Cool water releases to protect threatened fish at Glen Canyon Dam reduce hydropower, raising costs for ratepayers

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.

Utility groups say it will cost them millions of dollars to replace affordable power and will increase financial hardship for power users.

Tradeoffs are increasingly impossible to avoid as the Colorado River continues to decline and leaders grapple to reach agreement on how to share its dwindling supply.