Cool water releases to protect Grand Canyon fish would reduce hydropower generation at Glen Canyon Dam

To fight off predators of the humpback chub, a threatened fish native to the river, Glen Canyon Dam in northern Arizona would need to do what is known as a 'cool mix flow,' where cold water is released from deep in its reservoir to cool the river below.

But there are no hydropower turbines in the cool, deep section, so significant power generation would be lost.

As the Colorado River and its once massive reservoirs shrink from overuse and climate change, officials are faced with a decision that pits conservation against ratepayer costs for electricity.