CWTA - Watershed - Watershed Glossary




Connecticut Water Trails Association

"The difference between the right word and the nearly right word is the same as that between lightning and the lightning bug.” – Mark Twain

Table Of Contents

Connecticut Water Trails

Basic Concepts

Paddling Resources

Types Of Water Ways

Watershed Main Page

Connecticut Water Trails Program

Watersheds

Watershed Glossary

Ablation - The process by which ice and snow waste away owing to melting and evaporation.

Absorption - The entrance of water into the soil or rocks by all natural processes. It includes the infiltration of precipitation or snowmelt, gravity flow of streams into the valley alluvium (see Bank storage) into sinkholes or other large openings, and the movement of atmospheric moisture.

Acre-foot - A unit for measuring the volume of water, is equal to the quantity of water required to cover 1 acre to a depth of 1 foot and is equal to 43,560 cubic feet or 325,851 gallons. The term is commonly used in measuring volumes of water used or stored.

Acute Toxicity – Toxic effects (usually lethal or sub-lethal) due to short-term exposures to chemicals.

Advanced Wastewater Treatment – Wastewater treatment that extends beyond the secondary, or biological stage, of treatment and includes the removal of nutrients and suspended solids.

Aerobic – Containing oxygen. For instance: conditions that contain oxygen, organisms that require oxygen to survive or any chemical/biological processes that occur in the presence of oxygen.

Algae – Members of a large group of primarily aquatic organisms that contain chlorophyll and other pigments and can carry out photosynthesis, but lack true roots, stems, or leaves and range from single cells to large multi-cellular structures. Examples of algae include seaweed, kelp, dinoflagellates, and diatoms.

Algal Bloom – The rapid growth of algae in a system due to excessive amounts of nutrients and the appropriate physical and chemical conditions.

Alkalinity – A measurement of the buffering ability of water (or the capacity of water to resist changes in pH), or the ability of a base to neutralize an acid.

Anabranch - A diverging branch of a river which reenters the mainstream.

Anaerobic – Lacking oxygen. For instance, conditions that lack oxygen, organisms that can survive without oxygen, and any chemical or biological processes that occurs without oxygen.

Anchor ice - Ice in the bed of a stream or upon a submerged body or structure.

Annual flood - The highest peak discharge in a water year.

Annual flood series - A list of annual floods.

Anoxia – Absence of oxygen.

Anoxic – Lacking oxygen.

Antecedent precipitation index - An index of moisture stored within a drainage basin before a storm.

Anthropogenic – Of, relating to, or impacts resulting from human activity.

Aquaculture – The cultivation and harvest of aquatic plants and animals.

Aquifer – A stratum of rock or soil that contains groundwater.

Area-capacity curve - A graph showing the relation between the surface area of the water in a reservoir and the corresponding volume.

Assimilative Capacity – Capacity of a water body or watershed to receive and absorb pollutants while maintaining designated uses and water quality standards.

Average discharge - In the annual series of the Geological Survey's reports on surface-water supply--the arithmetic average of all complete water years of record whether or not they are consecutive. Average discharge is not published for less than 5 years of record. The term "average" is generally reserved for average of record and "mean" is used for averages of shorter periods, namely, daily mean discharge.

Backwater - Water backed up or retarded in its course as compared with its normal or natural condition of flow. In stream gaging, a rise in stage produced by a temporary obstruction such as ice or weeds, or by the flooding of the stream below. The difference between the observed stage and that indicated by the stage-discharge relation, is reported as backwater.

Bank - The margins of a channel. Banks are called right or left as viewed facing in the direction of the flow.

Bankfull stage - Stage at which a stream first overflows its natural banks. (See also Flood stage. Bankfull stage is a hydraulic term, whereas flood stage implies damage.)

Bank storage - The water absorbed into the banks of a stream channel, when the stages rise above the water table in the bank formations, then returns to the channel as effluent seepage when the stages fall below the water table.

Base discharge (for peak discharge) - In the Geological Survey's annual reports on surface-water supply, the discharge above which peak discharge data are published. The base discharge at each station is selected so that an average of about three peaks a year will be presented. (See also Partial-duration flood series.)

Base flow – The amount of stream flow contributed by groundwater sources.

Base runoff - Sustained or fair weather runoff. In most streams, base runoff is composed largely of groundwater effluent. The term base flow is often used in the same sense as base runoff. However, the distinction is the same as that between streamflow and runoff. When the concept in the terms base flow and base runoff is that of the natural flow in a stream, base runoff is the logical term. (See also Ground-water runoff and Direct runoff.)

Baseline Data – Information providing a look at existing chemical, biological, or physical conditions.

Basic hydrologic data - Includes inventories of features of land and water that vary only from place to place (topographic and geologic maps are examples), and records of processes that vary with both place and time. (Records of precipitation, streamflow, ground-water, and quality-of-water analyses are examples.) Basic hydrologic information is a broader term that includes surveys of the water resources of particular areas and a study of their physical and related economic processes, interrelations and mechanisms.

Basic-stage flood series - See Partial duration flood series.

Beneficial Use – Uses of a water resource, such as recreation, aquatic life, and human consumption, that are protected by state water quality standards.

Benthic Macroinvertebrates – animals without backbones or internal skeletons that live on or near the bottom of a water body.

Benthos – All organisms living at or near the bottom of an aquatic habitat.

Best Management Practices (BMPs) – Methods, measures, or practices to prevent and/or reduce water pollution. Examples include treatment requirements, operating procedures, erosion control practices, fertilizer and animal waste management, runoff control in urban systems, etc.

Bioaccumulation – The process by which contaminants accumulate within the tissues of an individual organism.

Biochemical Oxygen Demand (BOD) – The potential amount of oxygen consumed in the degradation of organic material by bacteria.

Biological Assessment – Evaluations of the condition of water bodies using surveys and other direct measurements of species diversity and species abundance (of macroinvertebrates, fish, and plants) to determine whether water bodies support survival and reproduction of desirable fish, shellfish, and other aquatic species and how aquatic life reacts to water quality.

Biological Diversity (Biodiversity) - The number and variety of living organisms on earth in all forms and at all levels, including ecosystem diversity, species diversity, and genetic diversity.

Biological Wastewater Treatment – Treatment process in which bacterial or biochemical activity is used to treat organic matter present in wastewater.

Biological Integrity – Supporting and maintaining the biological components of an aquatic ecosystem to a level comparable to that of natural habitats of the surrounding region.

Bioindicators – Organisms used to determine changes in water quality and/or pollutant levels within a system.

Biota – All of the organisms, including bacteria, plants, and animals, that live in a particular location or area.

Braiding of river channels - Successive division and rejoining (of riverflow ) with accompanying islands is the important characteristic denoted by the synonymous terms, braided or anastomosing stream. A braided stream is composed of anabranches.

Buffer – A vegetated area, forested or otherwise vegetated, located between water bodies such as stream, wetlands, and lakes, that provides a permanent barrier against runoff from development, agriculture, construction, and other land uses. Buffers are designed to filter pollutants in runoff before the pollutants reach surface waters.

Catchment area - See Drainage basin.

CFS - Abbreviation of cubic feet per second .

CFS-day - The volume of water represented by a flow of 1 cubic foot per second for 24 hours. It equals 86,400 cubic feet, 1.983471 acre-feet, or 646,317 gallons.

CFSM - (cubic feet per second per square mile) The average number of cubic feet of water per second flowing from each square mile of area drained by a stream, assuming that the runoff is distributed uniformly in time and area.

Channel (watercourse) - An open conduit either naturally or artificially created which periodically or continuously contains moving water, or which forms a connecting link between two bodies of water. River, creek, run, branch, anabranch, and tributary are some of the terms used to describe natural channels. Natural channels may be single or braided (see Braiding of river channels) . Canal and floodway are some of the terms used to describe artificial channels.

Channel storage - The volume of water at a given time in the channel or over the flood plain of the streams in a drainage basin or river reach. Channel storage is great during the progress of a flood event.

Channelization – Hydrologic modifications and straightening of stream shape that may cause dramatic changes in the stream ecosystem.

Chemical Oxygen Demand (COD) – A measure of the amount of organic matter present in water or wastewater.

Chlorophyl A – Green pigment found in photosynthetic organisms that can be used as an indicator of algal biomass.

Chronic Toxicity – Toxic effects (usually non-lethal) due to long-term exposures to chemicals.

Climate - The sum total of the meteorological elements that characterize the average and extreme condition of the atmosphere over a long period of time at any one place or region of the earth's surface. The collective state of the atmosphere at a given place or over a given area within a specified period of time.

Climatic year - A continuous 12-month period during which a complete annual cycle occurs, arbitrarily selected for the presentation of data relative to hydrologic or meteorologic phenomena. The climatic year is usually designated by the calendar year during which most of the 12 months occur. (See Water year.)

Cloudburst - A torrential downpour of rain, which by its spottiness and relatively high intensity suggests the bursting and discharge of a whole cloud at once.

Coastal Zone - Coastal waters and adjacent shorelands that influence the uses of the ocean and its ecology, or whose uses and ecology are affected by the ocean. The Coastal Zone may include islands, transitional and intertidal areas, salt marshes, wetlands, and beaches.

Collaboration – A problem solving process in which parties work together informally to resolve an issue. The issue may or may not be contentious.

Combined Sewer Overflow – Discharge of the combination of stormwater and sanitary wastewater during storms when the capacity of the sewer system to transport, store, or treat the increased flow is exceeded.

Combined Sewer System – A wastewater collection and treatment system for both stormwater runoff and municipal sewage.

Concentration time - See Time of concentration.

Concordant flows - Flows at different points in a river system that have the same recurrence interval, or the same frequency of occurrence. It is most often applied to floodflows.

Condensation - The process by which water changes from the vapor state into the liquid or solid state. It is the reverse of evaporation.

Confluence – The point at which two rivers/streams/etc. flow together.

Connectivity – A measurement of the continuity of a corridor (riparian corridor, etc.). Connectivity promotes valuable natural functions, such as movement of animals through their habitat, transport of materials and energy, which help maintain the integrity of natural communities.

Consensus – A method of making collaborative decisions in which everyone agrees they can live with the decision and/or attempts are made to address all parties interests.

Conservation storage - Storage of water for later release for useful purposes such as municipal water supply, power, or irrigation in contrast with storage capacity used for flood control.

Consumptive use – The quantity of water absorbed by the crop and transpired or used directly in the building of plant tissue together with that evaporated from the cropped area. The quantity of water transpired and evaporated from a cropped area or the normal loss of water from the soil by evaporation and plant transpiration. (see also Water requirement ) The quantity of water discharged to the atmosphere or incorporated in the products of the process in connection with vegetative growth, food processing, or an industrial process

Consumptive use, net - The consumptive use decreased by the estimated contribution by rainfall toward the production of irrigated crops. (See Effective precipitation (3).) Net consumptive use is sometimes called crop irrigation requirement.

Consumptive waste - The water that returns to the atmosphere without benefiting man.

Contents - The volume of water in a reservoir. Unless otherwise indicated reservoir content is computed on the basis of a level pool and does not include bank storage.

Control - A natural constriction of the channel, a long reach of the channel, a stretch of rapids, or an artificial structure downstream from a gaging station that determines the stage-discharge relation at the gage.

A control may be complete or partial. A complete control exists where the stage-discharge relation at a gauging station is entirely independent of fluctuations in stage downstream from the control. A partial control exists where downstream fluctuations have some effect upon the stage-discharge relation at a gaging station. A control, either partial or complete, may also be shifting. Most natural controls are shifting to a degree, but a shifting control exists where the stagedischarge relation experiences frequent changes owing to impermanent bed or banks.

Correlation - The process of establishing a relation between a variable and one or more related variables. Correlation is simple if there is only one independent variable; multiple, if there is more than one independent variable. For gaging station records, the usual variables are the short-term gaging-station record and one or more long-term gaging-station records.

Correlative estimate - A discharge determined by correlation. A correlative estimate represents a likely value of the discharge for any particular period--commonly a month--according to a specified method of analysis.

Cost-Effective Solution – A financially viable solution to a problem.

Cost-Sharing – Sharing the costs of constructing and implementing a Best Management Practice (BMP) between more then one funding source.

Critical Habitat – Areas that are essential for the conservation of federally endangered or threatened species. Such areas may require protection or certain management practices.

Cryology - Science of ice and snow.

Cubic feet per second - A unit expressing rates of discharge. One cubic foot per second is equal to the discharge of a stream of rectangular cross section, 1 foot wide and 1 foot deep, flowing water an average velocity of 1 foot per second.

Current meter - An instrument for measuring the speed of flowing water. The Geological Survey uses a rotating cup meter.

Cusec - This abbreviation for cubic foot per second, common in the British Commonwealth countries (except Canada), is not used by the U.S. Geological Survey; instead, CFS is used.

Cycle - A regularly recurring succession of events such as the cycle of the seasons. Use of cycle to describe a group of wet years followed or preceded by a group of dry years is to be avoided.

Dead storage - The volume in a reservoir below the lowest controllable level.

Decomposition – The breakdown of organic substances by microorganisms.

Dependable yield, n-years - The minimum supply of a given water development that is available on demand, with the understanding that lower yields will occur once in n years, on the average.

Depletion - The progressive withdrawal of water from surface- or ground-water reservoirs at a rate greater than that of replenishment. (see Recession curve and streamflow depletion.)

Depression storage - The volume of water contained in natural depressions in the land surface, such as puddles.

Designated Uses – Uses for water resources identified by state water quality standards that must be upheld or achieved as required by the Clean Water Act (CWA). Examples of designated uses include aquatic habitat, fisheries, and public water supply.

Detention – The slowing, collecting, or detaining of stormwater runoff prior to release into receiving waters.

Direct runoff - The runoff entering stream channels promptly after rainfall or snowmelt. Superposed on base runoff, it forms the bulk of the hydrograph of a flood. See also surface runoff. The terms base runoff and direct runoff are time classifications of runoff. The terms ground-water runoff and surface runoff are classifications according to source.

Discharge – The release or placement of wastewater, dredged or fill materials, or other substances directly into surface waters.

Discharge rating curve - See Stage discharge relation.

Dissolved Oxygen – The amount of oxygen present in the water column. Dissolved oxygen is important for aerobic organisms and proper biological functioning. Less then 5 parts per million of oxygen in water can cause stress to aquatic organisms. The lower the oxygen concentrations, the greater the stress.

Distribution graph (distribution hydrograph) - A unit hydrograph of direct runoff modified to show the proportions of the volume of runoff that occurs during successive equal units of time.

Diversion - The taking of water from a stream or other body of water into a canal, pipe, or other conduit.

Double-mass curve - A plot on arithmetic cross-section paper of the cumulated values of one variable against the cumulated values of another or against the computed values of the same variable for a concurrent period of time.

Drainage area - The drainage area of a stream at a specified location is that area, measured in a horizontal plane, which is enclosed by a drainage divide.

Drainage basin - A part of the surface of the earth that is occupied by a drainage system, which consists of a surface stream or a body of impounded surface water together with all tributary surface streams and bodies of impounded surface water.

Drainage density - Length of all channels above those of a specified stream order per unit of drainage area.

Drainage divide - The rim of a drainage basin. (See Watershed.)

Drought - A period of deficient precipitation or runoff extending over an indefinite number of days, but with no set standard by which to determine the amount of deficiency needed to constitute a drought. Thus, there is no universally accepted quantitative definition of drought; generally, each investigator establishes his own definition.

Duration curve - See Flow-duration curve for one type.

Ecological Integrity – Supporting and maintaining all components, biological, physical, and chemical components, of an ecosystem to a level comparable to that of natural habitats of the surrounding region.

Ecosystem – The network of a biological community and its surrounding interconnected physical and chemical environment.

Edge - The outer boundary of a habitat patch.

Edge effect - A condition in which otherwise suitable habitat becomes less suitable for a species because it is adjacent to non-habitat land. This degradation of habitat may occur due to predation from species that live outside the patch, or increased competition with species that live outside the habitat patch.

Effective precipitation (rainfall) - That part of the precipitation that produces runoff.

Effluent – Treated or untreated wastewater that is discharged into the environment from a treatment plant, sewer, or industrial facility.

Endemic- An adjective that describes species that occur only in a limited number of places.

EPT – Insect groups (Ephemeroptera, Plecoptera, and Trichoptera) that are generally intolerant of many types of pollution. Low EPT abundance may signify poor water quality.

Epilimnion - thermal stratification.

Erosion – The wearing away of rock and soil due to wind, weathering, water, ice, or other physical, chemical, or biological forces. The rate of erosion may be increased by land-use activities.

Estuary - A coastal area where fresh water from rivers and streams mixes with salt water from the ocean. Bays, sounds, and lagoons along coasts may be estuaries. Segments of rivers and streams connected to estuaries are considered part of the estuary.

Eutrophication – Process by which a water body undergoes an increase in dissolved nutrients, often leading to algal blooms, low dissolved oxygen, and changes in community structure. This process occurs naturally over time, but can be accelerated by human activities that increase nutrient inputs into aquatic ecosystems.

Evaporation - The process by which water is changed from the liquid or the solid state into the vapor state. In hydrology, evaporation is vaporization that takes place at a temperature below the boiling point.

Evaporation opportunity (relative evaporation) - The ratio of the rate of evaporation from a land or water surface in contact with the atmosphere, to the evaporativity under existing atmospheric conditions. It is the ratio of actual to potential rate of evaporation, generally stated as a percentage.

Evaporation pan - An open tank used to contain water for measuring the amount of evaporation. The U.S. Weather Bureau class A pan is 4 feet in diameter, 10 inches deep, set up on a timber grillage so that the top rim is about 16 inches from the ground. The water level in the pan during the course of observation is maintained between 2 and 3 inches below the rim.

Evaporation Total - The sum of water lost from a given land area during any specific time by transpiration from vegetation and building of plant tissue; by evaporation from water surfaces, moist soil, and snow; and by interception. *** It has also been called "evaporation," "evaporation from land areas," "evapotranspiration," "total loss," "water losses," and "fly off."

Evaporativity (potential rate of evaporation) - The rate of evaporation under the existing atmospheric conditions from a surface of water that is chemically pure and has the temperature of the atmosphere.

Evapotranspiration. Water withdrawn from a land area by evaporation from water surfaces and moist soil and plant transpiration.

Evapotranspiration, potential - See Potential evapotranspiration.

Excessive rainfall - See Rainfall, excessive.

Exotic species – A recently introduced species, or a species that is living in a location that is outside of its normal or historical range.

Extinct species- A species no longer in existence

Extirpated species – A species no longer surviving in regions that were once part of their range.

Facilitation - Assistance provided to a group of people by an impartial party (facilitator) in order to help the group conduct a satisfying meeting or series of meetings.

Fecal Coliform – Bacteria found in the fecal matter of warm-blooded animals. Fecal coliform is harmless to human health, but is used as an indicator of other harmful pathogens.

Field capacity. See Field-moisture capacity.

Field-moisture capacity. The quantity of water which can be permanently retained in the soil in opposition to the downward pull of gravity.

Field-moisture deficiency. The quantity of water, which would be required to restore the soil moisture to field-moisture capacity.

Firn (firn snow). Old snow on the top of glaciers, granular and compact but not yet converted into ice. It is a transitional stage between snow and ice. Also called ne've'.

Firn line - The highest level to which the fresh snow on a glacier's surface retreats during the melting season. The line separating the accumulation area from the ablation area.

First Flush - Stormwater that initially runs off an area that is more polluted than the stormwater that runs off later.

Flood - An overflow or inundation that comes from a river or other body of water and causes or threatens damage.

Flood-control storage - Storage of water in reservoirs to abate flood damage. (See Retarding reservoir.)

Flood crest - See Flood peak.

Flood event - See Flood wave.

Flood-frequency curve - A graph showing the number of times per year on the average, plotted as abscissa, that floods of magnitude, indicated by the ordinate, are equaled or exceeded.

Flood, maximum probable - The largest flood for which there is any reasonable expectancy in this climatic era.

Flood peak - The highest value of the stage or discharge attained by a flood; thus, peak stage or peak discharge. Flood crest has nearly the same meaning, but since it connotes the top of the flood wave, it is properly used only in referring to stage--thus, crest stage, but not crest discharge.

Floodplain – Area of land on each side of a stream channel that is inundated periodically by flood waters.

Flood plane - The position occupied by the water surface of a stream during a particular flood. Also, loosely, the elevation of the water surface at various points along the stream during a particular flood.

Flood profile - A graph of elevation of the water surface of a river in flood, plotted as ordinate, against distance, measured in the downstream direction, plotted as abscissa. A flood profile may be drawn to show elevation at a given time, crests during a particular flood, or to show stages of concordant flows.

Flood routing - The process of determining progressively the timing and shape of a flood wave at successive points along a river.

Floods above a base - See Partial-duration flood series.

Flood stage - The gage height of the lowest bank of the reach in which the gage is situated. The term "lowest bank" is, however, not to be taken to mean an unusually low place or break in the natural bank through which the water inundates an unimportant and small area.

Flood wave - A distinct rise in stage culminating in a crest and followed by recession to lower stages.

Floodway - A part of the flood plain otherwise leveed, reserved for emergency diversion of water during floods. A part of the flood plain which, to facilitate the passage of floodwater, is kept clear of encumbrances.

Flood zone - The land bordering a stream which is subject to floods of about equal frequency; for example, a strip of the flood plain subject to flooding more often that once but not as frequently as twice in a century.

Flow-duration curve - A cumulative frequency curve that shows the percentage of time that specified discharges are equaled or exceeded.

Forest influences - Effects resulting from the presence of forest or brush upon climate, soil water, runoff, streamflow, floods, erosion, and soil productivity.

Fragmentation – The process whereby a large patch of habitat is broken down into many smaller patches of habitat, resulting in a loss in the amount and quality of habitat.

Frazil (frazil ice) - A French-Canadian term for fine spicular ice, derived from the French for cinders which this variety of ice most resembles. When formed in salt water, it is known as lolly ice. It is composed of fine particles which, when first formed, are colloidal and not seen in the water in which they are floating.

Gage height - The water-surface elevation referred to some arbitrary gage datum. Gage height is often used interchangeably with the more general term stage although gage height is more appropriate when used with a reading on a gage.

Gauging station- A particular site on a stream, canal, lake, or reservoir where systematic observations of hydrologic data are obtained.

Geodatabase- A GIS-based computer program where both mapping information and other data such as water quality can be combined, mapped, and tracked.

GIS (Geographical Information Systems) – Computer program for storing, mapping, analyzing, and displaying geographically-referenced data, that is, data identified according to location.

Glacier. Bodies of land ice that consist of recrystallized snow accumulated on the surface of the ground, and that move slowly downslope.

Greenway- A linear open space established along a natural corridor, such as a river, stream, ridgeline, rail-trail, canal, or other route for conservation, recreation, or alternative transportation purposes. Greenways can connect parks, nature preserves, cultural facilities, and historic sites with business and residential areas.

Groundwater – Water occurring beneath the earth’s surface, typically in aquifers, that supplies wells and springs, and is a key source of drinking water.

Ground-water outflow - That part of the discharge from a drainage basin that occurs through the ground water. The term "underflow" is often used to describe the ground-water outflow that takes place in valley alluvium (instead of the surface channel) and thus is not measured at a gaging station.

Ground-water runoff - That part of the runoff which has passed into the ground, has become ground water, and has been discharged into a stream channel as spring or seepage water. See also Base runoff and Direct runoff.

Guttation - The loss of water in liquid form from the uninjured leaf or stem of the plant, principally through water stomata.

Habitat – An area with specific physical and environmental conditions in which a particular plant or animal lives.

Habitat Integrity – Supporting and maintaining the physical and environmental conditions of an aquatic ecosystem to a level comparable to that of natural habitats of the surrounding region.

Hardness – The presence of mineral, such as calcium and magnesium, in surface and/or ground waters.

Heat budget, annual (of a lake) - The amount of heat necessary to raise the water from the minimum temperature of winter to the maximum temperature of summer.

Heavy Metals – Metals that do not degrade over time and are thus an environmental concern. Examples of heavy metals are cadmium, mercury, nickel, and lead.

Historical Data – Background information on historical conditions of an ecosystem and activities that may have occurred on or near the site of interest. Historical data will help understand the existing conditions of the ecosystem and may be useful in determining target conditions for restoration, etc.

Human-Induced Disturbances – Disturbances to ecosystem structure and function due to human activities and land-uses.

Hydric soils – Soils inundated with water long enough to become anaerobic. Hydric soils are often indicative of wetlands.

Hydrograph - A graph showing stage, flow, velocity, or other property of water with respect to time.

Hydrologic budget - An accounting of the inflow to, outflow from, and storage in, a hydrologic unit, such as a drainage basin, aquifer, soil zone, lake, reservoir, or irrigation project.

Hydrologic cycle - A convenient term to denote the circulation of water from the sea, through the atmosphere, to the land; and thence, with many delays, back to the sea by overland and subterranean routes, and in part by way of the atmosphere; also the many short circuits of the water that is returned to the atmosphere without reaching the sea.

Hydrologic equation - The equation balancing the hydrologic budget.

Hydrologic Unit Cataloging (HUC) – Cataloging of watersheds of various geographical scales, using numerical codes, developed by the USGS.

Hydrology – Movement and distribution of groundwater and surface water in a system.

Hyetograph Graphical representation of rainfall intensity against time.

Hypolimnion - See Thermal stratification.

Hypoxia – Low dissolved oxygen concentrations in aquatic environments.

Impaired Water – Water bodies with decreased water quality due to pollution that are only partially supporting, or do not support, their designated uses.

Impervious Surface – A surface that does not allow water to penetrate. Examples of impervious surfaces include asphalt, rooftops, and concrete.

Infiltration – The process by which a liquid draining or seeping into the earth, stormwater pipes, etc.

Infiltration capacity - The maximum rate at which the soil, when in a given condition, can absorb falling rain or melting snow.

Infiltration index - An average rate of infiltration, in inches per hour, equal to the average rate of rainfall such that the volume of rain fall at greater rates equals the total direct runoff.

Interception - The process and the amount of rain or snow stored on leaves and branches and eventually evaporated back to the air. Interception equals the precipitation on the vegetation minus stem flow and throughfall

Interest – A concern, need, or value which in a dispute often gives rise to a specific stance (see:"position") taken by a disputing party. Substantive interests are those relating to the topics or issues under dispute, such as a technical or policy issue. Procedural interests relate to the fairness and efficiency of the methods or rules guiding discussions a decision making. Psychological interests relate to the parties' feelings, for example feelings of respect, appreciation, independence, enjoyment.

Intermittent Stream – A stream that flows only at certain times of the year, or does not flow continuously.

Irrigated area - The gross farm area upon which water is artificially applied for the production of crops, with no reduction for access roads, canals, or farm buildings.

Irrigation - The controlled application of water to arable lands to supply water requirements not satisfied by rainfall.

Irrigation Efficiency - The percentage of water applied that can be accounted for in soil-moisture increase.

Irrigation requirement - The quantity of water, exclusive of precipitation, that is required for crop production. It includes surface evaporation and other economically unavoidable wastes.

Irrigation, supplemental - See Supplemental irrigation.

Isohyet - See Isohyetal line.

Isohyetal line (isohyet) - A line drawn on a map or chart joining points that receive the same amount of precipitation.

Lag - Variously defined as time from beginning (or center of mass) of rainfall to peak (or center of mass) of runoff.

Land Use – The way land is used or developed. For instance, the types of buildings/structures permitted on the land and the types of activities permitted on the land. Particular land uses are often associated with different types of pollution, such as erosion and sedimentation from construction activities.

Land Use Planning – Planning and creating policies to guide the way in which land and resources will be used.

Leachate – Water that picks up contaminants as it flows through wastes, pesticides, fertilizers, or other potential pollutants.

Limnology - That branch of hydrology pertaining to the study of lakes.

Loading – Entry of pollutants into a body of water.

Long-period variations - Secular when a cycle or a change in trend is completed within a century; climatic when the period of change runs through centuries or a few millennia; geologic when the period runs into geological time.

Low-flow frequency curve. -A graph showing the magnitude and frequency of minimum flows for a period of given length. Frequency is usually expressed as the average interval, in years, between recurrences of an annual minimum flow equal to or less than that shown by the magnitude scale.

Lysimeter - Structure containing a mass of soil, and designed to permit the measurement of water draining through the soil.

Mass curve - A graph of the cumulative values of a hydrologic quantity (such as precipitation or runoff), generally as ordinate, plotted against time or date as abscissa. (See Double-mass curve, and Residual-mass curve.)

Maximum probable flood - See Flood, maximum probable.

Meander – A curve in a river or stream. The winding of a stream channel.

Meander amplitude - Distance between points of maximum curvature of successive meanders of opposite phase in a direction normal to the general course of the meander belt, measured between centerlines of channels.

Meander belt - Area between lines drawn tangential to the extreme limits of fully developed meanders.

Meander breadth. The distance between the lines used to define the meander belt.

Meander length - Distance in the general course of the meanders between corresponding points of successive meanders of the same phase. Twice the distance between successive points of inflection of the meander wave.

Meromictic lake - A lake in which some water remains partly or wholly unmixed with the main water mass at circulation periods is said to be meromictic. The process leading to a meromictic state is termed meromixis The perennially stagnant deep layer of a meromictic lake is called the monimolimnion. The part of a meromictic lake in which free circulation can occur is called the mixolimnion. The boundary between the monimolimnion and the mixolimnion is called the chemocline.

Mitigation – Actions taken to avoid, reduce, or compensate for the effects of human-induced environmental damage. It can include projects such as restoration and enhancement of negatively impacted ecosystems, or creation of an ecosystem.

Mitigation Banking – The restoration, creation, enhancement, or, in exceptional circumstances, the preservation of wetlands or other ecological resources which will compensate for unavoidable wetland or other ecological resource losses at another site or in future development. (NCSE)

Moisture - Water diffused in the atmosphere or the ground.

Moisture equivalent - The ratio of (a) the weight of water which the soil, after saturation, will retain against a centrifugal force 1,000 times the force of gravity, to (b) the weight of the soil when dry.

Monitoring - Repeated observation, measurement, or sampling at a site, on a scheduled or event basis, for a particular purpose.

Mudflow - A well-mixed mass of water and alluvium which, because of its high viscosity and low fluidity as compared with water, moves at a much slower rate, usually piling up and spreading over the fan like a sheet of wet mortar or concrete.

Natural Disturbances – Natural events that disturb the structure and function of an ecosystem such as floods, drought, earthquakes, fire, lightning, etc.

Non-Point Source (NPS) Pollution – Pollution that enters water bodies from a variety of sources. NPS pollution is caused by runoff from rainfall or snowmelt that moves over and through the ground, washing natural and human-made pollutants into surface waters and underground sources of drinking water.

No-till Farming – Farming method in which the soil is left undisturbed.

Normal - A central value (such as arithmetic average or median) of annual quantities for a 30-year period ending with an even 10-year, thus 1921-50; 1931-60, and so forth. This definition accords with that recommended by the Subcommittee on Hydrology of the Federal Inter-Agency Committee on Water Resources.

Nutrients – Substances, such as nitrogen and phosphorous, required by plants and animals for growth. In some circumstances, excessive nutrient additions to surface waters may result in excessive algal/plant growth and, subsequently, the accumulation and decay of increased organic matter.

Nutrient Management – A best management practice (BMP) developed to minimize the amount of nutrients entering surface and ground waters by limiting the amount of nutrients applied to the land to only as much as the crop is estimated to use.

Overland flow - The flow of rainwater or snowmelt over the land surface toward stream channels. After it enters a stream, it becomes runoff.

Oxygen Demanding Materials – Materials such as organic wastes, food wastes, etc. that use up dissolved oxygen in the water column as they decompose.

PAH's- Polycyclic aromatic hydrocarbons, a group of organic contaminants that form from the incomplete combustion of hydrocarbons such as coal, oil, gas, wood, garbage, or other organic substances.

Partial-duration flood series - A list of all flood peaks that exceed a chosen base stage or discharge, regardless of the number of peaks occurring in a year. (Also called basic-stage flood series, or floods above a base.)

Pathogen – A disease-causing organism (viruses, bacteria, or fungi can be pathogenic organisms).

Percolation - The movement, under hydrostatic pressure, of water through the interstices of a rock or soil, except the movement through large openings such as caves.

Percolation, deep - In irrigation or farming practice, the amount of water that passes below the root zone of the crop or vegetation.

Perennial Stream – A stream that flows continuously throughout the year.

Pesticides – Chemicals or substances designed to eliminate insects and other pests.

Pesticide Management – A best management practice developed to reduce the pollution of water, soil, air, and non-targeted organisms by limiting the use, quantity, placement, timing, and application method of pesticides.

Point Source Pollution - Pollution that can be traced to a single point, or output, such as a pipe.

Pondage - Small-scale storage at a waterpower plant to equalize daily or weekly fluctuations in riverflow or to permit irregular hourly use of the water for power generation to accord with fluctuations in load.

Pool - A deep reach of a stream. The reach of a stream between two riffles. Natural streams often consist of a succession of pools and riffles.

Pools - A section of a stream with slow-moving, deep water. In natural streams pools and riffles are alternating.

Position - Stance taken by a party which indicates specific perspectives or solutions that the party will or will not accept.

Potential evapotranspiration - Water loss that will occur if at no time there is a deficiency of water in the soil for use of vegetation.

Potential natural water loss - The water loss during years when the annual precipitation greatly exceeds the average water loss. It represents the approximate upper limit to water loss under the type and density of vegetation native to a basin, actual conditions of moisture supply, and other basin characteristics, whereas potential evapotranspiration represents the hypothetical condition of no deficiency of water in the soil at any time for use of the type and density of vegetation that would develop.

Potential rate of evaporation - See Evaporativity.

Precipitation - As used in hydrology, precipitation is the discharge of water, in liquid or solid state, out of the atmosphere, generally upon a land or water surface. It is the common process by which atmospheric water becomes surface or subsurface water . The term "precipitation" is also commonly used to designate the quantity of water that is precipitated. Precipitation includes rainfall, snow, hail, and sleet, and is therefore a more general term than rainfall.

Rain - Liquid precipitation.

Rainfall - The quantity of water that falls as rain only. Not synonymous with precipitation.

Rainfall excess - The volume of rainfall available for direct runoff. It is equal to the total rainfall minus interception, depression storage, and absorption.

Rainfall, excessive - Rainfall in which the rate of fall is greater than certain adopted limits, chosen with regard to the normal precipitation (excluding snow) of a given place or area. In the U.S. Weather Bureau, it is defined, for States along the southern Atlantic coast and the Gulf coast, as rainfall in which the depth of precipitation is 0.90 inch at the end of 30 minutes and 1.50 inches at the end of an hour, and for the rest of the country as rainfall in which the depth of precipitation at the end of each of the same periods is 0.50 and 0.80 inch, respectively.

Reach - 1. The length of channel uniform with respect to discharge, depth, area, and slope. 2. The length of a channel for which a single gage affords a satisfactory measure of the stage and discharge. 3. The length of a river between two gaging stations. 4. More generally, any length of a river.

Receiving Waters – Surface waters, whether natural or man-made, into which materials are discharged.

Recession curve - A hydrograph showing the decreasing rate of runoff following a period of rain or snowmelt. Since direct runoff and base runoff recede at different rates, separate curves, called direct runoff recession curves or base runoff recession curves, are generally drawn. The term "depletion curve" in the sense of base runoff recession is not recommended.

Recurrence interval (return period). The average interval of time within which the given flood will be equaled or exceeded once.

Regime - "Regime theory" is a theory of the forming of channels in material carried by the streams. As used in this sense, the word "regime" applies only to streams that make at least part of their boundaries from their transported load and part of their transported load from their boundaries, carrying out the process at different places and times in any one stream in a balanced or alternating manner that prevents unlimited growth or removal of boundaries. A stream, river, or canal of this type is called a "regime stream, river, or canal." A regime channel is said to be "in regime" when it has achieved average equilibrium; that is, the average values of the quantities that constitute regime do not show a definite trend over a considerable period--generally of the order of a decade. In unspecialized use "regime" and "regimen" are synonyms.

Regimen of a stream - The system or order characteristic of a stream; in other words, its habits with respect to velocity and volume, form of and changes in channel, capacity to transport sediment, and amount of material supplied for transportation. The term is also applied to a stream which has reached an equilibrium between corrosion and deposition or, in other words, to a graded stream.

Regulation - The artificial manipulation of the flow of a stream.

Re-regulating reservoirs - A reservoir for reducing diurnal fluctuations resulting from the operation of an upstream reservoir for power production.

Reservoir. A pond, lake, or basin, either natural or artificial, for the storage, regulation, and control of water.

Residual-mass curve - A graph of the cumulative departures from a given reference such as the arithmetic average, generally as ordinate, plotted against time or date, as abscissa. (See Mass curve.)

Restoration - The management of physical, chemical, or biological characteristics of a site with the goal of returning natural/historic functions to sites that formerly supported wetlands.

Retarding reservoir - Ungated reservoir for temporary storage of flood water. Sometimes called detention reservoir.

Return flow - That part of irrigation water that is not consumed by evapotranspiration and that returns to its source or another body of water. The term is also applied to the water that is discharged from industrial plants. Also called return water.

Riffle – A rapid in a stream. A section of a stream with fast-moving, turbulent, shallow water with a rocky bottom. In natural streams pools and riffles are alternating.

Riparian – Of, relating to, living on, or located on the banks of a watercourse such as a river, stream, lake, etc.

River Basin – Area encompassing all the land drained by streams and creeks flowing downhill into a major river. All water that falls within the basin flows into these streams and rivers.

Runoff – Water flowing across the land that does not infiltrate the soil, but drains into surface or ground waters, or when rainfall exceeds the infiltration capacity of the land.

Runout - See Water yield.

Second-foot - Same as CFS. This term is no longer used in published reports of the U.S. Geological Survey.

Sediment - Fragmental material that originates from weathering of rocks and is transported by, suspended in, or deposited by water or air or is accumulated in beds by other natural agencies.

Sediment discharge - The rate at which dry weight of sediment passes a section of a stream or is the quantity of sediment, as measured by dry weight, or by volume, that is discharged in a given time.

Sedimentation – The deposition of particles of soil, sand, silt, clay, or organic matter onto the bottom of any surface water or left behind as water leaves.

Seiche - The free oscillation of the bulk of water in a lake and the motion caused by it on the surface of the lake.

Shifting control - See Control.

Sinuosity – Describes the amount of curvature in a stream channel.

Situation Assessment - A social science activity that occurs early in a watershed planning process and involves identifying watershed stakeholders, learning what concerns stakeholders and what they hope to gain in a watershed planning process, and identifying potential conflicts.

Skimming - The diversion of water from a stream or conduit by a shallow overflow used to avoid diversion of sand, silt, or other debris carried as bottom load.

Snow - A form of precipitation composed of ice crystals.

Snow course - A line or series of connecting lines along which snow samples are taken at regularly spaced points.

Snow density - Ratio between the volume of melt water derived from a sample of snow and the initial volume of the sample. This is numerically equal to the specific gravity of the snow.

Snowline - The general altitude to which the continuous snow cover of high mountains retreats in summer, chiefly controlled by the depth of the winter snowfall and by the temperature of the summer.

Snowline, temporary - A line sometimes drawn on a weather map during the winter showing the southern limit of the snow cover.

Snow, quality of - The ratio of heat of melting of snow, in calories per gram to the 80 calories per gram for melting pure ice at 0 degrees C.

Soil moisture (Soil water) - Water diffused in the soil, the upper part of the zone of aeration from which water is discharged by the transpiration of plants or by soil evaporation. See Field-moisture capacity and Field-moisture deficiency.

Stage - The height of a water surface above an established datum plane; also gage height.

Stage-capacity curve - A graph showing the relation between the surface elevation of the water in a reservoir, usually plotted as ordinate, against the volume below that elevation, plotted as abscissa.

Stage-discharge curve (rating curve) - A graph showing the relation between the gage height, usually plotted as ordinate, and the amount of water flowing in a channel, expressed as volume per unit of time, plotted as abscissa.

Stage-discharge relation - The relation expressed by the stage-discharge curve.

Stage, flood - See Flood stage.

Stemflow - Rainfall or snowmelt led to the ground down the trunks or stems of plants.

Storage - 1. Water artificially impounded in surface or underground reservoirs, for future use. The term regulation refers to the action of this storage in modifying streamflow. See also Conservation storage, Total storage, Dead storage, and Usable storage. 2. Water naturally detained in a drainage basin, such as ground water, channel storage, and depression storage. The term "drainage basin storage" or simply "basin storage" is sometimes used to refer collectively to the amount of water in natural storage in a drainage basin.

Storage, bank - See Bank storage.

Storage, conservation - See Conservation storage.

Storage, dead. See Dead storage.

Storage, depression - See Depression storage.

Storage ratio. The net available storage divided by the mean flow for 1 year.

Storage-required frequency curve - A graph showing the frequency with which storage equal to or greater than selected amounts will be required to maintain selected rates of regulated flow.

Storage, total - See Total storage.

Storage, usable - See Usable Storage.

Storm. A disturbance of the ordinary average conditions of the atmosphere which, unless specifically qualified, may include any or all meteorological disturbances, such as wind, rain, snow, hail, or thunder.

Stormflow - See Direct runoff.

Storm seepage - That part of precipitation which infiltrates the surface soil, and moves toward the streams as ephemeral, shallow, perched ground water above the main ground-water level. Storm seepage is usually part of the direct runoff.

Stormwater Runoff – Runoff that picks up contaminants deposited on impervious surfaces during its flow to surface or ground waters.

Stream - A general term for a body of flowing water. 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. Streams in natural channels may be classified as follows

Stream Bank Stabilization – Prevention of stream bank erosion and deterioration through vegetation or other stabilizing structures.

Stream Corridor – Spatial scale defining the ecosystem surrounding a stream, linear in shape, that includes the stream channel, riparian vegetation, floodplains, streambanks, tributary streams, and trails, roads, and other development.

Stream Restoration – The management of morphological, ecological, and hydrological characteristics of a stream with the goal of returning natural/historic functions to the stream system.

Streamflow - The discharge that occurs in a natural channel. Although the term discharge can be applied to the flow of a canal, the word streamflow uniquely describes the discharge in a surface stream course. The term "streamflow" is more general than runoff, as streamflow may be applied to discharge whether or not it is affected by diversion or regulation.

Streamflow depletion - The amount of water that flows into a valley, or onto a particular land area, minus the water that flows out the valley or off from the particular land area.

Stream gauging - The process and art of measuring the depths, areas, velocities, and rates of flow in natural or artificial channels.

Stream-gaging station - A gaging station where a record of discharge of a stream is obtained. Within the Geological Survey this term is used only for those gaging stations where a continuous record of discharge is obtained.

Stream order - A method of numbering streams as part of a drainage basin network. The smallest unbranched mapped tributary is called first order, the stream receiving the tributary is called second order, and so on. It is usually necessary to specify the scale of the map used. A first-order stream on a 1:62,500 map, may be a third-order stream on a 1:12,000 map. Tributaries which have no branches are designated as of the first order, streams which receive only first-order tributaries are of the second order, larger branches which receive only first-order and second-order tributaries are designated third order, and so on, the main stream being always of the highest order.

Submeander - Small meander contained with banks of main channel, associated with relatively low discharges.

Subsurface runoff - See Storm seepage.

Supplemental irrigation - Commonly, irrigation as carried on in humid areas. The term means that the irrigation water is supplementary to the natural rainfall rather than being the primary source of moisture as in the arid and semiarid West. Supplementary irrigation is used generally to prevent retardation of growth during periods of drought.

Supplemental sources - When irrigation water supplies are obtained from more than one source, the source furnishing the principal supply is commonly designated the primary source, and the sources furnishing the additional supplies, the supplemental sources.

Surface runoff - That part of the runoff which travels over the soil surface to the nearest stream channel. It is also defined as that part of the runoff of a drainage basin that has not passed beneath the surface since precipitation. The term is misused when applied in the sense of direct runoff. See also, Runoff, Overland flow, Direct runoff, Ground-water runoff, and Surface water.

Surface water - Water on the surface of the earth.

Suspended Solids – Organic and inorganic particles suspended in the water column and carried by the water. The presence of suspended solids in water may reduce the amount of light reaching the water column, clog the gills of fish and other animals, and are often associated with toxic contaminants that bind to particles.

Tank - An artificial reservoir for stock water; local in Southwest.

Technical Advisors – In watershed planning, a group of individuals with expertise in particular subjects or issues regarding the watershed or the watershed planning process that can be called on for informational needs and other technical assistance.

Terrace - A berm or discontinuous segments of a berm, in a valley at some height above the flood plain, representing a former abandoned flood plain of the stream.

Thermal stratification (of a lake) - Vertical temperature stratification that shows the following: The upper layer of the lake, known as the epilimnion, in which the water temperature is virtually uniform; a stratum next below, known as the thermocline, in which there is a marked drop in temperature per unit of depth; and the lowermost region or stratum, known as the hypolimnion, in which the temperature from its upper limit to the bottom is nearly uniform.

Thermocline - See Thermal stratification.

Throughfall - In a vegetated area, the precipitation that falls directly to the ground or the rainwater or snowmelt that drops from twigs or leaves.

Time of concentration - The time required for water to flow from the farthest point on the watershed to the gaging station.

TMDL (total maximum daily load) - Calculation of the maximum amount of a pollutant that a water body can receive and still meet water quality standards and allocation of that amount to the pollutant's sources.

Total storage - The volume of a reservoir below the maximum controllable level including dead storage.

Total Suspended Solids (TSS) – The weight of all suspended solids in water.

Transitional Upland Fringe – Areas of land on each side of a stream bank, beyond the floodplain, that act as a transitional zone between floodplain and surrounding land.

Transpiration - The quantity of water absorbed and transpired and used directly in the building of plant tissue, in a specified time. It does not include soil evaporation. The process by which water vapor escapes from the living plant, principally the leaves, and enters the atmosphere.

Trend - A statistical term referring to the direction or rate of increase or decrease in magnitude of the individual members of a time series of data when random fluctuations of individual members are disregarded.

Tributary – A stream or river that feeds into a larger stream, lake, or river.

Turbidity – A measurement that indicates the amount of suspended solids in the water column.

Underflow - The downstream flow of water through the permeable deposits that underlie a stream and that are more or less limited by rocks of low permeability.

Unit hydrograph - The hydrograph of direct runoff from a storm uniformly distributed over the drainage basin during a specified unit of time; the hydrograph is reduced in vertical scale to correspond to a volume of runoff of 1 inch from the drainage basin.

Usable storage - The volume normally available for release from a reservoir below the stage of the maximum controllable level.

Vegetative Clearing – The removal of riparian and upland vegetation for land-use purposes.

Water balance - See Hydrologic budget.

Water content of snow - See Water equivalent of snow.

Water crop - See Water yield.

Water Cycle – The cycle in which water evaporates from surface waters, condenses into clouds, and falls again to the earth as rain or other forms of precipitation.

Water equivalent of snow - Amount of water that would be obtained if the snow should be completely melted. Water content may be merely the amount of liquid water in the snow at the time of observation.

Water loss - The basic concept is that water loss is equal to evapotranspiration, that is, water that returns to the atmosphere and thus is no longer available for use. However, the term is also applied to differences between measured inflow and outflow even where part of the difference may be seepage.

Water Quality Standards – Laws and regulations that maintain limits, or criteria, for certain chemical, biological, and physical parameters in order to protect designated uses.

Water requirement - The quantity of water, regardless of its source, required by a crop in a given period of time, for its normal growth under field conditions. It includes surface evaporation and other economically unavoidable wastes.

Water Table – The depth at which the ground is saturated with water.

Water year - In Geological Survey reports dealing with surface-water supply, the 12-month period, October 1 through September 30. The water year is designated by the calendar year in which it ends and which includes 9 of the 12 months. Thus, the year ended September 30, 1959, is called the "1959 water year."

Water yield (water crop or runout) - The runoff from the drainage basin, including ground-water outflow that appears in the stream plus ground-water outflow that bypasses the gaging station and leaves the basin underground. Water yield is the precipitation minus the evpotranspiration.

Watershed - Ecosystem consisting of three major components, stream channel, floodplain, and upland areas, that function together and drain to water bodies, including lakes, rivers, estuaries, wetlands, streams, and the surrounding landscape (groundwater recharge areas are also considered).

Watershed Advisory Group – Assembly of a group of key participants, such as local citizens, public officials, landowners, local business owners, and public interest groups, who represent a variety of community interests, are affected by watershed initiatives, and will play an active role in the watershed planning process.

Watershed Stakeholder - Anyone who has influence upon the quality of waters in a watershed (such as industry, municipalities, boaters, agriculture, forestry), and anyone who is impacted by the quality of waters in a watershed (such as fisherman, swimmers, waterfront homeowners), and thus has a "stake" in any potential water quality management measures.

Wetlands – Areas that are frequently inundated or saturated with water for periods of time long enough to support vegetation suited for survival in saturated soils. Wetlands may include bogs, swamps, marshes, etc.

Wetland Creation - Creation of wetlands at a location where there was previously no wetlands, or where no wetland has existed in the last 100-200 years (Lewis, 1989, Gwin, et. al., 1999).

Wetland Enhancement - The manipulation of the physical, chemical, or biological characteristics of a wetland (undisturbed or degraded) site the heighten, intensify, or improve specific function(s) or for a purpose such as water quality improvement, flood water retention or wildlife habitat resulting in a change in wetland function(s).

Wetland Establishment – The manipulation of the physical, chemical, or biological characteristics present to develop a wetland that did not previously exist on an upland or deepwater site resulting in a gain in wetland acres.

Wetland Protection/Maintenance - Removal of a threat to, or preventing decline of, wetland conditions be an action in of near a wetland. Includes purchase of land or easement, repairing water control structures or fences, structural protection such as repairing a barrier island, or preservation.

Withdrawal use of water - The water removed from the ground or diverted from a stream or lake for use.

Year. See Climatic year; Water year.

Zone of aeration - The zone above the water table. Water in the zone of aeration does not flow into a well.

Zone of saturation - The zone in which the functional permeable rocks are saturated with water under hydrostatic pressure. Water in the zone of saturation will flow into a well, and is called ground water.

Zoning – Designation and regulation of areas of land for particular land uses. Zoning is delineated in a town, county, etc. Zoning Ordinance.