1. (a) General Measurement Parameters. For each claimed water right that meets the general applicability criteria described in subdivision (a) of section 932, diverters must measure the following, as applicable:

   1. (1) Date and time of measurement;
   2. (2) Volume and rate of water directly diverted;
   3. (3) Volume and rate of water diverted to or collected to storage;
   4. (4) Volume and rate of water withdrawn from storage in any qualifying reservoir; and
   5. (5) Volume and rate of water released from any qualifying reservoir. This may include water that was released from the qualifying reservoir with or without having been stored.

2. (b) Large Diversion Parameters. In addition to the general measurement parameters described in subdivision (a), for any claimed water right or point of diversion that meets the large diversion applicability criteria described in subdivision (b) of section 932, diverters must measure the following, as applicable:

   1. (1) Date and time of measurement;
   2. (2) Volume and rate of water diverted from the stream. This may include water that is diverted for beneficial use as well as water that is put into conveyance infrastructure for beneficial use, for transfer to another stream, or for storage in an offstream reservoir, as applicable. Water diverted from the stream does not include water entering or leaving an onstream reservoir; and

   3. (3) For claimed water rights to store water in or withdraw water from qualifying reservoirs:

      1. (A) Total volume of water in the qualifying reservoir at the time of measurement; and
      2. (B) Volume and rate of water leaving the qualifying reservoir, including water that is withdrawn or released from the qualifying reservoir with or without having been stored.
3. (c) Rediversions. If not already being measured pursuant to subdivisions (a) or (b), the deputy director may require diverters to measure rediversions upon determining that rediversion data are necessary to understand the supply, demand, or availability of water.
4. (d) Volume measurements described in this chapter must reflect the discrete volumes diverted, withdrawn, or released in each measurement time interval and not the cumulative total volume, unless otherwise specified.
5. (e) Diverters may use any measuring device or combination of measuring devices along with an accompanying methodology to meet the measurement requirements described in this section.
6. (f) Diverters may cooperate on a local or regional basis to collectively meet the measurement requirements described in this section. A diverter or group of diverters who collectively measures under multiple claimed water rights must account for the general measurement parameters described in subdivisions (a) and (c) for each separate claimed water right.
7. (g) Measurement Location. No delivery, use, or significant loss of water due to percolation and evaporation shall occur between the point of diversion (or the location where water is withdrawn or released from a qualifying reservoir) and the measurement location unless such deliveries, uses, or losses are otherwise measured and/or accounted for.

8. (h) Measurement Frequency. Diverters must measure the required measurement parameters described in subdivisions (a) through (c) of this section, as applicable, whenever water is diverted or whenever water is withdrawn or released from a qualifying reservoir. Diverters must collect measurements of the required measurement parameters at the following frequencies:

   1. (1) For a claimed water right to divert only to a reservoir without any authorized direct diversion or diversion to underground storage, the required measurement frequency is determined based on the storage capacity of the reservoir and must be the most frequent of the values listed below. For a reservoir with a storage capacity that is:

      1. (A) Greater than 1,000 acre-feet, measurements must be collected on an hourly or more frequent basis.
      2. (B) Greater than 200 acre-feet, measurements must be collected on a daily or more frequent basis.
      3. (C) Greater than 50 acre-feet, measurements must be collected on a weekly or more frequent basis.
      4. (D) Greater than 10 acre-feet, measurements must be collected on a monthly or more frequent basis.
      5. (E) Less than or equal to 10 acre-feet, no measurement is required.

   2. (2) For all other claimed water rights, including claimed water rights that authorize direct diversion, diversion to underground storage, or a combination of direct diversion and diversion to surface and/or underground storage, the required measurement frequency is determined based on the maximum allowable diversion amount for the claimed water right and must be the most frequent of the values listed below. For a claimed water right with a maximum allowable diversion amount that is:

      1. (A) Greater than 1,000 acre-feet per year, measurements must be collected on an hourly or more frequent basis.
      2. (B) Greater than 200 acre-feet per year, measurements must be collected on a daily or more frequent basis.
      3. (C) Greater than 50 acre-feet per year, measurements must be collected on a weekly or more frequent basis.
      4. (D) Greater than 10 acre-feet per year, measurements must be collected on a monthly or more frequent basis.
      5. (E) Less than or equal to 10 acre-feet per year, no measurement is required.

   3. (3) For multiple claimed water rights held by the same diverter that authorize diversion from a shared point of diversion:

      1. (A) If all of the claimed water rights meet the criteria described in paragraph (1) of this subdivision, the required measurement frequency for each claimed water right is based on the storage capacity of the reservoir in accordance with the measurement frequency thresholds described in subparagraphs (1)(A) through (1)(E).

      2. (B) If any of the claimed water rights meets the criteria described in paragraph (2) of this subdivision:

         1. (i) At the shared point of diversion, the required measurement frequency for each claimed water right is based on the sum of the maximum allowable diversion amounts of the multiple claimed water rights sharing the point of diversion, in accordance with the measurement frequency thresholds described in subparagraphs (2)(A) through (2)(E).
         2. (ii) For any point of diversion that is not shared by multiple claimed water rights, the required measurement frequency is based on the maximum allowable diversion amount of the respective claimed water right in accordance with the measurement frequency thresholds described in subparagraphs (2)(A) through (2)(E).
      3. (C) In the event of any conflict between the measurement frequency requirements for a diverter with multiple claimed water rights that divert from the same point of diversion or to the same reservoir, the more stringent requirement shall control.

9. (i) Measurement Accuracy. For the purposes of this chapter, “accuracy” means the reported value of volume or flow rate compared with the actual value, expressed as a percentage. The percentage shall be calculated as 100 percent x [1 -- (error / actual value)], where the error is defined as the reported value minus the actual value, expressed as an absolute value; the actual value is determined through laboratory, design, or field-testing protocols; and the reported value is the value included in the non-provisional measurement data submitted to the board and determined by the measurement methodology.

   1. (1) Diverters are responsible for ensuring that the measurement methodology is implemented, operated, and maintained to meet the accuracy standards of this subdivision:

      1. (A) For measuring devices installed on or before January 1, 2016, measurement data must be at least 85 percent accurate or within ±15 percent error.

      2. (B) For measuring devices installed after January 1, 2016:

         1. (i) For measurements that must be collected on a daily or hourly basis as described in subdivision (h), measurement data must be at least 90 percent accurate or within ±10 percent error.
         2. (ii) For measurements that must be collected on a weekly or monthly basis as described in subdivision (h), measurement data must be at least 85 percent accurate or within ±15 percent error.
   2. (2) Diverters must notify the board in writing within 30 days of detecting that the measurement data do not meet or are unlikely to meet the accuracy requirements of this section. The notification must include the diverter's plan to take appropriate and timely corrective action to meet the accuracy requirements of this section.
   3. (3) If the measurement data fail to meet the accuracy requirements of this section, the diverter must repair or replace any measuring device as necessary or otherwise correct the measurement methodology at the diverter's own expense to meet such requirements.

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

History

1. New section filed 3-21-2016 as an emergency; operative 3-21-2016 (Register 2016, No. 13). Pursuant to Water Code section 1841(b), the regulation shall remain in effect until revised by the State Water Resources Control Board.

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