1. (a) Measurement Options. A diverter may choose any measuring device, or combination of devices, that meets the requirements of this section.

2. (b) Data.

   1. (1) Data Recording. The measuring device shall be capable of recording the date, time, and at least one of the following: total volume of water diverted, flow rate, water velocity, or water elevation. The data shall be recorded in a format retrievable and viewable using Microsoft Excel, Microsoft Access, or other software program authorized by the deputy director. The measuring device shall be capable of recording the required information as follows:

      1. (A) For direct diversion:

         1. (i) On an hourly or more frequent basis for a diverter with a claimed water right to divert 1000 acre-feet of water per year or more.
         2. (ii) On a daily or more frequent basis for a diverter with a claimed water right to divert 100 acre-feet of water per year or more.
         3. (iii) On a weekly or more frequent basis for a diverter with a claimed water right to divert more than 10 acre-feet of water per year.

      2. (B) For direct diversion by a diverter with multiple claimed water rights:

         1. (i) On an hourly or more frequent basis, where the sum of the diversions made under the claimed water rights from the same point of diversion or to serve the same place of use is 1000 acre-feet of water per year or more.
         2. (ii) On a daily or more frequent basis, where the sum of the diversions made under the claimed water rights from the same point of diversion or to serve the same place of use is 100 acre-feet of water per year or more.
         3. (iii) On a weekly or more frequent basis, where the sum of the diversions made under the claimed water rights from the same point of diversion or to serve the same place of use is greater than 10 acre-feet of water per year.
         4. (iv) In the event of any conflict between recording requirements for a diverter with multiple claimed water rights from the same point of diversion or to serve the same place of use, the more stringent requirement shall control.

      3. (C) For storage in a reservoir or pond:

         1. (i) On an hourly or more frequent basis for a reservoir or pond with a storage capacity of 1000 acre-feet or more.
         2. (ii) On a daily or more frequent basis for a reservoir or pond with a storage capacity of 200 acre-feet or more.
         3. (iii) On a weekly or more frequent basis for a reservoir or pond with a storage capacity of 50 acre-feet or more and less than 200 acre-feet.
         4. (iv) On a monthly or more frequent basis for a reservoir or pond with a storage capacity of greater than 10 acre-feet and less than 50 acre-feet.
         5. (v) In the event of any conflict between recording requirements for a diverter with multiple claimed water rights to divert to storage in a reservoir or pond, the more stringent requirement shall control.

   2. (2) Data Submittal.

      1. (A) Each diverter to which a measurement requirement applies shall submit the data from each measuring device to the board as required by chapter 2.7 of division 3 of this title, and within 30 days of any request or order by the board.
      2. (B) For a reservoir subject to drawdown and refill during the collection to storage season, or that is otherwise operated in a cyclical manner, the maximum and minimum water surface elevations, the corresponding reservoir volume, and the monitoring dates shall be measured and the resulting data maintained.
      3. (C) For each reservoir, if water is diverted or flows into the reservoir under more than one claimed water right, including groundwater or water purchased under a contract, the amounts reported to the board shall be limited to the amounts covered by the claimed water right being reported. A record of the alternative supplies entering the reservoir throughout the year shall be maintained to demonstrate that water stored is under a separate basis of right or contract.
   3. (3) Data Retention. Each diverter shall keep records of the data from each measuring device for a period of no less than 10 years.

   4. (4) Telemetry Requirements.

      1. (A) This paragraph applies to any diverter who either:

         1. (i) Diverts more than 10,000 acre-feet annually; or
         2. (ii) Owns or operates a reservoir or pond with a storage capacity of 10,000 acre-feet or more; or
         3. (iii) Diverts during the period from June 1 through September 30, and directly diverts more than 30 cubic feet per second at any time.
      2. (B) This paragraph applies to all claimed water rights to divert from a single or shared point of diversion if the sum of such claimed water rights meets the criteria of subparagraphs (A)(i) or (A)(iii) of this paragraph.
      3. (C) By January 1, 2020, diverters subject to this paragraph shall provide telemetered diversion data via a public website that displays the data on at least a daily basis, and that is updated weekly, at minimum. The data shall be provided to the board upon the request of the deputy director in a format retrievable and viewable using Microsoft Excel, Microsoft Access, or other software program authorized by the deputy director.

3. (c) Calculating Volume from Recorded Data. If a measuring device measures the flow rate, water velocity, or water elevation, and does not report the total volume of water diverted or delivered, the diverter shall report the conversion method used to convert the measured value to volume. The conversion method shall be approved by a qualified individual.

   1. (1) For a measuring device that measures flow rate, the report shall describe protocols used to record the duration of operation where volume is derived by the following formula: Volume = (flow rate) x (duration).
   2. (2) For a measuring device that measures flow velocity only, the report shall describe protocols used to determine the cross-sectional area of flow and the duration of operation, where volume is derived by the following formula: Volume = (velocity) x (cross-section flow area) x (duration).
   3. (3) For a measuring device that measures water elevation at the device (e.g. flow over a weir or differential elevation on either side of a device), the report shall describe protocols used to derive flow rate at the measuring device and the method or formula used to derive volume from the measured elevation value(s).

4. (d) Required Accuracy. The accuracy for each measuring device applies to the volume diverted or stored. “Accuracy” means the measured volume relative to the actual volume, expressed as a percent, and determined at the same frequency as is specified for monitoring in subdivision (b). The percent shall be calculated as 100 percent x [1- (error/actual value)], where the error is defined as the measured value minus the actual value, expressed as an absolute value. “Measured value” is the value indicated by the device or measurement method or determined through calculations, such as flow rate combined with duration of flow. “Actual value” is the value as determined through laboratory, design, or field testing protocols.

   1. (1) A measuring device installed on or before January 1, 2016, shall be certified to be at least 85 percent accurate by volume or within ±15 percent error based on periodic testing of the installed device.

   2. (2) A measuring device installed or replaced after January 1, 2016 that is used to measure the diversion of water shall be certified to be at least:

      1. (A) 95 percent accurate by volume or within ±5 percent error in the laboratory if using a laboratory certification.
      2. (B) 90 percent accurate by volume or within ±10 percent error based on periodic testing of the installed device if using a non-laboratory certification for a diverter with a claimed water right greater than or equal to 100 acre-feet per year.
      3. (C) 85 percent accurate by volume or within ±15 percent error based on periodic testing of the installed device if using a non-laboratory certification for a diverter with a claimed water right greater than or equal to 10 acre-feet per year.

   3. (3) A measuring device installed or replaced after January 1, 2016 that is used to measure the water stored in a reservoir or pond shall be certified to be at least:

      1. (A) 90 percent accurate by volume or within ±10 percent error based on periodic testing of the installed device for a reservoir or pond with a storage capacity of 200 acre-feet or more.
      2. (B) 85 percent accurate by volume or within ±15 percent error based on periodic testing of the installed device for a reservoir or pond with a storage capacity greater than 10 acre-feet and less than 200 acre-feet.
5. (e) Installation, Maintenance and Performance Requirements. A measuring device installed on or after February 1, 2026 must be installed in accordance with sections 933 and 934. The measuring device shall be maintained, operated, inspected, and monitored to ensure the accuracy standards of subdivision (d) of this section are met.

6. (f) Inadequate Measuring Device. If a measuring device fails to meet the accuracy requirements of subdivision (d) of this section, the diverter shall repair or replace the measuring device at their own expense to meet such requirements.

   1. (1) Notification. A diverter shall timely notify the board in writing upon detecting that the holder's measuring device does not comply with the accuracy requirements of subdivision (d) of this section. The notification shall include the diverter's plan to take appropriate, timely corrective action to comply with the accuracy requirements of subdivision (d) of this section.
   2. (2) Enforcement. Failure to timely repair or replace a measuring device that does not comply with the accuracy requirements of subdivision (d) of this section is a violation of this regulation.

Note: Authority cited: Sections 183, 1051, 1058, 1840 and 1841, Water Code. Reference: Sections 13, 1846 and 5103, Water Code.

History

1. Renumbering of former section 933 to section 939.4, including amendment of section heading and section, filed 1-21-2026; operative 2-1-2026 pursuant to Government Code section 11343.4(b)(3) (Register 2026, No. 4).