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Water Terminology

Absolute water right 

A property right to put water to beneficial use with a specified priority date.


A volume of water equal to one foot in depth covering an area of one acre.  Also 43,560 cubic feet, or 325,851 gallons. Used to measure stored water quantities.


To hear and settle a case by judicial procedure.


a soluble salt or a mixture of soluble salts present in some soils of arid regions in quantity detrimental to agriculture.

Alluvial water 

Ground water that is hydrologically part of a surface stream that is present in permeable soil material, usually small rock and gravel.


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


The right to take water from a stream, tributary or aquifer for beneficial use at a specified rate of flow, either for immediate use or to store for later use. Usually evidenced by a water court decree.


An underground deposit of sand, gravel or rock through which water can pass or is stored.  Aquifers supply the water for wells and springs.

Augmentation plan 

A court-approved plan that allows a water user to divert water out of priority so long as adequate replacement is made to the affected stream system preventing injury to the water rights of senior users.

Augmentation source 

The supply of water used to replace out-of-priority depletions.

Eneficial use 

Application of water without waste for human or natural benefit.


The exercise of a senior water right holder of "calling" for his or her water rights, requiring upstream junior water right holders to allow water to flow to the senior right holder.

Clean Water Act 

The federal law that sets forth 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 to the country's surface waters from both point and non-point sources of pollution.

Colorado Doctrine 

See appropriation.

Colorado Water Conservation Board 

The state agency vested with the authority to appropriate water of streams and lakes in amounts that are determined to be necessary to preserve the natural environment to a reasonable degree.


A contract between states that is ratified by those states' legislatures and by the U.S. Congress. The contract controls the division of water in a river system that flows across state boundaries.

Conditional water right 

The legal preservation of a priority date that provides a water user time to develop his or her water right, but reserves a more senior date. A conditional right becomes an absolute right when water is actually put to beneficial use.

Conservancy district 

Established by decree of a court under the Water Conservancy District Act of 1937. A conservancy district can obtain rights-of-way for works; contract with the United States or otherwise provide for construction of facilities; assume contractual or bonded indebtedness;  administer, operate, and maintain physical works; have authority to conserve, control, allocate, and distribute water supplies; and have contracting and limited taxing authority to derive the revenues necessary to accomplish its purposes. There are currently 45 conservancy districts in Colorado.


Obtaining the benefits of water more efficiently.

Conservation district 

Established under specific statues by the Colorado General Assembly. There are currently three conservation districts in Colorado;  the Colorado River Water Conservation District, the Southwestern Water Conservation District, and the Rio Grande Water Conservation District.  The mission is to oversee the conservation, use, and development of water in large geographical areas of the state.

Consumptive use 

Any use of water that permanently removes water from the natural stream system.

Continental Divide 

An imaginary boundary line that runs north-south along the crest of the Rocky Mountains, separating river and drainages that flow west to the Pacific Ocean from those that flow south and east to the Gulf of Mexico.

Cubic feet per second (cfs) 

A rate of water flow at 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.


A court decision about a water right that is then administered by Colorado's Water Resources Department.

Direct flow (also 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.


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.


A long period of below-average precipitation.

Due diligence 

The efforts necessary to complete a water appropriation action that demonstrates a good faith action to complete a diversion of water within a reasonable time period.


Water discharged after use, as in water leaving a wastewater treatment plant.

Effluent exchange 

The practice of using wastewater effluent from transbasin water, non-tributary water sources, or other sources without causing injury to other water rights as a replacement source of water for diversion of water farther upstream that would otherwise have been out of priority.

Endangered Species Act 

The federal law that governs how animal and plant species whose populations are dangerously in decline or close to extinction will be protected and recovered. The law protects not only threatened and endangered species, but also the ecosystems upon which they depend.

Energy Policy Act (EPACT) 

A 1992 federal law that states, among other things, that no toilet for household use manufactured after Jan. 1, 1994, shall use more than 1.6 gallons per flush and that shower heads and faucets manufactured after Jan. 1, 1994, may not use more than 2.5 gallons per minute.

Exempt wells 

Those wells that are exempt from water rights administration under a priority system (examples of exempt wells are household use only, domestic and livestock wells, and pre 1972 unregistered wells).

Firm annual yield 

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

Futile call 

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

Ground water 

Water found below the earth's surface.

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.

Instream flows 

Water flowing in its natural stream bed, such as water required for maintaining flowing streams, or for fish.

Interstate compacts 

See compacts

Junior rights 

Water rights that are more recent than older or more senior rights.

National Pollution Discharge Elimination System (NPDES) Permit 

A permit required under Section 401 of the Clean Water Act regulating discharge of pollutants to 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 decision-making for projects that may impact the quality of the human environment.

Non-consumptive use 

Water drawn for use that is not consumed, for example, water withdrawn for purposes such as hydropower generation. It also includes uses such as boating or fishing where the water is still available for other uses at the same site.

Non-exempt wells 

those that  are governed by the priority system and may be curtailed (included any other type of well not considered exempt).

Non-point source 

Pollution discharged over a wide land area, not from one specific location.  Runoff from city streets, parking lots, home lawns, agricultural land, individual septic systems and construction sites that finds its way into lakes and stream constitutes an important sources of water pollutants.

Non-tributary ground water 

Underground water that meets certain legislative criteria as to its effect on a stream system.

Point Source 

Pollutants discharged from any identifiable point, including pipes, ditches, channels, sewers, tunnels and containers of various types.


Water that is considered safe for domestic consumption; drinkable.

Prior appropriation doctrine 

A legal concept in which the first person to appropriate water and apply it to a beneficial use has the first right to use that amount of water from that source.  Each successive appropriator may only take a share of the water remaining after all senior water rights are satisfied. This is the historical basis for Colorado water law and is sometimes known as the Colorado Doctrine or the principle of "first in time, first in right."


The right of an earlier appropriator to divert from a natural stream in preference to a later appropriator.

Priority date 

The date of establishment of a water right. The rights established by application have the application date as the date of priority.

Raw water 

Untreated water.


An impoundment of collected water controlled by a dam (raw water) or storage tank (potable water).

Return flows 

The unused portion of water that returns to a stream or river after a beneficial use.


To use again, to intercept for subsequent beneficial use--either directly or by exchange--water that would otherwise return to the stream system.


To provide barren land with a new vegetative cover.


Water that flows on the earth's surface to streams, rivers, lakes, and oceans.

Safe Drinking Water Act (SDWA) 

Federal legislation that regulates the treatment of water for human consumption. Requires testing for and elimination of contaminants to levels for the protection of human health.

Senior rights 

Water rights that are staked the earliest with the water court.

Surface water 

Water present on the earth's surface.

System loss 

An amount of water, expressed as a percentage, lost from a water storage or distribution system due to leaks, evaporation, seepage and unauthorized use.

Transbasin diversion 

The conveyance of water from its natural drainage basin into another basin for beneficial use.

Transmountain diversion 

The conveyance of water from one drainage basin to another across the Continental Divide.

Treated water 

Water that has been filtered and/or disinfected; sometimes used interchangeably with "potable" water.


A stream or river that flows into a larger one.

Tributary drainage 

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

Tributary ground water 

Water present below the earth's surface that is hydrologically connected to a natural surface stream.

Urban runoff 

Excess water that doesn't infiltrate the soil, but flows to a storm sewer or open waterway.

Water and sanitation districts 

A special taxing district formed by the residents of the district for the combined purpose of providing potable water and sanitary wastewater services.

Water right 

A property right to make beneficial use of a particular amount of water with a specified priority date.


An area from which water drains to a given stream or river or river system.

Wellhead Protection Program 

An amendment to the federal Safe Drinking Water Act in 1986.  Initiated to minimize the potential for contamination of public ground water supplies.


Areas with standing water of a high water table either permanently or for some significant period each year. Generally includes swamps, marshes, bogs and areas with water-loving vegetation that grows in or around water.


A landscape concept to describe beautiful landscaping that has low water needs. The term was developed by Denver Water in 1981. It is derived from the Greek word xeros, meaning dry.