Prolonged drought in the Colorado River Basin pushed hydropower generation in the Southwestern United States to record lows this summer, the Energy Information Administration said in an analysis published on November 13. Generation from April through August 2026 was 19 percent lower than in the same period last year and 28 percent lower than the 10 year average, based on the agency’s Form EIA-923 plant data.
The Southwestern supply region covers Arizona and New Mexico and small parts of Nevada and California, and its two largest reservoirs are the constraint. Water elevations at Lake Powell, behind Glen Canyon Dam, and Lake Mead, behind Hoover Dam, both hit record lows, leaving less head and less water to run through the turbines.
The shortfall is not expected to close this year. In its November Short-Term Energy Outlook, the EIA expects Southwest hydropower generation to total 6.13 billion kilowatthours in 2026, 9 percent lower than last year and 24 percent lower than the 10 year average. Hydropower is expected to account for about 4 percent of the region’s generation mix in 2026.
Four percent sounds small, but hydro in the Southwest is dispatchable power that historically showed up for summer peaks. Replacing it means more gas fired generation and more imports over constrained interties, at higher cost, in a region where power demand is already rising. The EIA figures quantify the power side of a water allocation fight that the basin states and the federal government still have to settle for 2027.