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Adaptive Management: A dynamic planning and implementation process that involves applying scientific principles, methods and tools to improve management activities incrementally, as decision makers learn from experience and better information and analytical tools become available. Involves frequent modification of planning and management strategies – and sometimes goals and objectives – in recognition of the fact that the future cannot be predicted perfectly. Requires frequent monitoring and analysis of the results of past actions and application of those results to current decisions.
Anadromous fish: Fish that hatch in fresh water, migrate to the ocean to grow and mature and return to fresh water to spawn; includes salmon, steelhead, and sea-run cutthroat trout.
Backwater pool: Found along channel margins; created by eddies around obstructions such as boulders, root wads, or woody debris. Part of active channel at most flows; scoured at high flow. Substrate typically sand, gravel, and cobble.
Basin: See drainage area.
Bedload: Sediment moving on or near the streambed and frequently in contact with it.
Benthos: Organisms living on or within a stream’s substrate.
Best Management Practice: Nonstructural and low-structural measures that are determined to be the most effective, practical means of preventing of reducing pollution inputs from nonpoint sources in order to achieve water quality goals.
Canopy: That overhead branches and leaves of streamside vegetation.
Canopy cover: The vegetation that projects over the stream. Can arbitrarily be divided into two levels: Crown canopy is more than 1 m above the surface. Overhanging cover is less than 1 m above the water surface.
Canopy density: The percentage of the stream covered by the canopy of plants, sometimes
Carrying Capacity: The maximum average number of biomass of organisms or a given species that can be sustained on a long-term basis under a given flow regime by a stream or stream reach.
Cascade: Habitat type characterized by swift current, exposed rocks and boulders, high gradient and considerable turbulence and surface agitation, and consisting of a stepped series of drops.
Channel: A natural or artificial waterway of perceptible extent that periodically or continuously contains moving water. It has a definite bed and banks, which serve to confine the water.
Channel confinement: Ration of bankfull channel width to width of modern floodplain. Modern floodplain is the flood-prone area and may correspond to the 100-year floodplain. Typically, channel confinement is a description of how much a channel can move within its valley before it is stopped by a hill slope or terrace.
Channelization: Straightening of a stream or the dredging of a new channel to which the stream is diverted.
Confluence: The junction or union of two or more streams; a body of water produced by the union of several streams.
Cover: Anything that provides protection form predators or ameliorates adverse conditions of streamflow and/or seasonal changes in metabolic costs. May be instream cover, turbulence, and/or overhead cover, and may be for the purposes of escape, feeding, hiding, or resting.
Degradation: The geologic process by which stream beds and floodplains are lowered in elevation by the removal of material. It is the opposite of aggradation.
Deposition: The settlement or accumulation of material out of the water column and onto the streambed. Occurs when the energy of flowing water is unable to support the load of
Discharge: Volume of water flowing in a given stream at a given place and within a given period of time, usually expressed as cubic feet per second (cfs) or m3/second.
Dissolved oxygen: The concentration of oxygen dissolved in water, expressed in mg/L or as a percent saturation, where saturation is the maximum amount of oxygen that can theoretically be dissolved in water at a given altitude and temperature. Dissolved oxygen is absorbed by fish and other aquatic organisms through gills or membranes.
Diversion: A temporal removal of surface flow from the channel.
Diversity index: The relationship of the number of taxa (richness) to the number of individuals per taxon (abundance) for a given community.
Drainage area: Total land area draining to any point in a stream, as measured on a map, aerial photo or other horizontal plane. Also called catchment area, watershed, and basin.
Ecological services: The functions that a natural resource provides to benefit the environment and human uses.
Ecosystem: The living and nonliving components of the environment that interact or function together; includes plant and animal organisms, the physical environment and the energy systems in which they exist.
Embeddedness: The degree that larger particles (boulders, rubble, or gravel) are surrounded or covered by fine sediment. Usually measured in classes according to percentage of coverage of larger particles by fine sediments.
Endangered Species Act: A law passed by the U.S. Congress in 1973 that established programs for the conservation of threatened and endangered plants and animals and the habitats in which they are found. The U.S. Fish and Wildlife Service maintain the list of threatened and endangered species.
Enhancement: An improvement of conditions that provide for the betterment over natural conditions of the aquatic, terrestrial, and recreational resources.
Fine Sediment: The fine-grained particles in stream banks and substrate. These have been defined by diameter, varying downward from 6 millimeters (mm).
Fish habitat: The aquatic environment and the immediately surrounding terrestrial environment that, combined, afford the necessary biological and physical support systems required by fish species during various life history stages.
Flood: Any flow that exceeds the Bankfull capacity of a stream or channel and flows out on the floodplain; greater than bankfull discharge.
Floodplain: Any flat, or nearly flat lowland that borders a stream and is covered by its waters at flood stage.
Flow: (a) The movement of a stream of water and/or other mobile substances from place to place. (b) The movement of water, and the moving water itself. (c) The volume of water passing a given point per unit of time. See discharge.
base flow: The portion of the stream discharge that is derived from natural storage i.e., groundwater outflow and the drainage of lakes and wetlands or other source outside the net precipitation that creates surface runoff; discharge sustained in a stream channel, not a result of direct runoff and without the effects of regulation, diversion, or other works of humans. Also, called sustaining, normal, ordinary or groundwater flow.
instream flow: Streamflow regime required to satisfy a mixture of conjunctive demands being placed on water while it is in the stream.
intragravel flow: That portion of the surface water that infiltrates the stream bed and moves through the substrate pores. Also known as interstitial flow.
low flow: The lowest discharge recorded over a specified period of time. Also called minimum flow.
mean flow: The average discharge at a given stream location, usually expressed in m3/sec, computed for the period of record by dividing the total volume of flow by the number of days, months, or years in the specified period.
minimum flow: (a) The lowest discharge recorded over a specified period of time (preferred definition). (b) Negotiated lowest flow in a regulated stream that will sustain an aquatic population at agreed upon levels. This flow may vary seasonally. Also known as least flow.
peak flow: The highest discharge recorded over a specified period of time. Often thought of in terms of spring snowmelt, summer, fall or winter rainy season flow. Also called maximum flow.
Fry: The early life stage of salmon and trout after the yolk sac is absorbed.
Geomorphologic: Relating to the form or surface features of the earth.
Glide: An area with generally uniform depth and flow with no surface turbulence. Low gradient, 0-1 percent slope. Glides may have some small scour areas but are distinguished from pools by their overall homogeneity and lack of structure. Generally deeper than riffles with few major flow obstructions and low habitat complexity. There is a general lack of consensus regarding the definition of glides (Hawkins et al. 1993).
Gradient: (a) The general slope, or rate of change in vertical elevation per unit of horizontal distance, of the water surface of a flowing stream. (b) The rate of change of any characteristic per unit of length.
Habitat: The place where a population lives and its surroundings, both living and nonliving; includes the provision of life requirements such as food and shelter.
Habitat type: A land or aquatic unit, consisting of an aggregation of habitats having equivalent structure, function, and responses to disturbance.
Hydrograph: A graph showing, for a given point on a stream, the discharge, stage, velocity, or other property of water with respect to time.
Impervious surface: An impermeable ground coverage or surface, such as paved roads, sidewalks and structures, that alters the natural flow and quality of water.
Indicator Organism: Organisms that respond predictably to various environmental changes, and whose presence or absence, and abundance, are used as indicators of environmental conditions.
Instream Cover: Areas of shelter in a stream channel that provide aquatic organisms protection form predators or competitors and/or a place in which to rest and conserve energy due to a reduction in the force of the current.
Large organic debris: Any large piece of relatively stable woody material having at least a diameter greater than 10 cm and a length greater than 1 m that intrudes into the stream channel. Also known as LOD, large wood debris, log.
Macroinvertebrate: An invertebrate animal (without backbone) large enough to be seen without magnification.
Mainstem: The principal, largest, or dominating stream or channel of any given area or drainage system.
Microhabitat: That specific combination of habitat elements in the locations selected by organisms for specific purposes and/or events. Expresses the more specific and functional aspects of habitat and cover. Separated from adjoining microhabitats by distinctive physical characteristics such as velocity, depth, cover, etc.
Nonpoint source: Sources of pollution from diffuse sources such as stormwater runoff from agriculture, logging, and roadways.
Opportunities: Watershed conditions or features that are currently in a healthy, properly functioning condition and that are considered key to sustaining important watershed functions.
Optimal value: A value that reflects either a desired condition or response in an environmental indicator or the level below which ecological functioning is likely to be impaired.
Overbank storage: Flow of water out of the stream channel and onto the valley floor floodplain during flood flows.
Overhead cover: Material (organic or inorganic) that provides protection to fish or other aquatic animals from above; generally includes material overhanging the stream less than a particular distance above the water surface. Values of less than 0.5 m and less than 1 m have been used.
Permeability: A measure of the rate at which water can pass through a given substrate. Depends upon composition and degree of compaction of the substrate (usually gravel). The apparent velocity per unit of hydraulic gradient. Units: cm/hr.
Pool: (a) A portion of the stream with reduced current velocity, often with water deeper than the surrounding areas, and which is frequently usable by fish for resting and cover. (b) A small body of standing water, e.g., in a marsh or on the flood plain.
Pool-riffle ratio: The ration of the 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.
Productivity: (a) Rate of new tissue formation or energy utilization by one or more organisms. (b) Capacity or ability of an environmental unit to produce organic material. (c) The ability of a population to recruit new members by reproduction.
Problems: Watershed conditions or features that are not properly functioning or that are contributing to impairment of watershed and river health.
Reach: A section of stream defined by some functional characteristic and possessing similar physical features such as gradient and confinement. A reach may be simply the distance surveyed. More frequently, reaches are defined as: stream segments between named tributaries, changes in valley and channel form, major changes in vegetation type, or changes in landuse or ownership.
Refugia: Locations and habitats that support populations of organisms limited to small fragments of their previous geographic range.
Restoration: Return of an ecosystem to a close approximation of its condition prior to disturbance.
Riffle: Fast, turbulent, shallow flow over submerged or partially submerged gravel and cobble substrates. Generally broad, uniform cross section. Low gradient; usually 0.5-2.0 percent slope, rarely up to 6 percent.
Riparian: Pertaining to anything connected with or immediately adjacent to the banks of a stream or other body of water.
Riparian area: The area between a stream or other body of water and the adjacent upland identified by soil characteristics and distinctive vegetation. It includes wetlands and those portion of floodplains and valley bottoms that support riparian vegetation.
Riparian vegetation: Vegetation growing on or near the banks of a stream or other body of water on soils that exhibit some wetness characteristics during some portions of the growing season.
Riprap: A layer of large, durable materials (usually rock but sometimes broken concrete, etc.) used to protect a stream bank from erosion. May also refer to the materials themselves.
Rootwad: The root mass of the tree. Similar to butt ends.
Sediment: Fragmental material that originates from weathering of rocks and decomposition of organic material that is transported by, suspended in, and eventually deposited by water or air, or is accumulated in beds by other natural phenomena.
Sediment discharge: The mass or volume of sediment (usually mass) passing a stream transect in a unit of time. The term may be qualified, for example, as suspended-sediment discharge, bedload discharge, or total-sediment discharge, usually expressed as tons per day.
Sediment load: A general term that refers to sediment moved by a stream, whether is suspension (suspended load) or at the bottom (bedload). It is not synonymous with either discharge or concentration (see bedload).
Seep: An area of minor groundwater outflow onto the land surface or into a stream channel. Flows are too small to be a spring.
Stream Corridor: A stream corridor is usually defined by geomorphic formation, with the corridor occupying the continuous low profile of the valley. The corridor contains a perennial, intermittent, or ephemeral stream and adjacent vegetative fringe.
Substrate: The mineral and/or organic material that forms the bed of the stream.
Terraces: An embankment, or combination of an embankment and channel, constructed across a slope to control erosion by reducing the slope and by diverting or storing surface runoff instead of permitting it to flow uninterrupted down the slope.
Total suspended solids: The organic and inorganic material left on a standard glass fiber filter (0.45 μ filter); after a water sample is filtered through it; often referred to as Non-Filterable Residue.
Toxic metals: Metals present in industrial, municipal, and urban runoff, including lead, copper, cadmium, zinc, mercury, nickel, and chromium, in quantities that are harmful to humans or aquatic life.
Toxic substances: Any substances present in water, wastewater, or runoff that may kill fish or other aquatic life or could be harmful to public health. The substance may exhibit chronic toxicity or buildup in the food chain (biomagnification), or it may show acute toxicity and result in immediate death. Ammonia, acids, cyanides, phenols, toxic metals, and chlorinated hydrocarbons, among others, are examples of toxic substances.
Tributary: A stream feeding, joining, or flowing into a larger stream.
Turbidity: (a) Relative water clarity. (b) A measure of the extent to which light passing through water is reduced due to suspended materials. Measured by several non-equivalent standards (e.g., Nephelometric Turbidity Units, NTU; Formazin Turbidity Units, FTU; and Jackson Turbidity Units, JTU).
Watershed: A topographically discrete unit or stream basin that includes the headwaters, main channel, slopes leading to the channel, tributaries and mouth area.
See Drainage area.
Weir: (a) A notch or depression in a levee, dam, embankment, or other barrier across or bordering a stream, through which the flow of water is measured or regulated. (b) A barrier constructed across a stream to divert fish into a trap. (c) A dam (usually small) in a stream to raise the water level or divert its flow.
Wetland: Wetlands are lands transitional between terrestrial and aquatic systems where the water table is usually at or near the surface or the land is covered by shallow water (Cowardin et al., 1979). Wetlands include features that are predominantly wet, or intermittently water covered, such as swamps, marshes, bogs, muskegs, potholes, swales, glades, slashes, and overflow land of river valleys. According to the 1989 federal wetlands delineation manual, wetlands include lands saturated for at least 7 days to a depth of 12 inches. A newly proposed definition by the Bush Administration would be lands that have 15 days of standing water and 21 days of surface saturation. Land areas where excess water is the dominant factor determining the nature of soil development and the types of plant and animal species living at the soil surface. Wetland soils retain sufficient moisture to support aquatic or semi-aquatic plant life. An area subject to periodic inundation, usually with soil and vegetative characteristics that separate it from adjoining non-inundating areas.
Woody Debris: See large organic debris.
