Drain Lake Powell to Fill Lake Mead...

https://www.grandcanyontrust.org/advocatemag/fall-winter-2015/future-lake-powell

The idea is simple: take Lake Powell water and transfer it to Lake Mead where less water will seep into the banks. That is, fill Mead first and use Lake Powell if needed. This will effectively “drain Lake Powell.”
From our studies, we have learned that sending Lake Powell water into Lake Mead will generate more power than trying to continue generating electricity from the two existing power plants with low water levels at both lakes.