It shall be unlawful for any corporation or natural person to use for the development of water power, or for the main purpose of storing, cooling, diverting, and using, or any of them, water for steam raising or steam condensation, or both, in the generation of electric energy for use in public service, any dam constructed under any permit hereafter issued otherwise than under section two of this act, or to divert or use for said purposes, or for said main purpose, any stream or body of water the course, current, or cross-section of which shall have been changed or diminished at the point of diversion, or use, under any permit hereafter granted, otherwise than under section two of this act.
32 P.S. § 594