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Water Glossary

Absolute Water Right
a water right that has been put to beneficial use; See also conditional water right.
Acre-Foot (AF)
the volume of water required to cover one acre to a depth of one foot; the equivalent of 326,000 gallons and enough to satisfy the annual water needs of approximately eight people.
Acre Feet Annually (AFA)
the volume of water, measured in acre-feet, over the course of a year.
a judicial proceeding in which water rights are decreed priority dates based on their date of first use.
the act of ensuring that, in times of water shortage, water rights are satisfied in order of their priority; through administration, senior water rights holders are satisfied before water is delivered to junior water rights holders. This activity is overseen by the State Engineer and his subordinate Division Engineers.
Annual Yield
see Firm Annual Yield.
the application of water from a stream, tributary, or aquifer for beneficial use at a specified rate of flow; appropriations can be for out-of-stream use, in-stream use, or storage; usually evidenced by a water court decree.
an underground deposit of sand, gravel, or rock through which water can pass or is stored. Aquifers can be “confined” (trapped by non-porous layers of rock) or “unconfined” (seepage to adjoining layers possible) and are often the source of water for wells and springs.
Beneficial Use
the application and use of an amount of water that is reasonable and appropriate (e.g., without waste) for human or natural benefit; Colorado’s policy is to maximize beneficial use of all of the waters of the State.
Build Out
the estimated extent of residential, commercial, and industrial development in a given geographic area; usually related to upper limit of population to be served by water resource development.
in times of water shortage or scarcity, the exercise of senior water rights that forces curtailment of junior water rights.
a contract between states, tribes, or other governmental entities that apportions water from a river system crossing jurisdictional boundaries.
Colorado River Compact
a contract between Upper Basin States (New Mexico, Colorado, Wyoming, and Utah) and Lower Basin States (Arizona, Nevada, and California) that apportions water from the Colorado River. Upper Basin Compact: a contract that apportions Colorado River water among the Upper Basin States.
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 (the date upon which the holder first manifested an intent to appropriate). A conditional right becomes absolute when water is actually put to a beneficial use.
See also absolute water right.
Conjunctive Use
the combined use of surface water and groundwater to achieve the optimal beneficial use; often used in areas where available water resources have been nearly fully developed and/or appropriated. Conjunctive use involves carefully coordinating the storage, timing and delivery of both resources. Typically, surface water is used to the fullest extent possible when flows are available, while ground water is retained to meet demands when surface flows are low. Benefits of conjunctive use may include: better management capabilities with less waste; greater flood control capabilities; greater control over surface reservoir releases; and more efficient operation of pump plants and other facilities.
Cubic Feet/Second (cfs)
a measurement of volume of water passing by a fixed point each second. One cfs is equal to 7.48 gallons per second, 448.8 gallons per minute, and 646,300 gallons per day (equal to 1.98 acre-feet per day).
an official document issued by a water court which defines the amount, priority, use, and location of a water right. The document serves as a mandate to the State Engineer to administer the water rights involved in accordance with the decree.
the amount of water lost to the river system by the exercise of a water right; diversion of a particular water right is often many times greater than its depletion because much of the water diverted later returns to the river, either through surface run-off or underground seepage.
Depletion Allowance
in the Gunnison Basin, the additional amount of water which the Upper Gunnison River Water Conservancy District is entitled to deplete without being “called out” by the Aspinall Unit’s 1957 water right.
see Due Diligence.
a trench cut into the surface of the ground to transport water from a stream, canal, or storage facility to an actual point of use.
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.
Division Engineer
subordinate officers under the State Engineer; Division Engineers perform the functions of the State Engineer—administering water rights—in each of Colorado’s seven water divisions. The Gunnison watershed is in Division 4.
Due Diligence
the requirement for holders of conditional water rights to demonstrate to the water court that they are making good faith efforts toward constructing the facilities (e.g., ditch, reservoir, etc.) to apply the water right within a reasonable time. In Colorado, conditional water right holders must show due diligence to the water court every six years.
liquid attributed to human waste, i.e., sewage, arising from various uses of water; also often refers to water discharged after use, such as water leaving a wastewater treatment plant or industrial plant.
a process by which water rights in one part of a river (or other water supply) system are traded for the use of water rights in another part of the river system.
Firm Annual Yield
The yearly amount of water that can be dependably supplied from the raw water sources of a water supply system.
Fish Ladder
an inclined water channel structure with a series of baffles or weirs that helps fish gain upstream passage around dams. These baffles interrupt and slow the flow of water, simulating pools and rapids. Fish swim up the ladder just as they would swim up natural rapids.
Giga-Watt Hour (GWh)
a measurement that represents one thousand million watts used in an hour.
Ground Water
water found below the earth’s surface.
a human-made structure on a stream, canal, or other water channel through which water is diverted into a ditch or canal.
Headgate Management:
see Administration.
a graph showing the seasonal flow pattern of a river at a given point along its course; usually measured in cubic feet per second (cfs).
Instream Flows
water left in its natural stream channel to maintain the existing aquatic resources and associated wildlife and riparian habitat. In contrast to out-of-stream uses, this kind of water use does not require diversion.
Lower Colorado River Basin
the Colorado River and its tributaries in Arizona, Nevada, and California.
Marketable Yield
the amount of water the United States can provide after meeting all other purposes of the Aspinall Unit.
Megawatt Hour
a megawatt hour is 1,000 kilowatts of electricity used continuously for one hour. It is equivalent to the amount of electricity used by about 330 homes during one hour.
Natural Hydrograph
a river hydrograph (see Hydrograph) representing the natural seasonal flows of a river without the moderating influence of human-created features (dams, canals, etc.); in many western streams, this will often be a bellshaped curve, with snow-melt causing a peak flow in the spring or early summer months, and lower flow levels throughout the remainder of the year.
the process of meeting all of the legal requirements for establishing a legal right to the use of water. Once perfected, a conditional water right becomes an absolute water right.
Prior Appropriation
also called “first in time, first in right,” a method (used in many western states) of allocating water between competing users. In times of water scarcity, senior water rights are satisfied ahead of junior water rights. See Priority and Priority Date. A senior water user who wants to divert water from a surface or underground source of water may force the curtailment of upstream junior use; i.c. See Call.
the seniority of a water right as determined by its adjudication date and/or its appropriation date. The priority of a water right determines its ability to divert in relation to other rights in periods of limited supply, i.e., junior water rights defer to more senior water rights.
Priority Date
the date of establishment of a water right. A non-technical term, a “priority date” can be the date of appropriation (when water is first put to use), the date of adjudication (when the court issues a water right decree), or the date when a user first intended to appropriate water (in the case of a conditional decree).
Raw Water
untreated water.
an investigation of the additional water supply or water timing benefits that could result from the revised and more efficient usage of large water storage facilities, with an eye toward improving water supply reliability, environmental benefits, or both.
in a multi-dam system, regulating the dramatic peak flows generated by upstream dams through the measured release of water from the dam farthest downstream.
located or living along or near a river or stream.
River Basin
a physiographic region bounded by a drainage divide; consists of a drainage system comprised of stream and often natural or man-made lakes. See Watershed.
Second Fill
a legal allowance for a reservoir or other storage right to be refilled. Senior Rights: water rights with a relatively early priority date. see Priority Date.
Storage Right
a water right defined in terms of the volume of the water which may be stored in a reservoir or lake to be released and used at a later time either within the same year or during a subsequent year.
a process through which a senior water rights holder allows junior water rights holder(s) to be satisfied out of priority.
Subordination Agreement
a legal document by which a senior water right agrees to subordinate his water use to a junior right. See Subordinate.
Transmountain Diversion
the conveyance of water from one drainage basin to another. In Colorado, the term often refers to water being transported over or through the Continental Divide sometimes called “trans-basin diversion.”
a stream that flows into another stream or body of water.
water in a river system for which no water rights have been claimed.
Upper Colorado River Basin
the Colorado River and its tributaries in New Mexico, Colorado, Wyoming, and Utah.
Water Court
a state district court that hears matters related to water. To obtain a judicially recognized water right, change in water right, or augmentation plan, persons or entities file applications with a water court to be issued a decree or order. There are seven water courts in the state, one for each water division, corresponding to each major drainage basin.
Water Right
a right to use, in accordance with its priority, a certain portion of the waters of the state for irrigation, power, domestic use or another similar use. See also Absolute Water Right, Conditional Water Right, Appropriation, and Priority.
an area from which water drains to a single stream or river or river system or other body of water. See also River Basin.