State Water Law

Posted: Apr 6, 2010

In general, water resource allocation is governed by state, not federal, law.  Individual states determine the scope of private rights in water, how water rights are distributed, and what users can do with those rights. Nonetheless, the federal government still plays an important role, especially where state water law intersects with environmental concerns. For example, Congress has passed a comprehensive federal water pollution law (the Clean Water Act), that trumps less stringent state laws, and Congress requires the protection of endangered and threatened species (the Endangered Species Act) even where such protection might impact water uses.  Moreover, the Supreme Court has made clear that water is an article of commerce and thus even its allocation and use are within the scope of federal regulatory power.  Interstate water resources are most often addressed through interstate compacts under the Compact Clause of the U.S.  Constitution.  For example, the seven states in the Colorado River Basin signed the Colorado River Compact in 1922, and a water-sharing pact in 2007.   Interstate water allocation can also be addressed by congress, although congress is reluctant to become involved in such disputes. Disputes not resolved by compact or legislation can be addressed by the U.S. Supreme Court, which exercises its original jurisdiction in disputes between or among states.  The Supreme Court also maintains the authority to step in and resolve disputes that arise under existing compacts or federal legislation, as is currently taking place in a conflict between Montana and Wyoming over interpretation of the Yellowstone River Compact.  

A water right is a property right that gives its holder a right to use water for irrigation, power, domestic use and the like.  There are two general types of water rights in the United States; an appropriative right and a riparian right.  An appropriative right allows the holder to use a defined quantity of water for a designated purpose.  A riparian right allows for landowners whose property is adjacent to water to use that water in a reasonable way.  States generally allocate water in strictly one of these ways although some states, for example California, have a blended system.  Water rights are generallyappurtenant to the land on which they are used, meaning that although water rights are a separate property interest, they are bound up with the land and transfer when the land transfers.  In prior appropriation states however, a water right holder may explicitly sever the water right from the land, selling the land but retaining the water right.


Prior Appropriation Doctrine

Prior appropriation is the primary water rights system used in the arid Western states, In prior appropriation states, the earliest appropriator from a given source has a senior right to use that water before others are allowed to take any water.  For this reason, prior appropriation is often described as the doctrine of "first in time, first in right."  With the exception of Colorado, all prior appropriation states require water users to obtain a permit from the appropriate state water official.   The permit application date ultimately establishes one's priority date if the water rights is ultimately perfected.  In Colorado, a prospective water user obtains the functional equivalent of a permit from a water judge in one of the state's seven water courts.  

In addition to a permit, individual appropriators in a prior appropriation states must put water to a "beneficial use."  This usually means that water users cannot waste water.  Prior appropriation states also require users to use their water regularly or lose their rights to the water.  Typically, a water user will not lose their water unless it has not been used consistently over a period of at least 5 to 10 years, depending on the state law. 

Normally, state water or environmental agencies regulate the acquisition of new water rights and changes in existing rights in prior appropriation states.  Most of the intermountain West states, such as Colorado and Wyoming, follow a strict prior appropriation system for their surface water.  States along the Pacific Coast and along the eastern border of the Mountain states typically began with a riparian system (described below) but have evolved to a system that is almost exclusively based upon priorities.

Common Law Riparian Rights Doctrine

States east of the Great Plains historically had fewer conflicts over water use and adopted a more laissez faire attitude toward water resource regulation.  These states typically followed a riparian rights system that grants adjacent landowners a right to put water to any "reasonable use", at least on their riparian property.  Riparian rights are appurtenant to the land and do not depend on prior use.  They are also correlative with other riparians such that all must share if there is insufficient water to satisfy the needs of all riparian users.

Modern Permit Systems

Gradually, as water conflicts became more common in Eastern states, most of these states have shifted to a permit system that has more in common with prior appropriation systems than with riparian systems.  While these permit systems vary, most require a permit much like the permits granted in Western states.  The most important difference is that water shortages are typically handled through a type of forced sharing rather than priorities.

Beneficial Use

Coalbed Methane Produced Water
The recent Colorado Supreme Court case of Vance v. Wolfe held that water produced from coalbed methane (CBM) wells is a beneficial use under Colorado's water law.  The lawsuit was brought by ranchers claiming that CBM wells were depleting their hydrogeologically-connected water wells.

In response to the ruling, which would have subjected all of Colorado's CBM wells to the state's prior appropriation system within just a few months, the Colorado legislature passed HB 09-1303 which provides a three-year moratorium on integrating 'tributary' wells into the prior appropriation system to allow the state engineer and energy companies time to adjust and prepare substitute water supply plans.  The state engineer is also allowed to promulgate rules for wells which interact which 'nontribiutary' waters that do not impact nearby water rights.
In Western states, "beneficial use" is often described as the "basis, the measure, and the limit" of a water right.  This means that water must be put to a beneficial use in order to obtain and retain a water right.  A beneficial use of water is a use that "produces benefits, tangible or intangible, economic or otherwise," and is normally invoked by prior appropriation jurisdictions to prevent wasteful uses of water.  Although many state statutes and constitutions explicitly declare certain uses to be beneficial (such as irrigation, power generation, domestic uses, industrial uses, instream flows, and recreational uses), these lists are considered to be illustrative and not exhaustive. 

Reasonable Use

In riparian jurisdictions, every riparian owner has the right to use the water as long as the use is reasonable and not interfering unnecessarily with the rights of others.  This means that determining whether a use is reasonable is always considered in reference to the needs of the other riparian users.  There is no fixed rule on what constitutes a reasonable use because it always depends on the unique factual situation.  

Instream Flows

Instream flows are specific stream flows (measured in cubic feet per second) that have recently been considered a beneficial use of water in most prior appropriation jurisdictions.  These states recognize that by leaving a certain level of water in the stream there are benefits to fish and wildlife, recreation, navigation, power generation, and other uses.  While some states allow only certain state agencies to hold instream flow rights others allow for individuals to obtain them as well, including the conversion of a consumptive use right to instream use. Increasingly, states are allowing acquisition of temporary rights to water to preserve or restore streamflows.  This usually requires special legislative exceptions to the rule of abandonment, described below.

Surface Water

Surface water refers to any water on the surface of the land including water in streams and water bodies like lakes, ponds, flood water or seepage from another water supply.  In prior appropriation states, all surface water is considered subject to the claims of existing water rights holders, so a homeowner might run into trouble taking such modest water conservation measures as harvesting rainwater. The Colorado legislature recently enacted legislation to allow this practice. See "It's now legal to catch a raindrop in Colorado," New York Times, 6/29/09. The City of Tucson recently enacted the nation's first municipal rainwater harvesting ordinance, requiring new commercial buildings to supply half the water needed for their landscaping from harvested rainwater. See "Tucson rainwater harvesting law now drawing interest," Arizona Daily Sun, 7/6/09.


Groundwater is all water contained in geologic features beneath the surface of the land, including water in the soil, aquifers, and artesian wells.  States differ in their regulation of groundwater with some treating surface and groundwater differently and others treating them largely the same.  The differing rules include the rule of capture (currently applied in only a few states) which allows for a landowner to pump any amount of groundwater even to the harm of others.  There is also the American rule, or reasonable use which limits withdrawals to what is needed for reasonable and beneficial purposes.  Thecorrelative rights doctrine provides that landowners situated over a common source have equal rights to use the water in a reasonable manner.  However, many states now use the prior appropriation doctrine in administering groundwater with a permit system similar to that for surface rights. 

Storage Right

In some Western states, including Colorado and Wyoming, the right to impound water in a reservoir or an underground aquifer for later application to beneficial use is regulated separately from other water rights.  In general, a storage right allows its holder to fill their storage facility once to capacity during any calendar year, and is part of the same prior appropriation system as other water rights.  Some states regulate storage rights as part of their prior appropriation system making them subject to the same permit and adjudication system as other rights.  

Transfers and Exchanges

water right transfer is a change in ownership of an existing right, while a water right exchange is a change in the use of water under an existing right.  While water rights are generally considered appurtenant to the land, in most Western states a water right holder may sever the water right from the land and either sell or retain it as a separate right, as long as the holder files an application or informs the state of the severance.  In addition, most Western states allow water right holders to change the existing use of water under their current right without any loss in priority or diminution of the right, as long as they apply for an exchange or change in use with the state agency responsible for regulating water rights.  Water transfers and exchanges are usually allowed as long as they do not impair existing rights. 

Abandonment and Forfeiture

Two ways in which a  water rights holder may lose legal claim to the right are through abandonment and forfeiture.  In Western states, abandonment of a water right generally requires nonuse of the water along with a specific intent to abandon the right.  In many states, however, nonuse of water for a certain statutorily or judicially defined period of time creates a legal assumption that the right has been abandoned, an assumption that may be contested but will stand as a legal fact unless proven otherwise.  Additionally, many states recognize forfeiture of a water right as a distinct legal concept from abandonment.  Forfeiture occurs where a water right holder fails to use the water for a statutorily defined period of time, after which the holder loses the right.  Most Western states have statutorily defined defenses to abandonment and forfeiture, such as drought and ongoing legal proceedings, that a water right holder may invoke in an abandonment or forfeiture proceeding.

Public Access

In most states, including most Western states, the public has a right to access at least some waters running over private land, either because the state owns those waters, or because the public has an easement over them.  Some Western states allow members of the public to access all waters of the state for recreational purposes under the legal doctrine of public ownership, whereby the state owns all the waters in the state.  Other Western states allow members of the public to access all navigable streams of the state for recreational and navigational purposes.  

In most states that recognize a right of public access to waters running over private land, members of the public may not touch the bed or banks of those waters, but may only float on the water.  A few states, such as Montana, allow members of the public to touch the beds and banks of waters running over private land as long as it has a “minimal impact.”  Moreover, in order to have a right to waters running over private land, members of the public must be able to gain legal access to the waters in question (e.g., members of the public may not trespass on private land to reach the waters).  A minority of states do not recognize a right of public access to waters running over private land in any case.  

On November 17, 2008, the Montana Supreme Court clarified the definition of a "natural" body of water in a widely anticipated decision concerning access to Mitchell Slough, tributary to the Bitterroot River.  For an interpretation of this decision, see "Stream Access Decision," The Water Report, 1/15/09. The Utah legislature considered the issue in its 2009 session, as described in a story in the Salt Lake Tribune, 3/8/09. The Montana legislature enacted a bill confirming the public's right of access from bridges. See "Bridge access bill sails through," The Montana Standard, 4/3/09.

Links to State-Specific Resources


AK - State Water Law Summary


AZ - State Water Law Summary

Arizona Department of Water ResourcesArizona Water Institute


CA - State Water Law Summary

California Department of Water ResourcesCalifornia State Water Resources Control Board


CO - State Water Law Summary

Colorado Division of Water ResourcesColorado Water Conservation BoardColorado Water Trust


ID - State Water Law Summary

Idaho Department of Water ResourcesIdaho DEQ Water Quality Information


MT - State Water Law Summary

Montana DNRC Water Resoruces DivisionMontana DEQ Water Quality InformationMontana Water Trust


NE - State Water Law Summary


NV - State Water Law Summary

Nevada Division of Water Resources

New Mexico

NM - State Water Law Summary

New Mexico Office of the State EngineerNew Mexico Water Quality Control Commission


OR - State Water Law Summary

Oregon Water Resources DepartmentOregon Water WatchOregon Water Trust


UT - State Water Law Summary

Utah Division of Water RightsUtah Division of Water Resources


WA - State Water Law Summary

Washington Dept. of Ecology Water Resources ProgramWA Rivers ConservancyLandowner's Guide to WA Water Rights


WY - State Water Law Summary

Wyoming State Engineer's Office  

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