GLOSSARY OF WATERSHED AND WATER QUALITY TERMS

algae Small aquatic plants lacking stems, roots, or leaves which occur as single cells, colonies, or filaments.

algal bloom Rapid, even explosive growth of algae on the surface of lakes, streams, or ponds; stimulated by nutrient enrichment.

beneficial use Any of the various uses which may be made of the water, including, but not limited to, domestic water supplies, industrial and agricultural water supplies, recreation in and on the water, wildlife habitat, and aesthetics. Any use may not lower the ambient water quality.

benthic The bottom of lakes, streams or ponds.

best management practices Accepted methods for controlling nonpoint source pollution; may include one or more conservation practices.

chlorophyll a The dominant green, photosynthetic pigment in plants; a measure of aquatic plant production.

coliform bacteria A group of bacteria found in the colons of animals and humans, but also in natural soil and water where organic content is high. The presence of coliform bacteria in water is an indicator of possible pollution by fecal material.

cultural eutrophication An accelerated rate of lake aging induced by human sources of nutrients, sediment, and organic matter.

discharge In the simplest form, discharge means outflow of water. The use of this term is not restricted as to course or location and it can be used to describe the flow of water from a pipe or from a drainage basin. Other words related to discharge are runoff, flow, and yield.

dissolved oxygen Molecular oxygen freely available in water and necessary for the respiration of aquatic life and the oxidation of organic materials.

drainage area The land area contributing runoff to a stream or other body of water, and generally defined in terms of acres, square miles, or square kilometers.

effluent The sewage or industrial liquid waste which is released into natural waters by sewage treatment plants, industry, or septic tanks.

erosion The wearing away of the landscape by water, wind, ice, or gravity to smaller particles, usually sediment.

euphotic zone The depth to which one percent of incident surface light penetrates; the lighted zone of a waterbody.

eutrophic Literally, "nutrient rich." Generally refers to a fertile, productive body of water. Contrasts with oligotrophic.

eutrophication The natural process by which lakes and ponds become enriched with dissolved nutrients, resulting in increased growth of algae and other microscopic plants and reduced water clarity.

flow The rate of water discharged past a point expressed in water volume per unit time.

hydraulic residence time The amount of time it would take to completely fill a lake if it were empty.

hypolimnion The lowermost, non-circulating layer of cold water in a thermally stratified lake; usually deficient in oxygen.

limnology The branch of science pertaining to the study of the physical, chemical, biological, and ecological aspects of fresh water; the structure and dynamics of ponds, lakes, streams and wetlands.
littoral zone That portion of a lake or pond extending from the shoreline lakeward to the greatest depth occupied by rooted aquatic plants.

load The amount of substance, usually nutrients or sediment, discharged past a point; expressed in weight per unit time.

macrophyte The larger, non-microscopic aquatic plants found in shallow areas of lakes and streams.
mean depth A lake’s volume divided by its surface area.

mesotrophic Literally, "moderate nutrients." Generally refers to a moderately fertile body of water.

model A simulation by descriptive, statistical or other means, of a process otherwise difficult or impossible to observe directly.

nitrogen An essential nutrient for aquatic organisms, comprising 80% of the earth's atmosphere.

nonpoint source pollution Pollution discharged over a wide land area, not from one specific location.
nutrient loading The addition of nutrients, usually nitrogen or phosphorus, to a water body (often expressed as g/m2 of lake surface area per year) . The majority of nutrient loading in a lake usually comes from its tributaries.

nutrients Elements or compounds essential to life, including but not limited to oxygen, carbon, nitrogen, and phosphorus.

oligotrophic Literally, "nutrient poor." Generally refers to an infertile, unproductive body of water. Contrasts with eutrophic.

pelagic In the open waters of a lake; removed from shoreline effects.

pelagic zone The open area of a lake from the littoral zone to the center of the lake.

phosphorus An essential nutrient for aquatic organisms derived from weathered rock and human sources.

phytoplankton Usually microscopic aquatic plants (sometimes consisting of only a cell).

point source pollution Pollutants discharged from any identifiable point, including pipes, ditches, channels, sewers, tunnels, and containers of various types.

pollution Any alteration in the character or quality of the environment which renders it unfit or less suited for beneficial uses.

primary production The synthesis of organic compounds by green plants in the presence of elements (e.g. nitrogen, phosphorus) and light energy.

riparian area The area of land next to a stream, river or lake. Maintenance of natural plants in the riparian area serves to protect water temperature and acts like a filter for runoff.

secchi depth The mean depth at which a black and white disk 20 centimeters in diameter is no longer visible from the water surface; a measure of water transparency.

sediment Fragmented organic and inorganic material derived from the weathering of soil, alluvial, and rock materials removed by erosion and transported by water, wind, ice, and gravity.

sewage The water-carried human and animal waste from residences, buildings, industrial establishments, or other places, together with groundwater infiltration and surface water.

stormwater runoff Surface water runoff, usually associated with urban development, which carries both natural and human-caused pollutants. Stormwater runoff can be conveyed to lakes, ponds, and streams either through point or nonpoint sources.

suspended sediment Solids, either organic or inorganic, found in a body of water, which can be removed by filtration. The origin of suspended matter may be man-made wastes or natural sources such as silt.

trophic status Referring to the nourishment status of a water body, e.g. oligotrophic, mesotrophic, eutrophic.

turbidity Cloudiness caused by the presence of suspended solids, such as clay, silt, and microscopic organisms in the water; an indicator of water quality.

wastewater Treated or untreated sewage, industrial waste, or agricultural waste with such water as is present. Sometimes referred to as effluent.

water clarity The ability of water to transmit light; often reported as secchi depth.

water quality A term used to describe the chemical, physical, and biological characteristics of water with respect to its suitability for a beneficial use.

water quality standard Legally mandated and enforceable maximum contaminant levels of chemical, physical, and biological parameters for water. These parameters are established for water used by municipalities, industries, agriculture, and recreation.

water year The twelve month period from October 1 to September 30, and designated by the calendar year in which the water year ends.

watershed An area of land that is drained by a distinct stream or river system and is separated from other similar systems by ridge-top boundaries.

wetlands Lands where water saturation of the soil for at least part of the year is the dominant factor determining the nature of soil development and the types of plant and animal communities living in the surrounding environment. Other common names for wetlands are sloughs, ponds, swamps, marshes, and riparian areas.