A senior may not change an established use of the water to the detriment of a junior. This restriction includes a junior's reliance on a senior's return flow. A senior may not enforce a water right against a junior if such a right would not be put to beneficial use. Priority of appropriation. Current System of Appropriative Rights Acquisition of a water right is subject to the issuance of a permit by the State Water Resources Control Board.
Priority is based on the date a permit is issued.
The current priority-based permit system was implemented under the Water Commmission Act of 1913. A riparian right is the right to use water based on the ownership of property which abuts a natural watercourse. Water claimed by virtue of a riparian right must be used on the riparian parcel. Riparian rights were adopted in California as a part of the English Common Law when California entered statehood in 1850. At that time, however, gold miners were already operating under their own system of prior appropriation to claim water rights.