Longman Dictionary of Contemporary English
The Collaborative International Dictionary
Water power \Wa"ter pow"er\
The power of water employed to move machinery, etc.
A fall of water which may be used to drive machinery; a site for a water mill; a water privilege.
Wiktionary
n. 1 (&lit water power English) 2 (cx uncountable English) Mechanical or electrical energy derived from running or falling water; originally obtained from a waterwheel immersed in a stream; modern hydroelectric power is obtained from turbines fed from reservoirs 3 (cx countable English) A site capable of generating power or the right to use a site to generate power.
Wikipedia
Water Power is a pornographic film released c. 1976 directed by Shaun Costello. It was loosely based on the real-life exploits of the Illinois "Enema bandit", Michael H. Kenyon, who administered forced enemas to female college students in the 1960s and 70s. The film starred Jamie Gillis as a disturbed loner in the mode of Travis Bickle from Martin Scorsese's Taxi Driver. In preparing for his role, Gillis reportedly asked to be flown to Illinois to interview the man his character was based upon (his request was denied).
Usage examples of "water power".
What we had seen many miles back start from the mountain sides as slender rivulets, brawling over the worn boulders, were now great, rushing, full-tide streams, enough of them in any fifty miles of our journey to furnish water power for all the factories of New England.