Cal. Water Code § 35509

In the event that the boundaries of any district, which is authorized to exercise the powers granted by this article, are altered pursuant to the District Reorganization Act of 1965, Division 1 (commencing with Section 56000) of Title 6 of the Government Code, such powers may continue to be exercised only within that portion of the district originally authorized to exercise such powers, when provided by terms and conditions adopted pursuant to Section 56470 of the Government Code.