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Why we have to avoid presentation of NRW in precentages PDF Print E-mail
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Saturday, 07 October 2017 10:56


The acknowledged British NRW expert Allan Lambert has invited all his colleagues to join and support the initiative by which it is expected that the practice of showing the amount of Non-Revenue water and losses as a percentage of the delivered or input water volume in the system will cease and that it will not can be a Performance Indicator.

So far, this initiative has been supported by 132 NRW professionals from 24 countries. A list of professionals who have supported the initiative so far can be seen here >>.

Regrettably in most water supply in Bosnia and Herzegovina and in the region, it is still common for Non-Revenue Water as well as for losses to be expressed in percent, although this approach is completely wrong, as is clearly shown in the following example:

Let's say that one water supply system supplies 1000 m3 of water every day, and that 250 m3/day of water is lost through the Real losses and the same amount (250 m3/day) through Apparent losses. On the basis of the above, revenue water is the 500 m3/day, respectively the same amount of non-revenue water, accordingly, NRW = 500/1000 and NRW = 50%.

Furthermore, let's take that in same water supply increase the number of consumers and the quantity of water supplied, as well as the revenue water per 200 m3 / day. Now the situation would be that the delivered water quantity is 1200 m3/day, until the total losses (Real + Apparent) remained the same and did not change and still amount is 500 m3/day, and resulting in 700 m3/day. If the ratio of Non-Revenue water is now expressed in percentages, NRW = 500/1200 and NRW = 41.7%, regardless, any real improvement didn't do.


Based on stated, the NRW has been reduced for 8.3%, although it has absolutely no any loss reduction, what clearly shows how wrong is this approach is and how much it can create the wrong picture.

The alternative and only correct approach for water loss presentation through utilisation of the IWA Performance Indicators system evaluated on the basis of the IWA water balance by calculation based on the measurement of minimum night flows hydraulic measurement in the DMA , and in particular with presentation of the Infrastructure Leakage Index when it comes to physical losses, or ALI Apparent Losses Index) when it comes to commercial losses.

You can read more about IWA methodology and performance indicators here.