Environment at a Glance Indicators

Freshwater resources

Context

Freshwater resources are essential for human well-being, ecosystems and economic activity. However, the availability and quality of water vary widely across and within countries. Pressures arise from water abstractions and use – such as for public supply, irrigation, industry and energy production – and pollution originating from agriculture, industry and households. Infrastructure development and land-use change can further alter the ecological integrity of rivers, lakes, aquifers and wetlands.

Changing weather patterns are intensifying these pressures by disrupting the water cycle and increasing the frequency and severity of droughts, floods and other extreme events. These changes can reduce local and temporal water availability, worsen water quality and increase competition among users. Over-abstraction and pollution can further reduce river flows, deplete groundwater reserves, degrade wetlands and ecosystems, and threaten food security and economic activity.

Water challenges are often highly local and can also be transboundary. Effective management therefore requires taking into account spatial and seasonal variation in water availability and strengthening co-operation where water resources are shared across borders.

Policy challenges

The main challenge is to ensure sustainable management of water resources and services by maintaining adequate supplies of freshwater of suitable quality for human use, ecosystems and economic activities while strengthening resilience to droughts, floods and other severe weather risks. This requires integrated management of water and land resources and water-related ecosystems, supported by effective co-operation in transboundary watersheds and river basins. Key areas include:

• Water quantity is best managed through a combination of policies that manage demand, improve water use and reuse efficiency, and support the efficient allocation of water among competing uses.

• Water quality management requires preventing and reducing pollution from all sources, including through a systematic integration of water quality considerations into agricultural and other sectoral policies, as well as appropriate wastewater treatment. Both polluters and users should be held accountable.

• Water risks and disasters are best managed in a co-operative way through risk assessments and a mix of prevention and mitigation measures. Policy coherence across water management, land management, spatial planning, biodiversity protection, adaptation to changing weather conditions, and disaster risk reduction is crucial.

Policy instruments can support these objectives. Water pricing, abstraction and pollution charges, tradable water permits and smart metering, are important for managing demand, improve allocation and mobilise finance for water infrastructure and services. Their design should consider the affordability and distributional impacts.

Measuring progress and performance

Progress in sustainable water management can be assessed against domestic objectives and international commitments.

National frameworks commonly include water quality standards, abstraction permits, effluent limits and pollution reduction targets. International and regional agreements and frameworks include the OECD Council Recommendation on Water, the OSPAR Convention on the Protection of the North-East Atlantic Marine Environment, the International Joint Commission Agreement on Great Lakes Water Quality in North America and the EU Water Directives.

The indicators presented here focus on two core dimensions.

Indicator groups

• Water abstractions: water stress, total freshwater abstractions, abstractions for public supply and for irrigation

• Wastewater treatment: population connection rates and levels of treatment.

These indicators provide only a partial picture of water resource management. Important dimensions such as seasonal and basin-level scarcity, aquifer depletion ecological status, groundwater depletion, water quality and exposure to water-related hazards are not fully captured by the available internationally comparable data.

Water abstractions

Key messages

• Water pressures remain significant across OECD countries especially in arid and semi-arid regions, where competition among users is greatest.

• Water stress has diminished in a number of OECD countries since 2000 but progress has been uneven and some countries continue to experience medium to high levels of stress.

• Freshwater abstractions per person have generally declined across the OECD since 2000, indicating some decoupling from economic and population growth.

• Irrigation remains a major use of freshwater in many OECD countries and abstraction trends reflect differences in climate, agricultural structure and water management practices.

Main trends and recent developments

Pressures on water resources continue to increase, with increasing competition for access to water, especially due to the disruption of the water cycle and the increase of extreme weather events.

Water stress varies widely across and within countries. It has diminished in some OECD countries such as Belgium and Estonia since 2000. By contrast, countries such as Korea, Spain and Türkiye still experience medium water stress, while Israel experiences high water stress. In a few countries, such as Iceland, water resources are abundant and population density is low. However, most countries face seasonal or local water shortages, and several have large arid or semi-arid regions where water availability constraints economic development and human well-being. The water stress indicator does not capture environmental flow requirements.

Water abstractions have on average become increasingly decoupled from economic and population growth in OECD countries, with per person abstractions declining since 2000. However, results vary within and among countries, and available information on water resources remains insufficient for a comprehensive analysis. The highest per person abstractions are found in the OECD America region, followed by the OECD Asia-Oceania region and the OECD Europe region. Uses of water differ depending on economic structure and agricultural practices. While some countries devote over half of abstractions to public supply such as Luxembourg and Latvia, others allocate it mostly to agriculture including Greece, Japan, Mexico, Spain and Türkiye, or to electricity cooling such as Estonia, France, Slovenia and Poland. Extreme weather events also affect abstractions, for example by reducing electricity production during drought.

Irrigation abstractions have been declining since 2000 in some OECD countries, albeit at different rates. In some countries, such as Türkiye, it has increased in recent years.

Indicators

Comparability and interpretation

These indicators give insights into quantitative aspects of water resources but may hide important variations at the subnational (e.g. river basin) level, particularly in countries with extensive arid and semi-arid regions. Additionally, these indicators do not capture seasonal scarcity or infrastructure constraints affecting access to water. Data on abstractions refer to gross volumes, i.e. not accounting for returns to the environment and losses before use, for which there is very little data. Thus, water available for use is only a fraction of gross abstractions. Information on supply, use and returns by sector can be derived from water accounts and statistics. This information is available for many OECD countries but is often incomplete. The definitions and estimation methods may vary considerably from country to country and over time. In general, data availability and quality are better for water abstractions for public supply than for other sectors. For some countries, the data refer to water permits and not to actual abstractions.

For further details see the metadata in the source databases.

Wastewater treatment

Key messages

• Wastewater treatment coverage has improved across OECD countries since 2000 and in almost half of the countries, more than 80% of the population is connected to secondary or tertiary treatment.

• Significant differences remain in both connection rates and treatment levels, reflecting geography, settlement patterns, infrastructure and institutional capacity. Some countries have about 20% of their population unconnected to public systems, particularly in small or remote communities.

• Many countries now face the challenge of renewing ageing treatment plants and networks, while extending effective treatment to small and remote communities.

• Addressing pollutants such as pharmaceuticals, pesticides, microplastics and persistent chemicals require more advanced treatment and stronger pollution prevention measures where economically and environmentally justified.

Main trends and recent developments

Access to wastewater treatment has improved in OECD countries since 2000. However, connection rates to public wastewater treatment plants and the level of treatment continue to vary widely.

Almost half of OECD countries have over 80% of their population connected to a sewage treatment plant with secondary or tertiary treatment. Some countries still have more than 20% of their population not connected to a public wastewater treatment system. Countries that have reached the economic and technical limits in terms of sewage connection, must find means to serve small, isolated settlements, including through effective independent on-site treatment systems. Lower public wastewater connection rates may partly reflect reliance on decentralised or on-site treatment systems in rural and remote areas.

In many countries, the main challenge is to ensure proper financing for renewing and upgrading existing and often ageing networks and treatment plants. More efforts need to be made to increase advanced wastewater treatment where economically viable and environmentally justified, and to cope with new and emerging pollutants such as pharmaceutical residues or microplastics.

Indicators

Comparability and interpretation

The data show total connection rates and the extent of secondary and/or tertiary sewage treatment, providing an indication of efforts to reduce pollution loads. These indicators should be read alongside information on public wastewater treatment expenditure. Connection rate should not be interpreted as requiring 100% coverage: the optimal rate varies across countries depending on geography and settlement patterns.

Data on the share of the population connected to wastewater treatment plants are available for most OECD countries. In some cases, data are reported as wastewater treated in population equivalents (the pollution load produced within 24 hours by industrial facilities and services compared with the average load from one person). Such measures are not fully comparable across countries. Information on the level of treatment also remains partial and many figures are based on estimates.

For further details, see the metadata in the source databases.

Taxes relevant for water resources

Key messages

• Taxes relevant to freshwater management raise only a very small share of total tax revenue across OECD countries, amounting to USD 2.2 billion in 2024.

• Most of freshwater-related tax revenue came from resource and energy taxes, while transport and pollution tax bases contributed negligible amounts.

• Revenue figures provide only a partial view of economic instruments for water management, as important instruments such as water tariffs, abstraction charges, wastewater fees and other user charges may not be captured in environmentally related tax revenue statistics.

Main trends and recent developments

In OECD countries, freshwater-related taxes raised USD 2.2 billion in 2024, representing a very small share of total tax revenue (0.01%), compared to 0.02% in the early 2000s. Because tax rates are usually defined in physical units (e.g. per litre of fuel) and are set in nominal terms, they tend to decrease in real value over time unless adjusted for inflation. Without indexation or adjustment, environmentally related taxes risk losing effectiveness over time. As a share of total environmentally related tax revenue, freshwater-related taxes make up 0.27%, with resource taxes accounting for the largest share (0.24%), followed by energy taxes (0.03%), while transport and pollution tax contributed negligible amounts.

Indicators

Comparability and interpretation

To assess the “environmental friendliness” of tax systems, indicators on environmentally related taxes should be complemented with information describing the economic and taxation structure of each country. Moreover, some environmentally related taxes can have important environmental impacts even if they raise little (or no) revenue. In addition, revenue from fees and charges, and from royalties related to resource management, is not included.

Comparisons of ERTRs in OECD countries provide a useful starting point for analysing the impact of environmental taxation, however, comparing only the level of revenue does not provide the full picture of a country’s environmental policy, as it does not provide information on the levels of tax rates, or the exemptions applied. Other parts of the OECD PINE database, including information on tax rates and exemptions, allows deeper assessment of the environmental impacts of these taxes. In addition, governments may choose to implement environmental policy using a range of other instruments, including fees and charges, expenditures (both direct and subsidies) and regulation, some of which are also detailed in the PINE database. The database also includes for information on the use of alternative instruments in countries.

For further details see the metadata in the source databases.

Glossary

Freshwater-related tax revenue refers to revenue from market-based instruments, such as taxes and tradable permits and offsets, which aims manage the demand for water quantity, promote water efficiency, and increase the stocks of freshwater. Examples include transport taxes to limit waterway usage, energy taxes on water used in electricity production, pollution taxes on wastewater discharges, resource taxes on groundwater extraction, and revenue from tradable water abstraction rights.

The information on taxes and the associated tax revenue is extracted from the OECD Policy Instruments for the Environment (PINE) database, which contains quantitative and qualitative information on over 4 800 policy instruments in more than 150 countries. Policy instruments are tagged into 22 environmental domains following the PINE environmental domain tagging methodology (Chhun, B., et al., 2024). Each instrument is tagged in every domain it directly targets; indirect or incidental effects are not considered. An instrument may therefore be tagged in more than one domain, for example both Freshwater and Water Pollution. For additional examples and details see Chhun, B., et al. (2024).

Gross water abstraction: Freshwater removed from any surface or groundwater source, either permanently or temporarily in a given period of time. Mine water and drainage water are included. Water used for hydroelectricity generation is an in-situ use and is excluded.

Intensity of use of freshwater resources (or water stress): Water stress is expressed as gross freshwater abstraction in % of total available renewable freshwater resources (including inflows/outflows from/to neighbouring countries) or in % of internal freshwater resources (i.e. precipitation - evapotranspiration). Water used for hydroelectricity generation (which is considered an in-situ use) is excluded. The following stress levels can be distinguished:

• Low (less than 10%): generally, there is no major stress on the available resources.

• Moderate (10% to 20%): indicates that water availability issues are becoming a constraint on development and significant investments are needed to provide adequate supplies.

• Medium-high (20% to 40%): implies the management of both supply and demand, and conflicts among competing uses need to be resolved.

• High (more than 40%): indicates serious scarcity, and usually shows unsustainable water use, which can become a limiting factor in social and economic development.

Freshwater resources: the data refer to long-term annual averages over a period of about 30 consecutive years. Water stress is best measured as % of total renewable freshwater resources (internal flow plus inflows/outflows from/to neighbouring countries). The indicator expressed as % of internal resources (flow) is added because for some countries data on inflows/outflows from/to neighbouring countries is not available.

Sewage treatment connection rates: The percentage of the national population connected to a wastewater treatment plant. “Connected” means actually connected to a wastewater treatment plant through a public sewage network. It does not take into account independent private facilities (e.g. septic tanks), used where public systems are not economic.

• Primary treatment: physical and/or chemical process involving settlement of suspended solids, or other process in which the Biochemical Oxygen Demand consumed by micro-organisms over a period of five days (BOD5) of the incoming wastewater is reduced by at least 20% before discharge and the total suspended solids are reduced by at least 50%.

• Secondary treatment: Treatment of wastewater by a process generally involving biological treatment with a secondary settlement or other process, resulting in a BOD removal of at least 70% and a chemical oxygen demand (COD) removal of at least 75%.

• Tertiary treatment: treatment (additional to secondary treatment) of nitrogen and/or phosphorous and/or any other pollutant affecting the quality or a specific use of water: microbiological pollution, colour etc. Minimum treatment efficiencies: organic pollution removal of at least 95% for BOD and 85% for COD, and at least one of the following: nitrogen removal of at least 70%; phosphorus removal of at least 80%, and microbiological removal achieving a faecal coliform density less than 1000 in 100 ml.

Data sources

OECD, "Water: Freshwater - abstractions", OECD Environment Statistics (database), http://data-explorer.oecd.org/s/1jy.

OECD, "Water: Wastewater - connection rates to treatment ", OECD Environment Statistics (database), http://data-explorer.oecd.org/s/1jz.

OECD (2026), Environmental Performance of Agriculture in OECD Countries: Key Trends and Insights, OECD Publishing, Paris, https://doi.org/10.1787/5bbd8f58-en.

OECD, "Environmental policy: Environmentally related tax revenue", OECD Environment Statistics (database), https://doi.org/10.1787/df563d69-en

OECD, “Policy Instruments for the Environment (PINE)” (database), https://oe.cd/pine.

References and further reading

Chhun, B., et al. (2024), "Environmental domain tagging in the OECD PINE database", OECD Environment Working Papers, No. 232, OECD Publishing, Paris, https://doi.org/10.1787/be984b0a-en.

OECD Data Explorer, Environment datasets.

OECD, “OECD work on water”, OECD.org, http://www.oecd.org/environment/resources/water.htm.

OECD Council Recommendation on Water, http://www.oecd.org/environment/resources/Council-Recommendation-on-water.pdf.

UNEP (2025) Global Environmental Outlook 7. A Future We Choose. Chapter 6 Freshwater Global Environment Outlook 7 | UNEP - UN Environment Programme.

UNESCO WWAP (2026), The United Nations World Water Development Report 2026, Water for all people: equal rights and opportunities, UNESCO Paris, https://doi.org/10.54679/NXCL7067.

WMO (2026), State of Global Water Resources 2025. World Meteorological Organisation, Geneva. https://library.wmo.int/records/item/69923-state-of-global-water-resources-2025