Water Law: An Overview


Water is at the heart of agriculture. The availability of freshwater makes it possible to grow crops and raise livestock. Agricultural water use, in turn, is at the heart of discussions involving water law and policy.

Although water is one of our most plentiful resources, there is often not the right quantity of the right quality of water in the right place at the right time to satisfy demand. Consequently, there is keen competition among water users, including agriculture, municipalities, industry, recreational users, and conservationists.

Agriculture is a major user of ground and surface water in the United States, accounting for approximately 80 percent of the Nation’s consumptive water use and over 90 percent in many Western States. Water used in agricultural production is usually sourced from surface waters, such as rivers, lakes, streams, and ponds, or from groundwater stored in aquifers. In some circumstances, agricultural water is also harvested directly from rainfall and stored in above or below-ground cisterns.

Traditionally, management of water resources has focused on surface water or ground water as if they were separate entities. Although water is part of a connected system, it tends to be regulated based upon its source. Even within the category of surface water, water regulations can vary depending on whether the surface water is perennial, ephemeral, or man-made.

Broadly, water law can generally be divided into two substantive areas: rights to use water and restrictions on pollution of water. More specifically, water law concerns: (1) the balance between public rights and private rights to use water; (2) the relative rights of individual water users; and (3) water quality and the regulation of discharges to water. As it relates to agriculture, water law issues tend to fall into two categories: allocation rights and agricultural land use that negatively affects water quality.

Water allocation is generally governed by the states, with each state having its own regulatory system with very little federal intervention. State statutes and regulatory schemes control certain uses of water, such as transfers of water from one watershed to another, withdrawal of groundwater from overused aquifers, impoundment of water, and construction of wells.

Water quality, on the other hand, is governed mostly by federal law, primarily the Clean Water Act.

As the authors point out in their forward to the 5th edition of David H. Getches’ Water Law in a Nutshell:

A decision to use water for a particular purpose can have far-reaching impacts. For instance, transporting water from a rural area across a mountain range to a city may provide water to sustain the city’s population, but it may also force a decline in agricultural productivity and the farming community built on it, facilitate more rapid growth in the importing city, prevent future development of the exporting rural area, curtail recreational opportunities, make sewage treatment more difficult as streamflows to dilute wastewater discharge are diminished,  deprive the exporting area of groundwater recharge, and cause ecological changes in both areas. Balancing these conflicting interests and demands is made ever more complex, challenging, and essential in the face of chronic drought cycles intensified by climate change.

It is not surprising then that states have developed and continue to revise legal and regulatory schemes used to prioritize and clarify the relative rights of competing water users.

Private Surface Water Rights

The right to the use of surface waters, whether for irrigation, manufacturing, or another use, is generally governed by state law.

In the United States, three different use allocation systems have developed to determine the rights of private persons in water. The first is the riparian doctrine, which developed in the water-abundant eastern United States. The second is the system of prior appropriation or “first-in-time, first-in-right,” that developed in the western United States. Finally, a handful of states have adopted a hybrid system, which contains parts of both the prior appropriation and the riparian systems doctrines. Because water allocation regulation is complex, it is best to contact your state water agency to determine the system used by your state. List of State Water Offices.

The Riparian Doctrine

Riparianism limits the use of water to only those landowners with riparian land. In order to be classified as a riparian landowner, the landowner must own the parcel of land adjacent to the watercourse, i.e. a river, stream, lake, or pond, from which the landowner plans to use the water. Even then, the water may only be put to a reasonable use. The courts can enjoin landowners for unreasonable uses.

The riparian landowner has the right to make “reasonable use” of the watercourse. This means that the riparian landowner may make a reasonable use of the water as long as that use does not interfere with the reasonable use of another downstream riparian landowner. Reasonableness is determined by comparing the proposed use with the other uses of other riparian landowners. Any natural uses, such as water for drinking, watering livestock, or watering a garden, are considered reasonable under the law. Artificial uses, such as those for irrigation or industry, are considered reasonable uses under most states’ laws.

Non-riparian landowners generally have no right to use water, although some riparian jurisdictions may allow it. A majority of jurisdictions require proof of actual harm from the use of water on non-riparian land. The minority follows the Restatement (Second) of Torts § 855, which allows for the reasonable use of water on non-riparian land only if the user also owns riparian land.

Under riparian rights, landowners do not have to use water to keep their riparian rights. New uses may be started at any time as long as the new use is a reasonable one. Because the right is attached to the riparian land, non-use does not extinguish the right.

Today, almost all riparian states have moved towards allocating water through a permitting system, often called a “regulated riparian” system. Under the regulated riparian system, a central state agency controls who may use the water, how much they can use, and when they can use it. Regulated riparianism departs from common law riparianism by looking at the projected use before any water is ever actually used. Using the same “reasonable use” criteria as common law, the states first determine if a new use is reasonable. This allows the state to consider both the potential benefits to society and the compatibility with current uses before granting a new permit. In many cases, the permit is only required on consumptive uses and excludes non-consumptive uses, or uses that do not require a diversion or removal of water from the watercourse.

The permitting system allows the state to plan for and maximize water usage in the future. Even if a use is exempt from a permit, the user may still have to file a water use plan with the state in order to help with planning. However, the rules governing whether a use requires a permit vary from state to state. Further, in many states, agricultural uses are exempt from permit requirements.

Regulated riparian permits exist for a fixed period of years, unlike indefinite permits used in prior appropriation states. In times of water shortages, the state may adjust the quantity of water use allowed and can require a pro rata reduction across the board or based on seniority of use. Permits may also prioritize permitted users over non-permitted users when non-permitted user withdrawals hurt permitted users. Additionally, riparian landowners who do not obtain a permit within the required statutory time period may see a reduction or a forfeiture of their common law riparian rights.

The Prior Appropriation Doctrine

The prior appropriation doctrine dates back to the miners who first settled the West and needed water to develop their mining claims. Because the land needed was not adjacent to a watercourse, the miners could not use the riparian system. Instead, the miners used the “first in time, first in right” system, which was already being used to resolve disputes over water use. This led to the prior appropriation doctrine, where the first user had the right to continue using the water to the exclusion of the rights of those who came later.

The prior appropriation system is based on priority. The most senior appropriator has the highest priority and can defeat all other less senior appropriators in times of shortages. Unlike riparianism, there is no requirement that a senior appropriator use less water in times of a shortage. Water users can take in order of their respective priorities, with each user taking their full appropriative right until the water is gone.

The senior appropriator may enforce his rights by “calling the river.” This is a process that allows the senior appropriator to ensure the junior appropriators do not use water out of turn. The senior appropriator will either go to court or the state water agency to have their right enforced against a junior appropriator. If the senior appropriator’s water right would be lost through evaporation, instead, the senior only has a “futile call,” and the state will not enforce his right against the junior.

The rationale behind this theory is that it is better for water to be used by the junior appropriator rather than lost in transport to the senior appropriator.

The prior appropriation doctrine varies somewhat from state to state, although there are three general requirements: (1) the appropriator must intend to apply water to a beneficial use, (2) the water must be diverted from a natural course, and (3) the water must be applied to a beneficial use. A beneficial use is any use recognized by the state as being an appropriate use of water, such as domestic, municipal, agricultural, industrial and recreational uses. In all prior appropriative states, agricultural uses are considered beneficial uses. The beneficial use is the measure and limitation of the appropriative right. Once water is put to a beneficial use, the right is perfected and has priority over later appropriators. The senior appropriator then has the right to use their original right, even if a “better’ use arises later.

In order to have a valid appropriation, an appropriator must show the necessary intent to make an appropriation. The intent necessary is usually just the intent to divert water and apply the water to a beneficial use. In states that require a permit, the application for the permit shows the objective evidence of the necessary intent. A valid appropriation will be given a priority date, or the date the water was first used. Some states have developed the doctrine of relation back that allows the appropriator to use the date that the intent was formed as the priority date.

Historically, the appropriator was required to divert, or build some form of a diversion, in order to provide notice that the water was appropriated. A diversion is typically any alteration to a portion or a stream’s entire natural course. In many cases, the capacity of the diversion could be used to determine the extent of the quantity of water appropriated. Today, most prior appropriation states have adopted a permit system that satisfies the notice requirement of a diversion.

Hybrid Systems

Some states, such as California and Oklahoma, have developed hybrid allocation systems, which combine aspects of both the riparian and the appropriative rights systems. While there is no uniform system for all hybrid states, all hybrid systems contain elements of both riparian and prior appropriative rights.

Private Groundwater Rights

Water used in agriculture can also come from underground aquifers. While many groundwater aquifers are connected to surface waters, states’ groundwater allocation systems often differ from their surface water allocation systems. Additionally, multiple legal doctrines and combinations of doctrines are used by states to allocate groundwater rights, including the Absolute Dominion rule, Correlative Rights doctrine, Prior Appropriation doctrine, Reasonable Use doctrine, and Restatement of Torts rule.

Groundwater allocation systems often differentiate between on-tract and off-tract uses. On-tract use is where water is used on the tract where the pump is located. Off-tract use is where water is transferred to another location for use.

States often may not fall clearly within a particular doctrine and may use components of two or more systems. For this reason, it is best to contact your state water agency to determine the allocation system used by your state. List of State Water Offices.

Absolute Dominion Rule

Under the Absolute Dominion Rule, also called the “Absolute Ownership Rule” or the “English Rule,” a landowner may use as much ground water as possible. The rule does not take into account impacts on neighboring users, and, as a result, one owner could monopolize the entire aquifer without incurring liability. This doctrine creates an incentive to pump as much water as possible because of the lack of concern of incurring penalties from a neighboring user. Most states have rejected this doctrine, as malicious withdrawals of water could not be enjoined. The states that do continue to follow this doctrine allow for remedies for willful injury. States following this doctrine are Connecticut, Georgia, Indiana, Louisiana, Maine, Minnesota, Massachusetts, Mississippi, Rhode Island, Texas, and Vermont.

Correlative Rights Doctrine

The Correlative Rights Doctrine distributes water on an equitable basis among landowners and allows off-tract uses, although these uses are subordinate to on-tract uses. Like the Absolute Dominion Rule, the Correlative Rights Doctrine determines rights in groundwater based on ownership of land. The difference, however, is that landowners overlying the same aquifer are limited to a reasonable share of the aquifer’s total supply, rather than having an absolute right to groundwater or an unlimited right to pump.

This doctrine was first recognized in California in Katz v. Walkinshaw, 74 P. 766 (Cal. 1903). The court held that in times of shortages an overlying owner must limit withdrawals to a “fair and just proportion” of the underlying supply. Thus, when two users are both exporting water, the court would use the doctrine of prior appropriation. Finally, in disputes between an overlying landowner and an exporter, the overlying landowner receives a reasonable share of the water, even if the overlying owner is junior to the exporter. The states that apply this doctrine include:  Arkansas, California, Iowa, Minnesota, Oklahoma, and Vermont. Nebraska follows a combination of this doctrine and the Reasonable Use doctrine.

 Prior Appropriation Doctrine

Many western states have adopted a prior appropriation doctrine for groundwater. Similar to the prior appropriative system for surface water, the first landowner to beneficially use or divert water from a groundwater source is given priority over later users. The right, similar to the surface water system, is limited to the amount that is put to a beneficial use. Many states, today, have replaced this doctrine with a permit system, similar to the surface water permit system. This doctrine is in use in Alaska, Colorado, Idaho, Kansas, Montana, Nevada, New Mexico, North Dakota, Oregon, South Dakota, Utah, Washington, and Wyoming.

Reasonable Use Rule

Some states have adopted the doctrine of reasonable use, or the American rule, which requires the water to be put to a reasonable use on the overlying tract of land and does not permit water to be taken to another tract. Reasonable use has been construed broadly, and almost any use is considered reasonable as long as the water is used on the overlying land. The rule is considered a modification of the Absolute Dominion Rule with exceptions for wasteful uses and off-tract uses. This system is used in Alabama, Arizona, Delaware, Illinois, Kentucky, Maryland, Michigan, Missouri, New Hampshire, New Jersey, New York, North Carolina, Oklahoma, Pennsylvania, Virginia, and West Virginia.

Other states have adopted the reasonable use rule in conjunction with another groundwater rule. Florida has abolished all common law groundwater rights for a permit system but uses this doctrine in granting permits. Wyoming uses the reasonable use doctrine along with the Prior Appropriative system for groundwater. Nebraska, additionally, uses the reasonable use doctrine along with the Correlative Rights Doctrine.

The Restatement (Second) of Torts Rule

Finally, Ohio and Wisconsin have adopted the Restatement (Second) of Torts approach, which utilizes a variety of factors to determine if a use of water is appropriate. The Restatement’s rule is seen as a merger of the Absolute Dominion Rule and the Reasonable Use rule. Section 858 of the Restatement (Second) of Torts states:

Liability for Use of Groundwater

(1) A proprietor of land or his grantee who withdraws groundwater from the land and uses it for a beneficial purpose is not subject to liability for interference with the use of water by another, unless

(a) the withdrawal of groundwater unreasonably causes harm to a proprietor of neighboring land through lowering the water table or reducing artesian pressure,
(b) the withdrawal of groundwater exceeds the proprietor’s reasonable share of the annual supply or total store of groundwater, or
(c) the withdrawal of the groundwater has a direct and substantial effect upon a watercourse or lake and unreasonably causes harm to a person entitled to the use of its water.

(2) The determination of liability under clauses (a), (b) and (c) of Subsection (1) is governed by the principles stated in §§ 850 to 857.

Private Water Harvesting Rights

Rainwater harvesting involves capturing, diverting, and storing rainwater from rooftops for later use, including for agricultural irrigation. The practice is not regulated by the federal government and individual state regulations vary widely. Many states do not regulate rainwater collection, or when they do they allow and even encourage it by offering tax credits or exemptions for the purchase of harvesting equipment. Other states, especially prior-appropriation jurisdictions, place restrictions on the amount of rainwater that can be collected and/or the method by which it is collected.

Advances in technology have made atmospheric water harvesting (AWH) (or atmospheric water generation (AWG)) a potentially viable agricultural irrigation tool. Atmospheric water harvesting involves the capture and collection of small airborne water droplets or vapor using sorbents or mechanical refrigeration technology. Fog and dew harvesting are two examples. AWH is not federally governed nor specifically regulated by the States at this time; however, as technology efficiencies increase, the tool is likely to garner regulatory attention.

Public Rights to Water

While agricultural law generally implicates private water rights, it is also important to consider that the public may also have a legal interest in using the water at issue. Public water rights fall under four categories:

  • Rights associated with navigation;
  • The public trust doctrine;
  • Reserved water rights; and
  • Public interest protection


Navigable servitude is a United States constitutional law doctrine that gives the federal government the right to regulate navigable waterways as an extension of the Commerce Clause. Designed to keep waterways open for commercial navigation, it creates a dominant property right held by the federal government for the benefit of the general public.

Historically, the federal government gave each state ownership of the beds of the navigable waters within the state as part of the grant of statehood. State bed ownership provides another basis for public rights under state law. Federal and state definitions of navigable waters vary considerably, and in many states the public’s right to use waters has been expanded to include waterways used for recreational purposes.  In 2021, the EPA and Department of the Army announced their intent to review the definition of “waters of the United States.” The rule proposed to restore the regulations defining the “water of the United States” that was in place for decades until 2015. Under the final rule, four categories of water are federally regulated including: territorial seas and traditional navigable waters, perennial and intermittent tributaries to those waters, certain lakes, ponds and impoundments, and wetlands adjacent to jurisdictional waters.

Public Trust Doctrine

The Public Trust Doctrine is a common law doctrine rooted in Roman law that holds that certain natural resources like navigable waters are preserved in perpetuity for the benefit of the public. The state acts as a trustee of the common resource and has an obligation to manage it for the benefit of current and future generations. Attempts by a state to limit or eliminate public trust rights through a sale or by other means may be found invalid.

A number of states have embedded the doctrine in their own constitutions. Traditionally, the public trust applied to commerce and fishing in navigable waters, but in many states its uses have been expanded to include recreation. Notably, states interpret the doctrine and the meaning of public use and public benefit in diverse and shifting ways and as noted above, also define “navigable waters” or “waters of the state” differently.

Reserved Water Rights

The ability to fully develop water resources through irrigation of croplands or other projects, can be severely limited by federal reserved rights in water. Federal actions reserving public lands implicitly create a water right that allows for enough water to accomplish the purpose of the reservation. Examples include national parks, monuments, and forests, wild and scenic rivers, and Native American reservations. For Native American tribes, the necessary use is the amount of water needed to irrigate all of the tribe’s practicably irrigable acreage.

The priority date is the date the reservation is completed. Private rights established prior to the reservation have priority over the reserved rights. The federal right cannot be abandoned or lost through nonuse. Once asserted, it can take water from private right-holders whose rights were established subsequent to the reserved right.

Under the McCarran Amendment, 43 U.S.C. § 666, the federal government has waived sovereign immunity for the limited purpose of adjudicating western water rights. This Amendment authorizes the joinder of the United States in comprehensive stream adjudications, in both state courts and state water agencies. This Amendment has been construed to include the water rights of Native Americans to reduce the number of court proceedings to determine the same rights. The Amendment allows for the more efficient adjudication of water rights along streams in the Western States.

Public Interest Protections

Some states statutorily mandate public interest review of initial water right allocation or increases, requiring an appropriation permit from an administrative agency and allowing the permit to be issued only if the proposed appropriation conforms to the public interest or public welfare.

Historically, public interest criteria were satisfied if the permit applicant would benefit economically from the water use. More recently, public interest criteria are expanding to include environmental and other public concerns, requiring consideration of the cumulative effects of water withdrawals from ground or surface waters.  Similar protections include state statutes creating minimum streamflow requirements or authorizing instream flows.

Water Pollution

Water pollution law is extraordinarily complex. It can involve areas of common law such as nuisance, trespass, and negligence, but more often it involves an interconnected network of federal and state statutes and regulations, the cornerstone of which is the Clean Water Act (CWA). A partial list includes laws regulating surface water discharges from point sources; sedimentation and erosion; stormwater runoff; land uses in nutrient-sensitive waters and water supply watersheds; and sources of groundwater pollution. Federal regulatory programs also include regulation of wetlands and construction in navigable waters and establishment of total maximum daily loads in highly polluted surface water bodies.

As described on the US Environmental Protection Agency website:

The Clean Water Act provides a comprehensive system for the regulation of pollutants in the waters of the United States with the objective of restoring and maintaining the chemical, physical, and biological integrity of the nation’s waters. The CWA operates by authorizing water quality standards for surface waters, requiring permits for point source discharges of pollutants into navigable waters, assisting with funding for construction of municipal sewage treatment plants, and planning for control of nonpoint source pollution.

The Environmental Protection Agency (“EPA”) is the primary agency tasked with implementing and enforcing the CWA, although the agency can and does delegate permitting authority to individual states.

For more information on the CWA, see the Clean Water Act Reading Room and Overview.