ESS Standard for Quality Reports Structure (ESQRS)
National Statistical Institute
|Contact organisation unit|
“Environmental and Energy accounts” Department
|Contact person function|
|Contact mail address|
2, P. Volov Str.; 1038 Sofia,
|Contact email address|
|Contact phone number|
+359 2 9857 182
|Contact fax number|
Information on water reflects different aspects of water supply, water use, disposal and wastewater treatment and discharge at national and regional level.
Information on water abstraction makes it possible to identify the main sources and to quantify the distribution of water use between different activities.
The quantity of fresh and non-fresh water used are presented by categories of water supply and by basic economic activities - agriculture, mining and manufacturing, energy, services and households. Quantitative data are provided for public water supply about collection, treatment and water supply.
The quantities of generated wastewater are divided by main sources of anthropogenic activity. The observation of wastewater flows is from water source to water receiver. The total quantity of wastewater discharged into water bodies is divided by place of discharge and their treatment in urban and other wastewater treatment plants, as well as independent treatment of wastewater from the population. Data on urban wastewater treatment plants (UWWTP) according to the available treatment technology - primary, secondary and tertiary are presented.
Data about the relative share of population connected to water services, sewage and wastewater treatment as well as the share of population with irregular water supply due to water shortage are presented.
The information about available water supply and sewage network reflects the state of infrastructure and the growth rates of renovation. Detailed data about the type of pipes and years in which they have been put into exploitation is collected once at every five years.
The data are produced at administrative - territorial level and River Basin District level. The presented results on water use are calculated on the basis of reported statistical data, proportions and estimates.
· National Classification of Economic Activities (NCEA-2003, for international use NACE.BG 2003);
· Classification of Economic Activities (CEA-2008, for international use NACE.BG 2008);
· Unified Classification of the Administrative-Territorial and Territorial Units in
· List of settlements by river basins.
Information is ensured by conducting the following annual statistical surveys included in the National Statistical Programme:
· Water supply, sewage and treatment - exhaustive survey. Data is collected from public water supply companies dealing with water collection, treatment, water supply and wastewater collection, discharge and treatment (water supply companies/UWWTP operators and irrigation systems).
· Water use - partial statistical survey focused on the larger water users. Criterion for coverage is the usage by enterprises of more than 36 thousand m3 of water annually for their activity. Enterprises below this criterion submit data on a voluntary basis. The survey of enterprises for hydroelectricity generation is exhaustive.
|Statistical concepts and definitions|
Water abstraction is divided into two categories - fresh and non-fresh water.
Fresh water: to surface water are allocated water on land (including the
Non-fresh water: are the sea and transitional waters. Since 2006 only sea water is included to non-fresh waters as according to the Classification for characterization of surface types' water bodies under the Water Framework Directive, transitional waters are not identified in
Water supply categories: Self-supply; Public water supply, Irrigation systems and other supply: (raw and reused/ wastewater received from other users).
Gross water abstraction is a sum of fresh water abstracted for distribution and self-supply of the enterprises. Water for production of hydroelectricity is a separate category and not included in the total abstraction. Self-supply of households is not covered.
Returned water: The water abstracted from any fresh water source and discharged back into it without use (primarily at mining and quarrying, and construction activities).
Fresh water net abstraction: the fresh water gross abstraction minus returned water.
Water used is a sum of water used by the categories of supply:
Water losses are formed from physical losses in the transport of water, irregular use, errors in measurements, etc. The volume of losses is aggregated for a group of operators in order to avoid the double counting. On RBD level water losses are calculated using a regionalizing factor "supplied water". It is assumed that water losses in self water supply are negligible.
Water generated from point sources: water, which after use leaves the place of use and is discharged into the public sewerage and water bodies. Data is collected through statistical survey on water use, covering more significant water users. Wastewater generated by the households is result from data reported by public water works and estimation. Two categories are distinguished - wastewater and water from cooling processes.
Wastewater discharged after treatment: Amount of wastewater discharged from wastewater treatment plants of the enterprises and UWWTP (according to the latest level of treatment). Wastewater of households with own/independent treatment is also considered as treated.
Water discharged into water bodies: a sum of water discharged by the surveyed enterprises, public sewerage/UWWTP and households with own/independent treatment.
Collected wastewater into public sewerage: calculations are based on data reported by the Public water works and estimations. The quantities from non-point sources (rain-off, drainage and other unallocated water) are also included.
Urban wastewater treatment plants (UWWTP): covered are all operating plants treating wastewater from settlements. Wastewater treatment plants at enterprises, hotels, etc. are referred to a separate category. Design capacity BOD5 (tons O2/day): maximum flows and loads of the influent the facilities are designed for, which conform with the fixed standards.
Public water supply and sewage network - data refer to the network operated by public water supply operators. Also is included the sewage network of municipalities with organized discharge of wastewater in urban wastewater treatment plants.
Population connected to public water supply/public sewerage and UWWTP - data are the result of survey "Water supply and sewage". It is possible to overestimate the population in settlements with partially build water supply /sewage network, at which only a part of households is connected. Population with independent own wastewater treatment (via septic tanks, cesspools, etc.) is calculated as a difference between the total population and population with a public sewage system.
Measuring water qualities: they are reported by the respondents through water meters, and in case of their absence - using the capacity of the pumps, multiplied by the time of their work; energy consumption of pumps, specific factor, etc.
Legal entity which corresponding the criteria for coverage of statistical surveys on water.
· Suppliers of water - water supply and sewage operators and irrigation systems;
· Operators of urban wastewater treatment plants;
· Water users according to the criteria for coverage of ‘Survey on water use’;
· Producers of hydroelectricity.
Territory of the
2010 - 2019
The selection of the base period is determined in accordance with the research objectives and tasks.
Specialized statistical surveys - see section 3.3
|Frequency of data collection|
Data are collected through statistical questionnaires in electronic and paper format. Respondents provide the completed questionnaires in regional statistical offices, after which electronic forms are sent to the NSI central office.
Validation of primary data is an mandatory stage of the production of statistical
To improve the quality of data are applied a series of statistical procedures - from data collection to data validation. To determine the coverage of the statistical aggregations are used statistical data from other surveys and administrative data. The methodology is developed in accordance with the requirements for comparability, tools for data collection and procedures of verification and controls are improved.
Main users of statistical information of the survey are public institutions, local authorities, companies and others.
No information. Research on consumer satisfaction is not conducted.
|Data completeness - rate|
|Accuracy and reliability|
|Sampling errors - indicators|
There is no coverage error
|Over-coverage - rate|
There is no over-coverage in the data
|Common units - proportion|
|Non response error|
The data are validated for this type of error. Where direct measurment cannot be applied estimates are made.
|Unit non-response - rate|
The unit non-responce rate is near to zero if necessary, estimates are applied.
|Item non-response - rate|
The item non-responce rate is near to zero if neccessary, estimates are applied.
Well-established procedures and verification of all calculations are applied which minimizes the risk of type of error.
|Imputation - rate|
|Model assumption error|
|Data revision - policy|
|Data revision - practice|
The identified errors at registration in the primary data and revisions are regularly recorded and stored.
|Data revision - average size|
|Timeliness and punctuality|
The data are published according to the terms in the Release Calendar presenting the results of the statistical surveys carried out by the National Statistical Institute.
|Time lag - first results|
|Time lag - final results|
All publications are published timely, according to the Release Calendar presenting the results of the statistical surveys carried out by the National Statistical Institute.
|Punctuality - delivery and publication|
|Coherence and comparability|
|Comparability - geographical|
|Asymmetry for mirror flows statistics - coefficient|
|Comparability - over time|
Time series by key indicators at national level are available since 1990.
|Length of comparable time series|
|Coherence - cross domain|
Partial, regarding some indicators.
|Coherence - sub annual and annual statistics|
|Coherence - National Accounts|
|Coherence - internal|
|Accessibility and clarity|
Annual, according to the Release Calendar presenting the results of the statistical surveys carried out by the National Statistical Institute.
· Statistical Yearbook;
· Statistical Reference Book;
· Regional publication;
· Publications and reports to Eurostat.
Comprehensive data of water statistics are available to all users of the NSI website under the heading Environment: https://www.nsi.bg/en/node/5132
|Data tables - consultations|
Information service on request, according to the Rules for the dissemination of statistical products and services.
|Metadata - consultations|
|Documentation on methodology|
Data Collection Manual for the OECD/Eurostat Joint Questionnaire “Inland water” Ver. 4.0.
|Metadata completeness – rate|
|Cost and burden|
|Confidentiality - policy|
· Law on Statistics;
· Regulation (EC) No 223/2009 on European statistics (recital 24 and Article 20(4)) of 11 March 2009 (OJ L 87, p. 164), stipulates the need to establish common principles and guidelines ensuring the confidentiality of data used for the production of European statistics and the access to those confidential data.
|Confidentiality – data treatment|
Individual data are not published in accordance with article 25 of the Law on Statistics. The publishing of individual data can be performed only in accordance with article 26 of the same law.