Environmental water quality, also called ambient water quality, relates to water bodies such as lakes, rivers, and oceans.[1] Water quality standards for surface waters vary significantly due to different environmental conditions, ecosystems, and intended human uses. Toxic substances and high populations of certain microorganisms can present a health hazard[2] for non-drinking purposes such as irrigation, swimming, fishing, rafting, boating, and industrial uses. These conditions may also affect wildlife, which use the water for drinking or as a habitat. According to the EPA, water quality laws generally specify protection of fisheries and recreational use and require, as a minimum, retention of current quality standards.[3]

There is some desire among the public to return water bodies to pristine, or pre-industrial conditions.[4] Most current environmental laws focus on the designation of particular uses of a water body.