Completely cover a major river with waterwheels, then build windmills on all the land and some built platforms. That may get you... some of it?
Sounds like some sorta Hoover dam megaproject!
Simple math dicates you would need a perfect square 191 tiles wide to generate that kind of power with waterwheels.
1,210,000 power requires 12,100 waterwheels, or 13,445 if you count it as 90 instead.
Since waterwheels are 1x3x1 (not 3x3x1) and are powered by vertical flow, you can use a long perpetual motion stack/chamber. I read about this somewhere, but forgot where.
top: +==...=====|=+
|WW...WWWWW|~+===
|WW...WWWWW*~~~~~~<input
|WW...WWWWW+=====
+==...=====+
side:.+==================
.|WW...WWWWW*~~~~~~~~
.|WW...WWWWW*+======
.|WW...WWWWW*|
|(and so on)|
.|WW...WWWWW*|
=+WW...WWWWW*|
~~~~~~~~~~~~++
=============
If one made 5 chambers 100 waterwheels long and 25 z-levels deep, that would cause you to have 1250000 gross power. These 5 chambers would occupy a volume 21 tiles wide, about 105 tiles long, and 28 tiles deep.
if you account that each waterwheel takes ten power and each gear assembly takes five, that would make you need each chamber to span 27 z-levels to generate 1,210,000 net power.
This will require 135 mechanisms and 40,500 logs. Better embark in a jungle, and enjoy your tower-cap farms!
(And you'd want a pumpstack or two to reload the water...)