Water balance by country · Updated 2026-09-29
Water balance and water loss in New Zealand: National Performance Review, unmetered supply and Local Water Done Well
How New Zealand councils and water organisations calculate the IWA water balance for the Water New Zealand National Performance Review and the new economic regulator, with unmetered residential supply handled properly.
Calculator settings for New Zealand
- Units
- Metric
- Benchmark category
- Standard
- Meter location
- Boundary where metered; large unmetered residential share in many districts
- Typical per-capita use
- 200–300 L/person/day in unmetered districts; 150–200 metered
- Reporting
- Water New Zealand National Performance Review; DIA non-financial performance measures; Commerce Commission economic regulation
New Zealand reports water loss through the annual Water New Zealand National Performance Review, which publishes the ILI and real losses per connection for participating councils, and through the Department of Internal Affairs mandatory performance measure for water loss (DIA 3). Under the Local Water Done Well reforms, the new council-controlled water organisations will be economically regulated, and a defensible water balance is the foundation of the leakage targets they will be set.
The unmetered problem
Outside Auckland, Tauranga, Nelson and a handful of other districts, most residential connections are not metered. That puts a large volume in 'billed unmetered consumption' — often 50–70% of system input — and the balance stands or falls on how well that volume is estimated. Use a per-capita estimate built from metered sample areas or from metered districts with similar climate and housing (Tauranga's data is often used as a reference), and carry ±20–30%. Every percentage point of error in that estimate lands directly on real losses.
Other local specifics
- Where meters exist they are at the boundary; service pipe length is 0 m.
- Wellington's reticulation is old and pressure is high in hill suburbs, which is why the region's ILI has historically been well above the national median; enter pressure by zone rather than a single average.
- Christchurch and much of Canterbury run on bore water with minimal treatment — 'basic' for carbon. Auckland's Waikato and dam sources are 'traditional'.
- Bulk supply from a regional council to a district council goes in the bulk export rows.
Typical results
The National Performance Review median ILI has sat in band B in recent years, with a wide spread from under 2 to above 8. Real losses of 150–300 L/connection/day are common in unmetered districts. The reforms will push the sector toward ILI-based targets; establishing a consistent annual balance now, with versions saved year on year, is the cheapest way to prepare.