Reach assessments of ecological conditions and bed-sediment and tissue sampling also are conducted at these sites. Bed-sediment study is the assessment of concentrations and distributions of trace elements and hydrophobic organic contaminants in streambed sediment to assess spatial distribution. Benthic Invertebrates are animals without backbones that live in association with streams and lake bottom habitats. Examples are larval insects such as caddisflies and mayflies, and crustaceans such as crayfish. Comparison sites are similiar to indicator sites in that they represent a dominant land use within a basin, but are sampled less frequently.
Instantaneous discharge is the discharge at a particular instant of time.
Dissolved is that material in a water sample which passes through a 0.45 mm membrane filter. This is a convenient operational definition used by Federal agencies that collect water data. Therefore, in the mathematical calculation of dissolved-solids concentration, the bicarbonate value, in milligrams per liter, is multiplied by 0.492 to reflect the change. Drainage area of a stream at a specific location is that area, measured in a horizontal plane, enclosed by a topographic divide from which direct surface runoff from precipitation normally drains by gravity into the river from an upstream specified point. Figures of drainage area given herein include all closed basins, or noncontributing areas, within the area unless otherwise noted.