Riparian Areas adjacent to rivers and streams with a high density, diversity, and productivity of plant and animal species relative to nearby uplands. The maximum contamination level in public water systems that, in the judgment of the U.S. Environmental Protection Agency, are required to protect the public welfare. Species diversity An ecological concept that incorporates both the number of species in a particular sampling area and the evenness with which individuals are distributed among the various species. A measure of the ability of a liquid to conduct an electrical current. Stream-aquifer interactions Relations of water flow and chemistry between streams and aquifers that are hydraulically connected.
Stream reach A continuous part of a stream between two specified points.
The Study-Unit Survey relies primarily on sampling existing wells and, wherever possible, on existing data collected by other agencies and programs. Subsurface drain A shallow drain installed in an irrigated field to intercept the rising ground-water level and maintain the water table at an acceptable depth below the land surface. It is associated with the material retained on a 0.45- micrometer filter. Tissue study The assessment of concentrations and distributions of trace elements and certain organic contaminants in tissues of aquatic organisms. Urban Site A site that has greater than 50 percent urbanized and less than 25 percent agricultural area.