As used in this article, the term:

(1) "Board" means the Metropolitan North Georgia Water Planning District Governing Board created under Code Section 12-5-575.

(2) "Director" means the director of the Environmental Protection Division of the Department of Natural Resources.

(3) "District" means the entity established by this article that shall have planning responsibility for watershed and storm-water management, waste-water management, and water supply and conservation management within the district area.

(4) "District area" means any county which has a population of 500,000 or more according to the 2000 United States decennial census or any future such census and all counties geographically contiguous to any such county; provided, however, that any such contiguous county having population of 100,000 or less according to the 2000 United States decennial census or any future such census may, by majority vote of the governing authority thereof and with the written approval of the director, remove itself from the district area. The district area may be expanded from time to time as provided in this article.

(5) "Local government" means any county or municipality of this state lying in whole or in part within the district area.