Cal. Health & Safety Code § 115840

(a) In San Diego County, recreational uses shall not, with respect to a reservoir in which water is stored for domestic use, include recreation in which there is bodily contact with the water by any participant, unless both of the following conditions are satisfied:
1. (1) The water subsequently receives complete water treatment, including coagulation, flocculation, sedimentation, filtration, and disinfection, before being used for domestic purposes.
2. (2) The reservoir is operated in compliance with regulations of the department, as provided in Section 115830.
(b) The recreational use may be subject to additional conditions and restrictions adopted by the entity operating the water supply reservoir, if the conditions and restrictions do not conflict with regulations of the department and are designed to further protect or enhance the public health and safety.