SAN FRANCISCO — Gov. Jerry Brown’s administration is scaling back his troubled plans to redo California’s water system, releasing a new proposal that would build only one tunnel to ship water from Northern California instead of two, and put Southern and central California water agencies directly in charge of designing and building it.

The state posted the revised plan on a state website for contract proposals late Friday.

Brown had been pushing to launch construction of two giant $16 billion water tunnels to supply farms and cities to the south, but the project has failed to gain enough support from water agencies that would pay for it.

Environmental groups also have opposed the project, fearing Southern California water agencies would use the tunnels to drain too much water from California’s north.

The revised state proposal talks of building the tunnels in stages, with one of the four-story-high tunnels built now, and another at some indefinite date. Water contractors have previously talked of the possibility of permanently paring the project from two tunnels to one, in hopes of winning support for a smaller project.

The state did not immediately release a revised cost for the scaled-down proposal.

Osha Meserve, an attorney working for Northern California farmers opposing the project, said Tuesday the revised proposal makes “more clear the project they want to do is a failure. Now they’re trying to morph into something else.”

Asked for comment Tuesday, state water officials said they were preparing a response.

Bob Muir, a spokesman for Southern California’s giant Metropolitan Water District, the project’s main backer along with the Brown administration, referred questions to the state and to an association of state water contractors.