NOTE: These definitions are offered to assist the public in understanding some of Colorado’s most often used water terms. If you desire a legal definition, please contact a water attorney.



Loss of whole or part of a water right by intent to permanently discontinue use.

The loss of ice and snow from a glacier system. This occurs through a variety of processes including melting and runoff, sublimation, evaporation, calving and wind transportation of snow out of a glacier basin.

Absolute water right:
A water right, with a specified priority date, that has been placed to a beneficial use. See definition for conditional water right.

The process by which substances in gaseous, liquid or solid form are assimilated or taken up by other substances.

Gravity-driven waterways, similar in concept to a flume. Most are simple ditches with dirt banks, but they can be lined with concrete. They were important forms of irrigation in the development of agriculture in the American Southwest.

Acre-foot (AF):
The volume of water required to cover one acre of land to a depth of one foot (43,560 cubic feet or 325,851 gallons).

An adjustment in natural or human systems in response to actual or expected climatic stimuli or their effects, which moderates harm or exploits beneficial opportunities. Various types of adaptation can be distinguished, including anticipatory, autonomous, and planned adaptation.

The judicial process through which the existence of a water right is confirmed by court decree.

Adjudication date: The date of judicial determination of the extent, nature and limitations of a water right appropriation in a statutory court proceeding.

The adhesion of a substance to the surface of a solid or liquid; in water treatment, when activated carbon removes organic matter from wastewater.

The mixing or turbulent exposure of water to air and oxygen to dissipate volatile contaminants and other pollutants into the air.

Aeration tank:
A chamber used to inject air into water.

Life or processes that require, or are not destroyed by, the presence of oxygen.

Algal bloom:
A sudden onset of rapid growth of aquatic plant life caused by the introduction of high amounts of nutrients in a waterway. Runoff from agricultural and/or urban areas carrying large amounts of fertilizers, detergents or other compounds that promote plant growth can be the cause of an algal bloom. The sudden proliferation of algae rapidly decreases the amount of oxygen available for fish and other aquatic life and can cause a large fish kill.

The amount of pumping assigned to each contract annually.

Alluvial aquifer:
A water-bearing deposit of unconsolidated material (sand and gravel) left behind by a river or other flowing water.

Alluvial fan:
A fan-shaped deposit formed where a fast-flowing stream flattens, slows, and spreads typically at the exit of a canyon onto a flatter plain.

Deposits of clay, silt, sand, gravel or other particulate material that has been deposited by a stream or other body of running water in a streambed, on a flood plain, on a delta, or at the base of a mountain.

A diverging branch of a river which reenters the main channel.

Life or process that occurs in, or is not destroyed by, the absence of oxygen.

Annual Flood:
The highest peak discharge in a water year.

Annual mean temperature:
The average of all daily high and low temperatures.

Antecedent precipitation index:
An index of moisture stored within a drainage basin before a storm.

Resulting from or produced by human beings.

The right to take water from a stream and put it to beneficial use. Considered property rights and may be bought, sold, leased and exchanged. Appropriation establishes a water right by diversion, due diligence, and beneficial use.

Appropriation date: The date defining the priority of right to divert appropriated water in times of limited water supply.

Appropriation Doctrine:
The system of water law primarily used in the western United States under which: (1) The right to water is acquired by diverting water and applying to a beneficial use; and (2) A right to water use is superior to a right developed later in time.

The person or persons who put water to beneficial use.

Aquaculture water use:
Water use associated with the farming of finfish, shellfish, and other organisms that live in water, and offstream water use associated with fish hatcheries.

A pipe, conduit, or channel designed to transport water from a remote source, usually by gravity.

A geological structure underground that is water-bearing, usually referring to formations large enough to hold water for human use. Aquifers may be confined (located under an impenetrable layer of rock or sediment) or unconfined (water is able to move directly into and out of the aquifer from above or through permeable layers).

Aquifer system:
A body of permeable and poorly permeable material that functions regionally as a water-yielding unit; it comprises two or more permeable beds separated at least locally by confining beds that impede groundwater movement but do not greatly affect the regional hydraulic continuity of the system; includes both saturated and unsaturated parts of permeable material.

Area-capacity curve:
A graph showing the relation between the surface area of the water in a reservoir and the corresponding volume.

A small, deep, flat-floored channel or gully of an ephemeral or intermittent stream, usually with nearly vertical banks cut, into unconsolidated material. A term commonly used in the arid and semiarid regions of the Southwestern United States.

Artesian water:
Groundwater that is under pressure when tapped by a well and is able to rise above the level at which it is first encountered. It may or may not flow out at ground level. The pressure in such an aquifer commonly is called artesian pressure, and the formation containing artesian water is an artesian aquifer or confined aquifer.

Artesian well:
A well in which water under natural pressure rises to the surface without being pumped.

Artificial recharge:
Recharge at a rate greater than natural, resulting from deliberate or incidental human activities.

The envelope of gases surrounding the earth or another planet.

Atmospheric pressure:
The pressure exerted by the atmosphere on any surface beneath or within it; equal to 14.7 pounds per square inch at sea level.

Attribution of causes of climate change is the process of establishing the most likely causes for the detected change with some defined level of confidence.

Method used to allow wells to pump out-of-priority without injuring senior water rights downstream. Augmentation plans must be court approved.

Augmentation plan:
A way for junior appropriators to obtain water supplies through terms and conditions approved by a water court that protects senior water rights from the depletions caused by the new diversions. Typically this will involve storing junior water when in priority and releasing that water when a call comes on, purchasing stored waters from federal entities or others to release when a call on the river comes on, or purchasing senior irrigation water rights and changing the use of those rights to off-set the new user’s injury to the stream. These plans can be very complex, and it is suggested that an engineering consultant be hired to allow for proper consideration of all hydrologic and water right factors.

Average discharge:
In the annual series of the Geological Survey’s reports on surface water supply–the arithmetic average of all complete water years of record whether or not they are consecutive. Average discharge is not published for less than 5 years of record. The term “average” is generally reserved for average of record and “mean” is used for averages of shorter periods, namely, daily mean discharge.



A body of water in which the flow is slowed or turned back by an obstruction such as a bridge or dam, an opposing current, or the movement of the tide. In stream gaging, a rise in stage produced by a temporary obstruction such as ice or weeds, or by the flooding of the stream below. The difference between the observed stage and that indicated by the stage-discharge relation, is reported as backwater.

The margins of a channel. Banks are called right or left as viewed facing in the direction of the flow.

Bankfull stage:
Stage at which a stream first overflows its natural banks. (See also Flood stage. Bankfull stage is a hydraulic term, whereas flood stage implies damage.)

Bank storage:
The water absorbed into the banks of a stream channel, when the stages rise above the water table in the bank formations, then returns to the channel as effluent seepage when the stages fall below the water table.

Base discharge (for peak discharge):
In the Geological Survey’s annual reports on surface water supply, the discharge above which peak discharge data are published. The base discharge at each station is selected so that an average of about three peaks a year will be presented. (See also Partial-duration flood series.)

Base flow:
The part of the stream discharge that is not attributable to direct runoff from precipitation or melting snow; it is usually sustained by groundwater discharge. See Base runoff.

Base runoff:
Sustained or fair weather runoff. In most streams, base runoff is composed largely of groundwater effluent. The term base flow is often used in the same sense as base runoff. However, the distinction is the same as that between streamflow and runoff. When the concept in the terms base flow and base runoff is that of the natural flow in a stream, base runoff is the logical term. (See also Groundwater runoff and Direct runoff.)

Basic hydrologic data:
Includes inventories of features of land and water that vary only from place to place (topographic and geologic maps are examples), and records of processes that vary with both place and time. (Records of precipitation, streamflow, groundwater, and quality-of-water analyses are examples.) Basic hydrologic information is a broader term that includes surveys of the water resources of particular areas and a study of their physical and related economic processes, interrelations and mechanisms.

The drainage area of a river or lake.

Basin rank:
The relative seniority of a water right as determined by its date of adjudication and the date of appropriation.

Basin Roundtables:
Nine separate basin roundtables were established by the Colorado Water for the 21st Century Act for each of the state’s eight major river basins and the Denver metropolitan area. These basin roundtables facilitate discussions on water issues and encourage locally driven collaborative solutions.

Bed material:
Sediment composing the streambed.

Bed sediment:
The material that temporarily is stationary in the bottom of a stream or other watercourse.

A general term used for solid rock that underlies soils or other unconsolidated material.

Beneficial use:
The use of a reasonable amount of water necessary to accomplish the purpose of the appropriation, without waste. Some common types of beneficial use are: domestic, irrigation, municipal, wildlife, recreation and mining. Water in Colorado must be diverted for a purpose and used beneficially.

Best Management Practices (BMPs):
Practices that are technically and economically feasible and for which significant water conservation or water quality benefits can be achieved.

Using living organisms to remove pollutants from soil, water, or wastewater.

The global sum of all ecosystems on Earth. From the broadest biophysiological view, the biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere, hydrosphere and atmosphere.

Braided stream:
A stream characterized by an interlacing or tangled network of several small branching and reuniting shallow channels. Streams braid when they have a much greater sediment load than they can carry.



A large, more or less circular, basin-shaped volcanic depression whose diameter is many times greater than the volcanic vent.

In times of water shortage, the owner of a decreed water right may place a “call” on a stream to obtain a full supply by shutting off water users in inverse order of priority.

The process by which pieces of ice break away from the terminus of a glacier that ends in a body of water or from the edge of a floating ice shelf that ends in the ocean. Once they enter the water, the pieces are called icebergs.

Calving glacier:
A glacier with a terminus that ends in a body of water (river, lake, ocean) into which it calves icebergs.

Capillary fringe:
The zone above the water table in which water is held by surface tension. Water in the capillary fringe is under a pressure less than atmospheric.

Carbonate rocks:
Rocks (such as limestone or dolostone) that are composed primarily of minerals (such as calcite and dolomite) containing the carbonate ion (CO32-).

Center pivot irrigation:
An automated sprinkler system involving a rotating pipe or boom that supplies water to a circular area of an agricultural field through sprinkler heads or nozzles.

Cenozoic Era:
The third of the major eras of Earth’s history, beginning about 66 million years ago and extending to the present. It was the interval of time during which the continents assumed their modern configuration and geographic positions and during which Earth’s flora and fauna evolved toward those of the present. The era is generally divided into three periods: the Paleogene (66 million to 23 million years ago), the Neogene (23 million to 2.6 million years ago), and the Quaternary (2.6 million years ago to the present). Cenozoic rocks are extensively developed on all the continents, particularly on lowland plains, as, for example, the Gulf and Atlantic coastal plains of North America. They are generally less consolidated than older rocks, although some are cemented as a result of high pressure due to deep burial, chemical diagenesis, or high temperature—namely, metamorphism.

Change of right/use:
Any change in the way a water right is used, such as a change in type, place, or time of use, change in point of diversion, adding points of diversion, etc. It is not a change in use if a farmer changes the type of crop grown. Changes of water rights must be approved by the water court to assure that no injury occurs to other water rights.

The straightening and deepening of a stream channel to permit the water to move faster or to drain a wet area for farming.

Channel scour:
Erosion by flowing water and sediment on a stream channel; results in removal of mud, silt and sand on the outside curve of a stream bend and the bed material of a stream channel.

A deep, steep-walled, half-bowllike recess or hollow situated high on the side of a mountain and commonly at the head of a glacial valley; and produced by the erosive activity of mountain glaciers.

Cirque glacier:
A small glacier that forms within a cirque basin, generally high on the side of a mountain.

Rock, such as sandstone, or sediment composed principally of broken fragments that are derived from preexisting rocks which have been transported from their place of origin.

Clean Water Act (CWA):
The Clean Water Act (CWA) establishes the basic structure for regulating discharges of pollutants into the waters of the United States and regulating quality standards for surface waters. The basis of the CWA was enacted in 1948 and was called the Federal Water Pollution Control Act, but the Act was significantly reorganized and expanded in 1972. “Clean Water Act” became the Act’s common name with amendments in 1972. Under the CWA, EPA has implemented pollution control programs such as setting wastewater standards for industry. EPA has also developed national water quality criteria recommendations for pollutants in surface waters. The CWA made it unlawful to discharge any pollutant from a point source into navigable waters, unless a permit was obtained. EPA’s National Pollutant Discharge Elimination System (NPDES) permit program controls discharges. Point sources are discrete conveyances such as pipes or man-made ditches. Individual homes that are connected to a municipal system, use a septic system, or do not have a surface discharge do not need an NPDES permit; however, industrial, municipal, and other facilities must obtain permits if their discharges go directly to surface waters.

The long-term average of conditions in the atmosphere, ocean, ice sheets and sea ice described by statistics, such as means and extremes.

Climate change:
Changes in average weather conditions that persist over multiple decades or longer. Climate change encompasses both increases and decreases in temperature, as well as shifts in precipitation, changing risk of certain types of severe weather events, and changes to other features of the climate system.

Climate variability:
Natural changes in climate that fall within the observed range of extremes for a particular region, as measured by temperature, precipitation, and frequency of events. Drivers of climate variability include the El Niño Southern Oscillation and other phenomena.

Closed basin:
A basin draining to some depression or a pond within its area, from which water is lost only by evaporation or percolation; A basin without a surface outlet for flowing into another body of water.

Colorado Doctrine:
The doctrine regulating water usage by priority of appropriation as opposed to riparian rights. See appropriation doctrine.

Commercial water use:
Water for motels, hotels, restaurants, office buildings, other commercial facilities, military and nonmilitary institutions. Water may be obtained from a public-supply system or may be self-supplied.

An agreement between states apportioning the water of a river basin to each of the signatory states.

Compact call:
The requirement that an upstream state cease or curtail water diversions from the river system that is the subject of the compact so that downstream states’ compact entitlements may be met.

The ratio of the quantity of any substance present in a sample of a given volume or a given weight compared to the volume or weight of the sample.

The process of water vapor in the air turning into liquid water. Condensation is the opposite process of evaporation.

A modifier which describes a condition in which the potentiometric surface is above the top of the aquifer. Synonymous with artesian.

Confined aquifer:
An aquifer bounded above and below by confining units of distinctly lower permeability than that of the aquifer itself; an aquifer containing confined groundwater. Also known as an artesian aquifer.

Confined groundwater:
Groundwater under pressure significantly greater than atmospheric, with its upper limit the bottom of a bed with hydraulic conductivity distinctly lower than that of the material in which the confined water occurs.

Confining layer:
A body of impermeable or distinctly less permeable material stratigraphically adjacent to one or more aquifers that restricts the movement of water into and out of the aquifers.

The flowing together of two or more streams; the place where a tributary joins the main stream.

A coarse-grained sedimentary rock composed of fragments larger than 2 millimeters in diameter.

Conjunctive water use:
A practice whereby two or more independent sources of water are used in combination or alternately, for meeting one or more objectives, such as, improved reliability of supply, long-term cost effectiveness and environmental protection.

Concentrated animal feeding operation (CAFO):
An animal feeding operation (limited grass and vegetation, food is brought to the animals) that falls under Environmental Protection Agency definitions as exceeding animal number thresholds or contributing discharge to surface waters. CAFO categorization impacts whether the operation is subject to regulations under the Clean Water Act.

Condensation: the physical process by which a vapor becomes a liquid or solid; the opposite of evaporation, although on the molecular scale, both processes are always occurring.

Conditional water right:
A right obtained through the water court that fixes the priority of the water right with a date certain, even though the appropriation has yet to be completed. It gives the holder of that right time to complete the appropriation as long as they diligently pursue completion of the project. Every six years the court reviews what progress has been made toward completion of the project. Once the right has been perfected by use, the holder of the conditional right must then ask the court to make it an absolute water right.

Conjunctive use:
Combined use of surface and groundwater in a coordinated manner.

Connate water:
Water entrapped in the interstices of a sedimentary or extrusive igneous rock at the time of its deposition.

Conservancy district:
A special taxing district, created by a vote of the district’s electors, that has authority to plan, develop and operate water supply and/or potable water projects.

A chemical or biological substance in water, sediment or biota that can be measured by an analytical method.

Consumptive use:
The part of water withdrawn that is evaporated, transpired, incorporated into products or crops, consumed by humans or livestock, or otherwise not available for immediate use. Also referred to as water consumed.

Defined in the federal Safe Water Drinking Act as any physical, chemical, biological or radioactive substance or matter in air, water or soil.

Degradation of water quality compared to original or natural conditions due to human activity.

Contributing area:
The area in a drainage basin that contributes water to streamflow or recharge to an aquifer.

Continental drift:
The scientific theory of the movement of the Earth’s continents relative to each other. The hypothesis that continents drift was first introduced by Abraham Ortelius in 1596 and was fully developed by Alfred Wegener in 1912. In the 1960s the theory of plate tectonics incorporated and improved upon continental drift: the Earth’s surface seems to be broken into about ten major tectonic plates moving as the sea floor spreads, with the continents frozen into them.

The transfer of heat from a warmer region to a cooler one via movement of liquids and gasses.

The systematic and intentional flow or transfer of water from one point to another. Conveyance types include water instream conveyance, water distribution, and wastewater collection.

Conveyance loss:
Water that is lost in transit from a pipe, canal, conduit or ditch by leakage or evaporation. Leakage from an irrigation ditch, for example, may percolate to a groundwater source and be available for further use.

Cooperative agreements:
Methods for sharing water resources in cases of scarcity, which include legal agreements such as, for example, dry year leasing, transfers, augmentation plans, water conservation easements, water banking and substitute water supply plans.

A crack or series of cracks that open in the surface of a moving glacier in response to differential stresses caused by glacier flow. They range in shape from linear to arcuate, in length from feet to miles, and their orientation may be in any direction with respect to the glacier flow. The deepest crevasses may exceed 100 feet.

Collectively describes the portions of the Earth’s surface where water is in solid form, including sea ice, lake ice, river ice, snow cover, glaciers, ice caps and ice sheets, and frozen ground (including permafrost); therefore, there is a large overlap with the hydrosphere. The cryosphere is an integral part of the global climate system with important linkages and feedbacks generated through its influence on surface energy and moisture fluxes, clouds, precipitation, hydrology, atmospheric and oceanic circulation.

Crystalline rocks:
Rocks (igneous or metamorphic) consisting wholly of crystals or fragments of crystals.

The natural or artificial process of formation of solid crystals precipitating from a solution, melt of more rarely deposited directly from a gas. Crystallization is also a chemical solid-liquid separation technique in which mass transfer of a solute from the liquid solution to a pure solid crystalline phase occurs.

Cubic feet per second (cfs):
A measurement to indicate the speed of flow in a moving body of water, equal to a one foot cubic volume of water moving a linear distance of one foot in one second. One cfs will produce 724 acre-feet of water in one year.

To reduce or restrict the amount of water taken by a user.



Datum plane:
A horizontal plane to which ground elevations or water surface elevations are referenced.

An official document issued by the court defining the priority, amount, use and location of the water right.

Decreed water right:
A court decision placed on a water right that is then administered by Colorado’s Water Resources Department.

The amount of water delivered to a point of use.

The low, nearly flat tract of land at or near the mouth of a river, resulting from the accumulation of sediment supplied by the river in such quantities that it is not removed by tides, waves or currents. Commonly a triangular or fan-shaped plain.

The loss of water from surface water reservoirs or groundwater aquifers at a rate greater than that of recharge.

In relation to the study of geology, deposition is the geological process by which material is added to a landform or land mass. Wind, water and gravity transport and deposit previously eroded sediment that begins to build up layers. In relation to the water cycle (hydrologic cycle), deposition occurs when water vapor (gas) changes into ice (solid) without going through the liquid phase. The process of deposition is the opposite of sublimation.

Refers to the removal of salts from water. Desalination is primarily used to produce public supply water that meets drinking water standards. The primary types of desalination are (1) distillation, (2) electrodialysis, and (3) reverse osmosis. Additionally, many public water suppliers also dilute or blend saltwater with fresher water to produce potable water. In Colorado, desalination is also often used to refer to the removing of salts from soil by artificial means, usually leaching.

Designated groundwater:
Groundwater which, in its natural course, is not available to or required for the fulfillment of decreed surface rights, and which is within the geographic boundaries of a designated groundwater basin.

Designated [groundwater] basin:
Those areas of the state established by the Groundwater Commission located in the Front Range and Eastern Colorado, which have been determined that use of groundwater does not impact the surface river basin to which a designated basin would otherwise be tributary. Much of eastern Colorado is in designated basins.

Developed water:
Water that is produced or brought into a water system through the efforts of people, where it would not have entered the water system on its own accord.

Reasonable progress toward making a conditional water right absolute by putting unappropriated water to a beneficial use. This can include engineering, permitting, financing and construction of water facilities, and must be proven in water court through an application process.

Direct flow 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.

Direct runoff:
The runoff entering stream channels promptly after rainfall or snowmelt.

The volume of water that passes a given location within a given period of time, usually measured in cubic feet per second.

Discharge area:
An area in which groundwater is discharged to the land surface, surface water or atmosphere.

The extent to which a liquid substance introduced into a groundwater system spreads as it moves through the system.

Cut by erosion into valleys, hills and upland plains.

Dissolved solids:
Disintegrated organic and inorganic material in water. Excessive amounts make water unfit to drink or use in industrial processes.

1) Changing the natural flow of water to another location by using dams, canals or pipelines. 2) Point of withdrawal from surface water.

Division engineer:
The state engineer’s principal water official in each of the seven water divisions.

Domestic water use:
Water used for indoor household purposes such as drinking, food preparation, bathing, washing clothes and dishes, flushing toilets, and outdoor purposes such as watering lawns and gardens. Domestic water use includes potable and non-potable water provided to households by a public water supplier (domestic deliveries) and self-supplied water.  Also referred to as municipal water use.

The natural or artificial removal of surface and sub-surface water from an area.

Drainage area:
At a specified location, the area measured in a horizontal plane enclosed by a drainage divide.

Drainage basin:
Land area where precipitation runs off into streams, rivers, lakes and reservoirs. It is a land feature that can be identified by tracing a line along the highest elevations between two areas on a map, often a ridge. Large drainage basins contain thousands of smaller drainage basins. Also called a “watershed.”

Drainage divide:
Boundary between adjoining drainage basins.

Drip irrigation:
The watering of crops in which pipes or tubes filled with water slowly drip onto the ground. Less water is lost to evaporation than with other irrigation methods.

The difference between the water level in a well before pumping and the water level in the well during pumping. Also, for flowing wells, the reduction of the pressure head as a result of the discharge of water.

A period of abnormally dry weather marked by little or no rain that lasts long enough to cause water shortage for people and natural systems.

Drought conditions:
Hydrologic conditions during a defined period when rainfall and runoff are significantly less than average.

An elongated ridge of glacial sediment sculpted by ice moving over the bed of a glacier. Generally, the down-glacier end is oval or rounded and the up-glacier end tapers. The shape is often compared to an inverted, blunt-ended canoe. Although not common in Alaska, drumlins cover parts of the Eastern and Midwestern United States.

Dry-year leasing:
Negotiation of temporary water transfers for specific hydrologic and climatic conditions.

Dust storm:
A meteorological phenomenon common in arid and semi-arid regions that arise when a gust front or other strong wind blows loose sand and dust from a dry surface. Particles are transported by saltation and suspension, causing soil erosion from one place and deposition in another.



Water leaving a reservoir or process, such as a water or wastewater treatment plant.

Effluent exchange:
The practice of exchanging wastewater effluent for other water 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.

Elevation head:
The elevation of the bottom of the piezometer or measuring point in feet above sea level.

Endangered Species Act:
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 addition of nutrients such as nitrogen or phosphorus, from sewage effluent or agricultural runoff, to surface water. Enrichment greatly increases growth potential for algae and other aquatic plants.

Ephemeral stream:
A stream or part of a stream that flows only in direct response to precipitation; it receives little or no water from springs, melting snow or other sources; its channel is at all times above the water table.

Equitable apportionment decree:
Equitable apportionments are similar to interstate compacts in that they divide the waters of an interstate stream between two or more states, but they differ in the sense that they are established by either the U.S. Supreme Court or U.S. Congress.

The process in which materials like rock and soil are worn away by precipitation or natural elements, such as water, wind, ice or landslides.

Estuarine wetlands:
Tidal wetlands in low-wave-energy environments where the salinity of the water is greater than 0.5 part per thousand, and is variable owing to evaporation and the mixing of seawater and freshwater; tidal wetlands of coastal rivers and embayments, salty tidal marshes, mangrove swamps and tidal flats.

Area where the current of a stream meets the ocean and where tidal effects are evident; an arm of the ocean at the lower end of a river.

The process of changing a liquid to a gas (vapor); for example, when water turns into steam or water vapor.

A class of sedimentary rocks composed primarily of minerals precipitated from a saline solution as a result of extensive or total evaporation of water.

Loss of water from the soil by evaporation and by transpiration from the plants growing in the soil (commonly shortened to ET).

The process of surface water nutrient enrichment causing a water body to fill with aquatic plants and algae.

Eutrophic lakes:
Shallow, murky water bodies with concentrations of nutrients that cause excessive algae productions, eventually using up oxygen blocking light from reaching other organic matter in the water. Eutrophication is the name for this process.

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 location downstream.

Exempt uses:
Any recognized uses that are not subject to administration under the priority system.

Exempt well:
Small residential and livestock wells that are considered to be exempt from administration and can therefore be pumped out of priority. To obtain this type of exemption, strict criteria must be met as set forth by the legislature and administered by the State Engineer. Two statutes govern exempt wells: C.R.S. 37-92-602 for exempt wells outside of designated basins, and C.R.S. 37-90-105 for exempt wells inside designated basins.



Cropland, tilled or un-tilled, allowed to lie idle during the whole or greater part of the growing season.

Federal reserved rights:
An implied water right that occurs when the federal government withdraws its land from the public domain and reserves it for a federal purpose. The government by implication reserves appurtenant water then unappropriated to the extent needed to accomplish the purpose of the reservation.

Peat-accumulating wetland that generally receives water from surface runoff and/or seepage from mineral soils in addition to direct precipitation; generally alkaline; or slightly acid.

A glacially eroded or modified U-shaped valley that extends below sea level and connects to the ocean. Filled with seawater, depths may reach more than 1,000 feet below sea level.

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

An overflow of water onto lands that are used or usable by man and not normally covered by water. Floods have two essential characteristics: The inundation of land is temporary; and the land is adjacent to and inundated by overflow from a river, stream, lake or ocean.

Flood, 100-Year:
A flood that has a one in 100 chance of occurring in any given year, or a one percent chance. It can take as little as three inches of rain over a few hours to produce a 100-year flood.

Flood irrigation:
The application of irrigation water whereby the entire surface of the soil is covered by ponded water.

Land along a stream, river or lake that becomes covered with water during a flood.

Flow path:
An underground route for groundwater movement, extending from a recharge (intake) zone to a discharge (output) zone, such as a shallow stream.

A naturally or artificially made channel that diverts water.

Pertaining to a river or stream.

Fluvial deposit:
A sedimentary deposit consisting of material transported by suspension or laid down by a river or stream.

The layering or banding that develops in a glacier during the process of transformation of snow to glacier ice. Individual layers, called folia, are visible because of differences in crystal or grain size, alternation of clear ice and bubbly ice, or because of entrained sediment.

Free river:
An occasion when there are no calls upon a river: any legal water rights holder can draw as much as decreed under that right.

Low salt content water (less than 0.5 parts per thousand dissolved salts). Generally, water with more than 500 mg/L of dissolved solids is undesirable for drinking and many industrial uses. Water that contains more than 1,000 mg/L is sometimes used for irrigation.

Small channel in the soil surface for conveying irrigation water.

Furrow irrigation:
A method of irrigation in which water travels through the field by means of small channels between each group of rows.

Futile call:
A situation in which a junior priority will be permitted to continue to divert in spite of demands by a senior appropriator in the same watershed, because to curtail the junior from diversion would not be effective to produce water for beneficial use for the senior.



Gaging station:
A site on a stream, lake, reservoir or other body of water where observations and hydrologic data are obtained. The USGS measures stream discharge at gaging stations.

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

Geographic information system (GIS):
A computerized mapping system used to analyze geographically referenced information.

Pertaining to the form or general configuration of the Earth or of its surface features.

The science that treats the general configuration of the Earth’s surface; the description of landforms.

Relating to the Earth’s internal heat; commonly applied to springs or vents discharging hot water or steam.

A geothermal feature of the Earth where there is an opening in the surface that contains superheated water that periodically erupts in a shower of water and steam.

Glacial drift:
A general term for rock material transported by glaciers or icebergs and deposited directly on land or in the sea.

Glacial lake:
A lake that derives its water, or much of its water, from the melting of glacial ice; also a lake that occupies a basin produced by glacial erosion.

Glacial outwash:
Stratified detritus (chiefly sand and gravel) “washed out” from a glacier by meltwater streams and deposited in front of or beyond the end moraine or the margin of an active glacier.

Glacial lake:
An accumulation of standing liquid water on (supraglacial), in (englacial), or under (subglacial) a glacier.

Glacial stream:
A channelized accumulation of liquid water on (supraglacial), in (englacial), or under (subglacial) a glacier, moving under the influence of gravity.

A large, perennial accumulation of ice, snow, rock, sediment and liquid water originating on land and moving down slope under the influence of its own weight and gravity; a dynamic river of ice. Glaciers are classified by their size, location and thermal regime.

Glacier cave:
A cave formed in or under a glacier, typically by running water. Steam or high heat flow can also form glacier caves. Also called Ice Cave.

Glacier flow:
The movement of ice in a glacier, typically in a downward and outward direction, caused by the force of gravity. ‘Normal’ flow rates are in feet per day.

Glacier ice:
A mono-mineralic type of rock, composed of crystals of the mineral ice, formed through metamorphism of snowflakes. Metamorphism results in recrystallization, increased density and the growth of hexagonal crystals. This ice comprises the majority of the mass of a glacier.

Glacier table:
A rock that is balanced on a pedestal of ice and elevated above the surface of a glacier. The rock protects the pedestal of ice from melting by insulating it from the sun.

Global warming:
The observed increase in average temperature near the Earth’s surface and in the lowest layer of the atmosphere. In common usage, “global warming” often refers to the warming that has occurred as a result of increased emissions of greenhouse gases from human activities. Global warming is a type of climate change; it can also lead to other changes in climate conditions, such as changes in precipitation patterns.

Granitic rock:
A coarse-grained igneous rock.

Greenhouse gases:
Gases that absorb heat in the atmosphere near the Earth’s surface, preventing it from escaping into space. If the atmospheric concentrations of these gases rise, the average temperature of the lower atmosphere will gradually increase, a phenomenon known as the greenhouse effect. Greenhouse gases include, for example, carbon dioxide, water vapor and methane.

Wastewater from clothes washing machines, showers, bathtubs, hand washing, lavatories and sinks.

Water that saturates soils or fills gaps in rock underground; a supply of fresh water under the earth’s surface which forms a natural reservoir.

Groundwater barrier:
Rock or artificial material which has a relatively low permeability and occurs below the land surface where it impedes the movement of groundwater, and consequently causes a pronounced difference in the potentiometric surface on opposite sides of it.

Groundwater basin:
A general term used to define a groundwater flow system that has defined boundaries and may include permeable materials that are capable of storing or furnishing a significant water supply. The basin includes both the surface area and the permeable materials beneath it

Groundwater Commission:
A twelve member body created by the legislature, nine of which are appointed by the Governor to carry out and enforce the state statutes, rules, regulations, decisions, orders and policies of the Commission dealing with designated groundwater.

Groundwater flow:
The flow of water underground in aquifers, which may return to the surface through openings in the land surface (springs) or eventually seep into the oceans.

Groundwater flow system:
The underground pathway by which groundwater moves from areas of recharge to areas of discharge.

Groundwater management district:
Any district organized for the purpose of consulting with the Groundwater Commission on all designated groundwater matters within a particular district.

Groundwater recharge:
Inflow of water to a groundwater reservoir from the surface. Infiltration of precipitation and its movement to the water table is one form of natural recharge. Also, the volume of water added by this process.



Hanging glacier:
A glacier that originates high on the wall of a glacier valley and descends only part of the way to the surface of the main glacier. Avalanching and icefalls are the mechanisms for ice and snow transfer to the valley floor below.

Head gate:
A control structure or gate upstream of a lock or canal; a floodgate that controls the flow of water, as in a ditch.

The source and upper reaches of a stream or other water body, or the contributing smaller streams that come together to form a river.

Holding pond:
A pond or reservoir, usually made of earth, built to store wastewater or polluted runoff for discharge.

Holocene Epoch:
The younger of the two epochs that constitute the Quaternary Period and the latest interval of geologic time, covering approximately the last 11,700 years of the Earth’s history. The sediments of the Holocene, both continental and marine, cover the largest area of the globe of any epoch in the geologic record, but the Holocene is unique because it is coincident with the late and post-Stone Age history of mankind. The Holocene represents the most recent interglacial interval of the Quaternary period. The preceding and substantially longer sequence of alternating glacial and interglacial ages is the Pleistocene Epoch.

Hydraulic conductivity:
The capacity of a rock to transmit water. It is expressed as the volume of water at the existing kinematic viscosity that will move in unit time under a unit hydraulic gradient through a unit area measured at right angles to the direction of flow.

Hydraulic gradient:
The change of hydraulic head per unit of distance in a given direction.

Hydraulic head:
The height of the free surface of a body of water above a given point beneath the surface.

Study of practical applications of liquid in motion.

Hydroclimatic variables:
Physical parameters relevant to both hydrology and climate, including temperatures, precipitation and snowpack.

Hydroelectric power water use:
Water used in the generation of electricity at plants where the turbine generators are driven by moving water. Hydroelectric water use is most commonly an instream use.

Hydrogeologic unit:
Any soil or rock unit or zone which by virtue of its porosity or permeability, or lack thereof, has a distinct influence on the storage or movement of groundwater.

Hydrologic cycle:
The continuous movement of water on, above and below the surface of the Earth via various processes, such as evaporation, transpiration, sublimation, condensation, transportation, precipitation, deposition, infiltration/percolation, surface/groundwater flow and plant uptake. Also referred to as the water cycle.

Hydrologic drought:
Hydrologic drought is related to below-normal streamflow, lake and groundwater levels.

Hydrologic properties:
Those properties of a rock that govern the entrance of water and the capacity to hold, transmit and deliver water, such as porosity, effective porosity, specific retention, permeability and the directions of maximum and minimum permeabilities.

Hydrologic unit:
A geographic area representing part or all of a surface drainage basin or distinct hydrologic feature as delineated by the U. S. Geological Survey on State Hydrologic Unit Maps. Each hydrologic unit is assigned a hierarchical hydrologic unit code consisting of 2 digits for each successively smaller drainage basin unit.

Hydrologic regime:
The characteristic behavior and total quantity of water involved in a drainage basin.

The science dealing with the waters of Earth – their distribution and movement on the surface and underground; and the cycle involving evaporation and precipitation.

A water system, usually small, whose water pump is automatically controlled by pressure in a compressed air tank.

Describes the combined mass of water found on, under and over the surface of the planet.



Ice cap:
A dome-shaped accumulation of glacier ice and perennial snow that completely covers a mountainous area or island, so that no peaks poke through.

Ice field:
A continuous accumulation of snow and glacier ice that completely fills a mountain basin or covers a low-relief mountain plateau to a substantial depth. When the thickness become great enough, tongues of ice overflow the basins or plateaus as Valley Glaciers.

Ice sheet:
A thick, subcontinental to continental-scale accumulation of glacier ice and perennial snow that spreads from a center of accumulation, typically in all directions. Also called a Continental Glacier.

A block of ice that has broken or calved from the face of a glacier and is floating in a body of marine of fresh water. In order of increasing size, the following names are used: Brash Ice, Growler, Bergy Bit.

Igneous rock:
One of the three main types of rocks (the others being metamorphic and sedimentary) that is formed through the cooling and solidification of magma or lava. Igneous rock may form with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks.

A characteristic of some geologic material that limits its ability to transmit significant quantities of water under the head differences ordinarily found in the subsurface.

A body of water or sludge confined by a dam, dike, floodgate or other barrier.

Industrial water use:
Water used for fabrication, processing, washing and cooling. Includes industries such as chemical and allied products, food, mining, paper and allied products, petroleum refining and steel.

The process by which water on the ground surface penetrates through into sub-surface soil.

The entry of rainwater into a sewer system from sources other than infiltration, such as basement drains, manholes, storm drains and street washing.

Injection well:
As defined by the Environmental Protection Agency, any  bored, drilled or driven shaft, dug pit or hole in the ground into which waste or fluid is discharged, and any associated subsurface appurtenances, the depth of which is greater than the largest surface dimension of the shaft, pit or hole. Injection wells are subject to the Underground Injection Control program.

Injury occurs when the action of another results in a water rights holder losing water at the time, place and amount they would otherwise be entitled to.

Instream conveyance:
Flow of water from one water body to another without using the water.

Instream flow:
Water flowing in a natural stream bed; water required for maintaining adequate streamflow.

Instream flow rights:
In Colorado, the Colorado Water Conservation Board is authorized to appropriate or acquire water rights, subject to the priority system, that contribute to minimum streamflows or natural surface water levels or volumes in lakes to preserve the natural environment to a reasonable degree.

Instream use:
Water that is used, but not withdrawn, from a surface water source for such purposes as hydroelectric-power generation, navigation, water-quality improvement, fish propagation and recreation. Instream uses may change the flow characteristics or increase evaporative losses due to impoundments and release schedules.

Integrated drainage:
Drainage developed during geomorphic maturity in an arid region, characterized by coalescence of drainage basins as a result of headward erosion in the lower basins or spilling over from the upper basins.

Interbasin Compact Committee (IBCC):
The IBCC was established by the Colorado Water for the 21st Century Act to facilitate conversations among Colorado’s river basins and to address statewide water issues. Composed of 27 members.

Interbasin transfer:
A transfer of water from one river basin to another. Interbasin transfers may be tracked or regulated for different levels of watersheds such as a hydrologic unit level or a set of basin delineations made by a regulatory authority.

Intermittent stream:
A stream that flows only when it receives water from rainfall runoff or springs, or from some surface source such as melting snow.

Situated between or surrounded by mountains, mountain ranges or mountainous regions.

Internal drainage:
Surface drainage whereby the water does not reach the ocean, such as drainage toward the lowermost or central part of an interior basin or closed depression.

International treaty:
Formal agreement similar to interstate compacts, with the exception that treaties include international transboundary waterways, and therefore include negotiations between nations (or a few states of each nation).

Interruptible Water Leasing:
Authorized by state statute in 2003, a method by which farmers are allowed to lease water to cities during drought emergencies.

Interstate compacts:
Interstate waters are allocated under agreements between two or more states that govern specific interactions among those states, and require consent by the United States Congress. These compacts are intended to allow each state to exercise its own water law and to use its allocated water within its boundaries whenever it might choose.

Interruptible Supply Agreements:
Water rights transferred on a temporary basis for specific needs.

Interstate waters:
Waters that flow across or form part of state or international boundaries. Nearly all major rivers in Colorado flow across state boundaries.

Intrastate agreement:
Agreements among one state’s stakeholders regarding waters being divided within that state and apportioned among those stakeholders.

The controlled application of water for agricultural purposes through manmade systems to supply water requirements not satisfied by rainfall.

Irrigation water use:
Water that is applied by an irrigation system to assist crop and pasture growth, or to maintain vegetation on recreational lands such as parks and golf courses. Irrigation includes water that is applied for pre-irrigation, frost protection, chemical application, weed control, field preparation, harvesting, dust suppression and leaching of salts from the root zone. Irrigation water use estimates also include conveyance losses.

Irrigation district:
In the United States, a cooperative, self-governing public corporation set up as a subdivision of the state, with definite geographic boundaries, organized to obtain and distribute water for irrigation of lands within the district; created under authority of the State legislature with the consent of a designated fraction of the land owners or citizens and the taxing power.

Irrigation efficiency:
The amount of water stored in the crop root zone compared to the amount of irrigation water applied.

Irrigation return flow:
The part of artificially applied water that is not consumed by evapotranspiration and that migrates to an aquifer or surface water body.



Junior water right:
A water right that follows other rights in priority.



A type of topography that results from dissolution and collapse of carbonate rocks such as limestone, dolomite and gypsum, and that is characterized by closed depressions or sinkholes, caves and underground drainage.

A steep-sided hole or depression, commonly without surface drainage, formed by the melting of a large detached block of stagnant ice that had been buried in the glacial drift.

Kettle lake:
A body of water occupying a kettle, as in a pitted outwash plain or in a kettle moraine.



A shallow stretch of seawater (or lake water) near or communicating with the sea (or lake), and partly or completely separated from it by a low, narrow, elongate strip of land.

Lateral moraine:
A low ridge-like moraine carried on, or deposited near, the side margin of a mountain glacier.

Any liquid formed by the drainage of liquids from waste or by the percolation or flow of liquid through waste, including any constituents extracted from the waste and dissolved or suspended in the fluid.

The process of soluble materials which may include nutrients, chemicals, salts or contaminants being washed into a lower layer of soil and carried away by water.

(1) The flow of water from one hydrogeologic unit to another. The leakage may be natural, as through a semi-impervious confining layer, or human-made, as through an uncased well. (2) The natural loss of water from artificial structures as a result of hydrostatic pressure.

The study of physical, chemical, hydrological and biological aspects of freshwater.

The rigid outermost shell of a rocky planet. On Earth, it comprises the crust and the portion of the upper mantle that behaves elastically on time scales of thousands of years or greater.

Livestock water use:
Water used for livestock watering, feedlots, dairy operations and other on-farm needs.

Material that is moved or carried by streams, reported as weight of material transported during a specified time period, such as tons per year.



A mixture of molten or semi-molten rock, volatiles and solids that is found beneath the surface of the Earth. Magma may also contain suspended crystals, dissolved gas and gas bubbles, and it often collects in magma chambers that may feed a volcano or turn into a plutonic/intrusive igneous rock.

Main stem:
The principal trunk of a river or stream.

A water-saturated, poorly drained area, intermittently or permanently water covered, having aquatic and grass-like vegetation.

A stage in the evolutionary erosion of land areas in which the flat uplands have been widely dissected by deep river valleys.

Maximum contaminant level (MCL):
A designation given by the Environmental Protection Agency that indicates the greatest amount of a contaminant that may be present in drinking water without becoming a risk to human health.

Memorandum of Agreement (MOA):
A “conditional agreement” between two or more parties with a transfer of funds for services anticipated. The MOA is prepared in advance of a support agreement/ reimbursable order form that defines the support, basis for reimbursement, the billing and payment process and other terms and conditions of the agreement. Although MOAs do not obligate any funds themselves, they do establish the terms for future service and cite one of the appropriate authorities to do so.

Memorandum of Understanding (MOU):
Defines a “general area of understanding” between parties’ authorities with no transfer of funds for services anticipated. MOUs often state common goals and are used to outline the operation of a program so that it functions a certain way.

Metamorphic rock:
One of the three main types of rocks (the others being igneous and sedimentary) that is formed from the transformation (metamorphism) of other rocks (sedimentary, igneous or older metamorphic) subjected to intense heat and pressure causing profound physical and/or chemical changes.

Microirrigation system:
An irrigation system that wets only a discrete portion of the soil surface in the vicinity of the plant by means of applicators (such as orifices, emitters, porous tubing or perforated pipe) and operated under low pressure. The applicators may be placed on or below the surface of the ground or suspended from supports.

A naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure and specific physical properties. Minerals range in composition from pure elements and simple salts to very complex silicates with thousands of known forms.

A mineral-like substance that does not demonstrate crystallinity. Mineraloids possess chemical compositions that vary beyond the generally accepted ranges for specific minerals.

Minimum streamflow requirement:
Water right decreed to the Colorado Water Conservation Board requiring that a set amount of water be maintained in a water course for the purpose of reasonably maintaining the environment.

Mining waste:
Residues left over from the extraction of raw minerals from the earth.

Mining water use:
Water used for the extraction of naturally occurring. Includes uses associated with quarrying, milling and other preparations customarily done at the mine site, injection of water for secondary oil recovery or for unconventional oil and gas recovery, and other operations associated with mining activity. Mining water use is often considered industrial water use. But when mining water use is separated out, it does not include water associated with dewatering of the aquifer that is not put to beneficial use, or water used in processing, as these processing uses are included in industrial water use.

In reference to climate change, mitigation refers to any anthropogenic intervention to reduce the sources or enhance the sinks of greenhouse gases.

Moisture content:
Either: 1) the amount of water lost from soil upon drying to a constant weight, expressed as the weight per unit of dry soil or as the volume of water per bulk unit of soil volume; or 2) the water equivalent of snow on the ground.

Monitoring well:
A well that is used to obtain water quality samples or measure groundwater levels.

Of, pertaining to, or inhabiting cool upland slopes below the timber line; characterized by the dominance of evergreen trees.

A mound, ridge or other distinct accumulation of unsorted, unstratified glacial drift, predominantly till, deposited chiefly by direct action of glacier ice.

The place where a stream discharges to a larger stream, a lake or the sea.

Municipal water system:
A network of pipes, pumps and storage and treatment facilities designed to deliver potable water to homes, schools, businesses and other users in a city or town, and to remove and treat waste materials.

Municipal water use:
Water withdrawn by public and private water suppliers that furnish water to at least 25 people or have a minimum of 15 connections. Public suppliers provide water for a variety of uses, such as domestic, commercial, industrial, thermoelectric power and public water use.  Also referred to as public supply water use.



National Environmental Policy Act (NEPA):
Federal law enacted to ensure the integration of natural and social sciences and environmental design in planning and decision-making for federal projects or projects on federal lands.

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.

Native waters:
Surface and underground waters naturally occurring in a watershed.

Natural levee:
A long, broad, low ridge built by a stream on its flood plain along one or both banks of its channel in time of flood.

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 uses:
Any recognized beneficial uses of water that are administered under the priority system.

Non-exempt well:
A well allowed to be used for non-exempt uses such as irrigation.

Non-native waters:
Water imported or not originally hydrologically connected to a watershed or drainage basin physically or by statute; non-tributary groundwater and transmountain water are non-native.

Non-tributary groundwater:
Groundwater outside of the boundaries of any designated groundwater basin, the withdrawal of which will not, within one hundred years, deplete the flow of a natural stream at an annual rate greater than one-tenth of one percent of the annual rate of withdrawal.

Nonpoint source pollution:
Pollution that comes from diffuse sources that cannot be classified as “point sources.” Nonpoint source pollution can come from excess fertilizers, toxic chemicals from energy production, acid drainage from abandoned mines and other sources.

Not non-tributary groundwater:
Statutorily defined as groundwater located within those portions of the Dawson, Denver, Arapahoe and Laramie- Fox hills aquifers that are outside of any designated groundwater basin in existence on January 1, 1985. The withdrawal of which will deplete the flow of a natural stream at an annual rate of greater than one-tenth of one percent of the annual rate of withdrawal.

Any substance assimilated by living things that promotes growth. A water resource may be contaminated by excessive input of nutrients.



Offstream use:
Water withdrawn or diverted from a groundwater or surface water source for aquaculture, commercial, domestic self-supply, industrial, irrigation, livestock, mining, public supply, thermoelectric power and other uses.

Pertaining to mountains, in regard to their location and distribution; said of the precipitation caused by the lifting of moisture-laden air over mountains.

The movement of water molecules through a thin membrane. The osmosis process occurs in our bodies and is also one method of desalinating saline water.

Soil material washed down a hillside by rainwater and deposited upon more gently sloping land.

Outwash plain:
A broad, low-slope angle alluvial plain composed of glacially eroded, sorted sediment (termed outwash), that has been transported by meltwater. The alluvial plain begins at the foot of a glacier and may extend for miles. Typically, the sediment becomes finer grained with increasing distance from the glacier terminus.

A water rights term used to describe a surface water drainage system that has more decreed water rights claims on the system than can be satisfied by the physical supply of water available.

Overland flow:
The flow of rainwater or snowmelt over the land surface toward stream channels.

A bow-shaped lake formed in an abandoned meander of a river.



Climate during periods prior to the development of measuring instruments, including historic and geologic time, for which only proxy climate records are available.

Study of hydrologic processes and events, using geological, botanical and cultural evidence that occurred before the beginning of the systematic collection of hydrologic data and observations.

Particulate transport:
The movement of particles in subsurface water.

Peak flow:
The maximum instantaneous discharge of a stream or river at a given location. It usually occurs at or near the time of maximum stage.

A gently inclined erosional surface carved into bedrock that is thinly covered with fluvial gravel that has been developed at the foot of mountains. It develops when running water erodes most of the mass of the mountain.

Perched groundwater:
Groundwater separated from an underlying body of groundwater by an unsaturated zone; groundwater is held up by a perching bed whose permeability is so low that water percolating downward through it is not able to bring water in the underlying unsaturated zone above atmospheric pressure.

The downward movement of water in soil; the movement of water past the soil going deep into the groundwater.

Perennial stream:
A stream that normally has water in its channel at all times.

The ability of a material to allow the passage of a liquid. Loosely packed materials like sand and gravel allow water to pass through easily; denser materials like clay do not.

Physiographic province:
A region in which the landforms are distinctive and differ significantly from those of adjacent regions.

A description of the surface features of the Earth, with an emphasis on the origin of landforms.

Piedmont glacier:
A fan or lobe-shaped glacier, located at the front of a mountain range that forms when one or more valley glaciers flow from a confined valley onto a plain where it expands.

A well that is open only at the top and bottom of its casing.

Erosion by percolating water in a layer of subsoil, resulting in caving and in the formation of narrow conduits, tunnels or “pipes” through which soluble or granular soil material is removed.

Pit pond:
A depression in an outwash plain by the melting of a block of ice floated to its depositional site by meltwater and subsequently buried by sediment. As it melts, a depression in the surface of the outwash plain develops.

A surficial mineral deposit formed by mechanical concentration of mineral particles from weathered debris.

Plant uptake:
Process by which water is taken from groundwater flow and soil moisture up into plants’ roots and tissues.

Plate tectonics:
The scientific theory that describes the large scale motions of Earth’s lithosphere. The theory builds on the associated theories of continental drift and seafloor spreading.

A dry, flat area at the lowest part of an undrained desert basin in which water accumulates and is quickly evaporated; underlain by stratified clay, silt or sand and commonly by soluble salts; term used in Southwestern United States.

Playa lake:
A shallow, temporary lake in an arid or semiarid region, covering or occupying a playa in the wet season but drying up in summer; temporary lake that upon evaporation leaves or forms a playa.

Pleistocene Epoch:
The epoch of geologic time, informally called the ‘The Great Ice Age’ or the ‘Glacial Epoch’ that began ~1.8 million years ago and ended ~8,000 years ago. During this interval, continental glaciers repeatedly formed and covered significant parts of the Earth’s surface. Together, the Holocene and Pleistocene epochs comprise the Quaternary Period.

Point of diversion:
A specifically named place where water is removed from a body of water.

Point source pollution:
As defined by the Clean Water Act, the term “point source” means any discernible, confined and discrete conveyance, including but not limited to any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock, concentrated animal feeding operation or vessel or other floating craft, from which pollutants are or may be discharged. This term does not include agricultural storm water discharges and return flows from irrigated agriculture.

Polar glacier:
A glacier with a thermal or temperature regime in which ice temperatures always remain below the freezing point.

Any substance that, when present in a hydrologic system at sufficient concentration, degrades water quality in ways that are or could become harmful to human and/or ecological health or that impair the use of water for recreation, agriculture, industry, commerce or domestic purposes.

A small part of a stream reach with little velocity, commonly with water deeper than surrounding areas.

A measure of the water-bearing capacity of subsurface rock. With respect to water movement, it is not just the total magnitude of porosity that is important, but the size of the voids and the extent to which they are interconnected, as the pores in a formation may be open, or interconnected, or closed and isolated.

Portable pipe:
Irrigation system which is or can be moved between irrigation sets, such as sprinkler or gated pipe.

Potable water:
Water of a quality suitable for safe human consumption.

Potential evapotranspiration:
The amount of moisture which, if available, would be removed from a given land area by evapotranspiration; expressed in units of water depth.

Potentiometric surface:
An imaginary surface that represents the total head in an aquifer. It represents the height above a datum plane at which the water level stands in tightly cased wells that penetrate the aquifer.

Prairie pothole:
A shallow depression, generally containing wetlands, occurring in an outwash plain, a recessional moraine, or a till plain; usually the result of melted blocks of covered glacial ice; occur most commonly in the North-Central United States and in States west of the Great Lakes from Wisconsin to eastern Montana.

Any or all forms of water particles that fall from the atmosphere, such as rain, snow, hail and sleet. The act or process of producing a solid phase within a liquid medium.

Pressure head:
The height that water rises in a piezometer.

Prior Appropriation:
This type of water right is associated with western states, where water tends to be scarce. In short, the law of prior appropriation allows senior water rights holders who claimed their water rights first the full use of their water right by a certain date before the next holders can access theirs. The law is simplified as, “first in time, first in right.” One becomes a senior water right holder by being the first person to appropriate water by taking it from its location and applying it to some beneficial use, and obtaining a court decree verifying priority status. Since the system dates back to the 1850s, it becomes more complicated than this in some Colorado water systems.

(1) The right of an earlier appropriator to divert from a natural stream in preference to a later appropriator. (2) Seniority date of a water right or conditional water right to determine their relative seniority to other water rights and conditional water rights deriving water from a common source. Priority is a function of both the appropriation date and the relevant adjudication date of the right.

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

Public supply:
Water withdrawn by public governments and agencies, such as a county water department, and by private companies that is then delivered to users. Public suppliers provide water for domestic, commercial, thermoelectric power, industrial and public water users. The systems have at least 15 service connections (such as households, businesses, or schools) or regularly serve at least 25 individuals daily for at least 60 days out of the year.

Public supply deliveries:
Amount of water delivered from a public supplier to users for domestic, commercial, industrial, thermoelectric power or public use purposes.

Public supply water use:
Water withdrawn by public and private water suppliers that furnish water to at least 25 people or have a minimum of 15 connections. Public-supply water is delivered to users for domestic, commercial, industrial, thermoelectric power and public use purposes. Part of the total is used for public services, such as public pools, parks, firefighting, water and wastewater treatment, and municipal buildings, and some is unaccounted for because of leaks, flushing, tower maintenance and other system losses. Domestic deliveries represent the largest single component of public-supply withdrawals. Also sometimes referred to as municipal water use.

Public Trust Doctrine:
A common law doctrine that holds that it is the legal right of the public to use certain lands and waters and the responsibility of the state to preserve and protect the right of the public to the use of these lands and waters. Colorado does not have a public trust doctrine.

Public water use:
Water supplied from a public supplier and used for such purposes as firefighting, street washing, flushing of water lines and maintaining municipal parks and swimming pools. Generally, public-use water is not billed by the public supplier.



Quaternary Period:
A geologic time period that encompasses the most recent 2.6 million years — including the present day. Part of the Cenozoic Era, the period is usually divided into two epochs — the Pleistocene Epoch, which lasted from approximately 2 million years ago to about 12,000 years ago, and the Holocene Epoch, which began about 12,000 years ago. Quaternary rocks and sediments, being the most recently laid geologic strata, can be found at or near the surface of the Earth in valleys and on plains, seashores, and even the seafloor.



Rain shadow:
A dry area on the lee side of a mountainous area where the mountains block the passage of rain-producing weather systems, casting a ‘shadow’ of dryness.

Raw water:
Untreated water.

A continuous part of a stream between two specified points.

Recessional moraine:
An end moraine built during a temporary but significant pause in the final retreat of a glacier.

The process of adding water to an aquifer by injection or infiltration. Dug basins, injection wells or the simple spreading of water across a land surface all are means of artificial recharge.

Recharged area:

Reservoirs and ditches that are designed to replenish groundwater depletions, due to out of priority diversions, by artificially introducing water into the groundwater aquifer.

Recharge capacity:
The ability of the soils and underlying materials to allow precipitation and runoff to infiltrate and reach the zone of saturation.

Reclaimed wastewater:
Wastewater treatment plant effluent that has been diverted for beneficial uses such as irrigation, industry, or thermoelectric cooling instead of being released to a natural waterway or aquifer.

Reconstituted glacier:
A glacier formed below the terminus of a hanging glacier by the accumulation, and reconstitution by pressure melting (regelation), of ice blocks that have fallen and/or avalanched from the terminus of the hanging glacier. Also called Glacier Remaniè.

Recycled water:
Water that is used more than one time before it passes back into the natural hydrologic system, generally by the same user, or for similar purposes.

The layer or mantle of fragmented and unconsolidated rock material, residual or transported, that nearly everywhere forms the surface of the land and overlies or covers the bedrock.

Water discharged by a user or group of users into a wastewater-collection system.

In reference to a Superfund site, the methods used to remove or contain toxic or hazardous materials.

A natural or artificial place to store water; water storage created by building a dam; a pond, lake or basin used for the storage, regulation and control of water.

A monthly publication by the water court of a summary of water rights applications filed in the water court that month.

Return flow:
The amount of water that reaches a surface or groundwater source after it has been released from the point of use and thus becomes available for further reuse.

To use again; to intercept for subsequent beneficial use, either directly or by exchange. Water that would otherwise return to the steam system.

Reverse osmosis:
A water treatment method used to remove dissolved inorganic chemicals and suspended particulate matter from a water supply. Water, under pressure, is forced through a semi-permeable membrane that removes molecules larger than the pores of the membrane.

A shallow part of the stream where water flows swiftly over completely or partially submerged obstructions to produce surface agitation.

Pertaining to the banks of a body of water, a riparian owner is one who own the banks.

Riparian water rights:
The rights of an owner whose land abuts water. They differ from state to state and often depend on whether the water is a river, lake or ocean. The doctrine of riparian rights has its origins in English common law. Specifically, persons who own land adjacent to a stream have the right to make reasonable use of the stream. Riparian users of a stream share the streamflow among themselves, and the concept of priority of use (Prior Appropriation Doctrine) is not applicable. Riparian rights cannot be sold or transferred for use on non-riparian land.

Riparian Doctrine:
A legal concept in which owners of lands along the banks of a stream or body of water have the right to reasonable use of the water and a correlative right protecting against unreasonable use by others that substantially diminishes the quantity or quality of water. The right is appurtenant to the land and does not depend on prior use. Riparian rights are not recognized in Colorado.

Riparian water right:
The legal right held by an owner of land contiguous to or bordering on a natural stream or lake, to take water from the source for use on the contiguous land.

Refers to land, including wetlands, situated near a stream or river.

Riparian rights:
A concept of water law under which authorization to use water in a stream is based on ownership of the land adjacent to the stream.

Riparian zone:
Pertaining to or located on the bank of a body of water, especially a stream.

A natural stream of water of considerable volume, larger than a brook or creek.

Riverine wetlands:
Wetlands within river and stream channels; ocean-derived salinity is less than 0.5 part per thousand.

River basin:
The land area surrounding one river from its headwaters to its mouth; the area drained by a river and its tributaries.

An aggregate of minerals and/or mineraloids and does not have a specific chemical composition.

Rock cycle:
A fundamental concept in geology that describes the dynamic transitions through geologic time among the three main rock types (igneous, metamorphic and sedimentary).

Rock glacier:
A glacier-like landform that often heads in a cirque and consists of a valley-filling accumulation of angular rock blocks. Rock glaciers have little or no visible ice at the surface. Ice may fill the spaces between rock blocks. Some rock glaciers move, although very slowly.

(1) That part of the precipitation, snow melt or irrigation water that appears in uncontrolled surface streams, rivers, drains or sewers. (2) The total discharge described in 1, above, during a specified period of time. (3) Also defined as the depth to which a drainage area would be covered if all of the runoff for a given period of time were uniformly distributed over it.



Safe Drinking Water Act (SDWA):
Federal legislation that regulates the treatment of water for human consumption. Requires testing for and elimination of contaminants for the protection of human health.

An area where deposits of crystalline salt are formed, such as a salt flat; a body of saline water, such as a saline playa or salt marsh.

Saline water:
Water that contains 1,000 milligrams per liter (mg/L) or more of dissolved solids.

The concentration of dissolved solids or salt in water.

Saturated zone:
Those parts of the earth’s crust beneath the water table in which all voids are filled with water under pressure greater than atmospheric.

The condition of a liquid when it has been into solution the maximum possible quantity of a given substance at a given temperature and pressure.

Secondary wastewater treatment:
Treatment involving the biological process of reducing suspended, colloidal and dissolved organic matter in effluent from primary treatment systems and which generally removes 80-95% of the Biochemical Oxygen Demand (BOD) and suspended matter. Secondary wastewater treatment may be accomplished by biological or chemical-physical methods. It is accomplished by bringing together waste, bacteria and oxygen in trickling filters or in the activated sludge process. This treatment removes floating and settleable solids and about 90% of the oxygen-demanding substances and suspended solids. Disinfection is the final stage of secondary treatment.

Particles, derived from rocks or biological materials that have been transported by a fluid or other natural process, suspended or settled in water.

The act or process of forming or accumulating sediment in layers; the process of deposition of sediment.

Sedimentary rock:
One of the three main types of rocks (the others being igneous and metamorphic) that are formed by the deposition of sediment that form layers over time, producing heat and pressure that causes the layers to compact and cement together to form a solid aggregate rock.

A small area where water percolates slowly to the land surface.

Seepage may refer to either the slow movement of water through small pores or cracks into or out of a body of water, or the loss of water from a desired storage location into the ground.

A natural trace element that is both an essential nutrient in lower concentrations and an element toxic to wildlife in higher concentrations.

Self-supplied water:
Water withdrawn from a groundwater or surface water source by a user rather than being obtained from a public supply.

Senior water rights:
Water rights that have been established first and are older than junior rights.

Sewage treatment plant:
A facility designed to receive the wastewater from domestic sources and to remove materials that damage water quality and threaten public health and safety when discharged into receiving streams or bodies of water. The substances removed are classified into four basic areas: 1) greases and fats; 2) solids from human waste and other sources; 3) dissolved pollutants from human waste and decomposition products; and 4) dangerous microorganisms.

A system of underground pipes that collect and deliver wastewater to treatment facilities or streams.

Siliciclastic rock:
Rocks such as shale and sandstone that are formed by the compaction and cementation of quartz-rich mineral grains.

The deposition or accumulation of silt (or small-grained material) in a body of water.

A depression in an area underlain by limestone. Its drainage is subterranean.

The ratio of the channel length between two points on a channel to the straight-line distance between the same two points; a measure of meandering.

Snow water equivalent (SWE):
The amount of water contained within the snowpack. It can be thought of as the depth of water that would theoretically result if you melted the entire snowpack instantaneously.

The amount of mass in a compound that will dissolve in a unit volume of solution.

Source rocks:
The rocks from which fragments and other detached pieces have been derived to form a different rock.

Source water protection:
Plan for maintaining quality of a drinking water supply.

Specific yield:
The ratio of the volume of water that will drain under the influence of gravity to the volume of saturated rock.

Spray irrigation:
Watering crops via high pressure sprayers; this method leads to some water loss to evaporation.

The point at which the water table meets earth’s surface, causing water to flow from the ground.

Sprinkler irrigation system:
An irrigation system in which water is applied by means of perforated pipes or nozzles operated under pressure so as to form a spray pattern.

Height of the water surface above an established datum plane, such as in a river above a predetermined point that may (or may not) be at the channel floor.

State Engineer:
The chief executive office in the executive department of the state government who administers the adjudication decrees of water court, defining water rights.

The locations in which water is stored. They can be above ground in lakes, rivers and other waterways or below ground as groundwater.

Storage water rights:
Colorado law provides for “appropriation by storage” of water that will captured in reservoirs and subsequently be put to beneficial use in priority. Storage water applications are submitted to water court for adjudication and decree similar to other water rights.

Storm Sewer:
A sewer that carries only surface runoff, street wash and snow melt.

A body of flowing water. The term is usually applied to a body of water flowing in a natural surface channel, but is also applied to a body of water flowing in a well-defined open or closed conduit, a jet of water issuing from any opening such as a fissure in rock, a nozzle or as a current in a still body of water such as a lake or a sea.

Stream-aquifer interactions:
Relations of water flow and chemistry between streams and aquifers that are hydraulically connected.

Stream channel:
The physical confine of a stream (river) consisting of a bed and stream banks, and existing in a variety of geometries. Stream channel development is controlled by both water and sediment movement.

A general term that applies to water discharge in a natural channel that may or may not be affected by diversion or regulation.

Stream maturity:
The stage in the development of a stream at which it has reached its maximum efficiency, when velocity is just sufficient to carry the sediment delivered to it by tributaries; characterized by a broad, open, flat-floored valley having a moderate gradient and gentle slope.

Stream mile:
A distance of 1 mile along a line connecting the midpoints of the channel of a stream.

Stream order:
A ranking of the relative sizes of streams within a watershed based on the nature of their tributaries. The smallest unbranched tributary is called first order, the stream receiving the tributary is called second order, and so on.

Stream reach:
A continuous part of a stream between two specified points.

Any apparatus constructed to divert water, such as a head gate, pipe or well.

Application of irrigation water below the ground surface by raising the water table to within or near the root zone.

The transition of water from the solid phase (snow) directly to the vapor phase without melting.

The gradual downward settling or sinking of the Earth’s surface with little or no horizontal motion.

Substitute water supply plan:
A State Engineer approved temporary plan of replacement supply allowing an out-of-priority diversion while a plan for augmentation is proceeding through the water court.

The surface beneath a wetland, lake or stream in which organisms grow or to which organisms are attached.

Substrate size:
The diameter of streambed particles such as clay, silt, sand, gravel, cobble and boulders.

Subsurface drain:
A shallow drain installed in an irrigated field to intercept the rising groundwater level and maintain the water table at an acceptable depth below the land surface.

Subsurface drip irrigation:
Application of water below the soil surface through emitters, with discharge rates generally in the same ranges as drip irrigation. This method of application is different from and not to be confused with subirrigation, where the root zone is irrigated by water table control.

Subsurface runoff:
Runoff that travels over the land surface to the nearest stream channel.

Subsurface water:
All water that occurs below the land surface.

The federal program operated under the Comprehensive Environmental Response, Compensation, and Liability Act and Superfund Amendments and Reauthorization that funds and carries out the Environmental Protection Agency’s solid waste emergency and long-term removal and remedial activities.

Surface flow:
The river, lake and stream transport of water to the oceans.

Surface irrigation system:
Irrigation by means of flood, furrow or gravity. Flood irrigation is the application of irrigation water in which the entire soil surface is covered by ponded water. Furrow is a partial surface-flooding method of irrigation normally used with clean-tilled crops in which water is applied in furrows or rows of sufficient capacity to contain the design irrigation stream. Gravity is an irrigation method in which water is not pumped, but flows in ditches or pipes and is distributed by gravity.

Surface water:
All water naturally open to the atmosphere (rivers, lakes, reservoirs, ponds, streams, etc.); precipitation which does not soak into the ground or return to the atmosphere by evaporation or transpiration.

Surge irrigation:
A method of irrigation using computerized valves to turn the water supply on and off to move water more uniformly down the field.

Suspended loads:
Specific sediment particles maintained in the water column by turbulence and carried with the flow of water.

A slight depression, sometimes filled with water, in the midst of generally level land.

An area intermittently or permanently covered with water, and having trees and shrubs.



Rock that remains after processing ore to remove the valuable minerals.

A relatively small and deep, steep-sided lake or pool occupying an ice-gouged basin amid glaciated mountains.

Tectonic activity:
Movement of the Earth’s crust resulting in the formation of ocean basins, continents, plateaus and mountain ranges.

Temperature glacier:
A glacier with a temperature-regime in which liquid water coexists with frozen water (glacier ice) during part or even all of the year.

Terminal moraine:
The end moraine extending across a glacial plain or valley as an arcuate or crescent ridge that marks the farthest advance or maximum extent of a glacier.

The lower-most margin, end or extremity of a glacier. Also called Toe, End or Snout.

Area or surface over which a particular rock type or group of rock types is prevalent.

Tertiary wastewater treatment:
Selected biological, physica, and chemical separation processes to remove organic and inorganic substances that resist conventional treatment practices; the additional treatment of effluent beyond that of primary and secondary treatment methods to obtain a very high quality of effluent. The complete wastewater treatment process typically involves three phases: (1) the primary wastewater treatment process, which incorporates physical aspects, untreated water is passed through a series of screens to remove solid wastes; (2) the secondary wastewater treatment process, typically involving biological and chemical processes, screened wastewater is then passed a series of holding and aeration tanks and ponds; and (3) the tertiary wastewater treatment process consists of flocculation basins, clarifiers, filters, and chlorine basins or ozone or ultraviolet radiation processes.

Thermal pollution:
A reduction in water quality caused by increasing its temperature, often due to disposal of waste heat from industrial or power generation processes. Thermally polluted water can harm the environment because plants and animals can have a hard time adapting to it.

Thermoelectric power water use:
Water used in the process of generating electricity with steam-driven turbine generators.

Tidewater glacier:
A glacier with a terminus that ends in a body of water influenced by tides, such as the ocean or a large lake. Typically, tidewater glaciers calve ice to produce icebergs.

Tile drain:
A buried perforated pipe designed to remove excess water from soils.

Predominantly unsorted and unstratified drift, deposited directly by and underneath a glacier without subsequent reworking by meltwater, and consisting of a heterogeneous mixture of clay, silt, sand, gravel and boulders.

A pocket of water developed below a waterfall; a term used in the Southwestern United States; used loosely to mean a temporary pool.

The general configuration of a land surface or any part of the Earth’s surface, including its relief and the position of its natural and man-made features.

Total head:
The height above a datum plane of a column of water. In a groundwater system, it is composed of elevation head and pressure head.

Total maximum daily load (TMDL):
An evaluation of the condition of an impaired surface water source based on the Clean Water Act Section 303(d) list that established limitations on the amount of pollutants in water without adverse effects.

Toxic pollutant:
Pollutants or combinations of pollutants that may cause death, disease, behavioral abnormalities, cancer, genetic mutations, physiological malfunctions or physical deformation as a result of exposure, ingestion, inhalation or assimilation into an organism.

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

The rate at which water of the prevailing kinematic viscosity is transmitted through a unit width of an aquifer under a unit hydraulic gradient. It equals the hydraulic conductivity multiplied by the aquifer thickness.

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

The process by which water absorbed by plants (usually through the roots) is evaporated into the atmosphere from the plant surface (principally from the leaves).

In reference to the water cycle (hydrologic cycle), transportation refers to the movement of water, in any of its three forms, through the atmosphere.

Treated water:
Water that has been filtered and/or disinfected; sometimes used interchangeably with “potable” water.

A tributary is generally regarded as a surface water drainage system which is interconnected with a river system. Under Colorado law, all surface and groundwater, the withdrawal of which would affect the rate or direction of flow of a surface stream within 100 years, is considered to be tributary to a natural stream.

Tributary groundwater:
All subsurface water hydraulically connected to a surface stream, the pumping of which would have a measurable effect on the surface stream within one hundred years.

Lowest 6 to 12 miles of the atmosphere, characterized by a general decrease in temperature with height, appreciable water content and active weather processes.

An elongated depression in a potentiometric surface.

Found at high altitudes (alpine tundra) or altitudes (arctic tundra), a type of treeless ecosystem that is dominated by grasses, lichens, mosses and woody plants.

A cloudy condition of water due to suspended silt or organic matter.



Unappropriated water:
Water which has not been appropriated, and in which no other person has or claims superior rights and interests.

A condition in which the upper surface of the zone of saturation forms a water table under atmospheric pressure.

Unconfined aquifer:
An aquifer whose upper surface is a water table free to fluctuate under atmospheric pressure.

Unconfined groundwater:
Water in an aquifer that has a water table that is exposed to the atmosphere.

Unconsolidated deposit:
Deposit of loosely bound sediment that typically fills topographically low areas.

Unsaturated flow:
The movement of water in a porous medium in which the pore spaces are not filled to capacity with water.

Unsaturated zone:
The zone between the land surface and water table. Generally, water in this zone is under less than atmospheric pressure, and some of the voids may contain air and other gases at atmospheric pressure. Beneath flooded areas or in perched water bodies, the water pressure locally may be greater than atmospheric.

Of or pertaining to the place(s) from which groundwater originated or traveled through before reaching a given point in an aquifer.

A general term for non-wetland; elevated land above low areas along streams or between hills; any elevated region from which rivers gather drainage.

User supplied data:
Data or records of water uses provided by an owner/user which has not been verified by state officials.



Valley glacier:
A glacier that flows for all or most of its length within the walls of a mountain valley. Also called an Alpine Glacier or a Mountain Glacier.

Vernal pool:
A small lake or pond that is filled with water for only a short time during the spring.

The tendency of a liquid to evaporate.



Water that has been used and contains unwanted materials from homes, businesses and industries; a mixture of water and dissolved or suspended substances.

Wastewater treatment:
Any of the mechanical or chemical processes used to modify the quality of wastewater in order to make it more compatible or acceptable to humans and the environment.

Wastewater treatment return flow:
Water returned to the hydrologic system by wastewater treatment facilities.

A waterway used to drain excess irrigation water dumped from the irrigation delivery system.

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 bank:
A program operating under the rules of the State Engineer in each of Colorado’s seven water divisions to facilitate the lease, exchange or loan of legally stored water as an alternative to sale of water rights, while protecting against injury to other water rights.

Water column:
An imaginary column extending vertically through a water body from its floor to surface.

Water commissioner:
State water officials, appointed by the state engineer and working under the direction of the division engineers, who perform the day-to-day administration of surface and groundwater in each water district.

Water conservation:
The wise use of water with methods ranging from more efficient practices in farm, home and industry to capturing water for use through water storage or conservation projects.

Water court:
A special division of a District Court with a District Judge designated as and called the Water Judge to deal with certain specific water matters principally having to do with adjudication and change of point of diversion. There are seven water courts in Colorado.

Water cycle:
The continuous movement of water on, above and below the surface of the Earth via various processes, such as evaporation, transpiration, sublimation, condensation, transportation, precipitation, deposition, infiltration/percolation, surface/groundwater flow and plant uptake. Also referred to as the hydrologic cycle.

Water demand:
Water requirements for a particular purpose, such as irrigation, power, municipal supply, plant transpiration or storage.

Water development:
The process of building diversion, storage, pumping and/ or conveyance facilities.

Water districts:
Eighty geographical divisions of the state that originally were used for the granting of water rights. The districts are now largely used for administrative purposes.

Water divisions:
The seven geographical areas of the State of Colorado corresponding to the major natural surface water drainages.

Water exchanges:
Water taken at a time and place when it would otherwise be out of priority but other water rights that would be injured are satisfied with replacement from another.

Water exports:
Artificial transfer (by pipes or canals) of freshwater from one region or subregion to another.

Water gaps:
A deep, narrow pass in a mountain ridge through which a stream flows.

Water imports:
Artificial transfer (by pipes or canals) of freshwater to one region or subregion from another.

Water quality:
Term used to describe the chemical, physical and biological characteristics of water, usually in respect to its suitability for a particular purpose.

Water quality control:
Regulation of any activity or factor that may adversely affect the quality of water.

Water quality standard:
Recommended or enforceable maximum contaminant levels of chemicals or substances in water. These levels are established for water used by municipalities, industries, agriculture and recreation. Standards may also be narrative.

Water requirement:
Water needed for a particular purpose, such as irrigation, power generation, public water supply, plant transpiration, or storage, that no matter what the price, the same quantity of water is purchased, generally independent of price.

Water resources region:
Natural drainage basin or hydrologic area that contains either the drainage area of a major river or the combined areas of a series of rivers. In the United States, there are 21 regions of which 18 are in the conterminous United States, and one each in Alaska, Hawaii and the Caribbean.

Water resources subregion:
Subdivision of a water-resources region. The 21 water-resources regions of the United States are subdivided into 222 subregions. Each subregion includes that area drained by a river system, a reach of a river and its tributaries in that reach, a closed basin(s), or a group of streams forming a coastal drainage area.

Water right:
A property right to the use of a portion, in accordance with its priority, of the public’s surface or tributary groundwater resource obtained under applicable legal procedures.

Water security:
Reliable availability of water in sufficient quantity and quality to sustain human health, livelihoods and the environment.

Water stress:
Water stress occurs when demand for water by people and ecosystems exceeds available supply.

Water supplier:
Owner or operator of a public water system.

Water supply:
All of the processes that are involved in obtaining water for the user before use, including withdrawal, water treatment and distribution.

Water table:
The upper level of groundwater; the level below which soil and rock are saturated with water.

Water transfer:
Reallocation of water from one use to another through sale or lease, which can be a permanent or temporary legal arrangement.

Water treatment:
The processes that withdrawn water may undergo prior to use, including chlorination, fluoridation and filtration.

Water use:
In a restrictive sense, the term refers to water that is withdrawn for a specific purpose, such as for public supply, domestic use, irrigation, thermoelectric power cooling, or industrial processing. More broadly, water use pertains to the interaction of humans with and influence on the hydrologic cycle, and includes elements such as water withdrawal, delivery, consumptive use, wastewater release, reclaimed wastewater, return flow and instream use.

Water year:
The 12-month period, October 1 through September 30. The water year is designated by the calendar year in which it ends and which includes 9 of the 12 months. Thus, the year ending September 30, 1992, is called the “1992 water year.”

The land area that drains into a smaller river or stream; land area that divides river basins or collection points where all the water from different sources converges.

The specific conditions of the atmosphere at a particular place and time, measured in terms of variables that include temperature, precipitation, cloudiness, humidity, air pressure and wind.

Process whereby earthy or rocky materials are changed in color, texture, composition or form (with little or no transportation) by exposure to atmospheric agents.

Any structure or device used for the purpose or with the effect of obtaining groundwater for beneficial use from an aquifer. A shaft or hole into the Earth to tap an underground supply of water.

Wellhead Protection Program:
An amendment to the federal Safe Drinking Water Act in 1986. Initiated to minimize the potential for contamination of public groundwater supplies.

An area of land that is regularly wet or flooded, such as a marsh or swamp. Other common names for wetlands are sloughs, ponds and marshes.

Wetland function:
A process or series of processes that take place within a wetland that are beneficial to the wetland itself, the surrounding ecosystems and people.

Willow carr:
A pool or wetland dominated by willow trees or shrubs.

Water removed from the ground or diverted from a surface water source for use. May also be used to refer to the use itself; for example, public-supply withdrawals or public-supply use.



A method of landscaping that uses plants well-adapted to local climate that are drought-resistant.



The quantity of water (expressed as a rate of flow or total quantity per year) that can be collected for a given use from surface or groundwater sources.




Colorado River District. (2018). WATER GLOSSARY.

Colorado Water Conservation Board [CWCB]. (2004). Water Glossary. In Drought & Water Supply Assessment. Prepared by Bouvette Consulting Resolution Research & Marketing, Inc.

—–. (n.d.). Climate Change Definitions.

Eckhardt, G. (n.d.). Glossary of Water Resource Terms. The Edwards Aquifer Website.

Langbein, W.B., & Iseri, K.T. (2014, e.d.).General Introduction and Hydrologic Definitions (Geological Survey Water-Supply Paper 1541-A). Washington, D.C.: U.S. Geological Survey.

U.S. Geological Survey [USGS]. (2015). Water Science Glossary of Terms. USGS Water Science School.

—–. (2013). Glossary of Glacier Terminology.

—–. (2013). Water Basics Glossary. Water Resources of the United States.

—–. (2018). Water Use Terminology. Water Use in the United States.

—–. (1997). Chapter 11: Glossary. In National Handbook of Recommended Methods for Water Data Acquisition. Reston, VA: U.S. Geological Survey.

U.S. Global Change Research Program. (n.d.). Climate Change Glossary.

Waskom, R., & Neibauer, M. (2012). Glossary of Water Terminology. Colorado State University Extension (Fact Sheet No. 4.717). Fort Collins, CO: Colorado State University Extension.

Irrigation Innovation Consortium Glossary:
A collection of useful agricultural and landscape irrigation terms.

Colorado State University Extension Glossary of Water Terminology:
Definitions for terms commonly used by the Colorado State University Cooperative Extension.

The Edwards Aquifer Website Glossary:
A general glossary of water resource terms from the Edwards Aquifer homepage. Certain administrative and legal terms may not apply to Colorado.

U.S. Geological Survey Glossary:
A compilation of general hydrological terms and definitions commonly found in USGS reports.