Handed a budget proposal that predicts sky-high marijuana tax revenue, Colorado lawmakers say they will move cautiously in deciding how much to spend.

Last week, Gov. John Hickenlooper’s budget office predicted medical and recreational marijuana sales would net Colorado nearly $134 million in tax and fee revenue in the fiscal year beginning this summer. But Rep. Crisanta Duran, the chairwoman of the legislature’s Joint Budget Committee, said lawmakers aren’t convinced of Hickenlooper’s numbers and want to wait for a different forecast next month before estimating how much money they will have to spend.

“We really need some additional details, and we will give it a thorough review,” said Duran, a Denver Democrat. “My overall concern with these totals is that it’s pretty early in the process, and we don’t know if this will be a long-term revenue source for the state.”

Another JBC member, Sen. Kent Lambert, echoed Duran’s caution, saying he would prefer to see figures for how much the state actually collected in marijuana taxes in January — the first month for recreational sales. Those figures are also expected mid-March.

“We don’t know,” said Lambert, a Colorado Springs Republican. “We need a lot more data before we could have a real estimate of what that sustained revenue will be.”

Budget committee members are deep into planning next year’s spending plan, and Lambert said that makes it especially difficult to evaluate and incorporate new marijuana tax projections on the fly.

“This is a moving target,” he said.

But Hickenlooper’s proposal doesn’t call for the marijuana money to be put to general purpose. Instead, it directs all the available money — minus what is constitutionally required to go to school construction — into projects to counter the possible negative impacts of marijuana legalization. He has proposed putting $85 million over the next 18 months into youth marijuana-use prevention and into substance-abuse treatment.

Duran said she supports that idea.

“I think the substance-abuse dollars will be great to have an increase there,” she said.

Those priorities have led to sharply divided opinions elsewhere. Mason Tvert, one of the leaders of the marijuana legalization campaign in Colorado, blasted the proposal as funding “marijuana propaganda.” Diane Carlson, a spokeswoman for Smart Colorado, a group concerned about the effects of legalization, praised the governor’s proposal for addressing major issues in “a meaningful way.”

One county, Pueblo, has so far reported marijuana tax figures for January, when the county says the taxes brought in nearly $56,000. More numbers are expected next month, when Denver and state officials both will report January figures and the legislature’s economists give their own projection of what marijuana taxes will bring in for the state in the next fiscal year.

John Ingold: 303-954-1068, jingold@denverpost.com or twitter.com/john_ingold