Non-revenue Water (NRW) Management Review

GHD was appointed to undertake a peer review of the program to determine if the current activities will reverse the rapid rise in the level of Non-revenue Water (unaccounted-for-water) and to identify what was required to achieve Metrowater’s (New Zealand) NRW targets.

The review process was guided by an overall audit process, data pathway analysis that examined the data from its capture through to its application in forecasting future NRW levels. The analysis of migratory nature of losses within the equilibrium equation of the water balance requires identified the cause and effect of the various errors associated with measuring and/or determining the different volumetric components. This process facilitated the determination and quantification of the various components of real and apparent losses.

The review determined that refinement of Metrowater’s leakage and water loss management practices and systems was required, and confirmed that the data being utilised for NRW calculations was inconsistent. The review also identified those components of NRW that were most likely to contribute to their recent rapid rise in NRW.

Short, medium and long term measures were recommended to ensure the sustainable management and reduction of apparent and real losses. These measures included addressing the accuracy of bulk supply meters, adoption of the balanced uncertainty approach in calculating water imbalances, proposed forecasting methods for NRW levels as well as implementing appropriate leakage awareness, localisation and pin-pointing techniques.

A collaborative approach was taken that included the ‘embedding’ of the GHD team within Metrowater’s office; discussions with the bulk water supplier (e.g. Watercare) and continuation in communication between the teams after GHD’s visit providing additional information and clarity of issues.