Cal. Water Code § 75611

After the establishment of a ground water charge, each operator of a water-producing facility within the affected zone or zones of the district, until such time as such water-producing facility has been permanently abandoned, shall file with the district, on or before the 31st day of January and on or before the 31st day of July in each year, a statement setting forth the total production in acre-feet of water for the preceding six-month period (excluding the month in which the statement is due), a general description or number locating each water-producing facility, and the method or basis of the computation, of such water production.