1.1. Contact organisation
Statistical Office of the European Commission (Eurostat)
1.2. Contact organisation unit
Unit E2: Environmental statistics and accounts; sustainable development
1.3. Contact name
Confidential because of GDPR
1.4. Contact person function
Confidential because of GDPR
1.5. Contact mail address
e-mail contact : ESTAT-SDG-MONITORING@ec.europa.eu
1.6. Contact email address
Confidential because of GDPR
1.7. Contact phone number
Confidential because of GDPR
1.8. Contact fax number
Confidential because of GDPR
2.1. Metadata last certified
20 January 2026
2.2. Metadata last posted
20 January 2026
2.3. Metadata last update
20 January 2026
The indicator is part of the EU Sustainable Development Goals (SDG) indicator set. It is used to monitor progress towards SDG 6 on clean water and sanitation, which is embedded in the European Commission’s 2024-2029 priorities under 'Sustaining our quality of life: Food security, water and nature'.
Among other things, SDG 6 calls for ensuring universal access to safe and affordable drinking water, sanitation and hygiene, and ending open defecation. It also aims at improving water quality and water-use efficiency and encouraging sustainable abstractions and supply of freshwater. SDG 15 seeks to protect, restore and promote the conservation and sustainable use of terrestrial, inland water and mountain ecosystems.
This indicator can be considered similar to global SDG indicator 6.3.2 "Proportion of bodies of water with good ambient water quality".
Protection of water resources, water ecosystems and of drinking and bathing water is at the cornerstone of EU environmental policy. EU water policy provides a framework to comprehensively address water protection and for achieving good status for inland surface waters, transitional waters, coastal waters and groundwater. The Water Framework Directive is the main European legislation aiming to prevent water pollution and the EU Biodiversity Strategy for 2030 supports the implementation of the Water Framework Directive’s objective by requiring Member States to restore freshwater ecosystems.
The 8th Environment Action Programme sets the environmental policy agenda for the years from 2021 to 2030 and explicitly mentions water-related issues in two of its six priority objectives. These two objectives are: (1) pursuing a zero-pollution ambition for a toxic free-environment, including for air, water and soil and protecting the health and well-being of citizens from environment-related risks and impacts; and (2) protecting, preserving and restoring biodiversity and enhancing natural capital, notably air, water, soil, and forest, freshwater, wetland and marine ecosystems.
4.1. Data description
Biochemical oxygen demand (BOD) is used to measure water quality. It refers to the amount of oxygen required by aerobic microorganisms to decompose organic substances in a water sample over a period of five days in the dark at 20°C (BOD5), measured as milligrams per litre (mg O2/L) and weighted by the number of measuring stations. High values of BOD5 are usually a sign of organic pollution, which affects the water quality. The cleanest rivers have BOD5 values of less than 1 mg O2/L, moderately and heavily polluted rivers show values ranging from 2 to 8 mg O2/L.
Data presented for this indicator stem from the European Environment Agency (EEA) Waterbase database on the status and quality of Europe's rivers.
For time series analyses, only complete series after inter/extrapolation are used. As monitoring sites change over time, this leads to a recalculation of the whole time series with each update. Complete time series for 2007 – 2023 are based on a total of 2899 monitoring sites (2841 within 19 EU Member States) distributed over the following countries (number of monitoring sites in parentheses): Belgium (81), Bulgaria (67), Czechia (138), Germany (132), Estonia (49), Ireland (173), Spain (822), Croatia (21), Italy (801), Cyprus (18), Latvia (20), Lithuania (54), Austria (62), Poland (174), Portugal (77), Romania (93), Slovenia (18), Slovakia (35), Finland (6), Serbia (34) and Kosovo* (24).
The aggregate for EU_V includes data for 19 EU Member States (Belgium, Bulgaria, Czechia, Germany, Estonia, Ireland, Spain, Croatia, Italy, Cyprus, Latvia, Lithuania, Austria, Poland, Portugal, Romania, Slovenia, Slovakia and Finland).
Kosovo*: This designation is without prejudice to positions on status, and is in line with UNSCR 1244/1999 and the ICJ Opinion on the Kosovo Declaration of Independence.
4.2. Unit of measure
mg O2 per litre
4.3. Reference Period
Calendar year.
4.4. Accuracy - overall
The time series on Biochemical oxygen demand in rivers is considered robust for long-term trends due to extensive quality control and consistent methodology using generalized additive models (GAM) for data gap-filling. Precision is impacted by variations in national data reporting and water body delineation (spatial data). The time series are based on data collection methods and aggregation techniques, which include using annual averages that may not capture extreme events, varying sampling frequencies, data set gaps filled by inter/extrapolation, changes in monitoring sites requiring recalculation, and the conversion of BOD7 to BOD5 data.
4.5. Source data
4.5.1. Source data - Organisation
EEA (Waterbase database)
4.5.2. Source data - Comment
Data source: EEA Waterbase database on Water Quality ICM.
Data provider: European Environment Agency (EEA)
5.1. Frequency of dissemination
5.1.1. Frequency of dissemination - Grade
Every year5.1.2. Frequency of dissemination - Comment
Indicator is updated annually.
5.2. Timeliness
5.2.1. Timeliness - Grade
T+2 years5.2.2. Timeliness - Comment
New data points are disseminated within two years after the reference year.
6.1. Reference area
6.1.1. Reference Area - Grade
< 75% EU MS or no EU aggregate6.1.2. Reference Area - Comment
Data are presented for all EU Member States except Denmark, Greece, France, Luxembourg, Hungary, Malta, Netherlands and Sweden.
6.2. Comparability - geographical
6.2.1. Comparability - geographical - Grade
< 75% EU MS6.2.2. Comparability - geographical - Comment
Data comparability between EU Member States respectively other presented countries is limited due to monitoring programs, including methodology and spatio-temporal sampling density, varying from country to country. The reporting is voluntary so countries do not necessarily report all available data.
6.3. Coverage - Time
6.3.1. Time Coverage - Grade
> 10 years6.3.2. Time Coverage - Comment
Presented time series (aggregate changing according to the context EU_V) starts in 2007.
6.4. Comparability - over time
6.4.1. Comparability - over time - Grade
> 4 data points6.4.2. Comparability - over time - Comment
Length of comparable time series without methodological break is longer than 4 data points.
Only complete series after inter/extrapolation are presented.
7.1. Dissemination format - Publications
Analysis of indicator is presented in Eurostat's annual monitoring report on Sustainable development in the EU (progress towards SDGs in an EU context).
7.2. Dissemination format - online database
See table sdg_06_30
7.3. Dissemination format - other
Eurostat dedicated section on SDGs: Eurostat overview.
Copyrights: Eurostat Copyright/Licence Policy is applicable.
