The new record low arrived at Lake Mead a little earlier than first thought — and it happened during a rainstorm.
The reservoir east of Las Vegas briefly dropped to a new low water mark between 6 p.m. and 7 p.m. Saturday, when pelting rain couldn’t stop the surface of the lake from falling to 1,080.18 feet above sea level for the first time since it was first being filled in May 1937.
Forecasters initially thought the record would come early Sunday.
After the dip Saturday evening, the water level nudged back up slightly for a few hours before falling again, this time to 1,080.13 — an all-time low that would last all of about 24 hours.
By midnight Monday, Lake Mead had begun to shrink once again, as Hoover Dam continued to release water downstream to farms and cities in California and Arizona: hitting 1,080.12 by 1 a.m.; 1,080.04 by 1 p.m.; 1,080 even by 4 p.m.; and so on, record after record after record.
Analysts for the U.S. Bureau of Reclamation, which operates the dam, expected the lake to close out Monday below the 1,080 mark for the first time in 78 years. That milestone was reached at 5 p.m.
So far this month, the nation’s largest reservoir has been losing a foot or more of water a week. It now sits at about 38 percent of capacity, its surface almost 130 feet lower than it was in April 2000, when the ongoing drought was just settling into the mountains that feed the Colorado River.
Federal forecasters expect the lake to stay in record territory and continue to drop through the end of June, when it could dip as low as 1,073 feet above sea level. After that, the reservoir should begin to inch back up as Lake Powell delivers more water downstream. This should give record keepers time to update their ledgers before next April, when the water level will likely to enter historic territory once again.
Should Lake Mead start 2016 below the 1,075 mark, it will trigger the first federal shortage declaration on the Colorado and prompt Nevada and Arizona to cut back on the amount of water they take from the river.
Current projections call for the lake to remain just above that all-important shortage line on Jan. 1 of both 2016 and 2017, but those forecasts assume average or better snow accumulations in the mountains that feed the Colorado River — something that’s happened only three times in the past 15 years.
The Las Vegas Valley draws 90 percent of its water supply from Lake Mead using two intake pipes, one of which will stop working should the water level fall to 1,050 feet above sea level. The Southern Nevada Water Authority hopes to have its new, $817 million deep-water intake on line by the end of September.