KVIG Informative

Hoover Dam’s turbines were engineered in the 1930s to run on a reservoir the Bureau of Reclamation expected to stay full. Ninety-one years later, Lake Mead has fallen within a few feet of the elevation where those same turbines lose most of their power — and the agency that built the dam is now spending millions to re-engineer it for water levels its original designers never planned for.

The Boulder Canyon Project Act of 1928 authorized the dam’s construction, and the federal government awarded the building contract to Six Companies Inc. on March 11, 1931, with a notice to proceed issued April 20, 1931, according to the Bureau of Reclamation’s own project chronology.

Workers diverted the Colorado River around the construction site through a series of tunnels on Nov. 14, 1932, clearing the riverbed for the dam itself. The first concrete went into the canyon wall on June 6, 1933, and the final concrete pour was completed on May 29, 1935, according to the bureau’s chronology.

Lake Mead began storing water behind the new dam on Feb. 1, 1935. President Franklin D. Roosevelt dedicated the completed structure on Sept. 30, 1935, and the first of the dam’s generators went into full operation on Oct. 26, 1936, according to the bureau. By 1939, Hoover Dam was the largest hydroelectric facility in the world, a distinction it held until Grand Coulee Dam surpassed it in 1949, the bureau’s records show.

The last of the dam’s 17 main turbines came online by Dec. 1, 1961, giving the plant a combined nameplate capacity of roughly 2,080 megawatts, according to the bureau’s own power facts sheet. Revenue from that power paid off the dam’s original construction debt by 1987, with only flood-control costs still being repaid, due in 2037, the bureau says.

Donate

Donate

By the end of August 2026, Lake Mead’s surface stood at 1,038.83 feet in elevation, according to the bureau’s daily lake-elevation records — less than four feet above the 1,035-foot mark where the dam’s older turbines lose most of their generating capacity.

At 1,035 feet, Hoover Dam’s capacity using its original-style turbines would fall from 1,302 megawatts to about 382 megawatts, according to the bureau’s own technical assessments. Generation at the dam has already declined roughly 30 percent because of the prolonged Colorado River drought, the bureau said.

The bureau responded by unlocking about $52 million from Hoover Dam’s Post Retirement Benefit Fund — money originally set aside to cover employee retirement costs before those workers moved to federal retirement systems — to replace up to three of the dam’s older turbines with wide-head turbines built to keep generating down to roughly 950 feet of elevation, restoring at least 160 megawatts of capacity. Acting Reclamation Commissioner Scott Cameron and Assistant Secretary for Water and Science Andrea Travnicek announced the investment, saying it was meant to keep the dam producing power for decades to come.

Donate

Donate

Hoover Dam’s 17 turbines went online one at a time over 25 years, built for a reservoir Congress and the bureau expected to stay full behind a dam rated to hold water 590 feet deep. Ninety years after its first generator turned on, the agency that built Hoover Dam is now re-engineering its turbines for a lake it never planned to see this low.