Definitions for "Reference site"
a site on a waterbody which represents the best attainable physical habitat, water chemistry, and biological parameters for specific environmental conditions.
is a site located downstream (surface-water) or within (ground-water) a relatively undistrubed drainage basin that represent background conditions, but not neccessarily natural conditions, because most areas have been disturbed to some degree and atmospheric sources of contaminants do not respect basin boundaries.
a stream reach that has not been impacted by human activities and that serves as a comparison site for an "impacted" site
an area used as a control in a scientific experiment