Every water authority so established shall be governed by a board of 3 trustees. Such number shall be increased by one for each county, or part thereof, in excess of 3 included within the boundaries of the authority. The board of trustees for the authority shall be created in the following manner:
Upon the expiration of the term of a trustee who is in office on the effective date of this amendatory Act of 1975, the successor shall be a resident of whichever county is entitled to such representation in order to bring about the proportional representation required herein, and he shall be appointed by the county board of that county, or in the case of a home rule county as defined by Article VII, Section 6 of the Constitution of 1970, the chief executive officer of that county, with the advice and consent of the county board.
Thereafter, each trustee shall be succeeded by a resident of the same county who shall be appointed by the same appointing authority; however, the provisions of the preceding paragraph shall apply to the appointment of the successor to each trustee who is in office at the time of the publication of each decennial Federal census of population.
Within 60 days after the entry of the order of the circuit court declaring such water authority duly organized, the appropriate appointing authority shall appoint the board of trustees, one of whom shall be appointed to serve for a term of one year, one for a term of 2 years and one for a term of 3 years. If any water authority is required to have more than 3 trustees, the excess trustees shall be appointed originally for terms of one year. Upon the expiration of the term of each of such trustees, the appointing authority shall, unless the water authority has determined to elect trustees as provided in Section 5.1, appoint his successor, who shall serve for a term of 3 years. The appointing authority shall also have the authority to fill any vacancy which may occur in the board of trustees. The trustees shall be legal voters residing within the authority, and in case the territory thereof is located in more than one county, at least one of such trustees shall be a resident of each of the counties.
70 ILCS 3715/3