Environment at a Glance Indicators

Freshwater resources

Context

Freshwater resources are essential for environmental sustainability, economic development and social well-being. Their distribution varies widely among and within countries. The availability and quality of water are affected by multiple pressures, including abstractions and use - such as for public supply, irrigation, industrial processes or cooling of electric power plants – and pollution loads from agriculture, industry and households. Climate change and changes in weather patterns further exacerbate these challenges.

Human activity and infrastructure developments can affect the natural integrity of rivers, lake, aquifers and wetlands. If a significant share of a country’s water comes from transboundary rivers, tensions between countries can arise. In arid regions, limited freshwater availability, can lead to overuse beyond sustainable levels, putting ecosystems and livelihoods at risk.

One of the most important impacts of climate change is the disruption of the water cycle. It is accelerating, leading to more frequent and severe floods, droughts and storms. These events carry high economic and social costs, and worsen water quality (e.g. pollution of water sources after floodings or landslides).

These climate-related impacts are further intensified by water overexploitation, pollution and inefficient use. Over-abstraction of water can reduce river flows, deplete groundwater reserves and degrade water quality, cause wetlands loss and desertification, and threaten food security and economic production.

Policy challenges

The main challenge is to ensure sustainable management of water resources and services to maintain adequate supplies of freshwater of suitable quality for human use and well-being, and support aquatic and other ecosystems, economic activities, and address threats associated with droughts and floods resulting from climate change. This requires an integrated approach for the management of water and water-related ecosystems and effective co-operation between countries in transboundary river basins.

• Water quantity is best managed through a combination of policies that manage demand for water, promote water use efficiency, and allocate water where it is most needed.

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

• Water risks and disasters are best managed in a cooperative way through risk assessments and a mix of prevention and mitigation measures. Policy coherence across climate change adaptation, water management, land management, spatial planning, biodiversity protection and disaster risk reduction is crucial.

Policy instruments such as pricing of water and of water-related services are important for managing demand and promoting efficient use of water, for allocating water among competing uses and for generating finance to invest in water-related infrastructure and services. At the same time, the affordability of water for low-income households must be taken into account. Water pricing can also be complemented by a range of other instruments and measures, including abstraction and pollution charges, tradable water permits, smart metering, water reuse and innovation.

Measuring progress and performance

Environmental performance for water resources can be assessed against domestic objectives and international commitments. The 2030 Agenda for Sustainable Development (New York, September 2015) explicitly considers preserving water resources and promoting wastewater management for all under Goal 6 “Ensure availability and sustainable management of water and sanitation for all”.

At the national level countries have set receiving water standards, effluent limits, pollution load reduction targets and established water permits. Key international agreements and legislation include 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.

However, the information available to evaluate countries’ progress with water resource management remains insufficient to carry out a thorough analysis.

Indicator groups

• Water abstractions: water stress, total water abstractions (levels and intensities), water abstractions for public supply and water abstractions for irrigation.

• Wastewater treatment: sewage treatment connection rates

Water abstractions

Key messages

• Water resources face increasing pressure from economic activity and population growth, intensifying competition for access, especially in arid and semi-arid regions.

• Although water stress has diminished in many OECD countries since 2000 due to improved management and technologies, overall progress has been relatively modest. A few countries experience increasing stress levels.

• On average across the OECD, water abstractions have decoupled from economic and population growth, with per person abstractions declining since 2000. The highest per person abstractions are found in the OECD America region, followed by the OECD Asia-Oceania region and the OECD Europe region.

• Abstractions for irrigation have declined in many OECD countries since 2000 but have recently increased in others.

Main trends and recent developments

Pressures on water resources continue to increase, with competition for access to water increasing, due to economic and population growth.

Water stress varies widely across and within countries. It has diminished in some OECD countries such as Belgium and Estonia since 2000. By contrast, Korea, Spain and Türkiye experience medium water stress while Israel experiences high and increasing 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, others allocate it mostly to agriculture including Greece, Japan, Mexico, Spain, Türkiye, or to electricity cooling such as Estonia, France, Slovenia and Poland. Extreme climate 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 the Netherlands and Türkiye, it has recently increased.

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. 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 the use of water resources 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

• Since 2000, access to wastewater treatment has improved in OECD countries. In about half of the countries, more than 80% of their population is connected to at least secondary treatment facilities.

• Connection rates and treatment levels still vary widely. Some countries have over 20% of the population unconnected to public systems, particularly in small or remote communities.

• Ageing treatment systems and networks require significant investment and upgrading, particularly in countries facing capacity or technology gaps.

• Growing attention is needed to address emerging pollutants like pharmaceuticals, pesticides and microplastics, and to expand advanced treatment 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.

About 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.

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

• In 2023, freshwater-related taxes raised USD 1.7 billion across OECD countries, representing only about 0.01% of total tax revenue, compared to 0.02% in the early 2000s.

• Most of this revenue came from resource and energy taxes, transport and pollution tax bases contributed negligible amounts.

Main trends and recent developments

In OECD countries, freshwater-related taxes raised USD 1.7 billion in 2023, representing a very small share of total tax revenue (0.01%), compared to 0.02% in the early 2000s. Within environmentally related tax revenue, resource taxes accounted for the largest share (0.18%), followed by energy taxes (0.02%), 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 generated 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. The PINE database contains quantitative and qualitative information on over 4600 policy instruments in more than 145 countries worldwide. Policy instruments are tagged into 22 environmental domains that represent the focal issues (environmental externalities). Instruments can have both a direct and an indirect effect on several environmental domains; however, only the domain to which the instrument has a direct effect is considered. For more details, see the methodology for Environmental domain tagging the OECD PINE database.

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 (2025), Environmental Performance of Agriculture in OECD Countries: Key Trends and Insights, OECD Publishing, Paris, https://doi.org/10.1787/2679ba38-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), http://oe.cd/pinedatabase.

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 (2016), A Snapshot of the World’s Water Quality: Towards a global assessment, United Nations Environment Programme, Nairobi, Kenya, https://uneplive.unep.org/media/docs/assessments/unep_wwqa_report_web.pdf.

UNEP (2019), Global Environment Outlook 6, Chapter 9: Freshwater https://wedocs.unep.org/bitstream/handle/20.500.11822/27656/GEO6_CH9.pdf?sequence=1&isAllowed=y.

UNESCO WWAP (2019), The United Nations world water development report 2019: Leaving no one behind, UNESCO, Paris, https://unesdoc.unesco.org/ark:/48223/pf0000367306.