Water Losses – Non-revenue and Unaccounted-for Water

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Water Losses – Non-revenue and Unaccounted-for Water

Water loss is water that never reaches the customer. Water loss has impact on profitability and water quality.

Water loss greatly affects operational costs and treatment.

Non-revenue water is the water that is lost before it reaches the customer. Losses can be real or apparent.
 

Water Loss
Physical Loss (Real Loss)Commercial Loss (Apparent Loss)
Pipe breaks and leaksMetering errors
Storage overflowsWater theft
House connection leaksBilling anomalies

 

· Apparent losses are non-physical losses in utility operations due to meter inaccuracies, data handling errors in billing and unauthorized consumption.

This is water that is consumed but not properly measured, accounted or paid for.

· Real losses are physical losses such as leakage and storage overflows.

This water never reaches the consumer , but it inflates the water bill since this water is treated but unused.

 

water loss infographic.png
Image: The High Cost of Non-Revenue Water Infographic
Labeled: free to share with attribution 
Image source: Tata & Howard

 

According to the World Bank, in most developed countries there are no or insignificant water losses, but in developing countries it is estimated that, for example, illegal connections are about 40% of non-revenue water.

Validating water audits requires testing the production water meters and testing a random sample of customer meters, excluding the system errors in billing and eliminating illegal connections.

 

Non-revenue water (NRW) includes authorized unbilled consumption (such are water use by firefighters and religious institutions).

Non-revenue water is the difference between the volume of water delivered in a network and billed authorized consumption.

Unaccounted-for water (UFW) excludes authorized unbilled consumption.

Unaccounted-for water is the difference between the volume of water delivered in a network and legitimate consumption, both metered and unmetered.

 

System Input Volume

Authorised Consumption

Billed Authorised Consumption

Billed Metered Consumption

Revenue Water

Billed Unmetered Consumption

Unbilled Authorised Consumption

Unbilled Metered Consumption

Non-revenue Water

Unbilled Unmetered Consumption

Water Losses

Apparent Losses

Unathorised Consumption

Metering Inaccuracies

Real Losses

Leakage on Transmissions and Distribution Mains

Leakage and Overflows at Utility Storage Tanks

Leakage on Service Connections

 

System Input Volume is the amount of water that annually enters the water supply system.

Authorized Consumption is exported water which includes both metered and unmetered water.

Water Losses are the difference between system input volume and authorized consumption.

 

It is very important for utilities to identify how much water is lost as it affects their finances as utilities, i.e. consumers, have to pay for unused water. Moreover, water is unnecessarily wasted while being a scarce resource.

Addressing water loss should be done by investigating the issues in the infrastructure and utilities, as well as staff training.

Non-revenue water is often represented as the percentage that is lost from the total amount of water produced. However, this is not a valid representation since it does not precisely reflect the water loss.

If the loss in volume is constant, the percentage lost will vary with the amount of spent water. The percentage is indirectly proportional to the water consumption: if the water use decreases, the volume lost remains the same but the percentage increases.

This can be avoided by measuring the volume of water lost by connection per day or even losses per kilometer.

An alternative measurement of real losses is an Infrastructure Leakage Index (ILI). This is a ration of Current Annual Real Losses (CARL) to Unavoidable Annual Real Losses (UARL).

The World Bank estimated water utilities lose $14 billion every year due to non-revenue water. If only half of the loss is reduced, $2.9 billion could be saved and invested in providing clean water to 90 million people in need.

American Water Works Association (AWWA)recommend 10% as a benchmark for unaccounted-for water loss. Losses between 10 and 25% are recommended to be reduced while losses over 25% are concerning and should be addressed.

High NRW will lead to low utility efficiency:

wl1.png
Image: The Vicious NRW Cycle
Image Source: R. Liemberger

The goal is to transform the vicious circle in the virtuous circle:

wl2.png
Image: The Virtuous NRW Cycle
Image Source: R. Liemberger

 

The best ways to control the apparent losses is to eliminate:

· customer meter inaccuracies (installation and calibration procedures for large meters, calculation of the average weighted error (AWE) for customer meters, selection of customer meters, consumption profiles, meter sizing, meter installation, meter aging, optimum replacement period, comprehensive and/or targeted replacement programs),

· systematic data handling errors (data capture, data transmission, data processing, meter reading procedures, automatic meter reading (AMR), supervisory control and data acquisition (SCADA))

· unauthorized consumption (overall metering policy will identify unauthorized consumption. Utilities, however, must have autonomy to regulate the illegal connections. Politics is often an obstacle).

It is impossible to eliminate real losses. Some losses are simply unavoidable and some leakages are undetectable since they are too small or it is not economical to repair them. The best ways to reduce real loss :

· rapidly react to leakages (identifying leaks, optimizing pipeline repairs and managing water pressure)

· avoid storage overflows.

Reducing physical losses will reduce capital investments and reduce the utility energy consumption.

 

Stay tuned! The Water Network will soon publish an interview with a world-renowned expert on the subject of water losses and how to reduce them. 

 

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