Atlantis Dying

When a change in the tilt of Earth's axis causes climate patterns to shift, Atlantis's experts warn that in a hundred years, their lush land will become a desert. To save their civilization, the king must relocate a million people to the Atlantean colonies. But greedy barons who control the corrupt Legislative Plenum want a wall to prevent migrating workers from reaching the ships.
Darmon, First Consul to the King, knows the entire population won't fit in the current colonies, and Atlanteans, accustomed to the free energy supplied by Tuaoi crystals, won't live anywhere that doesn't have one.
Then a techgnosic breakthrough creates the first new Tuaoi in millenniums. With it, Atlantis can establish another colony. Darmon sets sail to find a site. While he's away, things go from bad to worse. The barons get their wall. Next, they construct aqueducts to drain vast lakes, despite being warned that it will hasten desertification.
The drought worsens, yet powerful factions continue to disregard the undeniable evidence, even as the desert envelops the capital. The wall forces the poor to flee the encroaching desert on foot.
Darmon's wife, Hathorah, a teacher at the Mystery School, is tasked with choosing a colony for the school. She and Darmon put to sea with a team of techgnosists to deliver the new Tuaoi.
A fierce storm forces their ship to take refuge in a river delta where they discover Atlantean farmers who'd fled overland. But it was far more than a storm, as they discover when they return to Atlantis.
Or what's left of it.