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Acre-foot - a volume of water that would cover one acre to a depth of one foot, or 325,850 gallons of water.

Adaptive plants - non-indigenous plants that easily adapt to the climate and thus require little or no supplemental irrigation once established.

Adjusted water budget - an amount of water used to maintain a landscape that is based on area and ET rate.

Agricultural irrigation - water distribution systems and practices in agriculture.

Air heat exchange - cooling method, involving no water loss, during which a fan blows air past finned tubes carrying re-circulating cooling water.

American National Standards Institute (ANSI) - an association involved in developing standards for a wide range of products including plumbing fixtures.

American Society of Mechanical Engineers (ASME) - a professional organization whose Codes and Standards Committee helps to write and publish ANSI standards.

American Water Works Association (AWWA) - a professional organization serving the drinking water supply profession.

American Water Works Association Research Foundation (AWWARF) - a non-profit organization that sponsors research for the drinking water supply profession.

Anti-Siphon Valve - a control valve with a built-in atmospheric vacuum breaker (backflow preventer). Most commonly used in residential irrigation systems.

Application efficiency - The ratio of the average depth of irrigation water infiltrated and stored in the root zone to the average depth of irrigation water applied, expressed as a percent.

Application rate - the amount of water delivered to a given area, typically expressed in inches or inches per hour for irrigation.

Applied water - water applied by irrigation, usually expressed as a depth of water in inches or feet.

Aquifer - Underground water-bearing geologic formation or structure.

Arable - Having soil or topographic features suitable for cultivation.

Arid - a climate characterized by less than 10 inches of annual rainfall.

Artificial recharge - the intentional addition of water to an aquifer.

Audit (end-use) - a systematic accounting of water uses conducted to identify opportunities for improved efficiency.

Automatic irrigation - delivery of water to a landscape using a timer, a system of valves, and sprinklers.

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 capacity (or available soil moisture) - The amount of water held in the soil that is available to the plants.

Available water-holding capacity (AWHC) - the amount of moisture plants can store in the root zone, usually expressed as a depth of water in inches or feet.


Backflow prevention device - a safety device used to prevent reverse flow of water back into a potable water supply line; typically used in conjunction with automatic irrigation systems.

Ball valve - a type of valve that controls the water by means of a rotating ball with a hole through the center of it. When the hole is aligned with the water flow the water flows freely through the valve with almost no friction loss. When the ball is rotated so that the hole is not aligned the flow is completely shut off.

Baseline - an established value or trend used for comparison when conditions are altered.

Benefit-cost ratio - benefits and costs measured in terms of money and expressed as a ration, with benefits divided by costs; typically used as an evaluation tool for different water efficiency measures and programs.

Best management practice (BMP) - a set of practices, measures or procedures that are beneficial, empirically proven, cost effective, and widely accepted by the professional community.

Block-rate pricing - a method of charging for water based on the volume used. As more water is used, the price increases (or decreases) through a series of blocks. These pricing structures are designed to encourage efficient use of a resource.

Bluegrass - a variety of cool-season turf grass; also a style of folk music.

Booster pump - a device to increase the water pressure is a system where some pressure already exists. For example, if water comes from a water company at 40 PSI of pressure but you need 80 PSI of pressure for an irrigation system, you would use a booster pump to increase the pressure.

Bubbler - a type of sprinkler head that delivers water a level area where the water slowly infiltrates to the soil. Typically used to irrigate shrubs and trees.

Budget (water budget) - an accounting of water use for a given activity or location over a fixed period of time.

Building footprint - the area covered by a building as represented in a two-dimensional plan.

Bushing - a small piece used to connect two pipes of different sizes together. A standard reducer bushing has one male end (for the larger pipe) and one female connection (for the smaller pipe).

Butterfly valves - a type of valve that uses a rotating disk to control the water flow. A true butterfly valve has two half-disks, hinged together in the center. When the disks or "wings" are folded together the water flows freely past them. When folded out into the water stream the wings block the flow. Most "butterfly valves" are really "rotating disk" valves. They are mostly used on larger pipe sizes, seldom less than 3" in size. Ball valves are used on smaller size pipes.


Catch-can test - a measurement of precipitation from a sprinkler system in which water is collected in graduated containers (catch-cans) placed at evenly spaced intervals for a specific period of time.

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

Central irrigation control - a computerized system that programs sprinkler clocks from a centralized location using a computer.

Check valve - a device that prevents drainage of water from the low points of an irrigation circuit after irrigation stops.

Cistern - a tank (often underground) use to store water (often rainwater or graywater).

Closed loop cooling tower - water-conserving cooling tower system in which water used for cooling is recycled through a piping system that cools the water; the water is cooled as air exchanges heat with the pipes.

Conservation - increasing the efficiency of energy use, water use, production, or distribution; the act of conserving or preserving from injury or loss; the protection of rivers, forests and other natural resources.

Conservation pricing - water rate structures that increase the price of water as more water is used with the goal of encouraging more efficient use.

Consumptive use (evapotranspiration) - 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.

Continuous-flow irrigation - system of irrigation water delivery where each irrigator receives his allotted quantity of water at a continuous rate.

Continuous flow system - the continuous use, by an industry, of deionized water to remove contaminants from products and equipment.

Cooling tower - water-conserving cooling device in which cooling water loses heat when a portion of it is evaporated.

Cooling tower makeup - water added to the recirculating cooling tower water stream to compensate for water evaporation losses.

Cooling water - water typically used to cool heat-generating equipment or to condense gases in a thermodynamic cycle.

Cooling water blowdown - procedure used to reduce total dissolved solids by removing a portion of poor-quality recirculating water.

Cooling water evaporation - cooling water recycling approach in which water loses heat when a portion of it is evaporated.

Cool-season grass - turf grass varieties that are typically not damaged by sub-freezing temperatures. Includes bluegrass, Kentucky bluegrass, perennial rye grass, red fescue, and tall fescue.

Coring - the mechanical cultivation of turf grass using hollow tines to remove cores of turf for the purpose of improving soil texture and increasing air and water circulation. Also called aeration.

Cost-beneficial - when the benefits are equal to or greater than the costs.

Cost-effectiveness - a comparison of total benefits against total 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.


Decreasing block rate - Pricing that reflects per-unit costs of production and delivery that go down as customers consume more water.

Deep percolation - the movement of water by gravity downward through the soil profile beyond the root zone; plants do not use this water.

Demand forecast - a projection of future water use.

Demand management - the practice of systematically reducing water use for a broad spectrum of utility customers through efficiency measures and conservation, often as an alternative to purchasing new water or expanding water treatment facilities.

Demand scheduling - method of irrigation scheduling whereby water is delivered to users as needed and which may vary in flow rate, frequency and duration. Considered a flexible form of scheduling.

Desalination - a process that converts seawater to freshwater through the removal of mineral salts and other dissolved solids.

Design Pressure - the total pressure available to operate an irrigation system.

Distribution efficiency - measure of the uniformity of irrigation water distribution over a field.

Distribution system - a system of pipes and valves that conveys water from a treatment plant to end users.

Ditch - a constructed open channel for conducting water.

Diversion (water) - removal of water from its natural channels for human use.

Diversion (structure) - channel constructed across the slope for the purpose of intercepting surface runoff; changing the accustomed course of all or part of a stream.

Draw Down - the depth (from the top of the well) to the water in a well when the pump is operating. The water level typically drops when the pump is running.

Drainage - the process of removing surface or subsurface water from a soil or area.

Drip irrigation - a type of micro-irrigation systems that delivers water is slow drips to plants through a network of plastic pipes and emitters.

Drought - climatic condition in which there is insufficient soil moisture available for normal vegetative growth for an extended period of time.

Drought condition - the hydrologic conditions during a defined drought period in which rainfall and runoff are much less than average.

Dual-flush toilet - a toilet designed to use a lower volume of water to flush liquid wastes and a higher volume of water to flush solid wastes.


Early closure flapper - a toilet flapper valve that closes sooner than normal to reduce the volume of water flushed.

Effective precipitation - the total depth of rainfall minus the volume lost to evaporation and leaching during a specific time period.

Efficiency - the use of a resource that maximizes the benefit and minimizes consumption of the resource.

Effluent - wastewater, treated or untreated, that flows out of a treatment plant, sewer, or industrial outfall.

Elevation head - a measurement of pressure.

Emitter - a drip irrigation system fitting that delivers water to plants at a slow and predictable rate.

End use - fixtures, appliances, plumbing devices, equipment, and activities that use water.

End user - a consumer of water; a utility water customer.

Energy Policy Act (1992) - a federal law enacted by President George Bush that established maximum allowable water-use requirements for toilets, urinals, showerheads, and faucets manufactured and sold in the United States.

Environment - the sum of all external influences and conditions affecting the life and development of an organism or ecological community.

Erosion - a gradual wearing away of soil or rock by running water, waves, or wind.

Established landscape - a landscape that has been in place for an extended period of time where the roots of the plants are well developed.

Evaporation - the process by which water changes from liquid to vapor.

Evapotranspiration (ET) - water lost from the surface of soils and plants through the processes of evaporation and transpiration combined.

Evapotranspiration (ET) rate - a measure of the amount of water required to maximize plant growth. This measure is calculated from climatic conditions and factors such as temperature, solar radiation, humidity, wind, time of year, precipitation, etc.


Fallow - land plowed and tilled and left unplanted.

Faucet aerator - a device that can be installed in a sink to reduce water flow rate by adding air to the water.

Faucet restrictor - a device inserted into a faucet that forces water through a smaller orifice for the purpose of reducing the flow rate.

Field capacity - the depth of water retained in the soil after ample irrigation or heavy rain when the rate of downward movement has substantially decreased, usually one to three days after irrigation or rain, expressed as a depth of water in inches or feet. Also called field moisture capacity.

Fixed charge - the portion of a water bill that does not vary with water use.

Fixed costs - costs for a utility that do not vary with the amount of water produced, delivered, and sold to customers.

Flat rate - a fee structure in which the price of water is constant regardless of the amount consumed.

Flood irrigation - a method of irrigating where water is applied from field ditches onto land that has no guide preparation such as furrows, borders or corrugations.

Floodplain - the land adjacent to a river or stream that is subject to flooding.

Flow rate - the amount of water moving through a pipe, fixture, stream, etc. Often measured in gallons per minute.

Flow restrictor - a washer-like disk that fits inside a faucet or showerhead and reduces the water flow rate.

Flushometer toilet - a tankless toilet with the flush valve attached to a pressurized water supply pipe. These toilets are typically found in large institutional and commercial buildings such as schools, airports, office buildings, etc.

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


Gate (irrigation) - structure or device for controlling the rate of flow into or from a canal or ditch.

Gated pipe - portable pipe with small gates installed along one side for distributing irrigation water to corrugations or furrows.

Gage - device for registering water level, discharge, velocity, pressure, etc.

Gage height - elevation of water surface measured by a gage.

Gauging station - specific location on a stream where systematic observations of hydrologic data are obtained through mechanical or electrical means.

gpc - gallons per cycles

gpcd - gallons per capita per day

gpd - gallons per day

gpf - gallons per flush

gph - gallons per hour

gphd - gallons per household per day

gpl - gallons per load (of laundry or dishes)

gpm - gallons per minute

gpy - gallons per year

Gravity flow - a water system that relies on gravity to provide the pressure required to deliver the water. Consists of a water source located at a higher elevation than the water delivery points.

Gravity-flush toilet - the standard tank style of toilet that uses water (at standard gravitational pressure) to perform flushing functions.

Graywater - domestic wastewater composed of wash water from kitchen sinks, bathroom sinks and tubs, clothes washers, and laundry tubs that can be used for non-potable purposes such as irrigation.

Green industry - the industry that includes design, maintenance, installation, and management of landscapes.

Groundwater - water beneath the earth's surface.

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 - the flow to groundwater storage from precipitation, infiltration from streams, and other sources of water; the use of reclaimed wastewater, by surface spreading or direct injection, to prevent saltwater intrusion into freshwater aquifers, to store the reclaimed water for future use, to control or prevent ground subsidence, and to augment non-potable or potable ground water aquifers.

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

Growing season - the period, often the frost-free period, during which the climate is such that crops can be produced.


Hardscape - landscaped areas covered by non-living materials such as concrete, bricks, rocks, wood, pavement, etc.

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.

Horticultural practices - activities to maintain plants and landscapes such a s fertilization, mowing, and thatch control.

Hydrology - science dealing with the properties, distribution, and flow of water on or in the earth.

Hydrozone - a portion of a landscaped area comprising plants with similar water requirements.


Increasing block rate - pricing that reduces water use by structuring water rates to increase per-unit charges as the amount used increases.

Incremental cost - the additional cost associated with adding a specific amount (increment) of capacity to a water supply.

Infiltration rate - the rate of water entry into the soil expressed as a depth of water per unit of time in inches per hour or feet per day. The infiltration rate changes with time during irrigation.

Instream flow - water flows for use within a defined stream channel e.g., flows intended for fish and wildlife.

Integrated resource planning - a planning process emphasizing least-cost principles and balanced consideration of supply and demand management options for meeting water needs.

Invasive plant - a non-indigenous plant that invades and takes over substantial areas of an ecosystem.

Investor-owned utility - a privately owned utility usually regulated by a state public utility commission.

Irrigated acreage - irrigable area actually irrigated in any one year.

Irrigation - application of water to lands for the purpose of growing plants.

Irrigation audit - an on-site evaluation of an irrigation system to assess its water-use efficiency as measured by distribution uniformity, irrigation schedule, and other factors.

Irrigation controller - a sprinkler clock or timer.

Irrigation cycle - a scheduled application of water by an irrigation system with a defined start time and duration. A cycle may include multiple watering zones.

Irrigation districts - special units of local government that control the bulk of surface water supplies in the western United States.

Irrigation efficiency - the ratio of the average depth of irrigation water that is beneficially used to the average depth of irrigation water applied, expressed as a percent. Beneficial uses include satisfying the soil water deficit and any leaching requirement to remove salts from the root zone.

Irrigation plan - a 2-D drawing/plan that illustrates the layout of an irrigation system.

Irrigation requirement - quantity of water, exclusive of effective precipitation, that is required for maintaining a landscape.

Irrigation scheduling - careful choice of irrigation application rates and timing to help irrigators maintain yields with less water.

Irrigation timer - a device that can be programmed to regulate the time and duration of irrigation; a sprinkler clock.

Irrigation water requirement - a measure of the water required in addition to precipitation to obtain desired crop yield.

Isolation valve - a valve used for isolating all or part of an irrigation system for repairs, maintenance, or winter shut-down (winterization). Common types of isolation valves are the ball valve, butterfly valve, and gate valve.


Kilowatt-hour (kWh) - a unit of electric power equivalent to the energy provided by one thousand watts acting for one hour.


Landscape area - the total area on a property that contains landscaping elements. Usually equivalent to the total area minus the building footprint and paved driveways and paths.

Landscape water requirement - a measure of the supplemental water required to maintain the optimum health and appearance of landscape plants and features.

Leaching - removal of soluble material from soil or other permeable material by the passage of water through it.

Leaching requirement - quantity of irrigation water required for transporting salts through the soil profile to maintain a favorable salt balance in the root zone for plant development.

Leak detection - Systematic methods for identifying water leakage from pipes, plumbing fixtures, and fittings.

Lifeline rate - a minimum, sometimes subsidized water rate created to help meet basic human needs.

Low-flow faucet - a faucet that uses no more than 2.5 gallons per minute at 80 pounds of pressure per square inch.

Low-flow plumbing - plumbing equipment that uses less water than was considered standard prior to January 1, 1994.

Low-flow showerhead - A showerhead that requires 2.5 gallons of water per minute or less.

Low-flush toilet - a toilet that requires 1.6 gallons of water per flush or less.

Low-volume urinal - a urinal that uses no more than 1.0 gallons per flush.

Low-water-use landscape - use of plants that are appropriate to an area's climate and growing conditions.

Low-water-use plants - plants that require less than 30% of reference ET to maintain optimum health and appearance.

Lysimeter - an isolated block of soil, usually undisturbed and in situ, for measuring the quantity, quality, or rate of water movement through or from the soil.


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

Marginal-cost pricing - a rate design method where prices reflect the costs associated with producing the next increment of supply.

Market penetration - the extent to which a water efficiency measure is actually implemented.

Matched precipitation rate - an equal rate of water delivery from sprinkler heads with varying arc patterns within an irrigation circuit. Matched precipitation rates are central to achieving uniform distribution or irrigation water.

Medium-water-use plants - plants that require 30 to 50 percent of reference ET to maintain optimum health and appearance.

Megawatt - one million watts; a measure of power plant output.

Meter - an instrument that measures the volume of water use.

Metering - use of metering equipment that can provide essential data for charging fees based on actual customer use.

mgd - million gallons per day.

mgy - million gallons per year.

Microclimate - the climate conditions of a specific habitat or place in a small, limited area.

Micro-irrigation - an irrigation system with small, closely spaced outlets used to apply small amounts of water at low pressure.

MOU - memorandum of understanding.

Mulch - a covering placed around plants to minimize weed growth and reduce evaporation. Typically leaves, bark, wood chips, straw, compost, or other organic materials.

Multiple start times - an irrigation schedule where the system is programmed to start and run several times during the day.


Native landscape - a landscape that features plants and grasses indigenous to the region.

Native plants - plants that are indigenous to a region and require litter or no supplemental irrigation after establishment.

Natural landscape - a landscape created to reflect the character and spirit of nature and the native surroundings.

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

Neutron probe - an instrument used to estimate soil moisture. Relates the rate of attenuation in pulsed neutron emissions to soil water content.

Nonconsumptive water use - water withdrawn for use but not consumed and thus returned to the source.

Non-residential water use - water use by industrial, commercial, institutional, public, and agricultural users.


Operating pressure - the pressure at which a device or irrigation system is designed to operate.

Ozonation - the process of applying to a liquid for disinfection.


Pan evaporation - evaporative water losses from a standardized pan. Pan evaporation is sometimes used to estimate crop evapotranspiration and assist in irrigation scheduling.

Peak demand - the highest total water use experienced by a water system.

Peak/off-peak rates - rates charged in accordance with the most and least popular hours of water use during the day.

Per capita use - the amount of water used by one person during one 24 hour period. Typically expressed as gallons per capita per day (gpcd).

Percolation - downward movement of water through the soil profile or other porous media.

Percolation rate - (1) the rate at which water moves through porous media, such as soil; and (2) intake rate used for designing wastewater absorption systems.

Permanent wilting point - soil water content below which plants cannot readily obtain water and permanently wilt. Sometimes called "permanent wilting percentage.

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 source - a specific site from which waste or polluted water is discharged.

Pop-up sprinkler head - a sprinkler head that retracts below ground level when it is not operating.

Potable water - water that is safe for drinking.

Pounds per square inch (psi) - a standard measure of water pressure.

Precipitation rate - the amount of water applied by a sprinkler system in a specific unit of time.

Present value - future expenditures expressed in current dollars by adjusting for a discount rate that accounts for financing costs.

Pressure gauge - a device used to measure water pressure. The best pressure gauges are "liquid filled", however most cheap gauges work well enough for irrigation system use.

Pressure loss - loss in water pressure caused by friction of water against the inner walls of pipe or system components.

Pressure reducer - a component designed to reduce water pressure in supply system pipe or irrigation lines.

Pressure regulator - a device used to limit water pressure.

Pressurized-tank toilet - a toilet that flushes by using pressure from the waterline entering a pressurized plastic vessel inside the tank.

Price elasticity of demand - a measure of the responsiveness of customer water use to changes in the price of water; measured by the percentage change in price.

Price gouging - excessive water rate increases that are unfair to water customers.

Pricing/rate structure - System used by water utility managers to charge customers for water usage.

Pricing signals - rate structures that encourage water conservation by customers.


Rain sensor - a device that automatically shuts off an irrigation system after a set amount of precipitation falls.

Rain switch - a simple on/off switch on an irrigation system that makes it easy to shut the system down during a rainstorm.

Rainwater harvesting - the capture and use of runoff from rainfall.

Rationing - mandatory water use restrictions typically imposed during a drought.

Recharge - the addition of water to the groundwater supply by natural or artificial means.

Recirculating cooling water - recycling cooling water to greatly reduce water use by using the same water to perform several cooling operations.

Reclaimed water - wastewater that is treated and reused to supplement water supplies.

Recycled water - a type of reuse water usually run repeatedly through a closed system; sometimes used to describe reclaimed water.

Reference evapotranspiration (ETº) - the evapotranspiration of a broad expanse of adequately watered cool-season grass 4 to 6 inches in height. A standard measurement for determining maximum water allowances for plants so that regional differences in climate can be accommodated.

Reservoir - a body of water, such as a natural or constructed lake, in which water is collected and stored for use.

Residential End Uses of Water Study (REUWS) - the Residential End Uses of Water study published by the American Water Works Association Research Foundation in 1999.

Residential water use - water use in homes and apartments.

Resistance block - type of soil moisture probe used to monitor soil moisture conditions to help determine when water should be applied.

Retrofit - replacement of existing equipment with equipment that uses less water.

Return flow - that portion of the water diverted from a stream that finds its way back to the stream channel, either as surface or underground flow.

Reverse osmosis - common process used to produce deionized water from municipal water.

Riparian - of, on, or pertaining to the bank of a river, pond, or lake.

Riser - the connection between a sprinkler or other irrigation device and the pipe that supplies the water to it.

Root zone - that depth of soil which plant roots readily penetrate and in which the predominant root activity occurs.

Runoff - the portion of precipitation, snow melt, or irrigation that flows over the soil, eventually making its way to surface water supplies.


Safe Drinking Water Act (SDWA) - federal drinking water quality legislation administered by the U.S. Environmental Protection Agency.

Saline - the condition of containing dissolved or soluble salts. Saline soils productivity is impaired by high soluble salt content. Saline water is that which would impair production if used to irrigate sensitive crops without adequate leaching to prevent soil salinization.

Scale - precipitate that forms on surfaces in contact with water as a result of chemical or physical change.

Seasonal rate structure - water rate structure that bills all water consumed during the summer or peak season at a higher rate than during the other seasons.

Secondary treatment - the second step in most publicly owned waste treatment systems, which removes floating and settleable solids and about 90 percent of the oxygen-demanding substances and suspended solids. Disinfection is the final stage of secondary treatment.

Secondary wastewater treatment plant - a facility that reduces pollutants and suspended solids to a greater level than that achieved by a primary treatment plant; the water goes through additional treatment processes, producing "cleaner" wastewater.

Sediment load - amount of sediment carried by running water.

Sedimentation - deposition of waterborne sediments due to a decrease in velocity and corresponding reduction in the size and amount of sediment which can be carried.

Seepage - the movement of water into and through the soil from unlined canals, ditches, and water storage facilities.

Self-closing faucet - a faucet that automatically shuts off the water flow after a designated amount of time, usually a few seconds.

Semi-arid climate - a climate characterized by 10 to 20 inches of annual precipitation.

Service area - the geographic area served by a water utility.

Simple payback period - the length of time over which the cost savings associated with a conservation measure must accrue to equal the cost of implementing the measure.

Simple water budget - a water budget that is the product of reference evapotranspiration, irrigated area, and a conversion factor.

Siphonic-jet urinal - a urinal that automatically flushes when the water flowing continuously through its tank reaches a preset level.

Softening - the removal of calcium and magnesium ions from water.

Soil amendment - the addition of organic and inorganic materials to soil to improve its texture, nutrient load, moisture-holding capacity, and infiltration rate.

Soil classification - the systematic arrangement of soils into classes of one or more categories or levels to meet a specific objective. 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 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 all 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 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 nozzle that delivers water in a fixed spray pattern.

Sprinkler heads - devices that distribute water over a given area for irrigation (or to put out fires). The primary purpose of sprinklers, however, is to get golfers wet on cold mornings.

Sprinkler irrigation - a method of irrigation in which the water is sprayed, or sprinkled, through the air to the ground surface.

Static water pressure - water pressure as measured when the water is not moving. The "not moving" part is critical, if the water is moving it isn't "static".. When measuring static water pressure all the water outlets on the pipe must be closed. So if you're measuring the static pressure at a house you connect the pressure gauge, then take the reading while all the faucets, the ice maker, etc., are turned off.

Stream rotors - sprinkler heads that deliver rotating streams of water in arcs or full circles at relative low precipitation rates.

Subirrigation - applying irrigation water below the ground surface either by raising the water table within or near the root zone, or by use of a buried perforated or porous pipe system that discharges directly into the root zone.

Submetering - use of separate meters to indicate individual water use in apartments, condominiums, and trailer homes, while the entire complex of units continues to be metered by the main supplier.

Subsurface irrigation - applying irrigation water below the ground surface either by raising the water table within or near the root zone, or by use of a buried perforated or porous pipe system that discharges directly into the root zone.

Surface soil - upper part of the soil ordinarily moved in tillage, or its equivalent in uncultivated soils, about 10 to 20 cm in thickness.

Surface water - an open body of water such as a river, stream, or lake.

Supplemental irrigation - the application of water to a landscape to supplement natural phenomena.

Surcharge - a special charge included on a water bill to recover costs associated with a particular activity, facility, use, or to convey a message about water prices to customers.

Surface irrigation - the application of water to land by surface flow.

Surface water supply - water supplied from a stream, lake, or reservoir.

Surge irrigation - a surface irrigation technique wherein flow is applied to furrows (or less commonly, borders) intermittently during a single irrigation set.


Tailwater - applied irrigation water that runs off the lower end of a field. Tailwater is measured as the average depth of runoff water, expressed in inches or feet.

Tall fescue - a hybridized cool-season turf grass characterized by deeper root systems and greater drought tolerance than bluegrass.

Tensiometer - instrument consisting of a porous cup filled with water and connected to a manometer or vacuum gage; used for measuring the soilwater matric potential (soil moisture content).

Thatch - the buildup of organic material at the base of turf grass blades. Thatch repels water and reduces infiltration capacity.

Tiered pricing - increasing block-rate pricing.

Time-of-day pricing - pricing that charges users relatively higher prices during utilities' peak use periods.

Toilet dam - a flexible rectangular device placed across the bottom of a toilet tank to reduce the amount of water used per flush.

Toilet displacement device - a toilet retrofit device (such as a dam, bag, bottle, or rock) used to displace water in the toilet tank in order to reduce the volume required for flushing.

Toilet flapper - the valve that controls flushing in a gravity-tank toilet.

Total dissolved solids (TDS) - a measure of the minerals remaining in water after evaporation has occurred.

Transpiration - the transfer of water vapor from plants to air.

Trapway - the outlet of a toilet where the waste exits to the drainline.

Turf - hybridized grass that forms a dense growth of blades and roots when regularly mowed.


Under-irrigation - the difference between the water stored in a plant root zone during irrigation and the amount needed to refill the root zone to field capacity.

Uniform rate - a pricing structure in which the price per unit of water is constant, regardless of the amount use.

Utility - public water service provider.


Valve - a device used to control the flow of water. Isolation valves are used to shut-off water for repairs. Control valves turn on and off the water to the individual circuits of sprinklers or drip emitters. Check valves allow the water to flow in only one direction. Master valves are located at the water source and turn on and off the water for the entire irrigation system when not in use.

Valve zone - an area where irrigation is all controlled by a single control valve. Each valve zone must be within only one hydrozone.

Variable charge - the portion of a water bill that varies with water use; also known as a commodity charge.


Warm-season turf grass - turf grass that grows vigorously during warm summer months but goes dormant or dies at temperatures below 50ºF. Includes bermuda grass, buffalo grass, St. Augustine grass, and zoysia grass.

Wastewater - spent or used water from individual homes, a community, a farm, or an industry that contains dissolved or suspended matter.

Wastewater treatment plant - a facility with an engineered system designed to remove pollutants, such as phosphorus and nitrogen, from municipal and industrial wastewater for discharge into surface waters.

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 budget - the amount of water required to maintain plants in a landscape; a method of establishing water efficiency standards by prescribing limits on water applications to landscapes.

Water conservation - activities designed to reduce the demand for water, improve efficiency in use, and reduce losses and waste of 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 delivery system - Reservoirs, canals, ditches, pumps, and other facilities to move water.

Water demand - water requirements for a particular purpose, as for irrigation, drinking, toilet flushing, bathing, clothes washing, etc.

Water efficiency - accomplishment of a function, task, process, or result with the minimal amount of water feasible; an indicator of the relationship between the amount of water required for a particular purpose and the quantity of water used or delivered.

Water efficiency measure - a specific tool or practice that results in more efficient water use and thus reduces water demand.

Water efficiency standard - criterion creating maximum or acceptable levels of water use.

Water efficient landscape - a landscape that minimizes water demand through design, installation, and management.

Water feature - a pool, fountain, water sculpture, waterfall, or other decorative element that includes water. Many water features recycle water thus reducing consumption.

Water harvesting - the capture and use of runoff from rainfall.

Water holding capacity - amount of soil water available to plants. See available soil water.

Water quality - the chemical, physical, and biological characteristics of water.

Water reclamation - the treatment of wastewater to make it reusable, usually for non-potable purposes.

Water recycling - the treatment of urban wastewater to make it reusable for a specific beneficial purpose.

Water reuse - using wastewater or reclaimed water from one application for another application. The deliberate use of reclaimed water or wastewater must be in compliance with applicable rules for a beneficial purpose (landscape irrigation, agricultural irrigation, aesthetic uses, ground water recharge, industrial uses, and fire protection).

Water right - under the riparian system, a legally protected claim to take possession of water occurring in a natural waterway and to divert that water for beneficial use; under the prior appropriation system, a property or legal claim to withdraw a specified amount of water in a specified time frame for beneficial use.

Watershed - the area of land from which all precipitation and runoff drain into a single water source.

Water surcharge - imposition of a higher rate on excessive water use .

Water system - a series of interconnected treatment and conveyance facilities owned and operated by a water supplier.

Water table - in an unconfined aquifer, the top of the saturated zone; the level at which a well penetrates the top of an unconfined aquifer.

Water transfers - selling or exchanging water or water rights among individuals or agencies.

Water use efficiency - employing water-saving practices to reduce costs and to slow the depletion of the water supply to ensure future water availability.

Weather station - a facility where meteorological data are gathered.

Weed - any undesirable or troublesome plant.

Wetlands - lands including swamps, marshes, bogs, and similar areas such as wet meadows, river overflows, mud flats, and natural ponds. An area characterized by periodic inundation or saturation, hydric soils, and vegetation adapted for life in saturated soil conditions.


Xeriscape™ - 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.

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