To protect the Colorado River in the USA, several states and Mexico have had to accept cuts in the water supply.
The US government said on Tuesday that regions dependent on the river's water had failed to sufficiently reduce their needs despite years of warnings.
That's why Washington will cut the water allocation.
The Colorado River is the lifeline of the western United States.
After more than two decades of well below average rainfall, the river has reached a critical level.
To avoid a "catastrophic collapse" of the river system and "a future fraught with uncertainty and conflict," water use in the river basin must be reduced, Tanya Trujillo of the Federal Water Resources Agency said on Tuesday.
Arizona's water allocation is set to decrease by 21 percent
Arizona's allotment from the river will drop 21 percent in 2023, according to Washington data.
Nevada receives eight percent less.
Mexico's share is to be reduced by seven percent.
The most populous western state, California, is the largest user of water from the Colorado River but will not be affected by cuts in the coming year.
The Colorado River supplies tens of millions of people and countless farmland.
It rises in the Rocky Mountains and meanders through Colorado, Utah, Arizona, Nevada, California and northern Mexico, where it empties into the Gulf of California.
It is mainly fed by the snow cover in the high altitudes, which slowly melts in the warmer months.
However, the reduced precipitation and higher temperatures resulting from climate change mean that less snow falls.