Cal. Water Code § 1840
(a)
(1) Except as provided in subdivision (b), a person who, on or after January 1, 2016, diverts 10 acre-feet of water per year or more under a permit or license shall install and maintain a device or employ a method capable of measuring the rate of direct diversion, rate of collection to storage, and rate of withdrawal or release from storage. The measurements shall be made using the best available technologies and best professional practices, as defined in Section 5100, using a device or methods satisfactory to the board, as follows:
(B) In developing regulations pursuant to Section 1841, the board shall consider devices and methods that provide accurate measurement of the total amount diverted and the rate of diversion. The board shall consider devices and methods that provide accurate measurements within an acceptable range of error, including the following:
(b)
(1) The board may modify the requirements of subdivision (a) upon finding either of the following:
(c) At least annually, a person who diverts water under a registration, permit, or license shall report to the board the following information: