districts had asked the agency to set a policy on use of federal water to grow marijuana, DuBray said.
Tuesday's decision is billed as a "temporary" policy, but only because a permanent decision requires a long process including public hearings, DuBray said.
"This is the policy decision," DuBray said.
If the agency discovers anyone using federal water to grow marijuana, it will refer the case to the U.S. Department of Justice, the Reclamation Bureau said.
Reclamation operates giant dams and vast networks of canals that provide water through much of the arid West. That includes the mammoth Columbia Basin Project in Eastern Washington, which provides water for more than 600,000 acres of various crops, including apples, potatoes and wine grapes.
This decision by the agency comes as marijuana is gaining more public and governmental acceptance.
For instance, a poll released last month found that three-fourths of Americans say it's inevitable that marijuana will be legal for recreational use across the nation, whether they support such policies or not. The Pew Research Center survey also showed increased support for ending mandatory minimum prison sentences for non-violent drug offenders.
Since California became the first state to legalize medical marijuana in 1996, at least 19 others and the District of Columbia have followed suit. Two states -- Colorado and Washington -- recently approved recreational use of marijuana. More than a dozen state legislatures considered legalization measures this year.