Waters of this State shall be protected and maintained for existing uses and the basic uses of water contact recreation, fishing, protection of aquatic life and wildlife, and agricultural and industrial water supply as identified in the Use Class designations. Consistent with the Federal Act, existing uses and the level of water quality necessary to protect existing uses for any water body shall be maintained. Certain waters of this State possess an existing quality that is better than the water quality standards established for them. The quality of these waters shall be maintained unless: The Department determines a change in quality is justifiable as a result of necessary economic or social development; and The change will not diminish uses made of, or presently existing, in these waters. To accomplish the objective of maintaining existing water quality: New and existing point sources shall achieve the highest applicable statutory and regulatory effluent requirements; and Nonpoint sources shall achieve all cost effective and reasonable best management practices for nonpoint source control. The Department shall ensure that existing uses are maintained and protected and support changes to designated uses and associated criteria in any circumstances where the designated use and criteria do not reflect and protect uses that are being attained. Changes in designated uses and associated criteria to less stringent uses and criteria may only be undertaken when: The designated use is not attainable because of natural causes; The designated use is not attainable because of irretrievable man-induced conditions; or Controls more stringent than the effluent limitations and national performance standards mandated by the Federal Act, and required by the Department, would result in substantial and widespread economic and social impact. The Department shall provide public notice and opportunity for a public hearing on the proposed change before: Permitting a change in high quality waters; or Changing the stream use designation. Water which does not meet the standards established for it shall be improved to meet the standards. Maryland’s Antidegradation Procedure Flow Chart.