The pioneers who settled the west adopted a system that recognized that water there was much more scarce than in the east or in England where earlier common law first developed.Western water law assumes that there is insufficient water to satisfy all potential users. When supplies are insufficient, water users with older or more senior rights are allocated water on a priority basis ahead of junior water rights holders.Governing legal mechanisms are often late in keeping pace with changed conditions.
- Eastern water law has primarily been based on a system of riparian rights for surface water use, and Tennessee has mostly followed such a structure.
- Western states' water law and eastern states' water law have traditionally been very different, and largely remain so today.
The right comes along with the land and does not depend on when the use begins or whether the use actually continues, in contrast to prior appropriation.
While treated as an interest in property, riparian rights are usually not absolute but are “usufruct” in nature (a strong right of usage, without undue diminishment, that is almost like ownership even if a state owns its waters).
Also, such rights may be severed and sold separately from real property interests.