Runoff Excess rainwater or snowmelt that is transported to streams by overland flow, tile drains, or ground water. Sediment Particles, derived from rocks or biological materials, that have been transported by a fluid or other natural process, suspended or settled in water. Species Populations of organisms that may interbreed and produce fertile offspring having similar structure, habits, and functions. A measure of the ability of a liquid to conduct an electrical current. Streamflow A type of channel flow, applied to that part of surface runoff in a stream whether or not it is affected by diversion or regulation.
Stream reach A continuous part of a stream between two specified points.
Study Unit Survey Broad assessment of the water-quality conditions of the major aquifer systems of each Study Unit. 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. An open body of water, such as a lake, river, or stream. It is associated with the material retained on a 0.45-micrometer filter.