The planners envisioned diverting water from some rivers in Alaska south through Canada via the Rocky Mountain Trench and other routes to the US and would involve 369 separate construction projects. The water would enter the US in northern Montana. There it would be diverted to the headwaters of rivers like the Colorado River and others.
The water would generate hydro-electricity during its trip via dams. The water supply would double the total amount of fresh water available to lower 48 states with its major focus being on the western states. This would solve the water shortage problems of the west for the foreseeable future. The amount of water available would in fact be so great that some water would be left over for use by Mexico via the Colorado River (which is currently significantly depleted as it enters Mexico).
Lyndon H. LaRouche, L. (1983) The Outline of NAWAPA, Schiller Institute, January 1983