Cal. Water Code § 75634.5

For the purpose of investigating compliance with any provisions of this division or any district ordinance, the district may inspect any water-producing facility within the boundaries of the district. The district shall give notice to the operator by certified mail not less than 15 days in advance of the scheduled inspection. The inspection shall be made with the consent of the operator of the water-producing facility or, if consent is refused, with a warrant duly issued pursuant to Title 13 (commencing with Section 1822.50) of Part 3 of the Code of Civil Procedure.