Lake Powell, the second-largest human-made reservoir in the United States, is facing a dual threat: falling water levels driven by prolonged drought and a steady reduction in its total storage capacity, according to a new report cited by CNN.
The reservoir, created by the construction of Glen Canyon Dam in 1963, has lost nearly 7% of its potential storage capacity over the past six decades. That loss is attributed to sediment accumulation on the lake bed, a process that gradually displaces the volume of water the reservoir can hold.
A shrinking basin
Unlike the cyclical nature of drought, which can ease with increased rainfall or snowpack, sediment buildup is effectively permanent on human timescales. As rivers feeding into Lake Powell carry silt and debris, that material settles at the bottom, reducing the usable volume of the reservoir over time.
The combination of this structural reduction and historically low water levels - driven by more than two decades of drought in the Colorado River Basin - has placed the reservoir under extraordinary stress. Lake Powell supplies water to millions of people across seven western U.S. states and also generates hydroelectric power through the Glen Canyon Dam.
Drought compounds the problem
Water levels at Lake Powell have fallen sharply in recent years, at times approaching thresholds that could threaten the dam's ability to generate electricity. The U.S. Bureau of Reclamation has taken emergency steps in recent years to prop up water levels, including releasing water from upstream reservoirs.
Scientists and water managers have warned that the Colorado River system is under increasing pressure from both climate change and growing demand from the cities, farms, and industries that depend on it. Warmer temperatures accelerate evaporation and reduce snowmelt runoff, which is the primary source of water feeding the river and its reservoirs.
Long-term implications
The findings highlight a challenge that goes beyond short-term weather patterns. Even if drought conditions were to ease significantly, the sediment already deposited on the lake bed would remain, meaning the reservoir's maximum capacity would not recover to its 1963 levels.
Water authorities across the region are assessing long-term strategies to manage reduced supply, including potential reductions in water allocations to states under the existing Colorado River Compact - an agreement that some experts argue was negotiated during an unusually wet period and does not reflect current hydrological realities.
The report adds fresh urgency to ongoing negotiations among western states over how to share a diminishing resource as climate pressures continue to mount.
