Water law is a system of enforceable rules that controls the human use of water resources. In the United States, these rules are created by statutes, court decisions, and administrative regulations. Much of U.S. water law is rooted in the common law system inherited from England. Under this system, courts resolved disputes by setting legal precedents that were followed by subsequent courts. Today, U.S. water law is a complex mix of federal and state regulations superimposed on a system of public and private water rights.
Because water is a mobile (moving) resource, many management problems are created that require legal resolution. As water moves through the hydrologic cycle , many people in succession can use it. For example, a hydropower plant can nonconsumptively use river water to generate electricity. Far downstream from the powerplant, and at a later date, a golf-course owner may use the same water to irrigate the fairways.
Consumptive uses alter the hydrologic cycle and may modify the environment. Because the same drop (or even the same molecule) of water can be reused many times by humans and also is needed to maintain environmental integrity, conflicts between different uses are frequent. Water law attempts to resolve these conflicts by encouraging desirable uses and discouraging undesirable ones. Uses are encouraged or discouraged through the complex interlinkings of water rights systems and the exercise of government power.
The exercise of government power and creation of water rights is based on societal values that have changed over time and vary from state to state. Although the U.S. common law system recognized public rights to navigate and to fish, most water rights historically
This water rights system oriented toward private rights often ignored public values such as recreation and environmental protection. But as societal values changed, the exercise of government power at times restricted traditional water rights.
In past decades, for example, many cities felt they had a right to use rivers for the routine disposal of raw sewage. But today, federal statutes prohibit such disposal and require sewage first be treated before the processed wastewater is discharged to waterways. In the American West, the right to remove all the water from a stream for use in irrigation was traditionally accepted. But today, federal statutes may require a minimum instream flow to protect endangered species or to maintain other designated instream uses. Public values have greater recognition today than in past decades, and are widely recognized by courts, legislation, and administrative regulations.
Either state or federal laws can create public and private water rights. These water rights are relational and take on meaning when the exercise of one right conflicts with the exercise of other rights.
In addition, water rights are rarely exclusive. This need to share water results in conflicts between individuals who have private rights, between individuals with private rights and people with public rights, and between those who have federal rights and those who have state rights. Water law is used to resolve conflicts between different claimants by determining the rights and obligations of each party in a dispute.
Private water rights evolved as a pragmatic system to allocate water use in different parts of the hydrologic cycle. In a simplified hydrologic cycle, water can be classified as groundwater , surface water, atmospheric water, or soil moisture. *
Each part of the hydrologic cycle is treated by the legal system as if it were disconnected. For example, the law establishing rights to surface water is often different from the law for groundwater. In some parts of the hydrologic cycle, private water rights are difficult to establish. For example, soil moisture cannot be easily extracted from the soil in which it is found. This type of water is treated as land, and no water rights are created. Although this practice ignores the reality of the hydrologic cycle, it does reduce potential conflicts with those who own land.
Until recently, capturing atmospheric waters was difficult. Property rights generally did not exist until the water reached the land surface. Although increasing precipitation through cloud-seeding is possible, assigning a water right to the "newly created water" is still problematic. Proving the amount of precipitation increase and determining where this amount actually fell makes the basis for a claim difficult to establish.
Groundwater science developed after early policymakers had already established a system of groundwater rights. Although these common-law approaches still exist, statutory regulations have been superimposed, modifying groundwater rights substantially.
One initial approach was to treat groundwater like part of the land, and give the owner of the land surface absolute ownership of the water below it. Another pragmatic approach, the so-called "rule of capture," was used on a limited basis. This right gave ownership to the person who pumped the water from the ground. Although these two approaches ignored the mobile nature of groundwater, the rights were easy to determine.
Today, the mobility of groundwater is accounted for in the dominant systems of water rights. In the eastern states, the doctrine of reasonable use allows water to be shared between surface owners. In the western states, the doctrine of prior appropriation establishes priorities between users.
Surface-water rights have the most developed set of water allocation laws. In the eastern states, the ownership of land adjacent to a river gives rise to a riparian water right. Initially, the right was attached to the riparian land and only that land. But over time, two kinds of riparian water rights evolved: natural flow and reasonable use.
Today, statutory permit systems often are imposed on private riparian rights. In the West, the prior appropriation doctrine evolved under different conditions. The need to move water long distances led to a system of temporal (time-based) preferences designed to protect investments. The right to water did not automatically come with ownership of land. Moreover, western states claimed they either owned all the water within the state, or they held it in trust for the people of the state. Thus, a private water right could be established only by following the requirements of state law.
This complex system of water laws controls almost all aspects of water use, including environmental protection. The system has never been static and will continue to evolve.
Olen Paul Matthews
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Beck, Robert E., ed. Water and Water Rights. Charlottesville, VA: The Michie Company, 1991.
Matthews, Olen Paul. Water Resources, Geography and Law. Washington, D.C.: Association of American Geographers, 1984.
Reisner, Marc. Cadillac Desert. New York: Penguin Books, 1987.
Trelease, Frank J. "Government Ownership and Trusteeship of Water." California Law Review 45 (1957):638.
Worster, Donald. Rivers of Empire. New York: Pantheon Books, 1985.
* See "Hydrologic Cycle" for a schematic of the water cycle.