In 2024, managers deliberately cooled the Colorado River to protect the Grand Canyon from invasive smallmouth bass. 2 years later, no bass recruitment had been detected, but the effort cost $19.1 million in replacement power

Managers at Glen Canyon Dam used an unusual strategy to protect native Colorado River fish from invasive smallmouth bass: they deliberately cooled downstream water during periods when the fish could reproduce. The “Cool Mix” operation combined colder water from lower river outlets with water passing through power-generating penstocks, keeping temperatures near or below 60°F. No smallmouth bass recruitment was detected in 2024, while preliminary 2025 monitoring also found none, though sampling was reduced.