Georgia and Atlanta have unsustainable growth which their natural resources can't support and are trying to pass off the externalities onto their neighbors. I am biased as a former resident of both Tennessee and Florida.
Atlanta's artificial lakes/reservoirs are from a similar time, new ones aren't being made fast enough if at all, and the population continues to grow. Dealing with multiple jurisdictions (the region known as Atlanta encompasses the city of Atlanta, many other cities, and is spread across several counties) further complicates the issue when it comes to funding and determining responsibility. You could argue the state of GA should step in. However, there's a huge political chasm between the metro Atlanta area and most of the rest of the state (A "fuck those city slickers" attitude is very common in rural Georgia and the smaller cities, Atlantans aren't viewed as Georgians given how many are transplants). The water in the Atlanta region also needs to travel down river to many other areas (and other states) in order to sustain those regions.
https://en.wikipedia.org/wiki/Lake_Mead#Drought_and_water_us...
With Ariz/Nev supply Cali with their excess solar to the desal plants.
Politically, the Colorado is a different animal. Mexico is downstream and historically has just had to lump it when the river runs dry. Which it has as the US built dams. And today, it has to make do with just a remaining 5% of the historical wetlands where the Colorado flows into the Sea of Cortez.