Discover Common Water-related Acronyms, Definitions, and Units of Measurement

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Acronyms (A-M)

Alternating current 

American Society of Civil Engineers, 

Advanced Metering Infrastructure

Automatic meter reading equipment 

American National Standards Institute, 

Automated remote metering 

American Society of Mechanical Engineers, 

Average winter consumption 

Alliance for Water Efficiency 

Applied water requirement, the gross amount of water that must be applied to a plant or grass to accommodate evapotranspiration (ET) including runoff and water required to overcome system efficiencies 

American Water Works Association, 

Best management practice 

A joint effort by state and federal agencies to resolve water supply and quality issues involving the San Francisco Bay and Sacramento-San Joaquin Delta. 

California Water Efficiency Partnership (Formerly CUWCC),

Conditions, covenants, and restrictions 

Consortium for Energy Efficiency, 

Commercial and Industrial 

Commercial, industrial, and institutional 

California Irrigation Management Information System, 

Customer information system 

Customer identification number 

California Urban Water Conservation Council. See CALWEP

Direct current 

Data collection unit (in an AMR system) 

Dwelling Unit 

Distribution uniformity- a measure of irrigation efficiency 

Draft Environmental Impact Report 

Energy factor 

Estimated generalized least-squares 

Environmental Impact Statement 

Environmental Protection Agency (US government), 

Energy Policy Act, first implemented in Oct. 1992 

Effective rainfall 

Evapotranspiration, water loss via evaporation from plant surfaces and soil at base of plant and transpiration from plant leaf or grass surfaces 

Reference ET for a standard crop of grass 4 inches to 7 inches tall 

High density, refers to MF and other types of units constructed in dense configuration 

Homeowners association 

U.S. Department of Housing and Urban Development, 

Irrigation Association, 

Industrial, commercial, institutional

Irrigation Efficiency 

Infrastructure Leakage Index 

Integrated resources planning 

Landscape coefficient (includes crop coefficient, and coefficients for shade and slope) 


Liters Per Minute 

Liters Per Hour 

Liters Per Flush 

Leadership in Energy and Environmental Design (U.S. Green Bldg Council) 

Low-impact development (for storm water quality) 

Maximum performance testing (of toilets and other fixtures). This is a trademarked label. 

Modified energy factor 

Multi-family dwelling unit 

Multi-family residential 

Meter interface unit. Also known as a Telemetry Interface Unit. 

Acronyms (N-Z)

Number. The number of cases from which a summary statistic or analysis is derived. 

National Institute of Standards and Technology,  

Net present value of a series of payments, costs, or benefits 

The probability value of a statistical hypothesis test; the probability of getting a value of the test statistic as extreme or more extreme than that observed by chance alone, if the null hypothesis is true. 

Project advisory committee 

Project oversight committee 

Point of use 

Public utilities commission 

Present value of a series of payments, costs, or benefits 

Ordinary least squares 

Coefficient of determination 

Read, bill, and collect 

Residential End Uses of Water Study (AWWA 1999, 2016). 

Radio frequency 

Root mean square error 

Ratio utility billing systems, a calculation method that uses a compensation factor to allocate utility costs among users, most often used in the context of multi-family or commercial billing 

Soil Conservation Service now Natural Resources Conservation Service, 

Single-family dwelling unit (detached unless otherwise specified) 

Smart Water Application Technology: class of irrigation controllers using soil, weather, or ET-based measurements to control irrigation scheduling 

St. Dev. 
Standard deviation 

Seemingly unrelated regression 

Subregional water reclamation system 

An inferential statistical test for comparing two means. A dependent or paired t-test is used to compare the mean difference score between paired measurements. 

Unavoidable annual real losses 

Ultra-low flow 

Ultra-low flow toilet. Standard "low consumption toilets". Refers to toilets which consume 1.6 gallons (6 liters) or less of water when flushed. A bit of a misnomer as toilets do not "flow" unless they are broken and are wasting water. 

Unified North American Requirements for toilet fixtures (and other devices) 

Water district 

Water factor 

Water Research Foundation,


Definitions of Words and Phrases (A-F)

A connection to a water system, which is billed for service. 

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

Adjustment factor 
A decimal fraction used to modify reference evapotranspiration to reflect an efficiency standard. 

Aerate, aerification 
Also called coring. 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. 

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

Allocation billing 
Used interchangeably with RUBS (see RUBS). Also, see Utility Allocation. 

Allocation types 
The basis by which utility expenses are apportioned to users. Common types include unit count, occupant count, occupant ratio, square footage, and a combination of occupant count and square footage. Less common types include bathroom count and fixture count. 

Apparent losses 
In a distribution system water audit apparent losses represent the "paper" losses that occur when volumes of water reach a use, but are not properly measured or recorded. They include customer meter inaccuracies, unauthorized consumption and data handling error in customer billing systems. Apparent losses cause water utilities a loss of revenue but also interject a degree of error in the assessment of customer consumption, making it more difficult to evaluate the success of water conservation and loss control measures. 

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 the irrigation system that reaches the soil surface. 

Appropriative water rights 
An exclusive right to take water as specified by the amount, source, use, location and period of time of its physical control. ‘First in time, first in right.’ 

Square footage or acreage measured or estimated from scale plans, photographs, or from on-site measurements. 

Arid climate 
A climate characterized by less than 10 inches of annual precipitation. 

As-built plans 
Site plans reflecting the actual constructed conditions of a landscape irrigation system or other facility installation. 

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. 

Audit (system) 
An accounting of water in all stages of the water delivery system including treatment and distribution. See resource on Water Audit Process Introduction. 

Authorized consumption 
In a distribution system water audit, the annual volume of metered and/or unmetered water taken by customers, the water supplier and others who are authorized to do so. Authorized consumption and Water losses sum to System input volume. 

Avoided cost 
The cost of an activity or facility that could be avoided by choosing an alternative course of action. 

Backflow prevention device 
A safety device used to prevent contamination of the potable water supply from the reverse flow 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 float actuated valve, part of the toilet trim in the toilet tank that controls the refill water flowing into the toilet tank when it is not full. 

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

Best management practice (BMP) 
A practice or combination of practices established as the most practicable means of increasing water use efficiency. 

Bill stuffer 
An advertisement or notice included with a utility bill. 

Billing cycle 
The regular interval of time when customer’s 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, either 100 cubic feet (abbreviated HCF or CCF) or 1000 gallons (kgals). 

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

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

Blow-out toilet 
A type of toilet, normally found in hospitals or sites subject to high use, that has an extra wide trapway, is generally supplied by at least a two-inch service line to the building, uses extra water (with a powerful flush) to remove waste from the bowl. 

Budget (water-use) 
See Water budget. 

A variety of cool-season turfgrass of the genus Poa. Commercially produced turfgrass mixes usually are a blend of bluegrass varieties

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. 

Business Classification Code (BCC) 
A numeric classification of customers into groups with similar uses or processes. See SIC code. 

(element abbreviation Ca) A mineral that is commonly found in water. It contributes to the hardness of water. 

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. 

Categorical variables 
Variables that are not scaled, but are "nominal," that is, there is no direction or number associated with the levels. 

Central irrigation control system 
A computerized system for programming irrigation controllers from a central location; using a personal computer and radio waves or hard wiring to send program information to geographically distant controllers. 

Check valve 
A device that prevents drainage of water down to the low points of an irrigation system after the system is shut off. Also called anti-drain valve. A valve that allows flow in only one direction, preventing backflow. 

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

Climate factor 
Evapotranspiration minus precipitation. One of the four factors used to determine landscape water use. 

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. These do not include multi-family residences, agricultural users, or customers that fall within the industrial or institutional classifications. 

Commodity rate 
Charging for water based on the volume of use. Not a flat or fixed rate. 

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

Conjunctive use 
The coordinated use and storage of surface and ground water supplies to improve water supply reliability and potentially increase the overall availability of water. 

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 pricing 
Billing rates that encourage water conservation. See Inclining block rate. 

Conservation rate structure 
A pricing structure billed by the quantity of commodity delivered and tied to the costs associated with that delivery, designed to provide an accurate price signal to the consumer. An increasing block rate structure, if the top tier equals the utility’s marginal cost of new water, is one example of a conservation rate structure. 

Consumer surplus 
The difference between what a commodity is worth to a consumer and what she actually pays for it. 

Continuous variables 
Variables that are numerical and can be scaled. 

Conversion factor 
A decimal fraction used to convert one unit of measure to another, such as inches of depth over a square foot to gallons (0.623). 

Cooling tower 
A mechanical device that cools a circulating stream of water by evaporating a portion of it. A cooling tower is part of a system that provides air conditioning or equipment cooling. It usually includes a heat exchanger, recirculating water system, fans, drains, and make-up water supply. 

Cool-season grass 
Grass that does not ordinarily lose its color unless the average air temperature drops below 32 F (0 C) for an extended period; it is not usually damaged by subfreezing temperatures. Cool-season grasses grow actively in cool weather of spring and fall and slowly in summer heat. Examples include bluegrass, fescue and ryegrass. 

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. 

An analysis that compares the financial benefits of water savings to the costs needed to achieve those savings. 

The resources needed for a course of action. 

Crop coefficient (Kc) 
A factor used to adjust reference evapotranspiration and calculate water requirements for a given plant species. (Also called plant factor or landscape coefficient) 

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

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

Cycles of concentration 
A measure of cooling tower water recirculation. Calculated as the ratio of chloride concentration in fresh make-up water to the chloride concentration in cooling tower water. 

Declining block rate 
A commodity rate 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 domestic use. 

Demand management 
Measures, practices or incentives deployed by utilities to change the pattern of demand for a service by its customers or slow the rate of growth for that service. 

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 process of removing salt from brackish water or sea water, producing water suitable for fresh water uses and a concentrated brine. 

Developed water 
Water that has been captured in reservoirs, diverted from rivers/streams, or accessed by wells for use by society. 

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

Displacement device 
An object or device that displaces water in a toilet tank. The displaced volume no longer flushes through the toilet. Displacement objects include dams, bottles or bags. Bricks are discouraged due the possibility the brick could degrade in the tank. 

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

Distribution uniformity (DU)
An expression of how evenly water is applied to a landscape by an irrigation system. DU is calculated in the field by analyzing the results of catch-can tests. 

Door hanger 
An advertisement, notice, or product hung on a resident’s doorknob – often used to promote customer participation in water conservation programs. 

Door-to-door-drop-off or canvas 
Refers to a method of retrofit kit delivery involving a person leaving a kit at the door and, in the case of a canvas, returning later to offer installation assistance or verify owner installation. 

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. 

Dual and multiple programming 
The capacity of an irrigation controller to schedule the frequency and duration of irrigation cycles to meet varying water requirements of plants served by a system. Grouping plants and laying out irrigation stations by similar water requirements facilitates multiple programming. 

Dual-distribution system 
A system distributing both potable and lower-quality water. Distribution is through separate piping networks. 

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

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

A measure of the amount of water used versus the minimum amount required to perform a specific task. In irrigation, the amount of water beneficially applied divided by the total water applied. 

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

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

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

End use 
A fixture, appliance, or other specific object or activity that uses water. 

Energy Policy Act of 1992 (EPAct) 
This Act established water use standards for toilets, urinals, showerheads, and faucets installed in the United States. 

Escalation rate 
The average rate of increase in the inflation-adjusted future cost of water supply. 

Estimated Water Use (EWU) 
The amount of water estimated to be needed by the landscape during one year. 

The lower course of a river where its flow is commingled by the sea, resulting in brackish water. 

ET factor 
A factor used to set a landscape water efficiency goal. Also know as an "adjustment factor". 

Evapotranspiration (ET) 
The quantity of water evaporated from soil surfaces and transpired by plants during a specific time. 

External costs and benefits 
An external cost is when one party adversely affects another party either by reducing its productivity or well being. An external benefit is where one party beneficially affects another party either by increasing its productivity or its well being, or lowering its costs. 

External costs and benefits. 

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

Fecal coliform 
The coliform bacteria group that are 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. 

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

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

Flapper valve 
A pliable valve in the opening at the bottom of a toilet tank that regulates water flow into the toilet bowl. 

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. 

A commercial/institutional type toilet, which generates a flush by the opening of a valve directly connected to the pressurized building water system. 

Definitions of Words and Phrases (G-M)

Untreated wastewater that has not been contaminated by any toilet discharge, has not been affected by infectious, contaminated, or unhealthy bodily wastes, and that does not present a threat from contamination by unhealthful processing, manufacturing, or operating wastes. Graywater can be used for non-potable applications such as irrigation. Graywater includes wastewater from bathtubs, showers, bathroom washbasins, clothes washing machines, and laundry tubs but does not include wastewater from kitchen sinks or dishwashers. 

Green industry 
The trades, professions, and disciplines related to landscape and irrigation research, design, installation, and management. 

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

Groundwater banking 
Storing surface water in a groundwater basin, or using surface water in lieu of groundwater, to increase the available groundwater supply. 

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

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

Hardware efficiency 
A percentage or fraction value that represents the portion of water applied by an irrigation system that is beneficial to the plants. See distribution uniformity. 

H-axis clothes washer 
Horizontal-axis clothes washer. 

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-using plants 
Plants with a crop coefficient greater than 0.7. 

Historic basis 
Past water consumption history. 

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

Hot water on demand system
A system of pumping hot water more quickly from the water heater to the fixture calling for water for the purpose of reducing the wait time (and associated waste) for hot water. 

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

Hydrologic cycle 
Movement of water as it evaporates from rivers, lakes or oceans, into the atmosphere, returns to earth as precipitation, flows into rivers to the ocean and evaporates again. 

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. Impact heads have large radii and relatively low precipitation rates and do not provide matched precipitation rates for varying arc patterns. 

Inclining block rate 
A commodity rate whose unit price increases with increasing water use. 

Incremental benefits and costs 
The next unit of cost required to achieve the next unit of benefit. 

Individual metering 
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. 

Industrial user 
Water users that are primarily manufacturers or processors of materials as defined by the Standard Industrial Classifications (SIC) Code numbers 2000 through 3999. 

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

The rate of change in a price index. 

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. 

Institutional user 
Water-using establishment dedicated to public service. This includes schools, churches, hospitals, and government facilities. All facilities serving these functions are considered institutional regardless of ownership. 

Instream uses 
The beneficial uses of water within a river or stream, such as providing habitat for aquatic life, sport fishing, river rafting or scenic beauty. 

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

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 (IE) 
A value representing the amount of water beneficially applied, divided by the total water applied. Also, the product of decimal equivalents representing hardware efficiency and management efficiency. 

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. Layout of pipes may be depicted diagrammatically, but location of irrigation heads and irrigation schedules should be specified. 

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. 

Landscape coefficient 
A factor used to determine evapotranspiration for a specific site and set of plants. The landscape coefficient is a function of plant type, plant density and microclimate. 

Landscape irrigation auditor 
A person who has had landscape water audit training and passed a certification exam. 

Landscape water budget (LWB) 
A volume of applied irrigation water expressed as a monthly or yearly amount, based on ETo and the plant material being watered. 

Law of the River 
A collection of interstate agreements, international treaties, legislation, and judicial decisions that form the basis of allocation decisions for the Colorado River. 

Leak correlator 
An electronic device that uses probes placed on exposed portions of a water distribution system to pinpoint the location of a leak. 

Leak detection 
The procedure of pinpointing the exact location of leaks from water pipes and fittings. 

Leakage management 
The organized, proactive functions of a water utility to control distribution system leakage to a economic minimum. Includes appropriate combinations of active leakage control (flow analysis, leak detection) and repair, pressure management, and system rehabilitation. 

Leak noise logger 
A device that gathers and stores sounds used in detecting and pinpointing water distribution system leaks across a given area of the system 

Leak survey 
The systematic process of listening for leaks in a distribution system. 

Life-cycle analysis 
Examines the costs and benefits of an action over its entire expected life span. 

Limited turf areas
Restriction of turfgrass to a prescribed fraction of the landscape area. 

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 standards (2.2 gpm or less at 80 psi). 

Low flow showerhead 
A showerhead that meets 1992 EPAct standards (2.5 gpm or less at 80 psi) 

Low flow toilet 
A 3.5 gpf toilet, as mandated by California in a 1977 law that took effect 1980. 

Low head drainage 
Drainage of water from irrigation lines at the lowest elevations in an irrigation station. 

Lower basin states 
The states of Nevada, Arizona and California, which form part of the Colorado River watershed. 

Low-water-using plants 
Plants with a crop coefficient of less than 0.3. 

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

Management efficiency 
A percentage or fraction of the total applied water that represents the portion beneficially applied. This is determined by scheduling, maintenance, and repair of irrigation systems. 

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

Market price 
The price for a commodity in a market. 

Mass mailing
Mailing information or retrofit kits to many customers – often using a mailing service. 

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. 

Mediterranean climate 
A climate characterized by moderate temperatures throughout the year, dry summers and rainy winters. 

Medium-water-using plants 
Plants with a crop coefficient of 0.4 to 0.6. 

Device that measures utility usage. 

Meter (water) 
An instrument for measuring and recording water volume. 

Meter register 
Mechanical device (sometimes used synonymously with the term "Face") that uses a system of gear reductions to integrate the rotation of the moving element of a meter’s measuring chamber into numerical units. 

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

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

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

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. 

Multiple linear regression 
Method of determining the relationship between several independent or predictor variables and a dependent variable. The dependent variable must be a continuous variable. 

Multiple start times 
An irrigation controller’s capacity to accept programming of more than one irrigation start-time per station per day. 

Municipal and industrial (M&I) 
Water supplies serving humans or man-made activities, as opposed to agricultural water supply. 

Definitions of Words and Phrases (N-Z)

NAICS (formally SIC codes) 
North American Industry Classification System. A consolidation of the codes for the US, Canada and Mexico. Produced by the US Office of Management and Budget. 

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

Net present value 
The present value of benefits minus the present value of costs. 

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) added to real losses and apparent losses. 

Operation and Maintenance. 

Water use occurring outside the natural stream channel. 

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

Opportunity costs 
The true costs faced by a decision maker, measured as the highest valued alternative that is foregone when an action is taken. 

A groundwater basin is being overdrafted when, over a number of years, the average amount of water withdrawn from the basin exceeds the average amount of water flowing into the basin. 

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

Partial-capture submetering 
Type of submetering where only a portion of the total water consumption in each unit is measured. 

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

Per capita residential use 
Average daily water use (sales) to residential customers divided by population served. 

Per capita use 
Water use per person. 

Percent switch 
A feature of an irrigation controller that allows percent changes in the duration of programmed irrigation. 

Plant factor 
See crop coefficient. 

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

Positive displacement meter 
A type of water meter used to measure relatively low flows (such as residential uses). 

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

Pounds-per-square-inch (psi) 
A unit measure of pressure. In this case, the pressure exerted by water in a distribution system. 

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

Pressure assist toilet 
A toilet that uses the water distribution system pressure to compress air in a bladder that fills with water after the toilet is flushed. The compressed air forces the water from the bladder into the toilet bowl at an increased velocity. 

Pressure loss 
The reduction in water pressure due to friction of water against the inner walls of pipe and components. 

Pressure reducer 
A water system component that reduces the downstream pressure of water, often used in irrigation systems, always used in drip systems. 

Pressure regulation 
Maintaining distribution system water pressure within certain limits. 

Pressure regulating valve 
1) A device, often installed downstream of the customer meter, to reduce high pressures to a set amount. Often required where the existing system pressure exceeds 85 psi. 2) A device installed on input water supply mains or irrigation systems to regulate water pressure in a zone or district metered area (DMA) to protect against pressure surges and to control leakage. 

Pressure testing 
Subjecting a fully loaded section of a water distribution system to maximum normal pressure (or normal pressure plus a safety factor) against a closed downstream shut-off. 

Pressure zone 
A three dimensional zone in the water distribution system where the pressure is allowed to vary only within certain limits, generally dictated by the elevation of the water tank serving the zone. 

Pressure-compensating emitter 
A drip-irrigation emitter designed to deliver water at a consistent flow rate under a range of operating pressure. 

Price elasticity
A measure of the responsiveness of demand to changes in price. 

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 filtration. 

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. 

Public service announcement (PSA) 
An inexpensive or free advertisement or message on mass media that serves the public good. 

Public Trust Doctrine 
Doctrine rooted in Roman law, which holds that certain natural resources are the property of all, to be held in trust for the citizens by the state. 

Public user 
Publicly owned water customers, such as schools, parks, and government buildings. Also referred to as institutional customers. 

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

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. Real losses represent a waste of water and energy resources since they are volumes of water extracted from a source, treated to prevailing standards, but never reaching beneficial use. 

In a radio frequency (RF) based AMR system, the device that receives the meter data transmissions for the central data collection device. 

Recirculating task 
Water that is employed for the same task multiple times. In a cooling tower, water is used to carry heat away from a heat source, cooled by evaporation in a cooling tower, and returned to the heat source to repeat the task. 

Reclaimed water 
Municipal wastewater effluent that is given additional treatment and distributed for reuse in certain applications. Also referred to as recycled water. 

Reclamation (water) 
Treatment of degraded water for a beneficial purpose. 

Recycled water 
Used to describe reclaimed water. 

Reference evapotranspiration (ETo) 
The water requirements of a standardized landscape plot, specifically, the estimate of the evapotranspiration of a broad expanse of well-watered, 4-to-7 inch-tall cool-season grass. 

Remote-control valve 
An electric solenoid valve, wired to an irrigation controller, that controls the flow of water to an irrigation station. 

In a radio frequency (RF) based AMR system, the device that receives and amplifies the meter RF signals in order to transmit them to the receiver. 

Retention rate 
The percent of devices that remain in-place over time after initially being installed or distributed. 

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

Retrofit on resale 
A regulation that requires plumbing fixtures to be upgraded to current code at the time property is sold. 

Use of treated municipal wastewater effluent 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 components if System input Volume that are billed and produce 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 rights 
A water right based on the ownership of land bordering a river or waterway. 

Surface flow of water off of a specific area. 

Seasonal block rate 
A commodity rate that is higher in the peak irrigation season than the off-peak season. 

Seasonal demand
Partitioning of 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 light suspended solids. Disinfection is often the final step of secondary treatment. 

Secondary wastewater treatment plant 
A facility that employs secondary wastewater treatment. 

Semiarid climate 
A climate characterized by 10 to 20 inches of annual precipitation. 

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

Service area (territory) 
The geographic area(s) served by a utility. 

Short-term program 
A temporary water conservation program put in place to deal with a specific concern such as a water shortage. 

SIC Code (Standard Industrial Classification) 
A system devised by the federal government to classify industries by their major type of economic activity. The code may extend from two to eight digits. This term has been superceded by the NAICS. 

Single-family (SF) unit 
A residential dwelling unit built with the intent of being occupied by one family. It may be detached or attached (i.e., townhouses). 

Soil amendment 
Organic and inorganic materials added to soils to improve their texture, nutrients, moisture holding capacity, and infiltration rates. 

Soil improvement 
The addition of soil amendments. 

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. 

Solar radiation 
Energy from the sun. The single most dominant factor in determining ET values, measured by a lysimeter. 

Spray head 
A sprinkler irrigation nozzle installed on a riser that delivers water in a fixed pattern. Flow rates of spray heads are high relative to the area covered by the spray 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 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. 

An irrigated area controlled by a single irrigation valve. 

Storm drainage 
Surface runoff of water resulting from rain or snow storms. 

Stream rotors 
Sprinkler irrigation heads that deliver rotating streams of water in full or partial circles. Some types use a gear mechanism and water pressure to generate a single stream or multiple streams. Stream rotors have relatively low precipitation rates, and multiple stream rotors can provide matched precipitation for varying arc patterns. 

Structured plumbing system 
Properly sized and well insulated hot water main and hot water risers, including a dedicated hot water main segment connecting the farthest hot water point of use to the water heater. 

The practice of using meters to measure master-metered utility consumption by individual users. Also, see partial-capture submetering and total-capture submetering. 

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. 

Sunken costs 
Costs that have already been incurred and are not reversible. 

Supply-side measures 
Increasing water supply by developing more raw water, generally building reservoirs and canals or drilling groundwater wells. 

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

System input volume
In a distribution system water audit, this is the annual volume put into the distribution system. It includes water from an agency's own sources as well as imported water. 

Tall fescue 
A hybridized cool-season turfgrass characterized by deeper roots and more drought tolerance than bluegrass. 

Telemetry interface unit 
A device that translates meter data prior to transmission to a receiver. Also known as a Meter Interface Unit (see MIU). 

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

Toilet flapper 
A pliable valve in the opening at the bottom of a toilet tank that regulates water flow into the toilet bowl. 

Toilet displacement device
See Displacement device. 

Toilet tank fill cycle regulator 
A device that reduces the amount of water that goes into the overflow tube and hence into the toilet bowl during a toilet flush. 

Total-capture submetering 
Type of submetering where all of the actual water consumption in each unit is measured. 

A radio frequency (RF) system component that sends usage data from a meter to a receiver. 

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

Trihalomethanes (THMs) 
Four chemicals that are a reaction by-product when chlorine is added as a disinfectant to water containing certain organic material. These chemicals are called disinfection by-products and are regulated by the USEPA. Some of them are suspected carcinogens. 

Turbine meter 
A type of water meter that generally utilizes a propeller to measure high flows (such as for irrigation or commercial/industrial users). 

Hybridized grasses that, when regularly mowed, form a dense growth of leaf blades and roots. 

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. A calculation exists to determine the UARL and includes miles of water main, average system pressure and number of service connections as input parameters. The ratio of current annual real losses over the UARL gives the Infrastructure Leakage Index, ILI 

Ultra Low Flush Toilet (ULFT) 
A toilet that flushes with 1.6 gallons or less. 

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

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

Uniform block rate 
A commodity rate that does not vary with the amount of water use. 

See distribution uniformity. 

United States Bureau of Reclamation (USBR, the Bureau) 
Federal agency that built and operates water projects in the western United States. Part of the Department of Interior. 

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

UPC (uniform plumbing code) 
The model plumbing code, prepared by International Association of Plumbing and Mechanical Officials, that the 22 western States use as the basis for their State plumbing codes. 

Upper basin states 
The states of Wyoming, Colorado, Utah and New Mexico which form part of the Colorado River watershed. 

Usable groundwater storage 
The quantity of additional space available for water storage in a groundwater basin without outflow. 

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

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

Utility allocation 
Determining resident charges for utilities by means of a formula rather than measured usage. 

Device to control the flow of water. 

Variable costs 
The costs that change in response to changes in level of output. 

Warm-season grass 
Grasses that grow vigorously in warm summer months and then generally lose their green color and are dormant in winter, if the average air temperature drops below 50 to 60 F; some may die if exposed to subfreezing temperatures for extended periods. Examples of warm season grasses include Bermuda, Zoysia and Buffalo grasses. 

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

Wastewater treatment plant 
A facility designed to remove contamination from municipal and industrial wastewater prior to discharge into surface waters. 

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

Water audit 
1) An on-site survey of an irrigation system or other water use setting to measure hardware and management efficiency and generate recommendations to improve its efficiency. 2) For water distribution systems, a thorough examination of the accuracy of water agency records and system control equipment to identify, quantify, and verify water and revenue losses. See also Audit (site), Audit(system), Audit (irrigation). 

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

Water banking 
A process whereby unused water allocations are held in storage and made available for future water allocations. 

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

Water budget approach 
A method of establishing water-efficiency standards for landscapes by providing the water necessary to meet the ET of the landscaped area. 

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-less urinal 
A urinal that works without water or flush valves. Instead a cartridge filled with a sealant liquid is placed in the drain. The lighter than water sealant floats on top of the urine preventing odors from being released into the air and allowing urine to pass into the sewer system without the use of water. The urinals are installed into the regular waste lines and the cartridge and sealant must be periodically replaced, but water supply lines and flush valves are not necessary. The urinal bowl surfaces are urine repellent and daily cleaning procedures are typically the same as for flushed urinals. 

Water loss control
See Audit (system). 

Water losses
In a 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 meter size 
Normally corresponds to the pipe bore, for example 1". For some models a second designation refers to the matching pipe end connections. For example, a 5/8" x 3/4" meter has a nominal 5/8" and ¾" straight pipe threads. 

Water rationing 
Mandatory water restrictions temporarily placed on customers, as with short-term or drought programs. 

Water reuse 
Use of treated municipal wastewater effluent 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 right 
A legal entitlement authorizing water to be diverted from a specified source and put to beneficial, non-wasteful use. It is a property right, but the holder doesn’t possess the water itself – they possess the right to use it. The primary types of water rights are appropriative and riparian (See). There are also prescriptive (openly taking water to which someone else has the right) and pueblo (a municipal right based on Spanish and Mexican law) water rights. 

Water sales 
Water deliveries that are metered and billed based on the quantity of use. 

Water softener 
A device that reduces water hardness by replacing calcium and magnesium ions with sodium ions. 

Water transfers 
The exchange of a water allocation from a willing seller to a buyer, usually between irrigation district (seller) and urban water agency (buyer). 

Water use efficiency 
A measure of the amount of water used versus the minimum amount required to perform a specific task. In irrigation, the amount of water beneficially applied divided by the total water applied. 

Water use profile 
A quantitative description (often displayed graphically) of the different water uses at a residence, business site, or utility service area. 

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

A land area, defined by topography, soil, and drainage characteristics, within which raw waters are contained. They can collect to form a stream or percolate into the ground. 

Waterworks bronze 
Refers to one of two generally accepted alloys, one with a nominal composition of 81% copper, 3% tin, 7% lead and 9% zinc or another with a nominal composition of 85% copper, 5% each tin, lead and zinc. 

A lowland area, such as a marsh or swamp, that 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. 

Wholesale water agency 
A water utility that develops and distributes water not for delivery to individual customers, but to other retail water purveyors. 

Willingness to accept 
The amount one would have to pay an individual if she could be induced by a payment to go without an item. 

Willingness to pay 
The amount an individual would be willing to pay if she could obtain the item by making a payment. 

Landscaping practice 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. 

Zero read test 
A test for water leakage on customer piping using a feature of the customer’s water meter.

Units of Measurement

acre-feet, = 325,851 gallons or 43,560 cubic feet 

acre-feet per annum (year) 

British Thermal Unit 

Hundred cubic feet = 748 gal. 

Cubic feet = 7.48 gal. 

Gallons, 1 gallon = 0.134 cubic feet 

Gallons per capita per day 

Gallons per capita per day 

Gallons per day 

Gallons per flush (of a toilet or urinal) 

Gallons per minute 

Gallons per square foot 

Hundred cubic feet = 748 gal. 


One thousand gallons = 134 cubic feet 



Liters per capita per day 

Liters per flush (of a toilet or urinal) 

Million gallons 

Millions of gallons per day 

Millions of gallons per year 


Pounds per square inch 

Square feet