By Victoria Cavaliere
April 24 (Reuters) - Nevada's Lake Mead, the largest capacity reservoir in the United States, is on track to drop to its lowest water level in recorded history on Sunday as its source, the Colorado River, suffers from 14 years of severe drought, experts said on Friday.
The 79-year-old reservoir, formed by the building of the Hoover Dam outside Las Vegas, was expected to dip below 1,080 feet on Sunday, lower than a previous record of 1,080.19 feet last August, according to the U.S. Bureau of Reclamation.
Predictions show that on May 31, the reservoir will have dipped again to 1,075 feet, well below its record high levels of around 1,206 feet in the 1980s, according to Bureau of Reclamation data.
Lake Mead supplies water to agriculture and about 40 million people in Nevada, Arizona, Southern California, and northern Mexico.
The water source and several other man-made reservoirs springing from the 1,450-mile (2,230-km) Colorado River, have dropped to as low as 45 percent of their capacity as the river suffers a 14th straight year of crippling drought.
About 96 percent of the water in Lake Mead is from melted snow that falls in "upper basin" states of Colorado, Utah, New Mexico, and Wyoming, officials said.
Over the past 14 years, snowfall has dropped in the Rocky Mountains, leading to a drop in snow pack runoff that feeds the river, according to Bureau of Reclamation statistics. In 2013, runoff was at 47 percent of normal.
The lake's levels are nearing a critical trigger where federal officials will have to start rationing water deliveries to Nevada, Arizona and parts of California. States in the region have enacted action plans to lessen greenhouse gas emissions linked to climate change.
A study carried out by the Bureau of Reclamation and the seven states in the Colorado river basin concluded that the drought was not likely to end soon, and that large metropolitan cities like Las Vegas and Phoenix grew rapidly during a rare wetter period for the river.
On average, the Colorado River Basin temperature is projected to increase by five to six F degrees during the 21st century, the report said. Mean annual runoff is projected to decrease by 8.5 percent by 2050. (Reporting by Victoria Cavaliere; Editing by Sandra Maler)