Water plays a critical role in American agriculture. While the federal government controls water quality through laws such as the Clean Water Act, states impose their own regulations to govern the allocation of water rights. Different sets of regulations often apply to surface water and groundwater. In allocating surface water rights, many states follow the riparian doctrine, but others follow the prior appropriation doctrine. Still other states, such as California, have combined elements of these approaches.
The riparian doctrine arose in eastern states, which enjoy a plentiful water supply, while the prior appropriation doctrine arose in the drier western states.
The riparian doctrine holds that only property owners that own land adjacent to a watercourse (such as a river or lake) can use the water. Their use must be reasonable and must not interfere with reasonable use by another property owner who borders the same watercourse downstream. Irrigation, industry, and watering livestock or plants are typically considered reasonable uses. The right remains with the riparian property owner regardless of whether they use it.
By contrast, the prior appropriation doctrine allows the first person who diverts a certain amount of water from a natural course for a beneficial use to take priority over other users of that water source. They can continue to take that amount of water for that use, even in a water shortage, without accounting for the needs of other water users. Each user fully exercises their right to water in order of priority until the water supply is exhausted. Any agricultural use is considered a beneficial use.
As mentioned above, states often allocate groundwater differently from surface water. Several overlapping legal doctrines apply in this area, and different states use different doctrines, or even combinations of doctrines. For example, the traditional absolute dominion rule allows a property owner overlying an aquifer to use as much groundwater as they choose, regardless of how their consumption affects property owners overlying the same aquifer. Only about 10 states follow this rule.
Used in New York and many other states, the reasonable use doctrine modifies the absolute dominion rule. The reasonable use doctrine allows a property owner to use groundwater only for reasonable uses on the tract of land overlying the aquifer. (Most uses are considered reasonable.) They cannot transport the groundwater to another tract. As long as these requirements are met, there are no restrictions on the quantity of groundwater that a property owner can take from the aquifer. Ohio and Wisconsin follow a rule known as the Restatement (Second) of Torts rule, which combines features of the absolute dominion rule and the reasonable use doctrine.
On-Tract and Off-Tract Uses
Some states distinguish between on-tract and off-tract uses of groundwater. On-tract use, which often receives priority, involves using water on the land where the water is pumped. Off-tract use occurs when a property owner transports water to a tract of land where there is no pump.
Meanwhile, California and several other states apply the correlative rights doctrine. This rule allocates groundwater rights according to property ownership, as does the absolute dominion rule, but each property owner who shares access to an aquifer must take only a reasonable share of the water supply.
Many other western states, such as Oregon, Washington, Utah, and Colorado, apply a prior appropriation doctrine that echoes the doctrine for surface water. This allows the first person to divert groundwater for a beneficial use to take priority over later users of that source.
Federal Reserved Water Rights
When the federal government sets aside public lands, such as national parks or national forests, the government automatically receives a right to a quantity of water that allows it to accomplish the purpose of the public land. Federal reserved rights remain valid even if they are not used. They can limit the rights of private property owners, but a priority system governs these rights. Thus, if a private property owner established their right before the federal government reserved the land, they can take priority over the federal reserved right.
Reserved Rights and Native Americans
One type of federally reserved land is a Native American reservation. Water rights reserved to the federal government in these situations cover the quantity of water that is necessary to irrigate all the land on the reservation that can be viably irrigated.