LAS VEGAS (AP) — Nevada has taken a dramatic, but not immediate, step toward limiting the amount of Colorado River water used in the most populous part of the nation’s most arid state, after lawmakers gave Las Vegas-area water managers the levers to limit flows to single-family homes.

Gov. Joe Lombardo signed a law passed by the Democratic-controlled Legislature to let the Southern Nevada Water Authority restrict the amount of water provided to homes — if the federal government further dials back Nevada’s share of water drawn from the river.

“This legislation builds on our efforts to protect sustainable growth on the county and state levels,” the Republican governor said in a Tuesday signing statement that cited goals of balancing economic expansion with ensuring “clean and stable water into the future.”

In the Las Vegas area, ornamental lawns are already banned, swimming pool sizes are limited, almost all water inside homes is recycled, “water cops” patrol for leaks and fountains on the Las Vegas Strip use reclaimed water. Water agencies in Southern California, Phoenix and Salt Lake City joined last year in widening calls to rip out thirsty turf.

The new law pushes the region ahead of other places in the U.S. West in efforts to crack down on water wasters. But it's not a first. A water district serving homes in a celebrity enclave near Los Angeles threatened last year to slow deliveries to a trickle for wealthy customers who find monetary fines no deterrent to busting their water budgets.

In Arizona, Gov. Katie Hobbs announced last week that developers of projects in fast-growing Phoenix suburbs will have to show they can provide water to new homes from sources other than the depleted groundwater supply. The city of Scottsdale in January cut off water to homes in a neighboring unincorporated community, Rio Verde Foothills.

Southern Nevada Water Authority officials who sought the Nevada law insist they only intend to enact limits if necessary, and only after water authority board members approve a mechanism for limiting supply.

One method might be a device to restrict the flow to homes, Colby Pellegrino, water authority deputy general manager for resources, told the Legislature in testimony about the law.

“The future of the Colorado River is uncertain,” said Bronson Mack, spokesperson for the agency that delivers water from the Lake Mead reservoir to some 2.4 million Las Vegas-area residents and a tourism-dependent economy that attracts some 40 million visitors per year.

Mack said Friday that 80% of the nearly 580,000 single-family homes the authority serves would feel no effect if officials enforced the limit set in the law: 163,000 gallons (617,022 liters) of water per year. Apartment, hotel, commercial and industrial customers are exempt.

The average Las Vegas-area home uses about 122,000 gallons (461,820 liters), Mack said, well below the limit. The new law aims to curb excess water use by the top-most 20% of residential users, who the authority says draw 45% of the water.

“We want to make sure we have tools in the toolbox so we can manage water demands and continue to ensure we meet the community’s water needs in the future,” Mack said.

The law drew bipartisan support and backing from environmental groups including the Sierra Club and Great Basin Water Network. It comes amid increasingly aggressive efforts by federal, state, municipal and tribal officials in seven Western U.S. states that rely on the river to limit use.

In May, water administrators in Arizona, Nevada and California announced a breakthrough pact to cut their combined use of the dwindling Colorado River in exchange for funding from the U.S. government, and to avoid forced cuts by federal water administrators.

The Colorado River carries snowmelt from the Rocky Mountains to the Gulf of California in Mexico. Along the way it is tapped and dammed to provide some 40 million people with drinking water and hydropower, as well as crucial irrigation for farms that grow most of the nation’s winter vegetables. It has become threatened in recent years by climate change, rising demand and a multi-decade drought.