working group workshop · 7/23/2020  · summary of select previous studies continued: study...

WORKING GROUP WORKSHOPDWR WATER Use Studies Update

July 23, 20209AM – 11AM

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Meeting Purpose and Agenda

9:00 Welcome and LogisticsSabrina Cook, Chief Water Use Efficiency Implementation SectionWater Use Efficiency Branch, DWR

9:10 The Indoor Residential Water Use Study OverviewShem Stygar, P.E. Project Manager ‐ DWR

9:20 Sampling StrategyAnil Bamezai, Ph.D., Principal, Western Policy Research

9:50 Short Stretch Break9:55 Disaggregation Analyses and Data Issues

Monthly: David Mitchell, General Partner, M. CubedHourly: A.R. El‐Khattabi, Ph.D., Project Statistician, Xylem Inc.End‐Use: Peter Mayer, P.E., Principal, Water DM

10:50 Next Steps, Schedule, and Future Opportunities for Stakeholder EngagementSabrina Cook, Chief Water Use Efficiency Implementation Section

11:00 Adjourn

Purpose: Provide working group with updates on the IRWUS studies progress and solicit comments and feedback.

Working Group MembershipLong Beach Water DepartmentLos Angeles Department of Water and PowerMesa Water DistrictMunicipal Water District of Orange CountyNatural Resources Defense CouncilPacific InstitutePlumbing Manufacturers InternationalRancho California Water DistrictSacramento Suburban Water DistrictSan Francisco Public Utilities CommissionSan Jose Water

Santa Clarita Valley Water AgencySonoma-Marin Saving Water PartnershipSouth Tahoe Public Utility DistrictStanford UniversityValley County Water DistrictValley WaterWalnut Valley Water DistrictWateReuse CAWaterNow AllianceWest Yost AssociatesWestern Municipal Water District

ArcadisAssociation of California Water AgenciesCalifornia American WaterCamrosa Water DistrictCity of SacramentoCoachella Valley Water DistrictCounty of NapaEastern Municipal Water DistrictEcolabIrvine Ranch Water DistrictKennedy Jenks Consultants

Introductions –Poll Questions

1. What perspective do you represent?

2. Which California region do you represent?

Opening Remarks –The Water Use Studies Group

Sabrina Cook, Chief Water Use Efficiency Implementation SectionWater Use Efficiency Branch, DWR

WaterUseStudiesWorkingGroupIndoor Residential Water Use Study Focus

Second Meeting, July 23, 2020 Sabrina Cook, Ph.D., Water Use Efficiency Implementation Section Chief

C A L I F O R N I A D E P A R T M E N T O F W A T E R R E S O U R C E S

Reminder:DWR Studies Legislated Deadlines

Indoor Residential Water Use – Report to Legislature on current standard and recommendations

January 1, 2021

Outdoor Landscape Area information (related) January 1, 2021

Outdoor Water Use Standard October 1, 2021Variances October 1, 2021CII Large Landscapes Dedicated Meters October 1, 2021CII Classification and Performance Measures October 1, 2021Objectives Guidelines and Methodology October 1, 2021Waterboard Regulations June 30, 2022

Water Code:• 10609.4. (b) (1) The department, in coordination with the board, shall conduct

necessary studies and investigations and may jointly recommend to the Legislature a standard for indoor residential water use that more appropriately reflects best practices for indoor residential water use than the standard described in subdivision (a). A report on the results of the studies and investigations shall be made to the chairpersons of the relevant policy committees of each house of the Legislature by January 1, 2021, and shall include information necessary to support the recommended standard, if there is one. The studies and investigations shall also include an analysis of the benefits and impacts of how the changing standard for indoor residential water use will impact water and wastewater management, including potable water usage, wastewater, recycling and reuse systems, infrastructure, operations, and supplies.

C A L I F O R N I A D E P A R T M E N T O F W A T E R R E S O U R C E S

Indoor Residential Water Use Overview

C A L I F O R N I A D E P A R T M E N T O F W A T E R R E S O U R C E S

Shem Stygar, P.E. Project ManagerCalifornia Department of Water Resources

Indoor Water Use Studies Working Group Meeting, July 23, 2020

• W.C. 10609.4 (a) sets indoor water use standards for 2025, 2030, and beyond 2030

• Authority to change the Indoor Standard resides with Legislature

• Water supplier sets their Objective:

Objective = (IndoorR + OutdoorR + Large Landscapes,Loss) + Variances + Bonus Incentives

but….

Is Water Code 10609.4(a) an appropriate standard?

Background:

Summary of Select Previous Studies:

• Indoor use based on 2-week sampling of residential end-uses (REUs)

• Combine REU analysis with 1-year of monthly billing data

• Identify population through household surveys• No Multi-Family Residential (MFR) analysis

Summary of Select Previous Studies continued:

Study Participating Agencies

No. of SFR with REU Analysis

1999 WRF REU Study

12 Nationwide4 in So. CA 1,188

2011 CA SF Water Use Efficiency Study

10 CA Agencies 735

2016 WRF REU Study

9a North America0 in CA

762

2011 CA SF Water Use Efficiency Study - Included CA AgenciesDavisEBMUD

Irvine Ranch WDLas Virgenes MWDL.A. DWPRedwood CitySFPUCSan Diego County Water AuthoritySonoma County Water Agency

a - 9 Agencies participated in REU, 23 agencies with monthly analysis

Why another Indoor Use Study?• Unsupported Assumption: indoor residential use (IR-

gpcd) is uniform & consistent:– Previous studies may or may not represent diversity of indoor

use in CA– Short-term REU analysis, small sample size combined with 1-

year monthly billing data– Other methods (e.g. proportion) assume uniform & consistent

IR-gpcd• Policy decisions require accurate representation of

supplier diversity

Legislative Report - Study Scope• Statewide sampling strategy

– Customer level data from representative census tracts– Single-Family, Multi-Family, Dedicated Irrigation accounts– Cross-Check analyses– Understand sampling Error

• Monthly disaggregation– 5 to 10 years per account with QA/QC

• Hourly disaggregation– 1 year per account with QA/QC

Legislative Report Study Scope (continued..)

– End-Use Analysis (Flume)• Non-invasive & cost-effective• 5 to 10 second reads for 30 days with QA/QC• Characterize how to gain indoor efficiency

– Sample Size:• Roughly 896,000 customer accounts• Approximately 6.7% of CA population

Indoor Residential GPCD• Disaggregated at SF / MF Customer Level• Aggregated to Census tract• Aggregated to Water supplier• Aggregated to State

Participating Urban Water Suppliers

Monthly and Bi-Monthly (18 Total)Eastern Municipal WDFolsom*Redwood CityCity of SacramentoCal-Water (10)Bakersfield / Bear Gulch / Chico / East LA / Livermore / Palos Verdes / Salinas / South San Francisco / Stockton / Visalia

Coachella Valley WDIrvine Ranch WDMoulton Niguel WDSanta Cruz

Hourly (4 Total)Eastern Municipal WDFolsom*Redwood CityCity of Sacramento

Study TeamMonthly Analysis Team

+ &

Hourly Analysis Team

&

Water DM

&

Western Policy Research

Technical Advisory TeamIndoor Residential GPCD Estimate:• By Supplier• Statewide

C A L I F O R N I A D E P A R T M E N T O F W A T E R R E S O U R C E S

SAMPLING STRATEGY

Anil Bamezai, PhDWestern Policy Research

Study Team

• Study Design, Final Report Preparation (DWR, Anil, Peter)

• Billing Data Modeling (M.Cubed, A&N Technical Services)

• 1-hour AMI Data Modeling (Valor)• 5-second logger data modeling (Flume, Autoflow)

Study Design Objectives & Challenges• Objectives

– Estimate Statewide Indoor GPCD– Estimate How Variation in Indoor GPCD Correlates With

Drivers of Indoor Use• Challenges

– Time and Budget Constraints—Not Possible to Work With a Large Set of Water Agencies

– Agency Participation Voluntary– Agency Must Have Good, Suitable Data

Solution: Census Tract Based Analytics• Work With a Carefully Selected Group of Agencies• Estimate Indoor GPCD By Census Tract• Bin Census Tracts Into Similar Groups (“Strata”) Based On

Housing and Demographic Characteristics• Estimate Indoor GPCD First By Strata (Weighted Average

Across Tracts Falling Within Strata)• Estimate Statewide Indoor GPCD (Weighted Average

Across Strata)

Census Tract Binning Into Strata• End Use Studies Offer Important Clues About Drivers of

Indoor Use– Persons Per Household – Dwelling Age– Socioeconomic Characteristics– Employed/Retired

• Census Tracts Can Be Characterized on All Four Dimensions

Tract By Housing Age Distribution0

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Fine Stratification Reduces Error

• CA has 8000+ Tracts• Distributed Over 54

Strata• No Strata too large• Design Captures

Infrequently Found Characteristics

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Next Steps• Prepare Statewide Estimate of Indoor GPCD• Evaluate What Drives Variation in Indoor GPCD

Across Tracts• Evaluate/Correct For Potential Sources of Bias

Questions and Comments

Short Stretch Break31

C A L I F O R N I A D E P A R T M E N T O F W A T E R R E S O U R C E S

Indoor Residential Water Use Study

Monthly Data Analysis Status ReportDavid Mitchell, M.Cubed

Study Team

• David Mitchell, M.Cubed• Tom Chesnutt, A&N Technical Services• David Pekelney, A&N Technical Services

Monthly Data Analysis Study Objectives• Legislative Report

– Collect Data– Process/Clean Data (QAQC)– Develop/Test Methods To Estimate Indoor Water use

• Expanded Study– Expand Sample– Apply Preferred Method(s)

• Additional Area of Inquiry:– What Effect is Pandemic Having on Residential Water Use?

Study Participants• City of Folsom• City of Sacramento• City of Santa Cruz• Redwood City• Coachella Valley MWD• Eastern MWD• Irvine Ranch WD• Moulton Niguel WD• California Water Service

Sample Coverage18 Urban Water Service Areas560 Census Tracts896,000 Residential Customers

Billing Data Span2011 – 2020 = Many millions of meter reads

• In Ideal World, we have for each sampled home…– Measurements of indoor water use– Count of people in each home

• In Actual World, we have for each sampled home …– Measurements of total water use (indoor + outdoor)– Average occupancy for homes in same census tract

Estimating Indoor GPCD

DANGER

STATISTICAL INFERENCEAHEAD

Indoor Use Must Be Inferred

• Is Winter Use a good proxy for indoor use?– In some locations, Yes.

In others, No.

• Winter Irrigation Occurs in Many Parts of CA

Too much year-to-year variation for this to be just indoor water use

Winter Use is Jumping Off Point• 3 methods based on minimum winter use

Min Winter Use

Irrigation Meters

Landscape Area

Rainfall Deviation

These provide basis for adjusting minimum winter use for outdoor irrigation

Look at Dedicated Irrigation Meter Water Use

Seasonal Range in Irrigation

Water Use

Min Winter Use

Method Assumes Same Relationship Applies to Residential Irrigation

Example:

• Min Irr/Seasonal Range = 6.9%

• Residential Range(418 – 188) = 230 GPD

• Residential Outdoor Use(230) * 6.9% ≈ 15.9 GPD

• Residential Indoor Use188 – 15.9 = 172.1 GPD

Look at Variation in Winter Use with Landscape Area

Indoor Water Use

Landscape Area

Outdoor Water Use

• Estimate relationship between winter use and residential landscape area

• Use model to predict indoor use

Look at Variation in Winter Use with Rainfall Deviation

Indoor Water Use

Above Normal Rainfall

Outdoor Water Use

• Estimate relationship between winter use and rainfall deviation

• Use model to predict indoor use

Below Normal Rainfall

Normal Rainfall

Going from GPD to GPCD• We divide the indoor estimate by average household

size to estimate GPCD

• We apply a bias correction to this estimate because:

What we can estimate What we really want

E[GPD] / E[Persons] only approximates E[GPD/Persons]

• These corrections are typically small

Margin of Error• We attach a margin of error to

each estimate• The margin of error conveys

the level of [un]certainty in the estimate

• The margin of error is just as important as the point estimate

30

35

40

45

50

55

60

Irrigation MeterMethod

LandscapeArea Method

RainfallDeviationMethod

Indo

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PCD

Example Estimates with Margin of Error, 90% Confidence Level

Spatial & Temporal Variation in GPCD

• There is significant variation in GPCD across– Census Tracts– Time

Multi-Family Poses Significant Challenge

GPCD = GPD/Meter (can get from billing data)

÷ Housing Units/Meter (Uh oh, most utilities don’t have this)÷ Persons/Housing Unit (can get from Census*)

* Tract-level estimates. What we really want is actual occupancy in sampled homes.

Next Steps• Finalize Indoor GPCD Estimates (End of July)

• Compare to AMI-Based Estimates

• Prepare Statewide Estimate (Anil Bamezai)

• Produce Documentation/Report

Questions and Comments

C A L I F O R N I A D E P A R T M E N T O F W A T E R R E S O U R C E S

Indoor Residential Water Use Study

Hourly Data Disaggregation Analysis Status Report

Ahmed Rachid (A.R.) El-Khattabi, PhDProject Statistician, Xylem Inc

Study Team

• Christine Boyle, Ph.D., Xylem Inc.• Ahmed Rachid El-Khattabi, Ph.D., Xylem Inc.

Legislative Report Study Objectives• Phase 1: Data cleaning

– Collect hourly / AMI data– Process and clean data– Reconcile hourly data with monthly data

• Phase 2: Estimation– Develop methods to estimate indoor usage on subsample– Apply to entire sample– Estimate indoor water usage

• Additional Area of Inquiry:– What Effect is Pandemic Having on Residential Water Use?

Overview

• City of Folsom• City of Sacramento• Eastern MWD• Redwood City

4 Urban Water Service Areas336 Census Tracts290,000 Residential CustomersStudy period: January 2019 – December 2019 2019 (Trillions of hourly reads)Sacramento Folsom

Eastern MWD

CityRedwood

City Participants

Overview of Methodology –Phase 1: Clean and Filter Data

AMI Data Apply FiltersSegment by

Customer Class and Census

Tract

Common Issues• Implausible/anomalous reads• Double reads• Incomplete days

Overview of Methodology –Phase 2: Three approaches to infer indoor usage

Numerical Approach

Clustering Approach

Min Month Approach100

Overview of MethodologyPhase 2: Numerical Approach

• Examine water usage at hourly level• Yardstick for max amount of water used

per hour based on:– Appliance end-use studies*– Average persons per household (Census

Tract)• Hourly usage amount is labeled as

– Indoor if read yardstick

100

Dishwasher ~ 30 gal per wash

Washing machine ~ 30 gal per load

Shower~ 18 gal per shower

Toilet flush~ 2 gal per flush

100 gallons per hour is a reasonable yardstick for indoor water use.

*Source for appliance estimates: DeOreo et al (2011) California Single Family Water Use Efficiency Study.

Overview of MethodologyPhase 2: Minimum Month Approach

• Examine water usage at daily level– May vary by customer

• Daily water use during month where outdoor usage is expected to be minimal– e.g. February

• Daily quantity is considered indoor if– Daily total (min month daily average)

Illustration using Customer X

Overview of MethodologyPhase 2: Clustering Approach

• Examine both hourly and daily usage

• Each customer may have sets of days where they use water in particular ways

• Group together days based on how much water is used at each hour of the day – Groupings are referred to as

“usage profiles”

Usage Profiles for Customer Account X

Overview of MethodologyPhase 2: Clustering Approach (cont’d)Assignment determined by rules in terms of frequency, typical seasonal water use, flow rates

1. Indoor Only Profile*

2. Indoor + Outdoor Profile

3. Outdoor only Profile

4. Atypical Profile

*We also apply a filter for indoor leaks

Overview of MethodologyCalculate gallons per capita per day (GPCD)For each customer account, 𝑖,

1) Start by calculating each customer accounts’ indoor 𝐺𝑃𝐷𝑇𝑜𝑡𝑎𝑙 𝐼𝑛𝑑𝑜𝑜𝑟 𝑈𝑠𝑎𝑔𝑒

𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝐷𝑎𝑦𝑠2) Then calculate 𝐺𝑃𝐶𝐷

𝐺𝑃𝐷𝐶𝑒𝑛𝑠𝑢𝑠 𝐸𝑠𝑡𝑖𝑚𝑎𝑡𝑒 𝑜𝑓 𝑃𝑒𝑟𝑠𝑜𝑛𝑠 𝑝𝑒𝑟 𝐷𝑤𝑒𝑙𝑙𝑖𝑛𝑔

3) Apply bias correction

Questions and Comments

C A L I F O R N I A D E P A R T M E N T O F W A T E R R E S O U R C E S

Indoor Residential Water Use Study

Single-Family End Use Analysis Status Report

Peter Mayer, WaterDM

Study Team

• Flume• Autoflow

• City of Folsom– 20 volunteer participants

Participants

End Use Analysis Study Objectives

• Legislative Report– Collect hi-resolution (5-second) data – 30 days– Disaggregate into component end uses (toilet, shower, faucet,

irrigation, etc.)– Detailed household survey– Compare indoor / outdoor disaggregation with hourly and monthly

methods• Future Studies

– Expand sample and include individually metered multi-family units– Explore future efficiency potential

• How and where can future indoor reductions be achieved?

Next Steps• Complete data collection and QA/QC

• End use disaggregation (Autoflow)

• Summarize results (Peter Mayer & Anil Bamezai)

• Produce legislative report and recommendations for further studies

Questions and Comments

Wrap-Up: Indoor Residential Water Use Study Schedule

• Data analysis complete – end of August• Changing IR-gpcd standard, benefits and impacts on water supply,

wastewater, and recycled water – end of August• Working Group Meeting: DWR and Water Board recommendations –

end of September• Stakeholder Meeting: Public Review Draft Report to Legislative– end

of October• Final Report to Legislature – end of November

THANK YOU!Contact: wue@water.ca.gov

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