A: Water use restrictions are more stringent in western states. These states adhere to the prior-appropriation system of water law. When disputes over water use arise, priority is given to parties having senior water rights. Many western states have also specified preferred uses that are given priority over other senior water rights.

Eastern states generally follow riparian water law, which specifies that the water flowing on or under one’s land may be used as long as it is put to reasonable use. Generally, a riparian landowner is not subject to quantity limitations.

Thus, geothermal heat pump users are more likely to be subject to water quantity limitations in the western states. However, these limitations may only apply to commercial applications since domestic use of geothermal heat pumps may be considered a preferred use, exempt from most water use restrictions. As yet, few states have actually defined the status of geothermal heat pump systems in their statutes. Their status is therefore subject to interpretation of state regulatory agencies. Most state statutes describe domestic use in similar language.

Note: If water rights issues become too limiting, closed-loop systems may be required.