working group workshop · 7/23/2020 · summary of select previous studies continued: study...
TRANSCRIPT
WORKING GROUP WORKSHOPDWR WATER Use Studies Update
July 23, 20209AM – 11AM
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Be comfortable. We will take a short break mid-meeting
Have fun and be courteous.• Honor time and share the airtime• Think innovatively and welcome new ideas
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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Tracts By Income & Poverty0
2040
6080
100
Perc
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opul
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low
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Tracts By Retired Population0
2040
6080
100
Perc
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opul
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ver 6
5 Ye
ars
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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
0.0%
2.0%
4.0%
6.0%
8.0%
10.0%
12.0%
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53
Perc
ent o
f All
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ts in
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Strata
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
or G
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: [email protected]
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