The organization and establishment of the agency shall be as follows:

(1) The respective county commission of the Counties of Lauderdale and Limestone shall each nominate by majority vote three candidates for each of two memberships on the board of directors of the agency. Candidates shall be selected from persons residing in these counties and active in municipal, industrial, agricultural, commercial or citizen organizations engaged in promoting comprehensive and unified development of the resources of the watershed as a basis for its general economic growth. The probate judge of each county shall certify the nominations for the two directorships from his county to the Governor, who shall, upon receipt thereof, appoint from the nominees from each county two directors, one from each group of three nominated for each directorship. One member from each county shall be appointed for a two-year term, one member from Lauderdale County for a four-year term, and one member from Limestone County for a six-year term. However, such terms shall continue in all events until successors are appointed. Successors shall be appointed for terms of six years. In the event of a vacancy on the board, the Governor shall appoint a successor for the unexpired term.

(2) The Governor shall appoint an additional director from his cabinet or staff to serve during the Governor's term of office, and succeeding Governors shall similarly appoint such a director.

(3) The respective county commissions of the Counties of Lauderdale and Limestone shall each nominate by majority vote three incumbent mayors of the incorporated cities and towns within the county and submit such nominations to the Governor, who shall appoint one mayor from each county to serve as a director, for a term of four years, or during his continuance in office as mayor, if his incumbency in such office be less than four years.