Cal. Wat. Code § 75619
If the district has probable cause to believe that the production of water from any water-producing facility is in excess of that disclosed by the sworn statements covering such water-producing facility, or if no statements are filed covering any water-producing facility, the district may cause an investigation and report to be made concerning the production of water from such water-producing facility.
The district may fix the amount of water production from such water-producing facility at an amount not to exceed the maximum production capacity of such water-producing facility; provided, however, that where a water-measuring device is permanently attached thereto, the record of production, as disclosed by such water-measuring device, shall be presumed to be accurate and the burden is upon the district to establish to the contrary.
Ca. Water Code § 75619