Glossary of Terms

  • A

    AWWA
    American Water Works Association. The drinking water industry's trade association; headquarters are in Denver.

    acre-foot
    A volume of water equal to 1 foot in depth covering an area of 1 acre, or 43,560 cubic feet; approximately 325,851 gallons. One acre-foot of water serves about four residential households for one year.

    alluvial water
    Ground water that is hydrologically part of a natural surface stream system.

    appropriate (verb)
    To take the legal actions necessary to create a right to take water from a natural stream or aquifer for application to beneficial use.

    appropriation
    The right to take water from a natural stream or aquifer for beneficial use at a specified rate of flow, either for immediate use or to store for later use. Usually confirmed by a water court decree. (See prior appropriation, riparian rights and water right.)

    aquifer
    An underground layer of sand, gravel or rock through which water can pass and is stored. Aquifers supply the water for wells and springs. They may be alluvial or nontributary in nature.

    ascending block rates (or increasing block rates)
    A rate structure that divides a customer's water use into blocks, or consumption amounts, with the rate for each subsequent block priced higher than the previous block.

    augmentation plan
    A court-approved plan that allows a water user to divert water out of priority as long as adequate replacement is made to the affected stream system and water right in quantities and at times so as to prevent injury to the water rights of other users.

    augmentation source
    The supply of water used to replace depletions in an augmentation plan.

    average winter consumption 
    The amount of water used on average by a customer during the winter; provides a good indication of indoor water use.

  • B

    backflow prevention
    Prevention of the flow of any foreign liquids, gases or substances into the distribution pipelines of a potable water supply; accomplished by an air gap or mechanical backflow obstacle.

    beneficial use
    Lawful and prudent use of water that has been diverted from a stream or aquifer for human or natural benefit.

    block
    A volume of water used in setting water rates; a quantity or volume of water sold at a particular rate.

    bypass flow
    Water that is allowed to flow past a diversion structure or storage facility.

  • C

    call
    A demand that upstream water rights with more recent (junior) priority dates than the calling right cease diverting; the exercise of a senior water right holder in "calling" for his or her water rights, requiring junior water right holders to allow water to pass to the senior right holder.

    Citizens Advisory Committee (CAC)
    A nine-member public standing committee that advises the Denver Board of Water Commissioners on policies and programs and facilitates public involvement in the review of the agency's activities. Members are appointed by the Board of Water Commissioners.

    Clean Water Act
    The federal law that establishes how the United States will restore and maintain the chemical, physical and biological integrity of the country's waters (oceans, lakes, streams and rivers, ground water and wetlands). The law provides protection for the country's waters from both point and nonpoint sources of pollution.

    coliform
    A bacteria that originates in the digestive system of mammals. If found in water, it alerts lab technicians that pathogens might be present.

    combined service area
    The area in which water service is provided by Denver Water, including the City and County of Denver and suburban areas served via contracts with Total Service, Read and Bill and Master Meter (wholesale) distributors. Includes both "in fill" and expansion areas that would logically be served by Denver Water in the future.

    compact
    A formal agreement between states concerning the use of water in a river or stream that flows across state boundaries.

    compact call
    The requirement that an upstream state cease or curtail diversions of water from the river system that is the subject of the compact to satisfy the downstream state's compact entitlements.

    conduit
    A 24-inch or larger diameter pipe carrying raw or potable water from or to treatment facilities, reservoirs and delivery points feeding a distribution system.

    conjunctive use
    Coordinated use of surface and ground water supplies to meet demand so that both sources are used more efficiently.

    conservation
    Obtaining the benefits of water more efficiently, resulting in reduced demand for water. Sometimes called "end-use efficiency" or "demand management."

    consumption pattern
    The variation in the amount of water a customer uses over time.

    Continental Divide
    An imaginary boundary line that runs north to south through the Rocky Mountains, separating rivers that flow west to the Pacific Ocean from those that flow south and east toward the Gulf of Mexico and the Atlantic Ocean.

    cubic feet per second (cfs)
    A rate of water flow passing a given point, amounting to a volume of one cubic foot for each second of time. Equal to 7.48 gallons per second, 448.8 gallons per minute or 1.984 acre-feet per day.

    cumulative impact analysis
    A review of the cumulative environmental, social and economic impacts of proposed water projects and activities associated with development within an ecosystem or drainage area.

  • D

    demand forecast
    A prediction of future water use. Most water demand forecasting models are either directly or indirectly based upon projected changes in demographic data, such as population, etc.

    demand management
    Reductions of water usage accomplished with temporary measures, such as drought restrictions, or with long-term conservation programs, which include replacing inefficient fixtures with more efficient ones, installing and maintaining low-water-use landscapes or by changing customer attitudes toward water conservation.

    descending block rates (or decreasing block rates)
    A rate structure that divides a customer's water use into blocks, or consumption amounts, with the rate for each subsequent block priced lower than the previous block.

    designated basin
    An area in which the use of ground water is assumed not to impact the major surface river basin to which the designated basin would otherwise be tributary. Much of eastern Colorado is in designated basins.

    direct flow (or direct right)
    Water diverted from a river or stream for use without interruption between diversion and use except for incidental purposes, such as settling or filtration.
    distribution main
    See water main.

    distributor
    A suburban entity, generally quasi-municipal or municipal, with which Denver Water has contracted to provide water service outside of Denver.

    diversion
    The removal of water from its natural course or location, or controlling water in its natural course or location, by means of a ditch, canal, flume, reservoir, bypass, pipeline, conduit, well, pump or other device.

    drought
    A long period of below-average precipitation.

    due diligence
    The efforts necessary to bring an intent to appropriate water to fruition; actions that demonstrate a good faith intention to complete a diversion of water within reasonable time.

    duty of water
    The amount of water that, through careful management and use, without wastage, is reasonably required to be applied to a tract of land for a length of time that is adequate to produce the maximum amount of crops ordinarily grown there.

  • E

    effluent
    The water leaving a water or wastewater treatment plant.

    effluent exchange
    The practice of using wastewater effluent as a replacement source for diversion of water upstream.

    Endangered Species Act
    The federal law that sets forth how the United States will protect and recover animal and plant species whose populations are in dangerous decline or close to extinction. The law protects not only threatened and endangered species but also the habitat upon which species depend.

    Energy Policy Act (EPACT)
    The 1992 federal law that states, among other things, that no toilet manufactured after January 1, 1994, shall use more than 1.6 gallons per flush (except "blowout" toilets and commercial toilets) and that showerheads and faucets manufactured after January 1, 1994, may not use more than 2.5 gallons per minute.

    environmental impact statement (EIS)
    Detailed analysis of the impacts of a project on all aspects of the natural environment required by federal National Environmental Policy Act for federal permitting or use of federal funds.

    exchange
    A process by which water, under certain conditions, may be diverted out of priority at one point by replacing a like amount of water at a downstream location.

    expansion
    Undeveloped areas adjacent to the boundaries of existing distributor contract areas that those distributors would logically be expected to serve in the future and that have been included in Denver Water’s combined service area.

  • F

    FERC
    Federal Energy Regulatory Commission; formerly the Federal Power Commission.

    Federal Land Policy Management Act (FLPMA)
    A federal law that requires land-use planning and management programs, along with land acquisition and disposition on national forest systems, including lands with the Department of Interior and the Department of Agriculture. The act requires that the lands be managed in a manner to protect the quality of scientific, scenic, historical, ecological, environmental, water resource and archaeological values.

    finished water
    Treated potable water that is considered safe and suitable for delivery to consumers.

    firm annual yield
    The yearly amount of water that can be dependably supplied from the raw water sources of a given water supply system.

    flat rates
    The rate when customers are charged the same amount per bill based on a pre-determined formula (square footage, irrigable area and water-using devices) rather than being charged for actual consumption.

    flume
    A sloped channel used to convey water that is commonly constructed of wood or concrete. Some specialized flumes are used to measure flow, such as the Parshall flume, by means of a calibrated throat or cross section See weir.

    futile call

    A situation in which a junior (more recent) priority is allowed to continue to divert in spite of a downstream senior call when curtailing the junior would not produce any additional water for the senior.

  • G

    gallons per account per day (GAD)
    A term generally used to approximate the average amount of water used by a customer account on a daily basis. The formula used to determine the gallons per account per day is:

    total treated water delivered (in one year)
    divided by total accounts of water service area (customers)
    divided by 365 days a year = gallons per account per day.

    gallons per capita per day (GCD)
    A term generally used to approximate the average amount of water used per day, per person, in one year. It generally is compiled on a system-wide basis. The formula used to determine gallons per capita per day is:

    total treated water delivered (in one year)
    divided by total population of water service area
    divided by 365 days a year = gallons per capita per day.

    ground water
    Water found below the Earth’s surface.

  • H

    headwaters
    The beginning of a large stream or river.

    hydrologic cycle
    The movement of water from the atmosphere to the Earth and back again to the atmosphere. The three stages are: precipitation, runoff or infiltration, and evaporation.

  • I

    in fill
    Undeveloped areas within the combined service area that Denver Water would be expected to serve in the future.

    integrated resource plan (IRP)
    A method for long-range planning using environmental, engineering, social, financial and economic considerations; includes using the same criteria to evaluate both supply and demand options while involving customers and other stakeholders in the process.

  • J

    junior rights
    Water rights that were obtained more recently and therefore are junior in priority to older or more senior rights. See priority.

  • K

    KAF
    One thousand acre feet.

  • M

    mg/L
    Milligrams per liter; a measurement describing the amount of a substance (such as a mineral, chemical or contaminant) in a liter of water. One milligram per liter is equal to one part per million.

    master meter
    Distributors outside the city limits of the City and County of Denver that receive water service from Denver Water under agreements whereby the distributor operates and maintains the water distribution systems to supply individual customers. Denver Water bills only the distributor for water delivered through large master meters, and the distributors establish the rates for and bill the customer.

    maximum contaminant level
    The highest allowable amount of a constituent in water. Drinking water quality criteria are established by the U.S. Environmental Protection Agency as regulatory standards.

    miner's inch (or statutory inch)
    A measurement of water flow. In Colorado, 38.4 miner's inches is considered equivalent to one cubic foot per second.

    multi-family residential
    A planning term used to describe a building in which two or more families live in separate but attached dwellings, such as apartment houses, townhomes and condominiums.

  • N

    National Pollution Discharge Elimination System (NPDES) permit
    A permit required under Section 401 of the Clean Water Act regulating discharge of pollutants into the nation's waterways.

    National Environmental Policy Act (NEPA)
    The federal law enacted to ensure the integration of natural and social sciences and environmental design in planning and in decision making that may impact the quality of the human environment.

    natural replacement
    The ordinary replacement of older, less efficient water fixtures (toilets, faucets, etc.) with new, more efficient fixtures as the older fixtures wear out, break or are replaced.

    net demand
    The water demand that is expected to occur in the future after reductions for natural replacement and conservation. It represents the actual demand that should be experienced in the future at customers' premises. Usually expressed in thousand acre feet (KAF).

    nonconsumptive use
    Water drawn for use that is not consumed, such as water diverted for hydroelectric generation. It also includes uses such as boating and fishing, where water is still available for other uses at the same site.

    nonpoint source
    The source of pollution discharged over a wide land area, not from one specific area, that finds its way into streams, lakes and oceans, such as runoff from streets, parking lots, lawns, agricultural land, individual septic systems and construction sites.

    nonpotable
    Water not suitable for drinking. See potable, reuse.

    nontributary ground water
    Underground water in an aquifer that neither draws from nor contributes to a natural surface stream in any measurable degree.

  • P

    participation agreement
    An agreement in which a distributor or developer pays for the cost of the distribution facilities such as conduits, treated water reservoirs or pump stations required to provide service within that district from the nearest existing available source.

    parts per billion
    A unit frequently used to measure contamination concentration (parts of contamination per billion parts of water). One thousand parts per billion is equal to one part per million.

    parts per million
    A unit used to measure contamination concentration (parts of contamination per million parts of water). One part per million is equal to one milligram per liter. (This term is becoming obsolete as instruments measure smaller particles.)

    point source
    The source of pollution discharged from any identifiable point, including ditches, channels, sewers, tunnels and containers of various types.

    potable
    Water that does not contain pollution, contamination, objectionable minerals or infective agents and is considered safe for domestic consumption; drinkable. See nonpotable, reuse.

    pressure pipe
    Pipe used to distribute potable water throughout the city for fire fighting and domestic purposes.

    pressure regulating valve (PRV)
    A device that takes pressure from a high zone through a valve and regulates it to a zone of lower pressure.

    pressure zone
    Geographical area within a water distribution system defined by a number of valves with at least two feeds.

    prior appropriation
    The water law doctrine that confers priority to use water from natural streams based upon when the water rights were acquired. Water rights in Colorado and other western states are confirmed by court decree; holders of senior rights have first claim to withdraw water over holders who have filed later claims. See water right, riparian rights, priority and appropriation.

    priority
    The right of a senior water rights holder to divert from a natural stream before a junior holder.

    projected savings
    An estimate of the amount of water that will not be used because both suppliers and customers are implementing certain efficiency practices.

  • R

    ramping
    Controlling streamflow so that flow changes are gradual and do not adversely impact safety and property downstream.

    rated capacity
    The volume of water a treatment plant is capable of producing under normal operating conditions.

    raw water
    Untreated water.

    read and bill distributor
    Distributors outside the city limits of Denver who receive water service from Denver Water under agreements in which the distributor operates and maintains portions of the system used to supply individual customers, and Denver Water is responsible for billing each customer on an individual basis.

    reservoir
    A body of water used to collect and store water, or a tank or cistern used to store potable water.

    reservoir surcharge
    Water in a reservoir that resides above the spillway.

    retrofit
    An umbrella term that refers to the modification of something for more efficiency. In the case of water conservation, retrofit refers to modifications to plumbing fixtures to increase efficiency.

    return flows
    Water that returns to a stream after it has been used.

    reuse
    To use again; recycle; to intercept, either directly or by exchange, water that would otherwise return to the stream system, for subsequent beneficial use. See potable, nonpotable.

    reverse osmosis
    A water treatment technique that forces water through a dense membrane to remove impurities.

    riparian rights
    Water rights that are acquired together with title to the land bordering a source of surface water; the right to put to beneficial use surface water adjacent to one's land. Riparian rights are most common in states east of the Mississippi River and do not exist in Colorado. See appropriation, prior appropriation and water right.

    run-off
    Water that flows on the surface of the Earth into streams, rivers, lakes and oceans.

  • S

    Safe Drinking Water Act (SDWA)
    Federal legislation passed in 1974 that regulates the treatment of water for human consumption and requires testing for and elimination of contaminants that might be present in the water.

    safety factor
    An amount of water added to demand projections to protect against unforeseen changes in water supply and demand.

    secondary treatment
    Treatment of wastewater to a nonpotable level so that it may be returned to the stream. See tertiary treatment, nonpotable.

    sludge
    A semi-liquid mass of accumulated settled solids deposited from the treatment plant process. Most water treatment plant sludge is inert and can be used as components in some manufactured products and as a base for fertilizer. Also called "residual solids."

    spill water
    Water released from a reservoir because the reservoir lacks sufficient storage capacity.

    statutory inch
    See miner's inch.

    storage
    Water held in a reservoir for later use.

    supply management
    Methods by which a utility maximizes use of available untreated water.

    surface water
    Water located on the Earth's surface.

    sustainability
    A decision-making concept describing development that meets the needs of the present without compromising the ability of future generations to meet their own needs.

    system development charge (SDC)
    A one-time connection charge that provides a means for financing a portion of the source of supply, raw water transmission facilities, treatment plants and backbone treated water transmission facilities required to provide service to a new customer. Sometimes called a tap fee.

    system loss
    An amount of water, expressed as a percentage, lost to leaks, seepage and unauthorized use.

    Systemwide Environmental Impact Statement (SEIS)
    The result of a Foothills Agreement requirement that federal agencies conduct an environmental impact statement analysis to determine the cumulative effects of the entire Denver Water system prior to the permitting of new water supply projects. The Systemwide Environmental Impact Statement was initiated in 1981. When Denver requested permits for the Two Forks Dam and the Williams Fork Extension Project in 1984, all three studies were combined into one document, the Metropolitan Denver Water Supply Environmental Impact Statement.

  • T

    tap
    A physical connection made to a public water distribution system that provides service to an individual customer.

    tap allocation
    The process used for distributing 3/4-inch taps among applicants when shortages of treatment, transmission or distribution facilities and/or water supplies require a method of rationing taps.

    tap fee
    See system development charge.

    ten-acre rule
    A policy implemented by Denver Water that requires Board approval for the use of potable water to irrigate tracts of land of ten acres or larger. Requires that any new development or renovation of ten acres or more be reviewed and approved for landscaping by the Board of Water Commissioners. Approval is contingent on demonstrating that an alternative source to irrigation with potable water is not reasonably or practically available and that the irrigation is designed to maximize efficiency.

    tertiary treatment
    Treatment of wastewater to a level beyond secondary treatment but below potable. See also secondary treatment, nonpotable, potable.

    total service distributor
    Distributors outside the city limits of Denver who receive water service from Denver Water under agreements in which Denver Water operates and maintains all of the systems used to supply the distributor in a manner to provide complete and total service, just like that furnished inside Denver.

    transbasin diversion
    The conveyance of water from its natural basin into another basin.

    transmountain diversion
    The conveyance of water from one watershed to another, usually from the Western Slope to the Front Range.

    treated water
    Water that has been filtered and disinfected. Term is sometimes used interchangeably with potable water.

    tributary
    A stream or river that flows into a larger one.

    tributary drainage
    The area from which water drains by gravity into a water course.

    tributary ground water
    Water below the Earth's surface that is physically or hydrologically connected to natural stream water so as to affect its flow whether in movement to or from that stream.

    turbidity
    A measure of suspended solids in water; cloudiness.

  • U

    unaccounted-for water
    The difference between the total amount of water leaving treatment facilities and the total amount of water measured at customers' meters. Besides system losses, it also includes beneficial uses such as unmetered fire fighting and water used in system maintenance, along with meter under-registration.

    unconstrained demand
    The demand that would be experienced were it not for conservation and natural replacement. Usually expressed in thousand acre feet (KAF).

    uniform block rates
    A rate structure that charges the same rate for all blocks of water consumption.

    urban runoff
    Water from an urban area that neither infiltrates the soil nor is consumed, but flows into a storm sewer or open waterway

  • V

    valve
    Mechanical device for controlling or stopping flow of water in a pipe.

  • W

    water audit
    A service provided by Denver Water to its customers that identifies water waste and leaks and offers ways to conserve water.

    water balance
    Allocation of water uses by specific sites to compare with meter records.

    water main (or distribution main)
    A 12-inch or smaller diameter pipe along public streets or appropriate rights-of-way used for distributing water to individual customers.

    water right
    A property right to make beneficial use of a particular amount of water with a specified priority date. See appropriation, prior appropriation and riparian rights.

    watershed
    An area from which water drains and contributes to a given point on a stream or river.

    WaterWiser
    The Water Efficiency Clearinghouse. A source of information in print and/or electronic media accessible by phone, fax or Internet, sponsored by the American Water Works Association and the U.S. Environmental Protection Agency. (800-559-9855)

    weir
    A vertical structure in an open channel with a calibrated opening that measures water's rate of flow. See flume.

    wetlands
    Areas with standing water or a high water table that under normal circumstances support vegetation typically adapted to saturated soil conditions; generally includes swamps, marshes, bogs and areas with vegetation that grows in or around water.

  • X

    Xeriscape
    Landscaping concept that requires less water on vegetation that is suited to soils and climate. The term was developed by Denver Water in 1981. It is derived from the Greek word Xeros, meaning dry.

  • Other

    µg/L (micrograms per liter)
    Micrograms per liter; a measurement describing the amount of a substance (such as a mineral, chemical or contaminant) in a liter of water. It is expressed in terms of weight per volume. One µg/L is equal to one part per billion.