Marina operators, water managers and farmers who for decades have chased every drop of water across the booming Southwest and part of Mexico are closely tracking the reservoir water level already at its lowest point since it was first filled in the 1930s.
"We just hope for snow and rain up in Colorado, so it'll come our way," said marina operator Steve Biggs, referring to precipitation in the Rockies that flows down the Colorado River to help fill the reservoir separating Nevada and Arizona.
By 2016, continued drought could trigger cuts in water deliveries to both states. While water authorities say they've been saving water for potential dry days, the prospect of the first cuts is already prompting action.
"I've downsized in the last couple of years, probably a good thing the way this water shortage is going," said farmer Dennis Bagnall, who has planted just 225 of the 1,500 acres that are typically green this time of year on his farm south of Phoenix.
Last week, officials announced an $11 million pilot program involving the federal government and water agencies in Denver, Los Angeles, Las Vegas and Phoenix to pay farmers, cities and industries to reduce river water use.
"We can certainly hope for better conditions than we've experienced in recent times, but we have to actively and continue to plan for the worst case," said Michael J. Lacey, director of the Arizona Department of Water Resources.
This week, an update from the federal Bureau of Reclamation, the keeper of the Colorado River network's dams and reservoirs, will help set the course for water deliveries for the next two years. Administrators say they are confident they can meet current commitments next year.
Federal officials and water administrators in metro areas such as Las Vegas and Phoenix say they're committed to finding new ways to make every drop of river water count — from cloud seeding to pipelines to new reservoirs to desalination plants.
They point to agreements to leave surpluses unused in wet years, share pain in dry years and buy water designated for farms for city use.
But they're all watching Lake Mead, the biggest in a Colorado River basin that supplies water to California, Arizona, Colorado, New Mexico, Nevada, Utah, Wyoming and part of Mexico. The states get annual allotments dating to the Colorado River Compact of 1922.
Over the years, the amount hasn't kept pace with a post-World War II development boom in the Southwest, and pressure has increased with drought gripping the region for almost 15 years.
The effect of increased demand and diminished supply is visible on Lake Mead's canyon walls. A white mineral band often compared with a bathtub ring marks the depleted water level.
The lake has dropped to 1,080 feet above sea level this year — down almost the width of a football field from a high of 1,225 feet in 1983.
A projected level of 1,075 feet in January 2016 would trigger cuts in water deliveries to Arizona and Nevada.
At 1,000 feet, drinking water intakes would go dry to Las Vegas, a city of 2 million residents and a destination for 40 million tourists per year that is almost completely dependent on the reservoir.