1. The Commission may prescribe controls for diffuse sources as follows:
(a) To any diffuse source existing on July 1, 1979, if the Director determines that the source is significantly causing or adding to water pollution in violation of a water quality standard.
(b) To any diffuse source created after July 1, 1979, if controls are necessary to prevent the degradation of any water of high quality in the waters of the State.
2. The Department shall delegate, to each county or city which so requests, other than a county to which NRS 244A.571 and 244A.573 apply or a city within such a county, the Administration of the Department’s controls of diffuse sources, if the Director finds that the county or city has the necessary money and staff to administer the program effectively. If such a delegation is made both to a county and to a city within it, the city has authority within its corporate limits and the county has authority outside those limits.