A summary of California’s water rights system. The two major kinds of rights are riparian and appropriative. Riparian rights are for people who own property adjacent to a river; they can use river water to irrigate adjoining property. If the river is low, all riparian users are supposed to cut their water use proportionally. Appropriative rights can be used away from the river and are ‘first in time, first in right’. If there is a cutback, junior rights holders get none while senior rights holders get their full allotment. An appropriative right technically has a place and method of diversion, a maximum flow and maybe also a maximum volume for a year, and may have start and end dates of allowed diversion. There are a few other types of rights, but for the most part, appropriative rights allocate the most water in a system that was pieced together over a century.