Last verified Jul. 2026

A glossary of Colorado water terms

Terms marked with a citation are defined by statute; the rest describe administrative practice. Every definition here is linked from the pages in the basics and elsewhere on the site, so you can jump straight to a term and back.

Abandonment

Termination of a water right, in whole or in part, because the owner intended to permanently stop using the water. Non-use alone is evidence, not proof — intent is the legal test, and several kinds of non-use (approved conservation programs, land fallowing, water banking, an instream-flow loan to the Colorado Water Conservation Board) are expressly tolled by statute. C.R.S. § 37-92-103(2)

Absolute water right

A right whose appropriation is complete: the water has actually been diverted and put to beneficial use, and a court has confirmed it. Contrast a conditional water right, which is a placeholder for a project not yet built.

Acre-foot

The volume that covers one acre to a depth of one foot — 325,851 gallons. Storage rights and consumptive-use figures are usually stated in acre-feet, while direct-flow rights are stated in cubic feet per second.

Adjudication

The water court proceeding that confirms a water right and fixes its priority date. Colorado rights exist from the moment of appropriation, but they are only administrable once decreed.

Administration number

The number the state uses to rank rights in the field. For a right adjudicated in its own era it is simply the count of days from December 31, 1849 to the appropriation date — so a smaller number is more senior. Rights adjudicated in a later proceeding than they were appropriated carry a compound number reflecting the postponement doctrine. C.R.S. § 37-92-306

Appropriation

Putting a specific quantity of the state’s water to beneficial use by the procedures the law prescribes. An appropriation based on speculative resale, rather than on a real plan and a real place to use the water, does not count. C.R.S. § 37-92-103(3)

Appropriation date

The date the appropriator first took the steps that fixed the right — typically the first diversion, or a documented first step followed by diligence. This, not the adjudication date, is what usually determines seniority.

Plan for augmentation

A court-approved program that replaces the water a junior or out-of-priority diversion takes out of the stream, so senior rights are not injured. It is what makes most new wells and most new subdivisions possible in over-appropriated basins. C.R.S. § 37-92-103(9)

Beneficial use

The use of the amount of water that is reasonable and appropriate, under reasonably efficient practices, to accomplish the purpose of the appropriation without waste. It is both the measure and the limit of every Colorado water right. C.R.S. § 37-92-103(4)

Call (river call)

A senior right demanding its water, which obliges the division engineer to shut down junior diversions upstream until the senior is satisfied. When people say the river is "on call," they mean juniors are being curtailed.

cfs (cubic feet per second)

The rate unit for direct-flow rights. One cfs is about 449 gallons per minute, and running for 24 hours it yields just under two acre-feet. In DWR records the decreed unit "C" means cfs.

Change of water right

A court-approved change in the type of use, place of use, time of use, point of diversion, means of diversion, or place of storage of an existing right. Buying a right and using it somewhere else, or for something else, requires one. C.R.S. § 37-92-103(5)

Conditional water right

The right to perfect a water right at a fixed priority once the appropriation is completed with reasonable diligence. It holds a place in line for a project that has not yet been built, and must be re-confirmed periodically or it is lost. C.R.S. § 37-92-103(6)

Historical consumptive use

The portion of a right’s diversions historically consumed — evaporated, transpired by crops, or otherwise not returned to the stream. It is the quantity that can actually be moved in a change case, and it is normally far smaller than the decreed rate.

Decree

The water court judgment that confirms a water right: its source, structure, amount, uses, point of diversion, priority date, and any conditions. The decree is the right’s governing document — not the deed, and not the well permit.

Designated groundwater

Groundwater in one of the state’s designated basins on the eastern plains, administered by the Colorado Ground Water Commission rather than by the water courts and the priority system. C.R.S. § 37-90-103(6)

Diversion

Removing water from its natural course or location, or controlling it there, by ditch, canal, flume, reservoir, pipeline, well, pump, or other structure. C.R.S. § 37-92-103(7)

Division engineer

The state official who administers water rights within one of the seven water divisions — setting calls, ordering curtailment, maintaining the tabulation of priorities, and preparing the decennial abandonment list. Water commissioners work under them on individual stream reaches.

Exempt well

A small well — generally 15 gallons per minute or less, serving no more than three single-family dwellings — that is exempt from most of the priority-administration article and is permitted by the State Engineer instead of decreed by a water court. C.R.S. § 37-92-602(1)

Junior right

A right with a later appropriation date than another. In a shortage the junior goes without so the senior can be satisfied in full — Colorado does not pro-rate.

Nontributary groundwater

Groundwater whose withdrawal will not, within 100 years of continuous pumping, deplete a natural stream at an annual rate greater than one-tenth of one percent of the annual withdrawal rate. It is allocated by overlying land ownership rather than by priority. C.R.S. § 37-90-103(10.5)

Priority

The seniority of a water right by date, and its rank relative to other rights drawing from a common source. Priority is the whole architecture of Colorado water law. C.R.S. § 37-92-103(10)

Resume

The monthly published list of every application filed in a water division. It is how the world learns that someone has asked for a new right or a change, and it starts the clock for filing a statement of opposition.

Senior right

A right with an earlier appropriation date, satisfied first and in full before any junior gets water. Seniority, not size or need, decides who goes short.

Structure

The physical works a right diverts through — a ditch, headgate, reservoir, well, or pipeline. DWR records are organized by structure, and each is identified by a WDID.

Tributary water

Surface water, and the groundwater hydraulically connected to it, that forms part of a natural stream system. Colorado presumes groundwater is tributary unless it is proven otherwise — which is why a well can be curtailed by a river call miles away. C.R.S. § 37-92-103(11), (13)

Usufructuary right

A right to use a resource that someone else owns. A Colorado water right is usufructuary: the water belongs to the public, and what you hold is a right to divert and use a measured quantity of it, in priority, for a decreed purpose.

Water court

The district court in each of the seven water divisions that has exclusive jurisdiction over water matters, presided over by a water judge designated annually by the Colorado Supreme Court. C.R.S. § 37-92-203

WDID

The Water District IDentifier — the seven-digit code DWR assigns to a structure. The first two digits are the water district, the rest identify the structure. It is the fastest way to look a right up in state records.

Where these definitions come from

The statutory definitions live in two places. Article 92 of Title 37 — the Water Right Determination and Administration Act of 1969 — defines the terms used in surface-water and tributary-groundwater administration at C.R.S. § 37-92-103. Article 90 defines the groundwater terms, including designated and nontributary groundwater, at C.R.S. § 37-90-103. Where a term is used constantly in practice but never defined by statute — "call," "senior," "historical consumptive use" — the definition above describes how the state and the water courts actually use it, and says so.