The water level at Lake Mead, largest reservoir in the country (measured by water capacity), hit a historic low of 1,072 feet in early June 2016. The last time the water’s surface level had gone this far down was in 1937, while the reservoir was on the way up, being filled.
This is the second year in a row that Lake Mead has hit a record low; the previous one was set in late June 2015.
The man-made lake straddles the Nevada-Arizona border roughly 25 miles from Las Vegas and provides water to 25 million people in Arizona, California, Nevada, and Mexico, produces millions of megawatt hours of energy production, provides habitat for threatened and endangered species, and waters a tremendous agricultural crop, particularly during the winter months.
It’s now only about 37% full.
The lake last approached full capacity in the summer of 1983, 33 years ago. It’s been declining ever since, but especially over the past 16 years (compared to the last four in California), as drought in the Colorado River watershed throughout much of the west has taken its toll, and continues to.
Falling below a critical threshold at 1,075 feet triggered a Level 1 Water Shortage declaration, signaling the start of potential water cuts to Arizona and Nevada. If Lake Mead sinks to 1,025 feet, the Department of Interior will seize control of its management and water allocation. And if it falls to 900 feet, it will be considered "deadpool," meaning that water is no longer passing through the turbines.
However, the water level came up three feet in July and August, reaching the threshold of 1,075 in September. Though it’s not much by historic standards, it is a measurable change for the better. And almanac predictions suggest another 3 feet could be on the way by the end of the year, during a period that's anticipated to be unusually wet.
On a side note, electricity generation at Hoover Dam celebrated its 80th anniversary on October 26; on that date in 1936, water began turning the original Francis turbine generators, 17 of which were installed between 1936 and 1961.
