The Millennial Kingdom hydrological cycle is a reestablishment of the original condition of the earth, when Eden was at plateau at the top of a mountain that filled the whole Earth.
Ezekiel’s Hydrology
The New Deep
Ezekiel tells us that a great river will issue forth from the temple in the Jerusalem. This is part of a hydrological cycle which doesn't presently exist. It's established along with the Millennial Kingdom.
The Waters Shall Be Healed
Ezekiel describes water flowing from the temple in Jerusalem which will heal everything that it touches. It's necessary after the devastation of Earth during the tribulation. Fish will thrive again.