Hoover Dam, the Depression-era engineering marvel, turns 75 this month. While its new bridge crossing is set to open in November, the concrete monolith also is marking a dubious milestone this year—a 54-year low point for its water level, which threatens the dam’s hydroelectric output. Photo: Courtesy of Southern Nevada Water Authority Lake Mead reservoir level is at its lowest point in 54 years, putting electricity generation capability at risk. Engineered mitigation measures include a third water-intake tunnel and new turbine design. Lake Mead dipped to 1,085 ft in September, less than 40% of its capacity, following a decade of
Arch dams, classically curved monoliths situated in narrow valleys, are not as common as other types of dams, such as embankment dams and gravity dams. ENR takes a look at some of the biggest arch dams in the world, both completed and under construction.