(However, in Texas, malicious pumping may be judicially restrained.) In reasonable use jurisdictions there is generally no ownership interest in the ground water itself until it has been captured. Pumping may be judicially restrained to prevent waste or nonoverlying uses. In correlative rights jurisdictions the right to use ground water is also based on owning land overlying the ground water supply, although in California prescriptive rights can be obtained for nonoverlying uses. Pumping may be judicially restrained to prevent waste or to apportion an inadequate supply. In eastern correlative rights states, pumping may be judicially restrained during shortages, although the basis upon which shortages will be allocated is not predictable. Ground water rights are least well defined in the eastern correlative rights statutes, since judicial notions of what may constitute the "most beneficial" use of ground water may change over time.
Statutory States. In both eastern permit states and appropriation states, rights to use ground water are based on obtaining and complying with the terms of a state permit. However, most existing ground water uses were automatically grandfathered into the permit system. Pumping rates may be limited in a permit and further limited during shortages. In eastern permit states, public water supply uses and domestic uses will generally be protected during shortages. In appropriation states, senior users (i.e., those with an earlier priority date, or in other words, an older well) are protected during shortages without regard to use. A junior user with a higher use, however, may be able to condemn a senior's use right during shortages and thus pump water out of priority.
Well interference is where the cone of depression of one well intersects with the cone of depression of another well, reducing the yield of both wells. In an artesian aquifer, well interference may occur when the pumping from one well drops the water level below the pump of another well. Well interference may occur even when there is sufficient water available to supply all users—it may be the result of inadequate wells rather than an inadequate supply. Most ground water disputes have tended to be well interference disputes.
Common Law States. In absolute ownership states, a landowner is not liable for interfering with a neighbor's well. Thus the neighbor's only recourse is to drill a new well deeper than the neighbor's well. This has been described as "the race to the pumphouse." In reasonable use states a landowner complaining of well interference is entitled to relief only if the complained-of use is wasteful or not on overlying land. Thus plaintiffs complaining of well interference have little legal remedy in the absence of gross waste or nonoverlying uses. The courts' definition of what constitutes a wasteful use is rather generous. Arizona courts have defined overlying land to include only the tract of land where the well is