Stats NZ

Environmental-economic accounts: Water physical stocks, year ended June 1995–2020

Water physical stock accounts provide information on our national and regional water balance, including the inflows and outflows of water through the inland part of the hydrological cycle, changes in storage, and estimates of hydro-generation water use.

2 August 2022: We have replaced the ‘Water physical stock account, year ended June 1995-2020 CSV’ originally published with an updated file that shows a correction to the total outflows at North Island, South Island, and New Zealand levels.

Key facts

  • Average annual rainfall for the most recent five-year period (year ended June 2016–2020) was 3.1 percent below the previous five-year average (2011–2015).
  • In the five years to June 2020, the decrease in average rainfall was most apparent in the North Island. The average annual rainfall was 6.0 percent lower than for the previous five-year period compared with a decrease of 1.5 percent for the South Island.
  • In the year ended June 2020, the West Coast region received 30 percent (151,465 million cubic metres) of New Zealand’s precipitation. This was more than the entire North Island’s precipitation volume.
  • The North Island and South Island had noticeably different seasonal patterns in precipitation, with precipitation highest in the September quarter (July–September) for the North Island and in the December quarter (October–December) for the South Island.
  • As at June 2019, the volume of ice in New Zealand was 35 percent (23,669 million cubic metres) lower than the estimate for the year ended June 1995. The rate of change in ice volume has been increasing since 2007.
  • Almost 70 percent of New Zealand’s groundwater volumes are in the Canterbury region. In the year ended June 2013, Canterbury recorded the largest annual increase in groundwater volumes since our timeseries began in 1995, reaching 519,487 million cubic metres.
  • In the year ended June 2020, New Zealand’s total ground water volumes decreased 0.3 percent from the previous year to 751,977 million cubic metres.

About the water physical stock accounts 1995–2020

The water physical stock accounts present information on the hydrological cycle based on the System of Environmental-Economic Accounts (SEEA).

The water physical stock accounts focus on water quantity and provide estimates of national and regional water flows (precipitation, evapotranspiration, and rivers) and change in storage (ice, snow, soil moisture, groundwater, lakes and reservoirs, and hydro-electric generation water use), from 1995 to 2020.

The current release both extends the length of the time series and is the first to provide quarterly estimates.

Quarterly estimates enable us to:

  • analyse seasonal patterns, and any changes in seasonality
  • analyse extreme events which may be obscured in annual data
  • compare water statistics with other quarterly data, such as agricultural output or electricity generation
  • recalculate annual estimates on a different year end basis (for example, year ended March) to enable alignment with other annual data (for example, national accounts).

The annual estimates are based on a hydrological year (1 July to 30 June) and include information on most aspects of the hydrological cycle. The accounts do not currently include information on residential and industry water use.

The quarterly estimates are currently less complete than the annual estimates, providing information on some aspects of the hydrological cycle.

These estimates pull together data from the National Institute of Water and Atmosphere (NIWA) and the Institute of Geological and Nuclear Sciences Limited (GNS).

Definitions and metadata

Data and advice for compiling these statistics was supplied by the National Institute of Water & Atmospheric Research Ltd, and the Institute of Geological & Nuclear Sciences Ltd.

Environmental-economic accounts: Sources and methods (third edition) presents the data sources and methods used for each of Stats NZ’s environmental-economic accounts, including water physical stocks.

Methods and revisions since the 2018 release are discussed in the following two reports prepared by other agencies and published on Stats NZ's website:

ISSN 2624-0777

Related topics
Related releases