The San Diego County Water Authority now supports Gov. Jerry Brown’s twin tunnels project, a $17 billion plan to carry water south from the rivers of Northern California.

For five years, the Water Authority has been one of the fiercest critics of the plan.

It’s worked since 2013 with environmental groups opposed to the tunnels, and it’s spent countless employee hours trying to undermine the project. Just last month, Water Authority representatives tried to prevent Southern California’s largest water agency from spending $11 billion on the project.

Last week, the Water Authority board quickly – and without any warning – broke from years of thinly veiled opposition to become a tacit supporter of the tunnels.

“C’mon folks, the ship has sailed on this thing, it’s time to be part of the solution,” said Jim Madaffer, the vice chairman of the Water Authority board.

The Water Authority is still concerned about the project’s costs, which it once estimated could be more than $20 a month for water customers across the region, but other estimates put it at $5 a month or less.

Some Water Authority officials seem to think that by endorsing the tunnels now, they may be able to cut a better deal for ratepayers in the future, as costs of the project get divided up.

But the whiplash was a little hard for some Water Authority board members to take.

The board of Southern California’s biggest water agency, the Metropolitan Water District, voted last month to spend $11 billion on the tunnels, despite opposition from the Water Authority and the city of Los Angeles.

Metropolitan gathers water from the Colorado River and the rivers of Northern California and delivers it across Southern California. The Water Authority buys water from Metropolitan and resells it to local water agencies, like the city of San Diego.

The Water Authority’s four representatives on the Metropolitan board voted against the tunnels last month.

Last week, they balked at being forced to change their position – especially after years in which the Water Authority’s board was never asked to take a firm up or down vote on whether it favored the project.

“The four delegates have been up there without much direction from this board,” said Fern Steiner, one of the Water Authority’s representatives to the Metropolitan board. The Metropolitan board meets in Los Angeles.

Mark Muir, the chairman of the Water Authority’s board, admitted as much.

“We have taken a position to not take a position,” he said, describing the Water Authority’s stance until last week.

Whether the Water Authority’s new position means much remains to be seen.

The most immediate consequence seems to be that the Water Authority will no longer work so closely with environmental groups that oppose the project. Environmental groups oppose the project because it could destroy habitat and suck even more water out of the Sacramento-San Joaquin Bay Delta. The Water Authority is now on record saying it supports building both tunnels, come what may for the environment.

But it still has concerns about the cost to Southern California water customers.

Metropolitan may have to take a mulligan on its April vote. After it celebrated approving $11 billion to build the tunnels – a project decades in the making – Metropolitan was accused of violating California open meetings laws because several of its board members called one another before the tunnels vote to get one another’s support. Details of those calls were first reported by Voice of San Diego.

A revote would likely happen sometime in June.

Steiner said she plans to vote against the tunnels again, unless there’s changes to how the project is financed.

The Water Authority’s board cannot force San Diego representatives on the Metropolitan board to vote a certain way, but it can remove Metropolitan representatives who take votes the board doesn’t like.