SB 1157 (Chapter 679, Statutes of 2022) highlights:

• The indoor residential standard applies to both single family and multi-family housing units within a supplier’s service area.
• The indoor residential standard is based on a gallons per capita per day metric and will decrease over time (details below).  The state will not enforce indoor budgets for individual residential parcels. 
• Suppliers multiply population served by the indoor residential standard from DWR by 365 days to produce the supplier level annual indoor water use budget.
• Changes to the current statute will require additional/future legislative actions.  Until that time, the current statute is what suppliers will be required to meet (details below).

External Links

• California SB1157 | 2021-2022 | Regular Session

  Bill Text (2022-09-28) Urban water use objectives. [Chaptered by Secretary of State. Chapter 679, Statutes of 2022.]...

• All public water systems are required to submit an electronic Annual Report. Refer to the Technical Reporting Order (TRO) for further information. (State Water Board Drought Reporting Order (ca.gov))
• Total population in DDW records: The prefilled SDWIS value is not editable. If the water system is a state billed wholesaler, wholesale population type is displayed, if water system is a Community Water System, total Residential population type is displayed, otherwise, the sum of Residential, Transient, and Nontransient population types are displayed. the date displayed adjacent to the total count reflects the last updated date in our SDWIS database.
• All population types should be reported regardless of the public water system classification.

Population Type:

• Residential: report the number of persons who reside within the water system service area for more than half of the year (excludes transient and non-transient populations) includes all people who reside within the water system service area on a year-round basis, or have the ability to use a dwelling unit for over 6 months of the year (includes number of persons that use second homes, cabins, or other housing units).
• Transient: report the number of persons who are at the water system on the 60th busiest day of the year (excludes residential and non-transient populations) the number of persons served on the 60th busiest day; counting only those persons that are not residential or persons onsite for over 6 months out of the year, such as day-use visitors, campers, attendees at events, customers to a business, etc.
• Non-Transient: report the number of the persons who are at the water system for over 6 months per year (excludes residential and transient populations)
• Wholesale Population: The total number of persons serviced by water system buyers of water.

Annual Operating Period: Provide season that each population is present at the water system. If year-round, the Begin Date would be 01/01 and the End Date would be 12/31. If present only during the typical summer season, example Begin Date and End Date would be 05/01 through 09/30.

Method Used to Determine Population: Article 2. General Requirements §64412. Determination of Persons Served.

(a) The number of persons served by a community water system shall be determined by the water system using one of the following methods:

(1) Utilizing the most recent United States census data, or more recent special census data certified by the California Department of Finance, for the service area served by the water system;

(2) Multiplying the number of service connections served by the water system by 3.3 to determine the total population served;

(3) Determining the total number of dwelling units or efficiency dwelling units as defined in the Uniform Building Code (Title 24, California Code of Regulations), the number of mobile home park spaces and the number of individual business, commercial, industrial and institutional billing units served by the water system and multiplying this total by 2.8 to arrive at the total population served by the system.

(b) Each community water system shall report to the State Board annually the number of persons and the number of service connections served by the system using the procedures set forth in subsection (a).

(1) A variance for water use associated with evaporative coolers (VEC) represents the volume of water evaporative coolers used on operating days. Operating days (NDAYS) are days when the average temperature in the supplier’s service area was greater than 78 degrees Fahrenheit for at least one hour. VEC shall be calculated by multiplying the number of evaporative coolers in the service area (NEC) by the number of operating days (NDAYS), the average daily evaporative cooler operating hours (HO), and the average daily evaporative rate (REC). This formula is expressed mathematically follows:

VEC = NEC × NDAYS × HO × REC

(A) The number of evaporative coolers in the service area (NEC) may be estimated based on a representative sample of customers meeting the criteria specified in paragraph (D).

(B) The evaporative cooler operating hours (HO) may be a daily average based on a sample meeting the criteria specified in paragraph (D). A supplier shall use the service area average operating hours or the daily maximum operating hours, whichever is lower.

(i) The service area wide average operating hours shall equal the average of all operating hours based on the sample.

(ii) The service area daily maximum operating hours shall equal the number of hours in a day when the temperature was above 78 degrees Fahrenheit within the supplier’s service area.

(C) The evaporative cooler evaporation rate (REC) may be a daily average based on a sample meeting the criteria specified in paragraph (D). REC, in gallons per hour, shall be calculated by multiplying the average air exchange rate of the evaporative cooler units within the supplier’s service areas (CFM), in cubic feet per minute, by the average daily difference in hourly wet and dry bulb temperatures (ΔTBulb), in degrees Fahrenheit, and by a representative efficiency rate of 80 percent. To convert the heat absorbed, in British Thermal Units, to the volume of water evaporated by the coolers, in gallons, that product shall be divided by 8700. This formula is expressed mathematically as follows:

The average air exchange rate of the evaporative cooler units within the supplier’s service areas (CFM) and the average daily difference in hourly wet and dry bulb temperatures (ΔTBulb) shall be calculated according to the Department’s Methods for Estimating Residential Cooler Water Consumption and Prevalence using Account-Level Water and Energy Consumption Data dated April 15, 2022, or an alternative method that the supplier has demonstrated to the Department, in coordination with the Board, to be equivalent, or superior, in quality and accuracy.

(D) For the purposes of this section, the sample must represent at least 10,000 residential connections, or ten percent of residential connections, whichever is smaller.

(2) A variance for water use associated with seasonal populations (VSP), in gallons, shall be calculated by multiplying the number of dwelling units associated with seasonal occupancy (NDU) by the occupancy rate (RO) and by the residential indoor use standard

for the given time period (Sindoor). This formula is expressed mathematically as follows:

VSP = NDU × Ro × Sindoor

(A) The number of dwelling units associated with seasonal occupancy (NDU) shall be calculated according to the Department’s Methods for Estimating Seasonal Populations with Water and Energy Data or an alternative method that the supplier has demonstrated to the Department, in coordination with the Board, to be equivalent, or superior, in quality and accuracy.

(B) The occupancy rate (RO) shall be calculated by dividing the average number of seasonally occupied rooms (RS) by the average number of rooms occupied by permanent residents (RP) and multiplying the quotient by the average number of people per permanently occupied household (HP) and the average number of days households are seasonally occupied (SDAYS). This formula is expressed mathematically as follows:

The average number of days households are seasonally occupied (SDAYS) shall be calculated according to the Department’s Methods for Estimating Seasonal Populations with Water and Energy Data dated June 22, 2022, or an alternative method that the supplier has demonstrated to the Department, in coordination with the Board, to be equivalent, or superior, in quality and accuracy.

(C) Notwithstanding subdivision (b)(1)(B), a supplier is eligible for the variance for water use associated with seasonal populations if the supplier uses detailed daily or hourly Advanced Metering Infrastructure (AMI) data to effectively identify dwelling units with seasonal population and the associated water use represents 1 percent or more of the budget associated with the standard described in section 966 (c)(1). If the supplier uses detailed daily or hourly AMI data, then the occupancy rate (RO) shall be calculated by multiplying the water used by seasonally occupied homes (WSO) by the supplier’s residential service area population (P) and dividing the product by the water used for permanently occupied homes (WPO). The quotient shall be multiplied by the average number of days households are seasonally occupied (SDAYS). This formula is expressed mathematically as follows:

The average number of days households are seasonally occupied (SDAYS) shall be calculated according to the Department’s Methods for Estimating Seasonal Populations with Water and Energy Data dated June 22, 2022, or an alternative method that the supplier has demonstrated to the Department, in coordination with the Board, to be equivalent, or superior, in quality and accuracy.

(d) An urban retail water supplier may request a temporary provision to respond to negative impacts to wastewater collection, treatment, and reuse systems, if the supplier shows to the satisfaction of the Board that meeting the objective pursuant to section 966 would require adhering to the applicable residential indoor standard identified in Water Code section 10609.4 and that meeting the budget for efficient residential indoor use is causing challenges within wastewater collection, treatment, and reuse systems