Hoover Dam, one of the largest concrete dams in the United States, stands over 700 feet high in Black Canyon, approximately 30 miles southeast of Las Vegas. Behind it lies Lake Mead, the nation's largest reservoir, which supplies roughly 25 million people and supports highly productive farmland. Amid the driest period in over a thousand years for the region, with Lake Mead's levels at historic lows, the question of what would happen if the dam were removed is increasingly being considered. Such a change would reshape life across the Southwest due to its significant downstream impacts on the Colorado River.
Southern Nevada heavily relies on the Colorado River for about 90 percent of its water supply, primarily drawn from Lake Mead. While its newest intake connects to a tunnel beneath the lake, allowing withdrawals below the reservoir's 895-foot "dead pool" elevation, this system depends on water remaining over the intake. A drained reservoir would result in a much narrower river, its channel and elevation determined by the valley floor and accumulated sediment. An intake designed for a submerged lakebed might become unusable, requiring Southern Nevada to develop a replacement or substantially redesigned system connected to the new river channel, or secure another dependable water supply, prior to any dam removal.
Currently, Lake Mead allows much of the incoming sediment from the Colorado River to settle. During a drawdown or complete removal, treatment facilities could face increased sediment in the water they receive. The exposed ground would include thick deposits accumulated since 1935, and the river would begin cutting a channel through these deposits, leading to ongoing bank erosion. This adjustment would extend downstream, potentially increasing turbidity and depositing material in Lake Mohave below Davis Dam. A removal plan would therefore need to manage sediment releases alongside water flows.
Electricity generation from Hoover Dam would cease. The powerplant, which houses 17 main turbines, relies on the significant height difference between Lake Mead and the river below. With the reservoir gone, the existing plant, with its approximately 2,080 megawatts of nameplate capacity, could no longer generate electricity. Customers, including the City of Los Angeles, the Colorado River Commission of Nevada, tribal interests, and irrigation interests, would need to find replacement power sources.
Downstream infrastructure, including Davis Dam and Parker Dam, would remain in place. Davis Dam, 67 river miles below Hoover, impounds Lake Mohave, while Parker Dam creates Lake Havasu. These reservoirs, with a combined capacity less than one-tenth of Lake Mead's full capacity, regulate deliveries along the lower river, including water pumped to Southern California and central Arizona. Without Lake Mead's substantial storage, operators would have less room to retain wet-year runoff or hold back large inflows, making water deliveries more directly dependent on upstream releases and tributary flows.
The landscape within the drained Lake Mead basin would undergo a significant transformation. Water would withdraw from broad bays and concentrate along lower ground, with tributaries like the Virgin River extending across exposed reservoir beds toward the Colorado. Lake-based marinas would lose their water access, and existing access roads would end above a changing river corridor. Some exposed areas would be rocky, while others would reveal sediment accumulated over decades. The river would erode some deposits and carry sediment toward Black Canyon, potentially impacting Lake Mohave. Upstream controls from Glen Canyon Dam would remain, preserving the Colorado's upstream sediment supply and seasonal flows.
Ecologically, the deep-water habitat within Lake Mead would largely be replaced by flowing channels. Removing Hoover Dam would eliminate a barrier to fish movement at Black Canyon, although Davis Dam would remain downstream. Lake Mead supports a naturally reproducing population of native razorback suckers. Draining the lake would alter their habitat, and while reservoir removal could create additional river habitat, the loss of existing spawning and rearing areas would need assessment. Native-fish recovery would still depend on suitable flows and managing introduced predators already present in the Colorado system.
A narrower river replacing much of Lake Mead's broad open water would reduce evaporation at the reservoir site. The net water savings would depend on where water was stored afterward and losses from exposed ground and new vegetation. However, removing Hoover Dam would not increase the snowmelt entering the Colorado River Basin.
Far downstream, diversions would continue to carry water to farms and cities before the river reaches Mexico's delta. Keeping additional water in the channel would require changes in allocation and release policies. The connection between Las Vegas Bay and the Colorado River would also shift. Southern Nevada returns highly treated wastewater via Las Vegas Wash, earning credits for additional withdrawals. With Lake Mead receding toward a river channel, the receiving water at the end of the wash would change, necessitating a replacement drinking-water intake to account for the new mixing dynamics with the Colorado.
