In the United States there are primarily two methods of apportioning the use of water by individuals or organizations (for the purposes of agriculture, farming, irrigation):

• Riparian (land based)
• Prior Appropriation (use base)

Riparian Doctrine

The Riparian Doctrine links the ownership of lands adjacent to a source of water (typically a river or stream) and the use of the water.  Only those landowners who’s property forms the banks of the water have a right to make reasonable use of the water as it flows through / over their property.

In the even that the waters are not sufficient to satisfy the usage demands of all users, then the water is apportioned in proportion of the frontage that a landowner has along the water source.

Riparian apportionment is primarily used in the eastern part of the United States where surface waters are more plentiful.  In the central / western parts of the United States, the Prior Appropriation approach is used.

Doctrine of Prior Appropriation

The Prior Appropriation System (also know as the Colorado Doctrine) can be simplified to “first in time, first in right”.  In practice this means that the first person to withdraw water and apply that water to beneficial use has the first right to use the water within a particular water system.  They become “senior” in their rights to the water.  The second person to do so becomes the second most senior water rights holder and so on.  Based upon seniority, each individual water right must be fulfilled before the next water right can be fulfilled. 

Water rights under the Prior Appropriation System are separate property rights and can be sold separately from the land.

 

Images: Resource Concepts
Sources: Wikipedia:  Riparian Water Rights, Colorado Divison of Water Resources - Department of Natural Resources, Ley, T., Stroud, B., et al, Colorado Experience with Discharge Measurements at Parshall Flumes and Assessment of Parshall Flume Performance