Solar powered desalinization ships that collect sea water and takes them to the poles to freeze desalinate. Using the natural thermodynamic energy of the poles to remove thermal energy from sea water. There is recent technology on how to efficiently separate brackish water from ice and fresh water when freeze desalinating.
The size of one oil tanker could supply Los Angeles with its drinking water for a week. 52 rotating ships could supply fresh cheap and clean water to large cities with limited energy resources.