Hoover Dam Removal Would Drain Lake Mead, End Power and Force New Intakes

Water elevation is the working component that connects Lake Mead’s three major functions. It keeps Southern Nevada’s intake infrastructure submerged, provides pressure for Hoover Dam’s turbines and creates storage space that carries Colorado River water between wet and dry periods. Hypothetically removing the dam would cause all three functions to disappear together.

No Hoover Dam removal project has been announced. In this engineering scenario, taking out the more-than-700-foot concrete structure would drain Lake Mead toward a narrower river channel, end generation at Hoover’s 2,080-megawatt powerplant and require Southern Nevada to replace or substantially redesign the system supplying about 90 percent of its water.

A river could miss infrastructure built for a lake

Southern Nevada’s newest intake connects to a tunnel beneath Lake Mead, and its pumping station can withdraw water below the reservoir’s 895-foot dead-pool elevation. That configuration is designed around a lake covering the valley floor. Without the dam, the Colorado River’s position would instead be determined by low ground, accumulated sediment and continuing channel erosion.

The resulting river could run below or to one side of the existing intake. Engineers would need to establish a dependable connection to that moving corridor, while accounting for changes in flow, sediment and water quality. The problem would therefore extend beyond lowering a pipe: the intake, pumps and treatment system would have to operate across a different hydraulic environment.

Sediment would make that environment less predictable. U.S. Geological Survey mapping of Lake Mead’s floor identified deposits formed after impoundment as either thin, measuring less than one meter, or thick, measuring more than one meter. The deposits cover the original valley floors and are thickest in deltas at the mouths of the Colorado River and its tributaries.

The survey also found that falling lake levels had already allowed thick delta deposits to erode and move toward deeper parts of the reservoir. A complete drawdown would expand that process: the river would cut into exposed sand, silt and clay, potentially increasing turbidity at water-treatment facilities and carrying some material downstream into Lake Mohave.

Hoover’s turbines need the reservoir’s height

Hoover’s nine Arizona-side and eight Nevada-side main turbines rely on hydraulic head the elevation difference between Lake Mead and the river below the dam. As the reservoir fell during removal, that pressure source would contract and generating capability would decline. Once the dam and reservoir were gone, the existing 17-turbine plant could no longer generate electricity.

The same drawdown would eliminate most of the Lower Colorado River system’s storage buffer. Davis Dam, 67 river miles downstream, would continue holding Lake Mohave, while Parker Dam would retain Lake Havasu. Yet their capacities about 1.8 million acre-feet and 648,000 acre-feet respectively add up to less than one-tenth of Lake Mead’s full storage.

Operators would consequently have far less room to retain wet-year runoff, regulate major inflows or support deliveries during dry periods. Water users would depend more directly on releases from upstream reservoirs and tributary flows. Existing compacts, treaties, court decisions and allocation rules would also remain in force, so removing one structure would not remove the institutional system governing the river.

Exposed sediment would require long-term management

Allowing the river to erode a path is only one possible sediment-management approach. A broad review of reservoir practice describes bypassing sediment, routing it through during high flows and flushing deposits through low-level outlets. Drawdown flushing works best in narrow, steep reservoirs with enough flow and outlet capacity to keep sediment moving conditions that cannot simply be assumed across Lake Mead’s broad basins.

Lake Powell offers a limited illustration of the physical process, rather than a forecast for Lake Mead. As its water receded, the returning river cut through exposed sediment shelves. Some shelves became unstable and collapsed into the channel, showing how drawdown can produce repeated channel adjustments rather than reveal a fixed pre-reservoir riverbed.

Habitat would change as well. Much of Lake Mead’s deep water would give way to flowing channels, altering habitat used by fish including native razorback suckers. Removing Hoover would open Black Canyon to fish movement, but Davis Dam would remain another downstream barrier. Recreation facilities positioned for a reservoir would likewise lose their existing shoreline relationship.

A narrower river would reduce evaporation at the Lake Mead site, but the net savings would depend partly on whether and where that water was stored elsewhere. Removal would not increase Colorado River snowmelt, override downstream diversions or automatically deliver additional water to Mexico or the Gulf of California. It would exchange a reservoir and power system for an evolving river corridor while leaving the basin’s limited water supply unchanged.

By Thomas Caldwell — AMI’s senior editor for mechanical and mobility engineering, covering vehicle electronics, systems integration, electrification, chassis systems, propulsion, and safety policy.