Environment Agency, Ofwat, Defra and Met Office data: sewage, water, air and climate
The Environment Agency is the public body that regulates pollution, water quality and flood risk in England, and it publishes the official storm overflow spill data, river and bathing water results, and live flood information. Ofwat regulates water company prices and performance in England and Wales, Defra publishes air quality and waste statistics, and the Met Office keeps the UK's official weather and climate records. Fact-checkers use them together to test claims about sewage, rivers, water bills, pollution, flooding and record temperatures.
What it publishes
- Event Duration Monitoring (EDM) annual returns: how many times and for how many hours each storm overflow in England discharged, by water company, from 2016 onwards.
- Water quality sample results from rivers, lakes, estuaries, groundwater and the sea, by sampling point, through the Water Quality Explorer, downloads and an open API.
- Water Framework Directive classifications of ecological and chemical status for every river and lake water body, through the Catchment Data Explorer.
- Bathing water classifications and in-season sample results and pollution risk forecasts for every designated bathing water in England (Swimfo).
- Live flood warnings and alerts, and river, sea and groundwater levels and rainfall readings, with a free real-time flood monitoring API.
- An annual Environmental Performance Assessment rating England's nine water and sewerage companies from one to four stars.
- From Ofwat: price review decisions on bills, and the annual Water company performance report covering leakage, supply interruptions, sewer flooding and customer service.
- From Defra and the Met Office: daily air quality forecasts and measurements (UK-AIR), annual air quality and waste statistics, and national temperature, rainfall and sunshine records.
Key datasets
- Event Duration Monitoring: storm overflows annual returns
Spill counts and durations for every monitored storm overflow in England by company and site, one spreadsheet per year from 2020 plus a 2016 onwards trend table. Revised when companies correct data.
- Water Quality Explorer
Sample results for chemical and biological measures at tens of thousands of sampling points in England, replacing the old Water Quality Archive. Map view, bulk downloads and API.
- Catchment Data Explorer
Ecological and chemical status classifications for each river, lake, estuary, coastal and groundwater body in England, with the reasons for not achieving good status.
- Swimfo: bathing water quality
Annual classifications (excellent, good, sufficient, poor) and in-season results for designated bathing waters in England.
- Water and sewerage companies: environmental performance report
The Environment Agency's star ratings for England's nine water and sewerage companies, with company data reports on pollution incidents and permit compliance.
- Ofwat water company performance report
Ofwat's comparison of the 16 largest water companies in England and Wales on service and environmental metrics, with machine-readable tables. The site blocks automated requests but opens in a browser.
- Check for flooding
Current flood alerts and warnings for England, with river, sea and groundwater level readings.
- Defra UK-AIR and Check air quality
Measured pollutant concentrations from the national monitoring network and the Daily Air Quality Index forecast. Content is moving to the Check air quality and Get air pollution data services.
- Air quality statistics
Annual concentrations of nitrogen dioxide, particulate matter and ozone in the UK, and days of moderate or higher pollution.
- Met Office UK climate extremes
Official national records for maximum and minimum temperature, rainfall, sunshine and gusts, by country and month.
- Met Office UK and regional series
Monthly, seasonal and annual temperature, rainfall and sunshine for the UK, its countries and regions, from 1884 for temperature and 1836 for rainfall.
- Local authority collected waste statistics
England's household recycling rate and council-level waste and recycling figures.
APIs and downloads
- Flood monitoring APIReal-time JSON or CSV for flood warnings, water levels, flows and rainfall in England. No key needed; open licence.
- Hydrology data APIQuality-checked historical river level, flow, rainfall and groundwater readings. JSON and CSV, no key.
- Water Quality Explorer APIAPI documentation for sampling points and observations, with bulk downloads from the same site. No key needed.
- Environment Agency data catalogueDefra's data services platform with datasets in CSV, spreadsheet and GIS formats, including the EDM returns.
- Get air pollution dataDownload measured air pollution data from monitoring sites. Coverage is still being expanded; older data remain on UK-AIR's data pages.
- Met Office HadUK-GridGridded UK climate observations in NetCDF, downloadable free through the CEDA archive after registration.
When it publishes
Official statistics from Defra and the Environment Agency are pre-announced on the GOV.UK release calendar and published at 9:30am. Storm overflow EDM data usually appear in late March; bathing water classifications in November; the Environment Agency's environmental performance report and Ofwat's performance report in the autumn. Live flood and air quality data have no release schedule.
How to use it to check a claim
- For a sewage claim, find the year and company, then open that year's EDM spreadsheet and the summary table rather than relying on a press release headline.
- Note whether a figure is a count of spills or of hours spilled; both are in the EDM data and they can move in different directions.
- Check rainfall for the same year in the Met Office series before reading a rise or fall in spills as a change in company behaviour.
- For 'rivers in good health' claims, check in the Catchment Data Explorer whether the figure is ecological status, chemical status or overall status, and which classification year.
- For water company rankings, say whether you are using Ofwat's report (service and finance, England and Wales) or the Environment Agency's star ratings (environment, England only).
- For air pollution, separate emissions statistics from concentration statistics, and check whether a site is a roadside or background monitor.
- For record temperatures, use only values the Met Office lists as verified records; on-the-day readings are provisional.
Common mistakes
- Treating a spill count as a measure of how much sewage was released: EDM records duration, not volume.
- Comparing spill totals from the early years with recent ones, when far fewer overflows were monitored.
- Reading a bathing water classification as today's water quality; it is based on several years of samples.
- Mixing up the Environment Agency (England), Natural Resources Wales and SEPA (Scotland), which publish separate figures on different methods.
- Quoting Ofwat average bill changes as what every household will pay, when they are averages before inflation that vary by company.
Where can I download storm overflow spill data?
The Environment Agency's Event Duration Monitoring annual returns are on data.gov.uk and the Defra data services platform. Each yearly spreadsheet has a sheet per water and sewerage company listing every overflow, its spill count and total hours, plus summary tables. A separate file gives national trends from 2016. The data are revised if companies correct their returns.
Is Environment Agency data free to use?
Yes. Most Environment Agency datasets, including the flood monitoring API, water quality data and EDM returns, are published under the Open Government Licence, which lets anyone reuse them with attribution. The real-time APIs do not need a key. A few datasets that include third-party data carry their own conditions, set out on each dataset page.
What is the difference between Ofwat and the Environment Agency?
Ofwat is the economic regulator for water companies in England and Wales: it sets bills and service targets. The Environment Agency is the environmental regulator in England: it permits and prosecutes pollution, including from storm overflows and sewage works. Both publish annual company performance reports, but they measure different things.
Where are Scotland's and Wales's environmental data?
SEPA publishes Scotland's water classifications, bathing water results and flood warnings, and Natural Resources Wales does the same for Wales. Scottish Water and Welsh Water publish their own overflow data. These use their own methods, so figures are not always directly comparable with England's.
Questions answered using this source
- What is the highest temperature ever recorded in the UK?
- How do I make a Freedom of Information request?
- How do I check flood warnings and flood risk for my area?
- How do I check air quality in my area?
- Is the UK in drought?
- What does Ofwat do?
- How do I check water quality in my area?
- How much are water bills going up?
- What are UK greenhouse gas emissions?
- Where can I find official UK fuel prices?
- How much rain does the UK get a year?
- How much has the UK warmed?
Links checked 2026-10-13. This page describes what the source publishes and gives no verdict on any claim.