Water shortage in US West

There's a possibility water level in the two largest human-made reservoirs in the United States could drop to critically low levels by 2025, endangering the constant flow of Colorado River water that more than 40 million people depend on in the American West.

After a moderately dry summer, the US Bureau of Reclamation released models on Tuesday suggesting rising shortages in Lake Powell and Lake Mead the reservoirs where Colorado River water is stored are more likely than earlier projected.

Analyzed with an average year, only 55 per cent of Colorado River water is flowing from the Rocky Mountains down to Lake Powell on the Utah-Arizona line. Because of the below-average flow, government scientists say the reservoirs are 12 per cent more likely to decline to critically low levels by 2025 than they projected in the spring.

Hydrologist Carly Jerla said, "this is a pretty significant increase over what was projected in April due to the declining runoff this year."

The forecast could involve already-fraught negotiations between Arizona, California, Colorado, New Mexico, Nevada, Utah, Wyoming and Mexico over future shares of the river that supplies their cities and farms. Those talks will draft up new agreements by 2026 overuse of the river that's under siege from climate change and prolonged drought.

Some of the urban and agricultural water users have been forced to preserve water to secure the river long term, but it remains overlapped. And as cities like Phoenix and Las Vegas keep growing, the region is only getting thirstier.

"We know that warmer temperatures have contributed to the drought of the last 21 years, and we know that they have exacerbated it," Bureau of Reclamation Commissioner Brenda Burman said.

Unlike the 24-month projections that the agency uses to allocate water to the seven states and Mexico, the models released Tuesday simulate various weather and usage patterns to help water users prepare for different situations.

Scientists use what's called the Colorado River Simulation System to project future levels of the two reservoirs. They employed "stress testing" techniques based on river flows since 1988 to determine potential shortages if drought conditions persist.