N.C. Gen. Stat. § 162A-22

For the purposes of this Article "a regional water supply system" is defined as a public water supply system of a municipality, county, sanitary district, or other political subdivision of the State, or combination thereof, which provides, is intended to provide, or is capable of providing an adequate and safe supply of water to a substantial portion of the population within a county, or to a substantial water service area in a region composed of all or parts of two or more counties, or to a metropolitan area in two or more counties.