Lake Mead and Lake Powell now hold barely more water combined than Mead alone did in 1957, marking the lowest total storage ever recorded for the two reservoirs.
Record spring heat and record-low Upper Basin snowpack accelerated the decline, and researchers said the reservoirs have been losing 15,000 to 16,000 acre-feet a day for four of the past five months.
July 12 matched the prior low point before storage slipped further, and a new paper said fresh record lows are likely almost daily until snowmelt begins in late winter or spring 2027.
Federal forecasts already show Lake Powell could fall below the level needed for Glen Canyon Dam hydropower by next spring, despite emergency upstream releases and reduced outflows to Mead.
The new low underscores pressure on the Bureau of Reclamation, which is preparing a final plan to cut Colorado River use as drought and heat erode the system's buffer for cities and farms.