Federal officials said Thursday they will not release cool water this year from one of the Colorado River’s major reservoirs, which would have protected a threatened native fish downstream but put more strain on already struggling hydropower production. A “cool mix flow” is when cold water is released from deep in a reservoir — in this case Lake Powell — to cool the river below. Lake Powell is about 23% full after decades of overuse and evaporation of water as average temperatures rise because of climate change. With such a low reservoir, warm water near the surface gets sucked through the generators and sent downstream. Officials say cool water releases from Lake Powell in 2024 and 2025 successfully prevented smallmouth bass spawning.