Basin area Areas that do not receive adequate precipitation for ground-water recharge and streamflow. These areas can receive recharge and streamflow from upstream headwater areas. A region characterized by a series of generally north-trending mountain ranges separated by alluvial valleys. Benthic invertebrates Insects, mollusks, crustaceans, worms, and other organisms without a backbone that live in, on, or near the bottom of lakes, streams, or oceans. Chlorinated solvent A volatile organic compound containing chlorine.
Some common solvents are trichloroethylene, tetrachloroethylene, and carbon tetrachloride.
A layer of sediment or lithologic unit of low permeability that bounds an aquifer. Constituent A chemical or biological substance in water, sediment, or biota that can be measured by an analytical method. Contamination Degradation of water quality compared to original or natural conditions due to human activity. The portion of the surface of the Earth that contributes water to a stream through overland runoff, including tributaries and impoundments. The collection of ductless glands in animals that secrete hormones, which influence growth, gender, and sexual maturity.