IWA/AWWA Water Audit Method: Water Balance Water Imported Own Sources Total System Input ( allow for known errors ) Total System Input (allow for known errors) Water Supplied Water Exported Water Supplied Water Exported Water Losses Authorized Consumption Water Losses Authorized Consumption Real Losses Apparent Losses Unbilled Authorized Consumption Billed Authorized Consumption Non- Revenue Water Revenue Water Leakage & Overflows at Storage Billed Unmetered Consumption Billed Metered Consumption Billed Water Exported Leakage on Service Lines Leakage on Mains Customer Metering Inaccuracies Unauthorized Consumption Unbilled Unmetered Consumption Unbilled Metered Consumption Systematic Data Handling Error
7 Data Grading Criteria for Volume from own Sources Grading Volume from own Sources quantity WATER SUPPLIED << Enter grading in column 'E' Volume from own sources: 7 94, Million gallons (US)/yr (MG/Yr) Master meter error adjustment (enter positive value) : 10 2, over-registered Water imported: n/a MG/Yr Water exported: 10 7, MG/Yr WATER SUPPLIED: 84, MG/Yr ? ? ?
8 Data Grading Criteria for Master Meter Error Adjustment Grading Master Meter Error Adjustment quantity WATER SUPPLIED << Enter grading in column 'E' Volume from own sources: 7 94, Million gallons (US)/yr (MG/Yr) Master meter error adjustment (enter positive value) : 10 2, over-registered Water imported: n/a MG/Yr Water exported: 10 7, MG/Yr WATER SUPPLIED: 84, MG/Yr ? ? ?
The Grading Matrix – grading data and seeking improved data validity
Data Collection – Setting Reliable Inhouse Data Collection Procedures When launching the auditing process, it is important to bring together the utility staff most familiar with: Production Metering Customer Metering Customer Billing Distribution System operations & leak detection Mapping/Geographical Information Systems Hydraulic Modeling (if available) Strive to have the knowledgeable people participating- the water audit is not an administrative task (Dont assign water audit data collection to the secretary)
Data Collection Integrity – Avoid Reporting Bad Data Software features flags for bad data Its impossible for a utility to bill more water than they supply If this occurs, the software gives a red flag to alert the auditor to recheck the data inputs Unfortunately, some utilities are submitting water audits with such flagged data Suggestion: The lead person of the water utility should sign- off on the water audit when it is submitted to the reporting agency.
Accurately Quantifying Water Supplied Several steps exist to reliably quantify the water supplied quantity 1. Source water, imported water and exported water should always be metered a. Ideally, these meters should be the continuously recording type ideally linked to a Supervisory control and data acquisition (SCADA) System b. If meters are not linked to a SCADA System, then data should be collected as frequently as possible, at least weekly c. If meters are not continuously recording type, and are read infrequently, plan to upgrade the metering installation as soon as possible This is the most important quantity in the Water Audit! It is the largest number in the Water Audit Any error in this value carries throughout the entire Water Audit
Accurately Quantifying Water Supplied Testing Approach Volumetric Meter Test Comparative Meter Test
Accurately Quantifying Water Supplied 2. Meters should be regularly verified for accuracy a. Large meters can be compared with an inline insertion or strap-on meter measuring flow downstream of the primary meter i. Make certain that the temporary metering location is representative and accurate ii. Strive for minimum 24-hr period if using this method iii. Philadelphia Water Department conducts over 50 verifications each year in this manner b. Smaller meters might be tested using field test apparatus as is conducted on large customer meters c. Document/store the inaccuracy values to serve as a basis for data adjustments d. Recognize that calibration of the related instrumentation (differential pressure transmitters) does not verify the flow measuring capability of the meter! Insertion pito rod measuring and recording flow
Accurately Quantifying Water Supplied 3. Meters should be recalibrated, repaired or replaced regularly to maintain reliable performance a. New, current-technology meters should replace dated or defective meters b. Permanently installed insertion type meters can be a less costly means of establishing or renewing reliable metering c. Refer to AWWA M33 guidance manual Flowmeters in Water Supply for information on meter selection d. Many dated meters exist throughout the North American water industry Magnetic Flow meter replacement on 48-inch untreated water line 2008 in Philadelphia
Accurately Quantifying Water Supplied 4. Regularly determine Master Meter Error Adjustment a. Data should be reviewed at least weekly, but ideally, each business day, for trends/anomalies b. Balance flows to account for storage level changes and district water transfers c. Adjust for recorded inaccuracy levels of given meters d. Adjustments due to data error e. Adjustments due to data gaps f. Aggregate master meter error is: i. Added if source meter under-registration exists ii. Subtracted if source meter over-registration exists 16-inch turbine meter on wholesale account being verified via inline pito rod
Know Your Production Metering Configuration By monitoring the differences (A-B, B-C, A-C) on a daily basis, anomalies are detected when these relative differences begin to stray from typical trends
Adjusting for Data Gaps Production flow data should be reviewed on a frequent basis to monitor for data gaps Gaps occur due to: Unplanned interruption: lightning strike, power failure Planned interruption: instrumentation calibration Gaps in water flow data should be quantified and added back to the daily total
Assembling Data for the Annual Water Audit SCADA A history: raw data from the field SCADA B history: corrected, final data
Data Collection – Exported Water Quantity Extract the Exported Water Quantity from the Customer Billing System Dont double-count this quantity by including it additionally in Billed Authorized Consumption The Exported Water quantity is a separate item in the water audit because: It stems from one or more bulk quantity measurements It is typically billed under a different billing rate than retail customer sales
Data Collection – Unbilled Authorized Consumption Unbilled Authorized Consumption components metered and/or un- metered consumption, e.g.: Street cleaning Mains flushing Fire fighting Generally small portion of the water supplied volume Dont spend lots of time on quantify this value if data is not available Instead, use the default value for Unbilled Unmetered Consumption Improve data validity over time
Data Collection – Systematic Data Handling Error Deals with the customer meter reading and billing processes This quantity is perhaps the least understood component of apparent loss Like unauthorized consumption, every water utility has some amount of systematic data handling error, even if it is a low amount Important to include at least a minimal volume here – dont leave this volume at zero. The software does not provide a default value for this component Detailed auditing of billing records will likely lead to sources of this error and quantification of a value
Length of Private Pipe Can be difficult to understand the concept around this parameter, however: If customer water meters are typically located in a meter pit outside of the customer premises then this value is zero
Data Collection – Financial Data: Cost to Operate the System Includes costs for drinking water operations only – do not include sewer, stormwater or other costs in this quantity Typically includes power costs to treat and convey water, chemical and other costs at the water treatment plant, staff costs for drinking water only May include liability costs related to water events (ex: damage from main breaks) Dont include depreciation effects
Water Audit Data Collection Initiative Data Collection notables: 21 water utilities (19 USA, 2 Canada) 17 systems over 10,000 connections; 4 systems under 10,000 connections Observations from the data: Validation results: ave data validity score dropped from 78 to 74 after validation Wide variation in production costs: $183/mg (KY) to $2,110/mg (TN) – ave. $726/mg Customer retail costs: ave. $4.57/1,000 gals Range $1.11 to $8.38 Ave apparent losses: 15 gal/connection/day Ave real losses: 63 gal/connection/day
This is the BEST Performance Indicator for monitoring progress within an individual water utility. (Note: utilities with very low connection densities and meters located after the curb stop use this indicator in the form of gallons/mile of pipeline/day) Water Audit Data Collection Initiative 2011
Summary – key steps for valid data collection Standardized Water Audit Data Collection is occurring across the United States The data collection process is still relatively young but is maturing Water utilities should assign knowledgeable staff members from all functional areas to assemble the water audit The lead person of the water utility should review the water audit before it is submitted to the reporting agency Valid data is needed to accurately represent the water efficiency of the water utility and guide improvements