State water agencies in Arizona, California and Nevada announced a $200 million investment in Colorado River conservation projects on Wednesday, in a last-ditch effort to keep the basin’s biggest reservoir from dwindling to dangerously low levels.

The cross-border collaboration, which also includes the Department of the Interior, will aim to add 500,000 acre-feet of additional water to Lake Mead — the Colorado River’s largest reservoir — in 2022 and 2023, by facilitating initiatives that promote water conservation in the Lower Colorado River Basin, according to the partners.

That additional water, which is enough to provide for 1.5 million households each year, would boost the reservoir’s level by 16 feet, a news release from the agencies said.