No change in the jurisdiction over any territory in any city, village or township which has contracted for a supply of water from the authority, shall in any manner impair the obligations of such contract, but the same shall be carried out, insofar as such territory is concerned, by the authority and such municipality or municipalities as shall have jurisdiction to furnish water to such territory. No change in municipal jurisdiction over any territory within an authority shall in any manner affect the authority or its boundaries. If a new city shall be incorporated from a township in the authority and if such city shall exercise jurisdiction over the water supply system within its boundaries, then it shall be deemed to be a constituent municipality of the authority. If the territory within a water supply district, as defined in section 10 hereof, is incorporated as a new city having jurisdiction over the water supply system and if at the time of such incorporation there shall exist a contract with the authority for a water supply to such territory, then such city shall be a constituent municipality of the authority upon the approval of the legislative bodies of 2/3 of the cities, villages and townships constituting the authority and upon acceptance by the city of the articles of incorporation. If it shall be necessary to amend the articles of incorporation in order to give any such new city comparable rights with other constituent municipalities, the same may be accomplished upon the approval of the legislative bodies of 2/3 of the cities, villages and townships constituting the authority.