1. (a) A measurement method is a protocol for measuring water diversions, other than through a measuring device at each authorized point of diversion, where the method achieves the accuracy requirements of subdivision (d). The board encourages diverters on a local or regional basis to cooperate and establish a measurement method or methods to measure direct diversion, diversion to storage, and withdrawal or release from storage in an efficient and cost effective manner which meets the accuracy requirements of subdivision (d). Any measurement method shall be able to quantify the amount of water diverted under all separate claimed water rights being exercised. If the claimed water rights included in a measurement method have different requirements under section 939.4, the more stringent requirement shall control for all of the claimed water rights covered by the measurement method.

2. (b) Shared Measurement Point Upstream of the Delivery Point or Farm Headgate. A group of diverters may measure water diverted at a location upstream of their respective delivery points or farm headgates or at shared points of diversion if a written agreement is in place for the diverters to share a measuring device located at the shared point of diversion. Diverters using a shared measuring device under this subdivision shall report the following additional information to the board on an annual basis:

   1. (1) The methodology used to apportion the volume of water delivered from the shared point of diversion to each downstream diverter, including how water will be apportioned among the diverters participating in the agreement during periods of insufficient supply while preventing injury to any other legal user of water or to public trust resources.
   2. (2) The field or flow condition at each individual diverter's delivery point downstream of the point of measurement including the duration of water delivery to the individual diverter, annual water use patterns, irrigated acreage (including GIS map showing assessor's parcel number and USDA field identification number), crops planted, on-farm irrigation system, and other relevant distinctions in beneficial uses and water management practices.
   3. (3) Consumptive use of water for each individual diverter, if available.

3. (c) Data.

   1. (1) Data Recording. The measurement method shall be capable of reporting the date, time, and total amount of water diverted in accordance with the requirements of subdivision (b) of section 939.4. 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.
   2. (2) Data Submittal. Each diverter or claimant shall submit data from the measurement method to the board pursuant to chapter 2.7 of division 3 of this title, or within 30 days of request of the deputy director. Water use data for each twelve month reporting period shall be submitted on a form available on the board's website with the appropriate water use report including a Progress Report by Permittee, Report of Licensee, Supplemental Statement of Water Diversion and Use, and Water Use Reports of Registration and Certificate Holders.
4. (d) Required Accuracy. The accuracy of the measurement method to determine the volumes of water diverted, diverted to storage, and withdrawn or released from storage shall reasonably achieve accuracy standards comparable to the standards listed in subdivision (d) of section 939.4 for individual measuring devices. The accuracy of the measurement method shall be determined by a qualified individual.
5. (e) Operation and Performance Requirements. A measurement method shall be operated and maintained to meet the accuracy standards of subdivision (d).

6. (f) Inadequate Measurement Method. If a measurement method fails to meet the accuracy standards of subdivision (d), the measurement method shall be corrected to comply with such standards.

   1. (1) Notification. The diverters employing a measurement method shall notify the board in writing within 30 days of finding a measurement method does not comply with the accuracy standards of subdivision (d). The notification shall include a plan to take appropriate, timely corrective action.
   2. (2) Enforcement. Failure to correct defects or to ensure the measurement method complies with the accuracy standards of subdivision (d) is a violation of this chapter.

7. (g) Measurement Method Duration.

   1. (1) For diverters who submitted a measurement method to the board before February 1, 2026, the diverter's most recently submitted measurement method may remain in effect through September 30, 2026. Beginning October 1, 2026, diverters must adhere to the measurement and reporting requirements described in sections 931 through 939.
   2. (2) Incomplete measurement method documentation, documentation that does not meet the minimum standards of this section, and lapses in measurement methods shall not relieve a diverter of the requirement to fully comply with sections 939.4 and 939.5.
8. (h) Measurement methods submitted in accordance with the provisions of this section shall be timely implemented.

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

History

1. Renumbering of former section 934 to section 939.5, 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).