PSMFC Homepage
StreamNet's home page StreamNet's mission, services, and participants Locate fish-related data StreamNet's largest data resource, regularly updated ("integrated" interface). StreamNet's largest data resource, regularly updated (traditional interface). Locate data from a map interface. Obtain maps and GIS layers. Locate static data sets. Also, add your data sets to the archive. A full service library containing fish and wildlife literature and reports. Various other useful materials Links to other fisheries related resources on the Web 2004 U.S. District Court ruling on pesticides near salmon streams Stream reaches where hydroelectric development is discouraged Information and data in support of the NPCC Fish and Wildlife program Documents, reports, and newsletters produced by the StreamNet project Recommendations on how to cite data and information obtained from StreamNet Various other useful materials The latest data, but in the old look.


Other glossaries of fisheries terms are available from North Carolina Division of Marine Fisheries and from the United Nations Fisheries and Agriculture Organization.
(The FAO glossary does not work with all web browsers.)

Abatement -- Reducing the degree or intensity of, or eliminating, pollution.

Ablation -- The process by which ice and snow waste away as a result of melting and/or evaporation.

Acid Rain -- Rainfall with a pH of less than 7.0. Long-term deposition of these acids is linked to adverse effects on aquatic organisms and plant life in areas with poor neutralizing (buffering) capacity.

Acidic -- The condition of water or soil that contains a sufficient amount of acid substances to lower the pH below 7.0.

Acre -- A measure of area equal to 43,560 square feet (4,046.87 square meters). One square mile equals 640 acres.

Acre-foot (af) -- The volume of water that will cover one acre to a depth of 1 foot.

Aeration -- Any active or passive process by which intimate contact between air and liquid is assured, generally by spraying liquid in the air, bubbling air through water, or mechanical agitation of the liquid to promote surface absorption of air.

Aerobic -- Characterizing organisms able to live only in the presence of air or free oxygen, and conditions that exist only in the presence of air or free oxygen. Contrast with Anaerobic.

Affluent (Stream) -- A stream or river that flows into a larger one; a Tributary.

Alluvial -- Deposited by running water.

Alluvium -- Sediment or loose material such as clay, silt, sand, gravel, and larger rocks deposited by moving water.

Anabranch -- A diverging branch of a river which re-enters the main stream.

Analytical watershed -- For planning purposes, a drainage basin subdivision used for analyzing cumulative impacts on resources.

Aquaduct -- A pipe or conduit made for bringing water from a source.

Aquatic habitat -- Habitat that occurs in free water.

Aquifer -- An underground layer of rock or soil containing ground water.

Augmentation (of stream flow) -- Increasing steam flow under normal conditions, by releasing storage water from reservoirs.

Backbar channel -- A channel formed behind a bar connected to the main channel but usually at a higher bed elevation than the main channel. Backbar channels may or may not contain flowing or standing water.

Backwater -- (1) A small, generally shallow body of water attached to the main channel, with little or no current of its own.

Backwater pool -- A pool that formed from an eddy along a channel margin as a result of an upstream obstruction like a large tree, rootwad, or boulder.

Bank stability -- The properties of a stream bank that counteract erosion, for example, soil type, and vegetation cover.

Bankfull width -- The width of a river or stream channel between the highest banks on either side of a stream.

Bar (stream or river bar) -- An accumulation of alluvium(gravel or sand) caused by a decrease in water velocity.

Barrier -- A physical block or impediment to the movement or migration of fish, such as a waterfall (natural barrier) or a dam (man-made barrier).

Barrier net -- A net system that is placed across a river, stream or channel to block the passage of fish from dam turbine intakes or other hazards without blocking the water flow.

Base flow -- The sustained portion of stream discharge that is drawn from natural storage sources, and not effected by human activity or regulation.

Bed load -- Sediment that moves near the streambed.

Bed Material -- The sediment mixture of which a streambed, lake, pond, reservoir, or estuary bottom is composed.

Benthos -- All the plant and animals living on or closely associated with the bottom of a body of water.

Bog -- Freshwater wetlands that are poorly drained and characterized by a buildup of peat.

Boulder -- A large substrate particle that is larger that cobble, >256 mm in diameter.

Brackish -- Having a somewhat salty taste, especially from containing a mixture of seawater and fresh water.

Brackish Water -- Generally, water containing dissolved minerals in amounts that exceed normally acceptable standards for municipal, domestic, and irrigation uses. Considerably less saline than sea water. Also, Marine and Estuarine waters with Mixohaline salinity (0.5 to 30 due to ocean salts). Water containing between 1,000-4,000 parts per million (PPM) Total Dissolved Solids TDS). The term brackish water is frequently interchangeable with Saline Water. The term should not be applied to inland waters.

Braided stream -- A complex tangle of converging and diverging stream channels (Anabranches) separated by sand bars or islands. Characteristic of flood plains where the amount of debris is large in relation to the discharge.

Braiding (of River Channels) -- Successive division and rejoining of riverflow with accompanying islands.

Brook -- A natural stream of water, smaller than a river or creek; especially a small stream or rivulet which breaks directly out of the ground, as from a spring or seep; also, a stream or torrent of similar size, produced by copious rainfall, melting snow and ice, etc.; a primary stream not formed by tributaries, though often fed below its source, as by rills or runlets; one of the smallest branches or ultimate ramifications of a drainage system.

Canal -- A constructed open channel for transporting water.

Canopy -- A layer of foliage in a forest stand. This most often refers to the uppermost layer of foliage, but it can be used to describe lower layers in a multistoried stand. Leavs, branches and vegetation that are above ground and/or water that provide shade and cover for fish and wildlife.

Cascade -- A short, steep drop in stream bed elevation often marked by boulders and agitated white water.

Catchment -- (1) The catching or collecting of water, especially rainfall. (2) A reservoir or other basin for catching water. (3) The water thus caught.

Channel -- An area that contains continuously or periodically flowing water that is confined by banks and a stream bed.

Channelization -- The process of changing and straightening the natural path of a waterway.

Clay -- Substrate particles that are smaller than silt and generally less than 0.004 mm in diameter.

Cobble -- Substrate particles that are smaller than boulders and are generally 64-256 mm in diameter. Can be further classified as small and large cobble. Commonly used by salmon in the construction of a redd.

Confluence -- (1) The act of flowing together; the meeting or junction of two or more streams; also, the place where these streams meet. (2) The stream or body of water formed by the junction of two or more streams; a combined flood.

Contaminate -- To make impure or unclean by contact or mixture.

Cubic feet per second (Cfs) -- A unit used to measure water flow. One cfs is equal to 449 gallons per minute.

Culvert -- A buried pipe that allows streams, rivers, or runoff to pass under a road.

Debris flow -- A rapid moving mass of rock fragments, soil, and mud, with more that half of the particles being larger that sand size.

Debris torrent -- Rapid movement of a large quantity of materials (wood and sediment) down a stream channel during storms or floods. This generally occurs in smaller streams and results in scouring of streambed.

Decomposer -- Any of various organisms (as many bacteria and fungi) that feed on and break down organic substances (such as dead plants and animals).

Decomposition -- The breakdown of matter by bacteria and fungi, changing the chemical makeup and physical appearance of materials.

Dike -- (1) (Engineering) An embankment to confine or control water, especially one built along the banks of a river to prevent overflow of lowlands; a levee. (2) A low wall that can act as a barrier to prevent a spill from spreading. (3) (Geology) A tabular body of igneous (formed by volcanic action) rock that cuts across the structure of adjacent rocks or cuts massive rocks.

Dissolved gas concentrations -- The amount of chemicals normally occurring as gases, such as nitrogen and oxygen, that are held in solution in water, expressed in units such as milligrams of the gas per liter of liquid. Supersaturation occurs when these solutions exceed the saturation level of the water (beyond 100 percent).

Dissolved Oxygen (DO) -- The amount of free (not chemically combined) oxygen dissolved in water, wastewater, or other liquid, usually expressed in milligrams per liter, parts per million, or percent of saturation.

Ditch -- A long narrow trench or furrow dug in the ground, as for irrigation, drainage, or a boundary line.

Diversion -- The transfer of water from a stream, lake, aquifer, or other source of water by a canal, pipe, well, or other conduit to another watercourse or to the land, as in the case of an irrigation system.

Diversion channel -- (1) An artificial channel constructed around a town or other point of high potential flood damages to divert floodwater from the main channel to minimize flood damages. (2) A channel carrying water from a diversion dam.

Down log -- Portion of a tree that has fallen or been cut and left in the woods.

Drainage -- An area (basin) mostly bounded by ridges or other similar topographic features, encompassing part, most, or all of a watershed and enclosing some 5,000 acres.

Dredging -- Digging up and removing material from wetlands or waterways, usually to make them deeper or wider.

Drought -- Generally, the term is applied to periods of less than average or normal precipitation over a certain period of time sufficiently prolonged to cause a serious hydrological imbalance resulting in biological losses (impact flora and fauna ecosystems) and/or economic losses (affecting man). In a less precise sense, it can also signify nature's failure to fulfill the water wants and needs of man.

Dry Wash -- A streambed that carries water only during and immediately following rainstorms.

Eddy -- A circular current of water, usually resulting from an obstruction.

Effluent -- (1) Something that flows out or forth, especially a stream flowing out of a body of water. (2) (Water Quality) Discharged wastewater such as the treated wastes from municipal sewage plants, brine wastewater from desalting operations, and coolant waters from a nuclear power plant.

Embankment -- An artificial deposit of material that is raised above the natural surface of the land and used to contain, divert, or store water, support roads or railways, or for other similar purposes.

Enhancement -- Emphasis on improving the value of particular aspects of water and related land resources.

Ephemeral Streams -- Streams which flow only in direct response to precipitation and whose channel is at all times above the water table.

Erosion -- Wearing away of rock or soil by the gradual detachment of soil or rock fragments by water, wind, ice, and other mechanical, chemical, or biological forces.

Eutrophic -- Usually refers to a nutrient-enriched, highly productive body of water.

Eutrophication -- The process of enrichment of water bodies by nutrients.

Evaporation -- The physical process by which a liquid (or a solid) is transformed to the gaseous state. In Hydrology, evaporation is vaporization that takes place at a temperature below the boiling point.

Fill -- (Geology) Any sediment deposited by any agent such as water so as to fill or partly fill a channel, valley, sink, or other depression.

Fish flows -- "Artificially increased flows in the river system called for in the fish and wildlife program to quickly move the young fish down the river during their spring migration period. (See ""water budget."")"

Flash Flood -- A sudden flood of great volume, usually caused by a heavy rain. Also, a flood that crests in a short length of time and is often characterized by high velocity flows. It is often the result of heavy rainfall in a localized area.

Floodplain -- Land that gets covered with water as a result of the flooding of a nearby stream. Or level lowland bordering a stream or river onto which the flow spreads at flood stage.

Floodplain (100-year) -- The area adjacent to a stream that is on average inundated once a century.

Flow -- The amount of water passing a particular point in a stream or river, usually expressed in cubic-feet per second (cfs).

Flow augmentation -- Increased flow from release of water from storage dams.

Fluvial -- Migrating between main rivers and tributaries. Of or pertaining to streams or rivers.

Ford -- A shallow place in a body of water, such as a river, where one can cross by walking or riding on an animal or in a vehicle.

Freshet -- A rapid temporary increase in stream flow due to heavy rains or snow melt.

Freshwater marsh -- Open wetlands that occur along rivers and lakes.

Freshwater swamp -- Forested or shrubby wetlands.

Gabion -- A wire basket or cage that is filled with gravel and generally used to stabilize stream banks and improve degraded aquatic habitat.

Gaging station -- A particular site in a stream, lake, reservoir, etc., where hydrologic data are obtained.

Gallons per minute (Gpm) -- A unit used to measure water flow.

Glide -- A section of stream that has little or no turbulence.

Gradient -- Vertical drop per unit of horizontal distance.

Gravel -- See cobble.

Gray Water -- Waste water from a household or small commercial establishment which specifically excludes water from a toilet, kitchen sink, dishwasher, or water used for washing diapers.

Groundwater -- Subsurface water and underground streams that can be collected with wells, or that flow naturally to the earth's surface though springs.

Hazardous materials -- Anything that poses a substantive present or potential hazard to human health or the environment when improperly treated, stored, transported, disposed of, or otherwise managed.

Headwater -- Referring to the source of a stream or river

Heavy metals -- Metallic elements with high atomic weights, e.g., mercury, chromium, cadmium, arsenic, and lead. They can damage living things at low concentrations and tend to accumulate in the food chain.

Hydric -- Wet.

Hydrologic unit -- A distinct watershed or river basin defined by an 8-digit code.

Hydrology -- The scientific study of the water of the earth, its occurrence, circulation and distribution, its chemical and physical properties, and its interaction with its environment, including its relationship to living things.

Hyporheic zone -- The area under the stream channel and floodplain that contributes to the stream.

Incised River -- A river which cuts its channel through the bed of the valley floor, as opposed to one flowing on a floodplain; its channel formed by the process of degradation.

Infiltration (soil) -- The movement of water through the soil surface into the soil.

Inflow -- Water that flows into a reservoir or forebay during a specified period.

Instantaneous flows -- The velocity of a volume of water.

Instream cover -- The layers of vegetation, like trees, shrubs, and overhanging vegetation, that are in the stream or immediately adjacent to the wetted channel.

Instream flows -- See flows.

Intermittent stream -- Any nonpermanent flowing drainage feature having a definable channel and evidence of scour or deposition. This includes what are sometimes referred to as ephemeral streams if they meet these two criteria.

Invertebrate drift -- Stream and terrestrial invertebrates that float with the current.

Irrigation diversion -- Generally, a ditch or channel that deflects water from a stream channel for irrigation purposes.

KCFS -- A measurement of water flow equivalent to 1,000 cubic feet of water passing a given point for an entire second.

Kcfs-month -- One kcfs-month is a flow of 1,000 cubic feet per second for one month or 0.0595 million acre-feet.

Key watershed -- As defined by National Forest and Bureau of Land Management District fish biologists, a watershed containing (1) habitat for potentially threatened species or stocks of anadromous salmonids or other potentially threatened fish, or (2) greater than 6 square miles with high-quality water and fish habitat.

Landslide -- A movement of earth down a steep slope.

Large woody debris -- Pieces of wood larger than 10 feet long and 6 inches in diameter, in a stream channel.

Leave strips -- Generally narrow bands of forest trees that are left along streams and rivers to buffer aquatic habitats from upslope forest management activities.

Levee -- An embankment constructed to prevent a river from overflowing (flooding).

Limnology -- The study of lakes, ponds and streams.

Loading -- The influx of pollutants to a selected water body.

Lotic -- Meaning or regarding things in running water.

Macroinvertebrate -- Invertebrates visible to the naked eye, such as insect larvae and crayfish.

Macrophytes -- Aquatic plants that are large enough to be seen with the naked eye.

Mainstem -- The principle channel of a drainage system into which other smaller streams or rivers flow.

Mainstem passage -- The movement of salmon and steelhead around or through the dams and reservoirs in the Columbia and Snake rivers.

Mainstem survival -- The proportion of anadromous fish that survive passage through the dams and reservoirs while migrating in the Columbia and Snake rivers.

Mass movement -- The downslope movement of earth caused by gravity. Includes but is not limited to landslides, rock falls, debris avalanches, and creep. It does not however, include surface erosion by running water. It may be caused by natural erosional processes, or by natural disturbances (e.g., earthquakes or fire events) or human disturbances (e.g., mining or road construction).

Mesic -- Moderately wet.

Nonpoint source pollution -- Pollution that does not originate from a clear or discrete source.

Nutrient depletion -- Detrimental changes on a site in the total amount of nutrients and/or their rates of input, uptake, release, movement, transformation, or export.

Off-channel area -- Any relatively calm portion of a stream outside of the main flow.

Off-site enhancement -- The improvement in conditions for fish or wildlife species away from the site of a hydroelectric project that had detrimental effects on fish and/or wildlife, as part or total compensation for those effects. An example of off

Outfall -- The mouth or outlet of a river, stream, lake, drain or sewer.

Oxbow -- An abandoned meander in a river or stream, caused by neck cutoff. Used to describe the U-shaped bend in the river or the land within such a bend of a river.

Peat -- Partially decomposed plants and other organic material that build up in poorly drained wetland habitats.

Perennial streams -- Streams which flow continuously.

pH -- "The negative logarithm of the molar concentration of hydrogen ion. Or a more simple definition of pH is ""acidity."""

Plume -- The area of the Pacific Ocean that is influenced by discharge from the Columbia River, up to 500 miles beyond the mouth of the river.

Pluvial -- Of rain, formed by the action of rain, for example a body of water.

Point Source (PS) -- (1) A stationary or clearly identifiable source of a large individual water or air pollution emission, generally of an industrial nature. (2) Any discernible, confined, or discrete conveyance from which pollutants are or may be discharged, including (but not limited to) pipes, ditches, channels, tunnels, conduits, wells, containers, rolling stock, concentrated animal feeding operations, or vessels. Point source is also legally and more precisely defined in federal regulations. Contrast with Non-Point Source (NPS) Pollution.

Point Source (PS) Pollution -- Pollutants discharged from any identifiable point, including pipes, ditches, channels, sewers, tunnels, and containers of various types. See Non-Point Source (NPS) Pollution.

Pollutant -- (1) Something that pollutes, especially a waste material that contaminates air, soil, or water. (2) Any solute or cause of change in physical properties that renders water unfit for a given use.

Pool -- A reach of stream that is characterized by deep low velocity water and a smooth surface.

Pool/riffle ratio -- The ratio of surface area or length of pools to the surface area or length of riffles in a given stream reach; frequently expressed as the relative percentage of each category. Used to describe fish habitat rearing quality.

Rapids -- A reach of stream that is characterized by small falls and turbulent high velocity water.

Reach -- A section of stream between two defined points.

Rearing habitat -- Areas in rivers or streams where juvenile salmon and trout find food and shelter to live and grow.

Rearing pond -- An artificial impoundment in which juvenile salmon and steelhead are raised prior to release into the natural habitat.

Recreational Rivers -- Rivers or sections of rivers that are readily accessible by road or railroad, that may have some development along their shoreline, and that may have undergone some impoundment or diversion in the past.

Restoration -- The renewing or repairing of a natural system so that its functions and qualities are comparable to its original, unaltered state.

Riffle -- A reach of stream that is characterized by shallow, fast moving water broken by the presence of rocks and boulders.

Rift -- A shallow or rocky place in a stream, forming either a ford or a rapid.

Riparian area -- An area of land and vegetation adjacent to a stream that has a direct effect on the stream. This includes woodlands, vegetation, and floodplains.

Riparian habitat -- The aquatic and terrestrial habitat adjacent to streams, lakes, estuaries, or other waterways.

Riparian vegetation -- The plants that grow rooted in the water table of a nearby wetland area such as a river, stream, reservoir, pond, spring, marsh, bog, meadow, etc.

Ripple -- (1) To form or display little undulations or waves on the surface, as disturbed water does. (2) To flow with such undulations or waves on the surface.

Riprap -- Usually refers to rocks or concrete structures used to stabilize stream or river banks from erosion.

River Channels -- Natural or artificial open conduits which continuously or periodically contain moving water, or which forms a connection between two bodies of water.

River miles -- Miles from the mouth of a river to a specific destination or, for upstream tributaries, from the confluence with the main river to a specific destination.

River Reach -- Any defined length of a river.

River Stage -- The elevation of the water surface at a specified station above some arbitrary zero datum (level).

Riverine -- Relating to, formed by, or resembling a river including tributaries, streams, brooks, etc.

Riverine habitat -- The aquatic habitat within streams and rivers.

Rock -- See cobble.

Rootwad -- The mass of roots associated with a tree adjacent or in a stream that provides refuge and nutrients for fish and other aquatic life.

Run (in stream or river) -- A reach of stream characterized by fast flowing low turbulence water.

Runoff -- Water that flows over the ground and reaches a stream as a result of rainfall or snowmelt.

Salinity -- The concentration of salt in a body of water. The salinity of a saltwater wetland changes whenever freshwater is added when it rains, and each time the saltwater is added or removed when tide rises and falls.

Sand -- Small substrate particles, generally referring to particles less than 2 mm in diameter. Sand is larger than silt and smaller than cobble or rubble.

Scenic Rivers -- Rivers or sections of rivers that are free of impoundments, with shorelines or watersheds still largely primitive, and shorelines largely undeveloped but accessible in places by roads.

Scour -- The erosive action of running water in streams, which excavates and carries away material from the bed and banks. Scour may occur in both earth and solid rock material.

Secchi Depth -- A relatively crude measurement of the turbidity (cloudiness) of surface water. The depth at which a Secchi Disc (Disk), which is about 10-12 inches in diameter and on which is a black and white pattern, can no longer be seen.

Secchi Disc -- A circular plate, generally about 10-12 inches (25.4-30.5 cm) in diameter, used to measure the transparency or clarity of water by noting the greatest depth at which it can be visually detected. Its primary use is in the study of lakes.

Sediment -- The organic material that is transported and deposited by wind and water.

Sedimentation -- Deposition of sediment.

Silt -- Substrate particles smaller than sand and larger than clay.

Siltation -- The deposition or accumulation of fine soil particles.

Sinuosity -- The amount of bending, winding and curving in a stream or river.

Slope -- The side of a hill or mountain, the inclined face of a cutting, canal or embankment or an inclination from the horizontal.

Slope stability -- The resistance of a natural or artificial slope or other inclined surface to failure by landsliding (mass movement).

Slough -- A shallow backwater inlet that is commonly exposed at low tide.

Snag -- Any standing dead, partially dead, or defective (cull) tree at least 10 inches in diameter at breast height and at least 6 feet tall.

Soft Water -- Water that contains low concentrations of metal ions such as calcium and magnesium. This type of water does not precipitate soaps and detergents. Compare to Hard Water.

Stone -- Rock fragments larger than 25.4 cm (10 inches) but less than 60.4 cm (24 inches).

Stream -- A general term for a body of flowing water; natural water course containing water at least part of the year. In Hydrology, the term is generally applied to the water flowing in a natural channel as distinct from a canal. More generally, as in the term Stream Gaging, it is applied to the water flowing in any channel, natural or artificial.

Stream Channel -- The bed where a natural stream of water runs or may run; the long narrow depression shaped by the concentrated flow of a stream and covered continuously or periodically by water.

Stream gradient -- A general slope or rate of change in vertical elevation per unit of horizontal distance of the water surface of a flowing stream.

Stream morphology -- The form and structure of streams.

Stream order -- A hydrologic system of stream classification. Each small unbranched tributary is a first order stream. Two first order streams join to make a second order stream. A third order stream has only first and second order tributaries, and so forth.

Stream reach -- An individual first order stream or a segment of another stream that has beginning and ending points at a stream confluence. Reach end points are normally designated where a tributary confluence changes the channel character or order.

Streambank erosion -- The wearing away of streambanks by flowing water.

Streambank stabilization -- Natural geological tendency for a stream to mold its banks to conform with the channel of least resistance to flow. Also the lining of streambanks with riprap, matting, etc., to control erosion.

Streambed -- The channel through which a natural stream of water runs or used to run, as a dry streambed.

Streamflow -- The rate at which water passes a given point in a stream or river, usually expressed in cubic feet per second (cfs).

Streamlet -- A small stream.

Substrate -- The composition of a streambed, including either mineral or organic materials.

Surface erosion -- The detachment and transport of soil particles by wind, water, or gravity. Or a groups of processes whereby soil materials are removed by running water, waves and currents, moving ice, or wind.

Surface Water -- All waters whose surface is naturally exposed to the atmosphere, for example, rivers, lakes, reservoirs, ponds, streams, impoundments, seas, estuaries, etc., and all springs, wells, or other collectors directly influenced by surface water.

Suspended sediment -- Sediment suspended in a fluid by the upward components of turbulent currents, moving ice, or wind.

Thalweg -- (1) The lowest thread along the axial part of a valley or stream channel. (2) A subsurface, ground-water stream percolating beneath and in the general direction of a surface stream course or valley. (3) The middle, chief, or deepest part of a navigable channel or waterway.

Torrent -- (1) A turbulent, swift-flowing stream. (2) A heavy downpour; a deluge.

Tributary -- A stream that flows into another stream, river, or lake.

Turbidity -- "The term ""turbid"" is applied to waters containing suspended matter that interferes with the passage of light through the water or in which visual depth is restricted."

Urban runoff -- Storm water from city streets and gutters that usually contains a great deal of litter and organic and bacterial wastes into the sewer systems and receiving waters.

Velocity -- In this concept, the speed of water flowing in a watercourse, such as a river.

Viscosity -- A measure of the resistance of a fluid to flow. For liquids, viscosity increases with decreasing temperature.

Wash -- (1) To carry, erode, remove, or destroy by the action of moving water. To be carried away, removed, or drawn by the action of water. Removal or erosion of soil by the action of moving water. (2) A deposit of recently eroded debris. (3) Low or marshy ground washed by tidal waters. A stretch of shallow water. (4) (Western United States) The dry bed of a stream, articularly a watercourse associated with an alluvial fan, stream, or river channel. Washes are often associated with arid environments and are characterized by large, high energy discharges with high bed-material load transport. Washes are often intermittent and their beds sparsely vegetated. (5) Turbulence in air or water caused by the motion or action of an oar, propeller, jet, or airfoil.

Washout -- (1) Erosion of a relatively soft surface, such as a roadbed, by a sudden gush of water, as from a downpour or floods. (2) A channel produced by such erosion.

Water Pollution -- Generally, the presence in water of enough harmful or objectionable material to damage the water's quality.

Water quality -- A term used to describe the chemical, physical, and biological characteristics of water, usually in respect to its suitability for a particular purpose.

Water yield -- The quantity of water derived from a unit area of watershed.

Waterfall -- A sudden, nearly vertical drop in a stream, as it flows over rock.

Watershed restoration -- Improving current conditions of watersheds to restore degraded fish habitat and provide long-term protection to aquatic and riparian resources.

Weir (fish trap) -- Usually a barrier constructed to catch upstream migrating adult fish.

Wild Rivers -- Rivers or sections of rivers that are free of impoundments and generally inaccessible except by trail, with watersheds or shorelines essentially primitive and waters unpolluted.