Water quality criteria

Water quality criteria can include general narrative statements that describe good water quality and specific numerical concentrations that are known to protect aquatic life and human health. The criteria are adjusted as needed to reflect changes in law and science. Numerical criteria are for specific physical, chemical (toxics), and radiological characteristics of the waters (e.g. minimum of 4.0 mg/L dissolved oxygen, 2.5 ug/L ammonia, 3.8 ug/L copper). Narrative criteria include general protective statements known as the "free froms". This narrative criteria says that all state waters shall be free from substances attributable to sewage, industrial waste, or other waste in concentrations, amounts, or combinations which contravene established standards or interfere directly or indirectly with designated uses of such water or which are inimical or harmful to human, animal, plant, or aquatic life.

These numerical and narrative criteria describe water quality necessary to protect designated uses such as swimming, drinking and the propagation and growth of aquatic life.