Notwithstanding any other provision of this Act any person, firm, corporation, or agency of the public diverting or obtaining water at the time of the establishment of a Water Authority pursuant to this Act from any water source shall have the right of continuing to take from the same source, the quantity of water which is the rated capacity of the equipment used to divert or obtain water at the time of the establishment of the Water Authority having jurisdiction over the water source.
70 ILCS 3715/6a