An integrated activity for evaluating the physical, chemical, and biological character of water in relation to human health, ecological conditions, and designated water uses. Physical measurements of general conditions such as temperature, flow, water color. Biological measurements of the abundance and variety of aquatic plant and animal life and the ability of test organisms to survive in sample water. Monitoring can be conducted at regular sites on a continuous basis (""fixed station"" monitoring); at selected sites on an as needed basis or to answer specific questions (intensive surveys); on a temporary or seasonal basis (for example, during the summer at bathing beaches); or on an emergency basis (such as after a spill). Monitoring can be conducted for many purposes: characterize waters and identify changes or trends in water quality over time; identify specific existing or emerging water quality problems; gather information to design specific pollution prevention or remediation programs; determine whether program goals -- such as compliance with pollution regulations or implementation of effective pollution control actions -- are being met; and respond to emergencies, such as spills and floods.