Nature and the environment;Public sector
vann_kostra, Municipal water supply, water distribution system, waterworks, water consumption, water quality, drinking water, water leakages, water feesWater and waste water , KOSTRA , Nature and the environment, Public sector

Municipal water supply


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About the statistics

Municipal water supply is a statistic which describes topics in the water sector like municipal fees, self-cost, water pipelines, water works and people connected, water quality, household consumption etc. The statistic is part of the Municipality-to-State statistics (KOSTRA).


Definitions of the main concepts and variables

Booster pumps are installed on the pipelines to pump water to locations at higher altitude than the water source, and in general to keep the pressure at the right level. This is important in order to avoid damages to the pipelines and contaminations.

Capital costs consists of the following two costs: Depreciation of earlier annual investments and a calculated interest cost for capital goods. Both depreciation costs and calculated interest cost are derived from KOSTRA-form number 23.

Coloured water often occurs due to natural organic components (humus content). The humus components are not necessarily harmful on their own, but may create suitable conditions for undesirable bacterial growth. Humus may also combine with other contaminations.

Cost coverage refers to, in percent, how big a share of the annual water supply related costs the municipalities actually cover by water fees. Municipalities are not entitled to claim more than actual costs, neither are they obliged to claim full cost coverage.

Delivery failure includes both intended and unintended stops in the water supply.

E. coli is a bacteria used as indicator for possible faecal contamination.

Full cost ratio = ((Fee income) / (Fee calculation basis + Allocations - Use of funds)) x 100

Municipal waterworks are waterworks owned by the municipalities. Waterworks established as limited companies with more than 50 percent municipal ownership are included.

Number of inhabitants connected is estimated from total number of inhabitants in combination with information about the extensiveness of the water pipelines.

Operating costs constitutes the sum of administrative-, management- and maintenance costs. Figures are reported through The Municipal-State-Reporting system (KOSTRA), on form no. 23.

pH is a measure for water acidity. Water with a high acidic content has a corroding effect on the pipelines, which may cause release of heavy metals to the water.

Satisfactory water quality for the different parameters used in KOSTRA (E.coli, pH, colour and intestinal enterococci) is defined as follows: the number of non-complying water analyses throughout the year should be less than 5 per cent of the total number of analyses taken.

Water fees consist of a connection fee and a fixed annual fee. The connection fee is collected once only - during installation. Figures are reported through The Municipal-State-Reporting system (KOSTRA), on form number 22.

Water use covers the consumption of water within the area covered by the distribution system of a waterworks. The consumption is distributed by sector/industry, estimated from the amount of water abstracted from the source and the amount of water used in treatment operations. Water use in households consists of all water used in households, holiday homes, institutions and the like. Water use for other purposes includes, among others, water to livestock and irrigation.

Waterworks applies to the administration of the water supply services, including water source (basin) water treatment facility and/or distribution system (pipelines). The statistics includes only waterworks which supply at least 50 persons and/or at least 20 houses or cabins (thus smaller waterworks are not part).


Standard classifications

Norway's municipalities are grouped according to population and economic comparable groups. The classification is based on the report (in Norwegian only) Gruppering av kommuner etter folkemengde og økonomiske rammebetingelser 2020

Administrative information

Name and topic

Name: Municipal water supply
Topic: Nature and the environment

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Responsible division

Division for Energy, Environmental and Transport Statistics

Regional level

The figures are published on both national and regional (municipal and county) levels. In addition, municipalities are grouped in economically comparable groups.

Frequency and timeliness

Municipal-State-Reporting (KOSTRA) key figures are published annually on the 15 th of Mars (unrevised figures) and 15 th of June (revised figures).

International reporting

Not relevant for Statistics Norway (carried out by others e.g. the Norwegian Food Safety Authority)


Statistics Norway has until 2014 received an Excel file aggregated to municipality level from the National Institute of Public Health. These data has been imported directly for use in KOSTRA statistics. From 2015 Statistics Norway has generate this municipality file themselves based on data available from:http://www.mattilsynet.no/mat_og_vann/vann/vannverk/oversikt_over_vannverk.1878. Revised data sets are also saved at Statistics Norway.


Background and purpose

KOSTRA (Municipality-to-State-reporting) started up as a project in 1995 with the intention to provide relevant and up-to-date information about allocation of resources, priorities and meeting targets in municipalities and counties. The goal is to collect data in a co-ordinated way, and make the information flow a one time delivery per year for all steering-information needed by municipality. The number of municipalities and counties was gradually increased until the reporting year of 2001, and then all municipalities were included in the KOSTRA.

The key figures on municipal waterworks gives an overview on share of population supplied, basic facts on the pipelines (length, age, rate of renewal), number of booster pumps, water consumption, reliability in delivery, population provided with disinfected water, population provided with hygienically safe water, contribution margin ratio, full cost ratio, fee calculation basis and capital costs etc.

Users and applications

KOSTRA provide steering information about municipalities and counties to the different interest groups, inhabitants, media, the municipality itself, different state organs and controlling authorities etc.

Equal treatment of users

Not relevant

Coherence with other statistics

Municipal waste water treatment KOSTRA, municipal wastewater sector

Legal authority

The data are collected by Statistics Norway on behalf of Ministry of Health and Care Services and Ministry of Local Government and Regional Development with legal basis in the Regulation on Reporting from Local Government (in Norwegian only) . Statistics Norway make use of the collected data for official statistical purposes with legal basis in the Statistics Act (in Norwegian only) .

EEA reference

Council Directive 98/83/EC on the quality of water intended for human consumption.



Data includes all municipal water works supplying at least 50 persons and/or at least 20 houses or cabins (full count). Municipal water works only serving schools and kindergartens is excluded.

Information about fees and cost coverage includes all municipalities in the country (full count).

Data sources and sampling

Municipal waterworks: Originally the National Institute of Public Health collected annual data of Norwegian water works. But from 2010, the Norwegian Food Safety Authority took over the data collection and thus since then they have been the key source of information to the KOSTRA statistics on water. The task of aggregating from data from waterworks level to municipal level and statistics and quality checks has been carried out by National Institute of Public Health up to 2014, while 2015 and later Statistics Norway is carrying out that particular task themselves.

Costs and fees: The Municipal-State-Reporting system (KOSTRA).

Collection of data, editing and estimations

The waterworks report electronically once a yea to the Norwegian Food Safety Authority. Deadline is 15th of February every year.

The electronic forms in KOSTRA and by the Norwegian Food Safety Authority contain built-in consistency checks and logical tests. After arrival data are checked automatically and manually by Statistics Norway.

Unrevised data will be published on 15 th of Mars. There is a second deadline on the 15 th of April for municipalities to correct possible errors in the figures just published.

Data are being published on different levels, as basic data and key figures. Basic data is generally reported in absolute numbers, and will largely constitute aggregated numbers summed up for a certain period of time or at a time of year. Key figures, on the other hand, are commonly a ratio (made up of different basic data).

The reporting from municipal waterworks has to cover 95 per cent or more of the total population supplied in a given municipality. If not, the municipality is excluded from the calculations of KOSTRA key figures.

Calculations of the age of municipal wastewater pipelines on country level in the article - Todays Statistics - has been adjusted for pipelines of unknown age (not specified time period). Pipelines in these cases has been spread accordingly over the following time periods: (1) before 1910, (2) 1910-40, (3) 1941-70 and (4) 1971-2000 and (5) 2001 or later. These corrections constitute a few small exemptions, while the age figures in Statbank has not been corrected in this way (based solely on this years reporting and on the part of the pipelines which can be pinned down to one specific time period).

Seasonal adjustment

Not relevant


Not relevant. Publically available data.

Comparability over time and space

Key figures on country level and for regions (counties and KOSTRA groups) are up to 2007 based on just average calculations of reported data, while data from 2008 and later constitute statistical calculated estimates which take into consideration non responses in the dataset to a higher degree.

Accuracy and reliability

Sources of error and uncertainty

It may be attached some uncertainty to measurements carried out by the water works themselves, but the magnitude is hard to pin down. Data which are most uncertain are the following:

  • Total water delivery to the water distribution system is commonly estimated and not measured
  • The distribution of water delivered to households, food industry, service sector, leakage, manufacturing etc. is commonly estimated and not measured
  • Number of people with groundwater and disinfected surface water are estimated in those cases t hat the water works have more than one water source.

Non-response of  entire waterworks, or on specific parameters within the electronic form can lead to uncertainty in the final statistics.


Quality and consistency checks has primarily been carried out by the National Institute of Public Health until 2014, but from 2015 and later this task has been carried out by Statistics Norway (if proven necessary).