This came in over the transom from GPCA and seems pretty useful.
California Water Rights Primer
To mobilize water for human use, our society grants property rights to use water. No one is allowed to hoard or possess it because of its intrinsic properties and its necessity to all life and economic activity. The rights to use water also carry obligations to other water right holders, particularly not to harm the rights of other water right holders and not to harm the environment.
It is said by water lawyers, that water rights are social policy in times of drought.
In California, these are the more important types of water rights:
Search the State Water Board’s EWRIMS database for water right holders in your watershed (NOTE: Does not include groundwater users.)
Useful Water Rights Information from the State Water Board
Area of Origin Rights
The Big Water Projects in California Water Contractors
Through case law (that is, litigation), the California Supreme Court established that riparian right holders have priority for diverting and using water over most (if not all) appropriative right holders. Appropriators may divert only what is surplus to what riparian right holders divert from a stream.
Among appropriators in California, those with pre-1914 dates for filing their water claims have earliest priority each year to divert and use water. Their rights are not subject to review by the State Water Board. Appropriators whose rights come after 1914 have permits issued by the State of California that are subject to approval and review by the State Water Board. Actions before the State Water Board most commonly affect these water right holders. Until recently (see our analysis of the Delta water legislation and the 2010 water bond, coming soon!), the State Water Board has little, if any, jurisdiction over the water rights of riparians or pre-1914 appropriators.
In many California watersheds, however, few right holders know exactly what they are entitled to. This can give rise to conflict and litigation between neighbors or large water users seeking water from the same watershed. In some rivers and streams and groundwater basins, conflict has been resolved through “adjudication,” a process by which a judge hears all available evidence and then issues a decision dividing the waters between the water right holders in the watershed or groundwater basin. While usually effective in resolving conflict, adjudication of a water body is expensive and can take many years.