Glossary of Definitions & Acronyms

Water Conservation Toolbox

The following list of terms, definitions, and acronyms can be used as a quick reference for learners and others who have not yet become an expert in the field of water conservation.  These definitions are a compilation from numerous sources and are presented here with permission from the National Weather Service, the Virginia Department of Conservation and Recreation, the California Urban Water Conservation Council, and the Water Environment Federation.



Abandoned Well

Any well (drinking water, oil and gas, etc.) which is not used for a long period of time, is not maintained properly, and/or is not properly sealed when its useful life is over.


The process by which ice and snow dissipate due to melting and evaporation.


Enough water to cover an acre of land one-foot deep (i.e., 325,851 gallons, or 43,560 cubic feet).


Process by which a solute is attracted to a solid surface, used in stormwater management BMPs to enhance the removal of soluble pollutants.


To supply with air or expose to the circulation of air.  


Mechanical cultivation of turfgrass using hollow tines to remove cores of turf, thatch and soil; improves soil texture and increases air and water movement in root zone.  Also called coring.


A screen-like component of a faucet or showerhead that reduces volumetric flow by introducing air into the stream of water.


Living or occurring in the presence of oxygen.


Aluminum sulfate, added to water in drinking water treatment facilities to cause dirt and other particles to clump together and fall to the bottom of settling basins.


American National Standards Institute

Apparent Losses

Water losses that occur when volumes of water are not properly measured or recorded.  Also includes customer meter inaccuracies, unauthorized consumption and data handling errors in customer billing systems.

Application Rate

The depth of water applied to a given area over time, usually measured in inches per hour.

Applied Water

The portion of water supplied by an irrigation system that reaches the soil surface.


Permeable layers of underground rock, or sand that hold or transmit groundwater below the water table that will yield water to a well in sufficient quantities to produce water for beneficial use.

Area of Influence

The area covered by the drawdown curves of a given pumping well or combination of wells at a particular time.


Regions where precipitation is deficient in quantity such that agriculture is impracticable without irrigation.

Army Corps of Engineers

Branch of the U.S. Army; responsible for maintaining and regulating inland waterways.

Artesian Well

A well drilled in a confined aquifer where the elevation of the well water (i.e., potentiometric surface) is above the top of confined aquifer.  If this well flows at the land surface without mechanical pumping, it is a flowing artesian well.


American Society of Mechanical Engineers

Audit (system)

An accounting of water in all stages of the water delivery system including treatment and distribution.

Audit (end-use)

A systematic accounting of water uses conducted to identify opportunities for improved efficiency.

Audit (irrigation)

An evaluation of an irrigation system to determine the proper scheduling for the distribution characteristics of the system.  The Irrigation Association has a set standard of irrigation auditing procedures.

Audit (site)

A census of water uses at a site.  Performed to identify areas of potential water conservation.

Automatic Irrigation Controller

An irrigation timer capable of operating valve stations to set the days and length of time of water applications.

Automatic Valve

An irrigation valve which can be remotely operated.  The remote operation method may be either electrical (the most common) or hydraulic.  Automatic valves are commonly used as "control valves" for irrigation systems.

Available Water-holding Capacity (AWHC)

The amount of moisture in the root zone and available to plants.


Alliance for Water Efficiency


American Water Works Association


American Water Works Association Research Foundation


The backing up of water through a conduit or channel in the direction opposite to normal flow.

Backflow Prevention Device

A safety device, typically a type of check valve, used to prevent contamination of the potable water supply from the backflow of water from an irrigation system or other customer activity back into the potable distribution system.


The use of water to clean filters.  Water under high pressure is pumped in reverse through filters, removing trapped sediment and other material.


 A device that enables the filling of water tanks, particularly toilets, without overflow or backflow.


Water flow which results from precipitation that infiltrates into the sediment and eventually moves through the sediment to a surface water body.  This is also referred to as dry weather flow.

Benchmark (BM)

A permanent point whose known elevation is tied to a national network.  These points are created to serve as a point of reference.  Benchmarks have generally been established by the USGS, but may have been established by other federal or local agencies.  Benchmarks can be found on USGS maps.

Beneficial Rainfall

The portion of total rainfall that is available for use by the plant (effective rainfall).

Beneficial Use

Use of a [water] resource that includes, but is not limited to, domestic (including public water supply), agricultural, commercial, industrial, water-based recreational uses and the propagation and growth of aquatic life.

Best Management Practice (BMP)

A practice or combination of practices established as the most practicable means of increasing water use efficiency.

Billing Cycle

The regular interval of time when customer meters are read and bills are issued, generally every month (monthly) or two months (bi-monthly).

Billing Period

The elapsed time between two specific consecutive meter reads for billing purposes.

Billing Unit

The unit of measure used to bill customers, often either 100 cubic feet (abbreviated HCF or CCF) or 1,000 gallons (kgals).


Draining off the water in a cooling tower reservoir to avoid the buildup of excess dissolved solids.  Also referred to as blowdown.


A type of sprinkler head that delivers a relatively large volume of water to a level area where standing water gradually infiltrates into the soil.  The flow rate is large relative to the area to which the water is delivered. Bubblers are used to irrigate trees and shrubs.

Calcium (element symbol Ca)

An element that is commonly found in water.  It contributes to the hardness of water.


The process of using historical data to estimate parameters in a hydrologic forecast technique, routings, and unit hydrographs.


(1)The degree to which a material or object containing minute openings or passages, when immersed in a liquid, will draw the surface of the liquid above the hydrostatic level.  Unless otherwise defined, the liquid is generally assumed to be water.  (2)The phenomenon by which water is held in interstices above the normal hydrostatic level, due to attraction between water molecules.


Latin for ‘person’.

Catch-can Test

Measurement of a sprinkler system’s application rate.  Test involves placing graduated containers at evenly spaced intervals throughout an irrigated area and measuring the depth of water collected in the cans over a given period of time.


100 cubic feet of water, an amount equivalent to 748 gallons.

Central Irrigation Control System

A computerized system for programming irrigation controllers from a central location.

Check Valve

A device that allows fluids to flow in one direction.  Used in irrigation systems to prevent drainage of water from the low points of an irrigation circuit after irrigation stops.  Also used in reuse systems to prevent reuse water from flowing into the potable water system.


Water disinfection by chlorine gas or hypochlorite.


A tank use to store water, often stormwater or graywater.


Customers having similar characteristics (commercial, single-family residential, etc.) grouped together for billing or program purposes.

Clean Water Act

Water pollution control laws based upon the Federal Water Pollution Control Act of 1972 with amendments passed in 1977, 1981, and 1987; main objective is to restore and maintain the "chemical, physical, and biological integrity of the Nation's waters."

Climate Factor

Evapotranspiration minus precipitation.

Coliform Bacteria

Microorganisms (e.g., Escherichia coli) common to the intestinal tract of warm blooded animals.  The organisms’ presence in water is an indicator of fecal pollution.

Commercial User

Customers who use water at a place of business, such as hotels, restaurants, office buildings, commercial businesses or other places of commerce.  Typically does not include multi-family residences, agricultural users, industrial or institutional classifications.


An aerobic mixture of decaying organic matter, such as leaves and manure, used as fertilizer.

Compound Meter

A meter with two measuring chambers, generally a turbine for high flows and a positive displacement for low flows.


Any channel intended for the conveyance of water, whether open or closed to the atmosphere.

Cone of Depression / Cone of Influence

The depression, roughly conical in shape, produced in a water table, or other piezometric surface, by the extraction of water from a well at a given rate.  The volume of the cone will vary with the rate of withdrawal of water.

Confined Aquifer (artesian aquifer)

An aquifer with a dense layer of compacted earth material over it that blocks movement of water out of the aquifer.

Connection Fee

A charge assessed to a new account by a water utility that generally covers the cost of hooking up to the system and compensates the utility for prior water system improvements that made the capacity available.


The US Water Resources Council defines water conservation as activities designed to (1) reduce the demand for water, (2) improve efficiency in use and reduce losses and waste of water, and (3) improve land management practices to conserve water.

Conservation Rate Structure

A water billing structure that sets billing rates by the quantity of water delivered.  An increasing block rate structure is one example of a conservation rate structure.

Conservation Storage

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

Consumptive Use

Combined amounts of water needed for transpiration by vegetation and for evaporation from adjacent soil, snow, or intercepted precipitation.  Also called crop requirement, crop irrigation requirement, consumptive use requirement.


Mechanical cultivation of turfgrass using hollow tines to remove cores of turf, thatch and soil; improves soil texture and increases air and water movement in root zone. (See Aerification)


When the present value of benefits exceeds the present value of costs.

Cubic Feet per Second (cfs)

A rate of flow; the volume, in cubic feet, of water passing a reference point in 1 second.

Cubic Foot

A measurement of water equal to 7.48 gallons.

Curb Stop

Shut-off valve between the customer meter and the street service line from the water main.

Customer Class / Class

A group of customers (residential, commercial, industrial, wholesale, and so on) defined by similar characteristics or patterns of water usage.

Declining Block Rate

A water billing rate structure whose unit price decreases with increasing water use.

Dedicated Metering

Metering of water service based on a single type of use, such as metering for landscape irrigation separately from interior use.

Deep Percolation

The movement of water by gravity downward through the soil profile beyond the root zone of plants.

Deep Seepage

Infiltration which reaches the water table.

Deep Well

A well whose pumping head is too great to permit use of a suction pump.

Demand Forecast

A projection of future water use.

Demand Management Demand Scheduling Demand Side Measures

In the water industry, programs which encourage customers to modify the amount or timing of water use.  These measures may include encouraging customers to implement hardware or behavior changes, or change the volume or timing of their use, depending on the time of day or time of year.


The rate at which water passes a given point.  Discharge is often used interchangeably with streamflow.

Discount Rate

The financial rate used to calculate the present value of future benefits and costs.


The process of heating a liquid or solid until it sends off a gas or vapor and then cooling the gas or vapor until it becomes a liquid.

Distribution Facilities

Pipes, meters, storage, pumps and other facilities used to distribute water to end users.

Divining Rod

A forked branch or stick used in an attempt to locate subterranean water or minerals; it is said to bend downward when held over a source.




Minnesota Department of Labor and Industry.  Agency responsible for the Minnesota Plumbing Code.


Minnesota Department of Natural Resources

Domestic Consumption

The quantity, or quantity per capita, of water consumed in a municipality or district for domestic uses or purposes during a given period, generally one day.

Domestic Use of Water

The use of water primarily for household purposes, the watering of livestock, the irrigation of gardens, lawns, shrubbery, etc., surrounding a house or domicile.


The part of a septic system where the wastewater is released into the soil for absorption and filtration.


The lowering of the surface elevation of a body of water, the water surface of a well, the water table, or the piezometric surface adjacent to the well, resulting from the withdrawal of water therefrom.

Drip Irrigation

The slow, accurate application of water directly to plant root zones with a system of tubes and emitters usually operated under reduced pressure.


An extended period of below-average precipitation resulting in a reduction of water in available storage that can result in a cutback in water service to customers.

Drought Index

Computed value which is related to some of the cumulative effects of a prolonged and abnormal moisture deficiency. (An index of hydrological drought corresponding to levels below the mean in streams, lakes, and reservoirs.)

Dry Weather Flow

Streamflow which results from precipitation that infiltrates into the soil and eventually moves through the soil to the stream channel.  This is also referred to as base flow, or groundwater flow.

Dye Test

A test for water leaks, specifically by putting dye in a toilet tank to see if it appears in the bowl.


A branch of science concerned with the interrelationship of organisms and their environments; the totality or pattern of relations between organisms and their environment.


An ecological community together with its physical environment, considered as a unit.

Effective Porosity

The ratio, usually expressed as a percentage, of the volume of water or other liquid which a given saturated volume of rock or soil will yield under any specified hydraulic condition, to the given volume of soil or rock.

Effective Precipitation (EP)

The portion of total rainfall that is available for use by the plant. (see Beneficial Rainfall)

Efficiency Standard

A value or criteria that establishes target levels of water use for a particular activity.


Water, such as wastewater, treated or untreated, that flows out of a wastewater treatment plant, sewer, or industrial outfall.

Elevation Head

The distance from a datum (mean sea level) to the water level measurement point in a piezometer, with units of feet or meters.


A drip irrigation component that dispenses water to plants at a known rate, typically measured in gallons per hour.

Energy Policy Act (1992)

A federal law that established maximum allowable water use requirements for toilets, urinals, showerheads, and faucets manufactured and/or sold in the United States.


Environmental Protection Agency.  The U.S. agency responsible for efforts to control air and water pollution, radiation and pesticide hazards, ecological research, and solid waste disposal.

Estimated Water Use (EWU)

The amount of water estimated to be needed by the landscape during one year.


The process by which water changes state from liquid to vapor.

Evapotranspiration (ET)

Water lost from the surface of soils and plants through the processes of evaporation and transpiration combined.


Land tilled and left unplanted.

Faucet Aerator

A flow reduction device that screws on to the end of the kitchen or lavatory faucet to add air to the water flow.

Fecal Coliform

The coliform bacteria group present in the intestinal tracts and feces of humans and other warm-blooded animals.  Drinking water with fecal coliform can cause diarrhea and other gastrointestinal illnesses.

Federal Emergency Management Agency (FEMA)

An agency of the federal government having responsibilities in hazard mitigation; FEMA also administers the National Flood Insurance Program.

Federal Water Pollution Control Act (Clean Water Act)

The law to restore and maintain the "chemical, physical, and biological integrity of the Nation's waters."


Any one of a large number of natural and synthetic materials, including manure and nitrogen, phosphorus, and potassium compounds, spread or worked into the soil to increase its fertility.

Field Capacity

The residual water content retained in the soil after gravity drainage, defined as the condition that arises after a soil has been allowed to drain for three days under gravity-driven conditions.  Also called field moisture capacity.

Field Moisture Deficiency

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


A water treatment process that involves water passing through sand or other media, where particles and other constituents are trapped and removed from the flow.

Fixed Charge

The portion of a water bill that does not vary with water use.

Fixed Costs

Costs that do not change as output level changes over the time period being analyzed.

Fixed Rates

Part of a utility bill that is not affected by consumption.

Flow Rate

The rate at which a volume of water flows through pipes, valves, etc. in a given period of time.  Often reported as cubic feet per second (cfs) or gallons per minute (gpm).

Flush Valve

A valve used to expel sediment from irrigation lines.  Also, a type of flushing mechanism used in commercial toilets.


Water that contains relative low mineral content as opposed to seawater or salt water.

Gaining Streams

Streams that gain water from the subsurface.


That branch of hydrology relating to subsurface, or subterranean waters.


The study of the physical characteristics and properties of the earth, including geodesy, seismology, meteorology, oceanography, atmospheric electricity, terrestrial magnetism, and tidal phenomena.


gallons per cycles


gallons per capita per day


gallons per day


gallons per flush


gallons per hour


gallons per household per day


gallons per load (of laundry or dishes)


gallons per minute


gallons per year


Domestic wastewater that does not contain human wastes such as tub, shower, or washing machine water.


Water within the earth that supplies wells and springs; water in the zone of saturation where all openings in rocks and soil are filled, the upper surface of which forms the water table.  Also termed phreatic water.

Groundwater Divide

A line on a water table where on either side of which the water table slopes downward. It is analogous to a drainage divide between two drainage basins on a land surface.

Groundwater Hydrology

The branch of hydrology that specializes in groundwater; its occurrence and movements; its replenishment and depletion; the properties of rocks that control groundwater movement and storage; and the methods of investigation and utilization of groundwater.

Groundwater Mining

Pumping ground water from a basin where the safe yield is very small, thereby extracting groundwater at a rate greater than the recharge rate.

Groundwater Overdraft

Pumping of groundwater in excess of safe yield.

Groundwater Runoff

That part of the runoff which has passed into the ground, has become groundwater, and has been discharged into a stream channel as spring, or seepage water.


Water that has seeped beneath the earth’s surface and is stored in the pores and spaces between alluvial materials (sand, gravel or clay) or within rocks.

Groundwater Discharge/ Groundwater Outflow

The flow or pumping of water from an aquifer.

Groundwater Mining (overdraft)

Pumping of groundwater for irrigation or other uses, at rates faster than the rate at which the groundwater is being recharged.

Groundwater Recharge

Percolating or injecting surface water into a groundwater basin to increase the available groundwater supply.

Groundwater Table

The upper boundary of groundwater where water pressure is equal to atmospheric pressure, i.e., the water level in a borehole after equilibrium is reached, when groundwater can freely enter the hole from the sides and bottom.


The concentration of calcium and magnesium ions dissolved in water.


Landscaping that does not permit water to seep into the ground, such as concrete, brick and lumber.

Heavy Metals

Metallic elements (Example: cadmium, chromium, copper, lead, mercury, nickel, and zinc) which are used in some manufactured products; they are present in some industrial, municipal, and urban runoff.

High Efficiency Clothes Washer (HECW)

A type of clothes washer meeting certain water and energy standards.  They often involve a design where the tub axis is more nearly horizontal than vertical.  Clothes are tumbled through water that only fills a fraction of the tub.  Also known as a horizontal axis, tumble action or front-loading clothes washer.

High water use Landscape

A landscape made up of plants, turf and features that requires 50 to 80% of the reference evapotranspiration to maintain optimal appearance.

Historic Basis

Water consumption history.

Horticultural Practices

Activities to maintain plants and landscapes such as fertilization, mowing, and thatch control.

Hot Water On Demand System

A device for generating hot water quickly from a heat exchanger for the purpose of reducing the wait time (and associated energy waste) for hot water.

Hot Water Ratio Billing

The practice of estimating a resident’s total water usage based on metered hot water usage.


The degree of wetness, especially of the atmosphere.


Operated, moved, or brought about by means of water or another fluid.


The generation of electricity by converting the energy of flowing water into electric power.

Hydrologic (water) Cycle

The cycle of the earth's water supply from the atmosphere to the earth and back which includes precipitation, transpiration, evaporation, runoff, infiltration, and storage in water bodies and groundwater.

Hydrologic Model

A conceptual or physically-based procedure for simulating a process or processes which occur in a watershed.


Individuals who study the applied science of hydrology and solve hydrologic problems.  This study includes the occurrence, distribution, and circulation of water through the unending hydrologic cycle of: precipitation, consequent runoff, infiltration, and storage; as well as evaporation. It is concerned with the physical and chemical interactions of water with the rest of the earth, and its relation to the life of the earth.


Science dealing with the properties, distribution, and flow of water on or in the earth.


A portion of the landscaped area having plants with similar water needs that are served by a valve or set of valves with the same schedule.

Impact Head

A type of single-stream rotor that uses the impact of a stream of water to rotate a nozzle in a full or partial circle.


Material that does not permit fluids to pass through it.


The ability to repel water, or not let water infiltrate.

Inclining Block Rate

A water billing rate structure whose unit price increases with increasing water use.

Individual Metering

In multi-unit housing complexes, the installation of meters for each individual dwelling unit as well as separate common area metering with the local water utility providing customer read, bill and collect services.


Movement of water through the soil surface into the soil.

Infiltration Capacity

The maximum rate at which water can enter the soil at a particular point under a given set of conditions.

Infiltration Rate

The rate at which water permeates the soil surface, expressed as a depth of water per unit of time (inches per hour).

Infrastructure Leakage Index

In a water supply distribution system, the Infrastructure Leakage Index, ILI, is the ratio of the current level of annual real losses (mostly leakage) to the Unavoidable Annual Real Losses, UARL.  It is a good benchmarking performance indicator for comparisons of leakage standing among drinking water utilities.

Initial Moisture Deficiency

The quantity, usually expressed in depth of water in inches upon a unit area, by which the actual water content of a given soil zone (usually the root zone) in this area is less than the field capacity of this zone at the beginning of the rainy season.  Also called Initial Water Deficiency.

Irrigated Area

The portion of a landscape that requires supplemental irrigation, usually expressed in square feet or acres.


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

Irrigation Audit

An evaluation of an irrigation system to determine the proper scheduling for the distribution characteristics of the system.  The Irrigation Association has a set standard of irrigation auditing procedures.

Irrigation Controller

A mechanical or electronic clock that can be programmed to operate remote-control valves to control watering times.

Irrigation Cycle

A scheduled application of water by an irrigation station defined by a start time and its duration.  Multiple cycles can be scheduled, separated by time intervals, to allow infiltration of applied water.

Irrigation Efficiency

The percentage of water applied that can be accounted for by an increase in soil moisture for consumptive use by plants.

Irrigation Only Accounts

Accounts with a separate meter dedicated to non-sewered uses such as landscape irrigation or cooling towers.

Irrigation Plan

A two-dimensional plan drawn to scale expressing the layout of irrigation components and component specifications.

Irrigation Requirement

The quantity of water, exclusive of precipitation, that is required for crop production. It includes surface evaporation and other unavoidable losses.

Irrigation Scheduling

The process of developing a schedule for an automatic irrigation system that applies the right amount of water, matched to the plant needs, which varies daily, weekly, or seasonally.

Irrigation Station

A group of irrigation components, including heads or emitters and pipes, controlled / operated by a remote control valve.


Topography formed over limestone, dolomite, or gypsum and characterized by sinkholes, caves, and significant and rapid underground drainage.

Karst Topography

Regions that are characterized by formations underlain by carbonate rock typified by the presence of limestone caverns and sinkholes.

Kilowatt-hour (kWh)

A unit of electric power equivalent to the energy provided by one thousand watts acting for one hour.

Land Use

How a certain area of land is utilized (examples: forestry, agriculture, urban, industry).

Landscape Irrigation Auditor

A person who is qualified to conduct a landscape water audit.

Landscape Water Budget (LWB)

A volume of applied irrigation water expressed as a monthly or yearly amount, based on evapotranspiration and the plant material being watered.


Improving the natural beauty of a piece of land by planting or altering the contours of the ground.


Removal of soluble material from soil or other permeable material by the passage of water through it.

Leak Detection

A procedure for pinpointing the exact location of leaks from water pipes, fittings, and equipment.

Leakage Management

The practice of a water utility to control distribution system leakage.  Includes combinations of leakage control (flow analysis, leak detection) and repair, pressure management, and system rehabilitation.

Life-cycle Analysis

Examines the costs and benefits of an action over its entire expected life span.


The branch of hydrology that pertains to the study of lakes.

Littoral Zone

The area on, or near the shore of a water body.

Losing Streams

Streams which lose water to the subsurface.

Low Flow Detector

A part of a water meter register that indicates any flow through the meter. Also called a Leak Indicator.

Low Flow Faucet

A faucet fixture that meets 1992 EPAct (Energy Policy Act) standards (2.2 gpm or less at 80 psi).

Low Flow Showerhead

A showerhead that meets 1992 EPAct (Energy Policy Act) standards (2.5 gpm or less at 80 psi).

Low Flow Toilet

A toilet that meets 1992 EPAct (Energy Policy Act) standards (1.6 gpf or less).

Makeup Water

Fresh water introduced into a cooling tower to replace water lost to evaporation and blowdown.

Marginal Cost

The additional cost incurred by supplying one more unit of water.

Master Meter

A single meter that measures utility usage for an entire property, or an entire building, which usually includes common areas.

Matched Precipitation Rates

Equal water-delivery rate by sprinkler heads with varying arc patterns within an irrigation station.  Matched precipitation rates are required to achieve uniform distribution.

Matched Sprinkler Heads

Sprinkler heads with the same precipitation rate.


Minnesota Department of Health


Minnesota Department of Natural Resources


One million watts; a measure of power plant output.

Meter (water)

An instrument for measuring and recording water volume for a designated period of time.

Metered Water Ratio

A term relating to water loss.  The American Water Works Association recommends discontinuing use of this term. See Non-revenue water.


million gallons per day.


million gallons per year.


The climate of a specific place within a given area, generally varying by wind and evapotranspiration (ET).


Organisms too small to be seen with the unaided eye, including bacteria, protozoans, yeasts, viruses, and algae.


A naturally occurring substance (as ore, petroleum, natural gas, or water) obtained usually from the ground for human use.  An inorganic crystalline solid, with a characteristic chemical composition and defined physical properties.

Mixed Use Meter

A water meter that serves more than one type of end use, such as an office building and its surrounding landscape.


Minnesota Technical Assistance Program


Scrutinizing and checking systematically with a view to collecting data.


Minnesota Pollution Control Agency


Maximum Performance - organization that tests the performance of toilets


A protective covering of various substances, usually organic, such as wood chips, placed on the soil surface around plants to reduce weed growth and evaporation and to maintain even temperatures around plant roots.

Multi-family (MF)

Residential housing with multiple dwelling units, such as apartments and condominiums.

National Environmental Protection Act of 1969 (NEPA)

Law that requires environmental impact statements to be submitted for any major construction projects that use federal money.

National Pollutant Discharge Elimination System (NPDES)

Part of the Clean Water Act requiring municipal and industrial wastewater treatment facilities to obtain permits which specify the types and amounts of pollutants that may be discharged into water bodies.

Native and Adopted Plants

Plants indigenous to an area or from a similar climate that require little or no supplemental irrigation once established.

Native Landscape

A landscape that features plants and grasses indigenous to the region.

Natural Landscape

A landscape created to reflect the character and spirit of nature and the native surroundings.


Used generically for materials made of nitrogen and oxygen; sources include animal wastes and some fertilizers.

Nonpoint Source Pollution (NPS)

Pollution that cannot be traced to a single point (example: outlet or pipe) because it comes from many individual places or a widespread area (typically urban, rural, and agricultural runoff).

Non-potable Water

Water that does not, or may not, meet drinking water quality standards.

Non-revenue Water

In a distribution system water audit, non-revenue water equals the volume of unbilled authorized consumption (water for fire fighting, system flushing and similar uses).


National Resources Conservation Service


An element or compound, such as nitrogen, phosphorus, and potassium, that is necessary for plant growth.


Operations and Maintenance.

Observation Well

A non-pumping well used for observing the elevation of the water table or piezometric surface.

Operating Pressure

Distribution system water pressure measured in pounds per square inch (psi).  Municipal systems are generally maintained between 50 and 80 psi.


A condition where the average amount of water withdrawn from a groundwater basin exceeds the average amount of water flowing into the groundwater basin.


Application of water via sprinkler irrigation to areas other than the intended area.

Peak Use (demand)

The maximum demand occurring in a given period, such as hourly or daily or annually.

Peak/Off-peak Rates

Water rates that vary during the day, usually with a higher charge for water usage during the hours of greatest water demand and a lesser charge for usage during hours of lesser water demand.

Per Capita Use

Water use per person.

Perched Groundwater

Local saturated zones above the water table which exist above an impervious layer of limited extent.


Downward movement of water through the soil profile or other porous media.

Percolation Rate

The rate, usually expressed as a velocity, at which water moves through saturated granular material.  The term is also applied to quantity per unit of time of such movement, and has been used erroneously to designate Infiltration Rate or Infiltration Capacity.

Permanent Wilting Point

Soil water content below which plants cannot readily obtain water and permanently wilt. Sometimes called permanent wilting percentage.


The property of a membrane or other material that permits a substance to pass through it.


Passable; allowing fluid to penetrate or pass through it.


Term used to indicate the alkalinity or acidity of a substance, ranked on a scale from 1.0 (most acidic) to 14.0 (most basic), with 7.0 being neutral.  Affects many chemical and biological processes in water - a range of pH 6.5-8.2 is optimal for most organisms.


An element found in fertilizers and sediment runoff which can contribute to the eutrophication of water bodies.

Phreatic Surface

The free surface of groundwater at atmospheric pressure


An instrument used to measure water pressure head in a conduit, tank, soil, etc.

Plant Water Requirement

The amount of irrigation water needed to replace moisture depleted from the soil around plant roots as a result of evapotranspiration.

Point-of-use Meter

A meter that measures water flow at the actual usage point, such as a faucet or toilet.


An impurity (contaminant) that causes an undesirable change in the physical, chemical, or biological characteristics of the air, water, or land that may be harmful to or affect the health, survival, or activities of humans or other living organisms.


The property of being porous, having pores; the ratio of minute channels or open spaces (pores) to the volume of the sample.

Potable Water

Water that meets federal and state water quality standards for water delivered to utility customers.

Pounds per square inch (psi)

A standard measure of water pressure.

Precipitation Rate

Application rate for sprinkler irrigation, generally measured in inches per hour.

Primary Treatment

The first stage of a wastewater treatment process in which floating material and large suspended solids are removed by mechanical processes, such as settling.

Process Water

Water used by industrial water users for producing products.  Process water can include water used in manufacturing processes, water used for testing, cleaning and maintaining equipment and water used to cool machinery or buildings used in the manufacturing process.


Small single-cell microbes; frequently observed as actively moving organisms when impure water is viewed under a microscope; cause a number of widespread human illnesses, such as malaria, and thus can present a threat to public health.

Rain sensor

A device connected to an irrigation system that senses rainfall and automatically shuts off an irrigation system.  In 2013 the Minnesota Legislature enacted a requirement that all automatic irrigation systems must automatically sense and shut off irrigation systems when there is sufficient moisture.  (

Rain Shutoff Device

A device connected to an irrigation controller that overrides scheduled irrigation when significant precipitation is detected.

Rainwater Harvesting

The capture and use of runoff from rooftops.

Raw Water

Untreated water.

Real Losses

In a water distribution system audit, real losses are the physical loss of water from the distribution system prior to reaching the customer.  Real losses include leakage from piping and reservoir walls, as well as storage overflows caused by faulty control equipment or operator error.


Replenishment of a water body or an aquifer with water.

Recharge Areas

An area where water flows into the earth to resupply a water body or an aquifer.


To return to original condition.


A man-made facility for the storage, regulation, and controlled release of water.

Resource Conservation and Recovery Act (RCRA)

Legislation passed in 1976 aimed at protecting the environment, including waterways, from solid waste contamination either directly, through spills, or indirectly, through groundwater contamination.


1) Replacement of existing water fixtures or appliances with new and more efficient ones. 2) Replacement of parts for a fixture or appliance to make the device more efficient.


Use of treated municipal wastewater effluent or stormwater runoff for specific, direct, beneficial uses.  See reclaimed water. Also used to describe water that is captured on-site and utilized in a new application.

Revenue Water

In a distribution system water audit, the amount of water that is billed and produces revenue.

Reverse Osmosis

A process to remove dissolved solids, usually salts, from water.  Salty water is forced through membranes at high pressure, producing fresh water and a highly concentrated brine.

Riparian Area

The area along a waterway.


The portion of precipitation, melted snow or irrigation water that runs off the land into surface waters.

Safe Drinking Water Act (SDWA)

Federal drinking water quality legislation administered by the U.S. Environmental Protection Agency.


The state of being infused with so much of a substance (Example: water) that no more can be absorbed, dissolved, or retained.


The Soil Conservation Service, now known as the NRCS (National Resources Conservation Service).

Seasonal Block Rate

A water billing rate structure that charges higher rates during peak irrigation season than the off-peak season.

Seasonal Demand

Partitioning of water demand into baseline use (in the winter) and higher use due to seasonal factors such as irrigation and evaporative cooling.

Secondary Treatment

The second step in most wastewater treatment systems, which removes most of the oxygen-demanding substances (organics) and suspended solids via biological processes.

Sensitivity Analysis

The process where the assumptions of analysis are tested to determine how much influence they have on the results.

Soil Amendment

The addition of organic and inorganic materials to soil to improve its texture, nutrient content, moisture-holding capacity, and infiltration rate.

Soil Classification

The systematic arrangement of soils into classes of one or more categories.  Broad groupings are made on the basis of general characteristics, and subdivisions are made on the basis of more detailed differences in specific properties.

Soil Conservation

Protection of soil against physical loss by erosion and chemical deterioration by the application of management and land-use methods that safeguard the soil against all natural and human-induced factors.

Soil Improvement

The addition of soil amendments.

Soil Moisture

Water stored in soils.

Soil Moisture Deficit

The amount of water required to saturate the plant root zone at the time of irrigation, expressed as a depth of water in inches or feet.

Soil Moisture Replacement

The amount of water applied to replace a portion of the soil moisture deficit, expressed as a depth of water in inches or feet.

Soil Moisture Sensor

A device placed in the ground at the plant root zone depth to measure the amount of water in the soil.  Soil moisture sensors are also used to control irrigation and signal whether watering is required or not.

Soil Polymer

A natural or synthetic compound that has the capacity to hold water for use by plants.  Best suited for container plants or in sandy soil.  Can reduce irrigation frequency but does not reduce a plant’s water requirement.

Soil Texture

The classification of soil based on its percentage of sand, silt, and clay.

Source Protection

Protection of a water source, ranging from simple sanitary surveys of a watershed to the development and implementation of complex land use controls, in an effort to avoid water contamination.

Spray Head

A sprinkler irrigation nozzle installed on a riser that delivers water in a fixed pattern.

Spray Irrigation

Sprinkler irrigation using spray heads on fixed or pop-up risers and having relatively high precipitation rates.

Sprinkler Irrigation

Overhead delivery of water via spray heads, stream rotors, or impact heads.  Precipitation rates will vary depending on system layout and type of head used.

Sprinkler Run Time

The minutes of irrigation per day, based on the weekly irrigation requirement and irrigation days per week.

Sprinkler Station

A group of sprinklers controlled by the same valve.

Sprinkler Valve

The on-off valve, usually electric, that controls an irrigation or sprinkler station.


(1) Water artificially impounded in surface or underground reservoirs for future use. (2) Water naturally detained in a drainage basin, such as groundwater, channel storage, and depression storage.

Stormwater Runoff

Surface runoff of water resulting from rain or snow storms.  Also called storm drainage.


The lowering of ground surface due to extraction of material from subsurface. Can be caused by water or oil extraction from the ground.

Subsurface Drip Irrigation

The application of water via buried pipe and emitters, with flow rates measured in gallons per hour.

Sunk Costs

Costs that have already been incurred and are not reversible.

Surface Tension

The elastic-like force in a body, especially a liquid, tending to minimize, or constrict, the area of the surface.

Surface Water

Water that remains on the earth’s surface, in rivers, streams, lakes, or reservoirs.


The characteristic features of a land surface; topography.


The buildup of organic material at the base of turfgrass leaf blades.  Thatch repels water and reduces infiltration capacity.

The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA or Superfund)

Legislation passed in 1980 and amended in 1986 by the Superfund Amendments and Reauthorization Act (SARA); provides for short-term actions called removal actions in response to accidents and improper handling of hazardous materials which pose an immediate threat to human health and safety.  It also provides for long-term actions called remedial actions for cleanups of other sites which pose no immediate threat to public safety.

The Emergency Planning and Community Right-to-Know Act of 1986 (SARA Title III)

Law requiring federal, state and local governments and industry which are involved in either emergency planning and/or reporting of hazardous chemicals to allow public access to information about the presence of hazardous chemicals in the community and releases of such substances into the environment.

The Rivers and Harbors Act of 1899

Legislation regulating the discharge of refuse of any kind into navigable waters.


A measurement of energy equivalent of burning 100 cubic feet (often referred to as 1 CCF) of natural gas.

Tiered Pricing

Increasing block-rate pricing.


The detailed mapping or description of the features of a relatively small area, district, or locality; the relief features or surface configuration of an area.


The organic-rich upper layer of soil in which plants have most of their roots.


The passing of water through living plant membranes into the atmosphere.

U.S. Army Corps of Engineers (USACE)

In civil works, the USACE has authority for approval of dredge and fill permits in navigable waters and tributaries thereof; the USACE enforces wetlands regulations, and constructs and operates a variety of water resources projects, mostly notably levees, dams and locks.

U.S. Bureau of Reclamation (USBR)

The Federal agency whose mandate was to reclaim the arid west of the United States.  Operating in 17 western states, this agency builds, operates and maintains a variety of irrigation, power, and flood control projects.

U.S. Geological Survey (USGS)

The Federal Agency chartered in 1879 by Congress to classify public lands and to examine the geologic structure, mineral resources, and products of the national domain.  As part of its mission, the USGS provides information and data on the nation's rivers and streams that are useful for mitigation of hazards associated with floods and droughts.

Ultra Low Flush Toilet (ULFT)

A toilet that flushes with less than 1.28 gpf.

Unaccounted for water

A term relating to water loss.  The American Water Works Association recommends discontinuing use of this term.  See Non-revenue water.

Unavoidable Annual Real Losses (UARL)

The low level of leakage that a well managed water distribution system could, in theory, attain assuming that state of the art leakage control technologies are being effectively utilized.

Uniform Block Rate

A water billing rate structure that does not vary with the amount of water use.

Unmetered Water

Delivered water that is not measured for accounting and billing purposes.

UPC (uniform plumbing code)

The model plumbing code, prepared by the International Association of Plumbing and Mechanical Officials.


United States Department of Energy


United States Environmental Protection Agency

User Class

Customers having similar characteristics (commercial, single-family residential, etc.) grouped together for billing or program purposes.


United States Forest Service


Used alternately to describe a provided resource, such as water, gas, or electric as well as for the provider of the resource.

Vadose Zone

The zone just above the water table where soil pores may contain air or water, or both.  Also called the zone of aeration.


Device to control the flow of water.


Effluent water from residences, businesses and other water users that contains contamination.

Water Audit

An on-site survey and assessment of water-using hardware, fixtures, equipment, landscaping, irrigation systems, and management practices to determine the efficiency of water use and to develop recommendations for improving water use efficiency.

Water Balance

In a water distribution system water audit, the summary and accounting of all categories of water use.

Water Budget

The quantity of water needed to maintain plants and other features in an ornamental landscape.

Water Conservation

The US Water Resources Council defines water conservation as activities designed to (1) reduce the demand for water, (2) improve efficiency in use and reduce losses and waste of water, and (3) improve land management practices to conserve water.

Water Conservation Incentive

An effort designed to promote customer awareness about reducing water use and motivate customers to adopt specific conservation measures.

Water Conservation Measure

An action, behavioral change, device, technology, or improved design or process implemented to reduce water loss, waste or use.

Water Harvesting

The capture and use of rooftop runoff from rainfall.

Water Losses

In a water distribution system water audit, the difference between system input volume and authorized consumption.  Water losses are the sum of apparent losses and real losses.

Water Reuse

Use of treated municipal wastewater effluent or stormwater runoff for specific, direct, and beneficial uses.  See reclaimed water.  Also used to describe water that is captured on-site and utilized in a new application.

Water-efficient Landscape

A landscape that minimizes water requirements and consumption through proper design, installation, and management.

Water-Energy Nexus

The relationship between the amount of water utilized to generate and transmit energy, and the amount of energy utilized to collect, treat, store, and distribute potable water.


The pressurized water delivery pipeline that delivers water from the supply system to the customer's service line


A land area, defined by topography, soil, and drainage characteristics, within which stormwater runoff collects to a common stream or lake.


A lowland area, such as a marsh or swamp, which is saturated with moisture, and often the natural habitat of abundant wildlife.

Wetting Area (pattern)

The soil area wetted by a sprinkler, bubbler or low-volume emitter.


Water Research Foundation


A trademarked term denoting landscaping that involves the selection, placement, and care of low water use and native ground cover, turf, plants, shrubs, and trees.  Xeriscape is based on seven principles: proper planning and design, soil analysis and improvement, practical turf areas, appropriate plant selection, efficient irrigation, mulching, and appropriate maintenance.

Zero footprint

The complete reduction and/or offset of the potable water demand of a proposed urban development project by conservation, use of recycled water, or other measures.

Zone of Aeration

The zone just above the water table where soil pores may contain air or water, or both.  Also called the vadose zone.

Zone of Saturation

The zone where soil pores are filled with water.