England River Water Quality Dataset

748,160

Observations

51,207

Series

5,214

Subjects

2000–2025

Period covered

What this looks like

One real series from the dataset, and real rows from the head of its published extract. Neither is a mock-up: the rows below are the same rows, unchanged, that are in the file you would download.

Nitrate as nitrogen at TILL AT DODDINGTON BRIDGE

The longest single series this dataset holds — 26 annual values, one of 51,207. The dataset is not this chart.

Drawn to show the shape and resolution of what the dataset contains, not to make a point about TILL AT DODDINGTON BRIDGE. Gaps are breaks, never interpolated.

View the data behind this chart

Underlying data
Period	TILL AT DODDINGTON BRIDGE (mg/l as N)
2000	2.44
2001	2.80
2002	2.48
2003	2.64
2004	2.38
2005	2.69
2006	2.19
2007	2.06
2008	1.79
2009	2.14
2010	2.32
2011	1.89
2012	1.80
2013	2.11
2014	1.91
2015	1.61
2016	1.80
2017	1.79
2018	2.03
2019	1.67
2020	1.98
2021	1.71
2022	1.67
2023	1.63
2024	1.84
2025	1.69

Sample rows

12 of 471,154 rows Taken from the start of observations-quality-uk-ea-wims.csv. These are sample rows, not the dataset.

Sample rows from the England River Water Quality Dataset extract
`metric_id`	`subject_id`	`subject_kind`	`value`	`censored`	`censor_operator`	`censor_threshold`	`censor_limit`	`censor_reported`	`unit`	`period_start`	`period_end`	`period_kind`	`basis`	`confidence`	`source_id`	`source_ref`	`qualifier`	`superseded`	`retrieved`
ammoniacal-nitrogen	wq-ea-AN-01M05	geography	0.085857	—	—	—	—	—	mg/l as N	2000-01-01	2000-12-31	year	aggregated	high	uk-ea-wims	EA Water Quality Archive determinand 0111 at AN-01M05	annual mean	—	2026-08-28
ammoniacal-nitrogen	wq-ea-AN-01M05	geography	0.187	—	—	—	—	—	mg/l as N	2001-01-01	2001-12-31	year	aggregated	high	uk-ea-wims	EA Water Quality Archive determinand 0111 at AN-01M05	annual mean	—	2026-08-28
ammoniacal-nitrogen	wq-ea-AN-01M05	geography	0.5705	—	—	—	—	—	mg/l as N	2002-01-01	2002-12-31	year	aggregated	high	uk-ea-wims	EA Water Quality Archive determinand 0111 at AN-01M05	annual mean	—	2026-08-28
ammoniacal-nitrogen	wq-ea-AN-01M05	geography	0.088727	—	—	—	—	—	mg/l as N	2003-01-01	2003-12-31	year	aggregated	high	uk-ea-wims	EA Water Quality Archive determinand 0111 at AN-01M05	annual mean	—	2026-08-28
ammoniacal-nitrogen	wq-ea-AN-01M05	geography	0.065625	—	—	—	—	—	mg/l as N	2004-01-01	2004-12-31	year	aggregated	high	uk-ea-wims	EA Water Quality Archive determinand 0111 at AN-01M05	annual mean	—	2026-08-28
ammoniacal-nitrogen	wq-ea-AN-01M05	geography	0.059	—	—	—	—	—	mg/l as N	2005-01-01	2005-12-31	year	aggregated	high	uk-ea-wims	EA Water Quality Archive determinand 0111 at AN-01M05	annual mean	—	2026-08-28
ammoniacal-nitrogen	wq-ea-AN-01M05	geography	0.044333	—	—	—	—	—	mg/l as N	2006-01-01	2006-12-31	year	aggregated	high	uk-ea-wims	EA Water Quality Archive determinand 0111 at AN-01M05	annual mean	—	2026-08-28
ammoniacal-nitrogen	wq-ea-AN-01M05	geography	0.0916	—	—	—	—	—	mg/l as N	2008-01-01	2008-12-31	year	aggregated	high	uk-ea-wims	EA Water Quality Archive determinand 0111 at AN-01M05	annual mean	—	2026-08-28
ammoniacal-nitrogen	wq-ea-AN-01M05	geography	0.073625	—	—	—	—	—	mg/l as N	2009-01-01	2009-12-31	year	aggregated	high	uk-ea-wims	EA Water Quality Archive determinand 0111 at AN-01M05	annual mean	—	2026-08-28
ammoniacal-nitrogen	wq-ea-AN-01M05	geography	0.262778	—	—	—	—	—	mg/l as N	2011-01-01	2011-12-31	year	aggregated	high	uk-ea-wims	EA Water Quality Archive determinand 0111 at AN-01M05	annual mean	—	2026-08-28
ammoniacal-nitrogen	wq-ea-AN-01M05	geography	0.115222	—	—	—	—	—	mg/l as N	2012-01-01	2012-12-31	year	aggregated	high	uk-ea-wims	EA Water Quality Archive determinand 0111 at AN-01M05	annual mean	—	2026-08-28
ammoniacal-nitrogen	wq-ea-AN-01M05	geography	0.0911	—	—	—	—	—	mg/l as N	2013-01-01	2013-12-31	year	aggregated	high	uk-ea-wims	EA Water Quality Archive determinand 0111 at AN-01M05	annual mean	—	2026-08-28

Download these rows as CSV — the same twelve, with the column header, for testing a loader before committing to the full file.

Methodology

Individual sample results are read from the Water Quality Archive and reduced to annual figures per monitoring point. Results the laboratory reported as below its detection limit are excluded from the mean rather than counted as their limit or as zero, and a year is published only where such results were fewer than half of it and the year met the sample floor set for that determinand. pH and turbidity are published as annual medians rather than means, for different reasons: the pH scale is logarithmic, so arithmetic averaging of it is not a valid operation, while turbidity is dominated by storms, and a mean would report a single spate as the year. Nutrients keep the basis the Environment Agency reports them on — nitrate as nitrogen, orthophosphate as phosphorus — in their own metrics, rather than being converted into the ionic basis used by drinking-water standards. Metals are taken as the dissolved fraction only: the archive also publishes total concentrations including particle-bound metal, a modelled bioavailable fraction, and dry-weight concentrations in riverbed sediment measured in milligrams per kilogram, and mixing those would combine quantities differing by three orders of magnitude. The minimum number of samples a year must contain before it is published varies by determinand, because sampling frequency does: nutrients are sampled monthly at most points and metals commonly quarterly, so requiring the nutrient threshold of everything would have discarded the entire metals record rather than publishing a coarser one. Every published series carries its sample count, its censored share and, where the laboratory’s detection limit moved across the record, a note saying so — a falling limit changes how many results are censored without the water changing.

What this dataset cannot tell you

Read before relying on these figures

The archive’s public interface begins in 2000. The large improvement in English river chemistry that followed the Urban Waste Water Treatment Directive largely predates this and is not visible here.
Sampling frequency has fallen at many points over the period, so a national average computed year by year would partly measure which points were still being sampled rather than what was in the rivers.
These are river samples, not treated drinking water. Comparison against a drinking-water standard is a comparison between different things.
A concentration is specific to the point and the moment of sampling, and varies strongly with river flow.
Metals are the dissolved fraction. Environmental quality standards for several of them are written against a bioavailable fraction modelled from water chemistry, which is a different number and is not held, so these series describe exposure rather than compliance.
Metal series are heavily censored: in clean rivers most results sit below the laboratory detection limit. Those results are held as censored observations carrying their limit, and the annual mean is computed from the detected values only, which biases it upward by more the larger the censored share. Each series states that share.
Detection limits fell substantially over the record as instruments improved. A series whose censored share falls may be recording a laboratory getting better rather than a river getting cleaner, and the two cannot be separated from these data alone.
Escherichia coli results are read but no annual figure is published. Counts span orders of magnitude and rise sharply after rain, so an arithmetic mean is one storm and a median hides the storms; bathing water standards use percentiles of log-transformed counts, which is a method Hydrionis has not declared.

Coverage

Subjects	English freshwater river monitoring points with at least ten years of record — 5,214 held
Period	2000–2025
Units	%, NTU, mg/l, mg/l as C, mg/l as CaCO₃, mg/l as N, mg/l as P, mg/l as SO₄, pH, °C, µS/cm, µg/l
Update cadence	Annually
Identifier	`england-river-water-quality` v1.0.0

Fields

Data dictionary →

Every metric this dataset carries, with the unit it is stored in and the geography level it is reported at. Full definitions are in the data dictionary.

Identifier	Field	Unit	Reported at
`nitrate-as-n`	Nitrate as nitrogen Concentration of nitrate in water expressed as the mass of nitrogen it contains, the convention used in environmental monitoring.	mg/l as N	monitoring-station
`orthophosphate-as-p`	Orthophosphate as phosphorus Concentration of reactive orthophosphate expressed as the mass of phosphorus it contains.	mg/l as P	monitoring-station
`ammoniacal-nitrogen`	Ammoniacal nitrogen Combined concentration of ammonia and ammonium expressed as the mass of nitrogen, a standard indicator of recent organic or sewage pollution.	mg/l as N	monitoring-station
`dissolved-oxygen`	Dissolved oxygen The concentration of oxygen dissolved in water, essential for aquatic life.	mg/l	monitoring-station, river-gauge
`dissolved-oxygen-saturation`	Dissolved oxygen saturation Dissolved oxygen expressed as a percentage of the maximum the water could hold at its temperature and pressure.	%	monitoring-station, river-gauge
`ph`	pH The negative logarithm of hydrogen ion activity, measuring how acidic or alkaline water is.	pH	monitoring-station, supply-zone
`water-temperature`	Water temperature Temperature of the water body or supply at the point of measurement.	°C	monitoring-station, river-gauge, supply-zone
`conductivity`	Electrical conductivity The ability of water to conduct an electric current, proportional to its dissolved ion content.	µS/cm	monitoring-station, supply-zone
`alkalinity`	Alkalinity The capacity of water to neutralise acid, dominated in most natural waters by bicarbonate and carbonate.	mg/l as CaCO₃	monitoring-station, supply-zone
`turbidity`	Turbidity The cloudiness of water caused by suspended particles, measured by light scattering.	NTU	monitoring-station, supply-zone
`suspended-solids`	Suspended solids at 105 °C Mass of particulate matter retained on a filter and dried at 105 °C, per litre of water.	mg/l	monitoring-station
`bod-5-day`	Biochemical oxygen demand (5 day, ATU) Oxygen consumed by micro-organisms breaking down organic matter in a water sample over five days at 20 °C, with nitrification suppressed by allylthiourea.	mg/l	monitoring-station
`dissolved-organic-carbon`	Dissolved organic carbon Concentration of organic carbon passing a filter, expressed as the mass of carbon.	mg/l as C	monitoring-station
`total-oxidised-nitrogen`	Total oxidised nitrogen as N Combined concentration of nitrate and nitrite expressed as the mass of nitrogen.	mg/l as N	monitoring-station
`nitrite-as-n`	Nitrite as nitrogen Concentration of nitrite expressed as the mass of nitrogen it contains.	mg/l as N	monitoring-station
`total-phosphorus-as-p`	Total phosphorus as P Concentration of all forms of phosphorus, dissolved and particulate, expressed as the mass of phosphorus.	mg/l as P	monitoring-station
`lead-dissolved`	Lead, dissolved Concentration of lead passing a filter, in the dissolved fraction of river water.	µg/l	monitoring-station
`cadmium-dissolved`	Cadmium, dissolved Concentration of cadmium passing a filter, in the dissolved fraction of river water.	µg/l	monitoring-station
`mercury-dissolved`	Mercury, dissolved Concentration of mercury passing a filter, in the dissolved fraction of river water.	µg/l	monitoring-station
`nickel-dissolved`	Nickel, dissolved Concentration of nickel passing a filter, in the dissolved fraction of river water.	µg/l	monitoring-station
`zinc-dissolved`	Zinc, dissolved Concentration of zinc passing a filter, in the dissolved fraction of river water.	µg/l	monitoring-station
`copper-dissolved`	Copper, dissolved Concentration of copper passing a filter, in the dissolved fraction of river water.	µg/l	monitoring-station
`arsenic-dissolved`	Arsenic, dissolved Concentration of arsenic passing a filter, in the dissolved fraction of river water.	µg/l	monitoring-station
`chromium-dissolved`	Chromium, dissolved Concentration of chromium passing a filter, in the dissolved fraction of river water.	µg/l	monitoring-station
`iron-dissolved`	Iron, dissolved Concentration of iron passing a filter, in the dissolved fraction of river water.	µg/l	monitoring-station
`manganese-dissolved`	Manganese, dissolved Concentration of manganese passing a filter, in the dissolved fraction of river water.	µg/l	monitoring-station
`aluminium-dissolved`	Aluminium, dissolved Concentration of aluminium passing a filter, in the dissolved fraction of river water.	µg/l	monitoring-station
`chloride-river`	Chloride in river water Concentration of chloride in river water.	mg/l	monitoring-station
`sulphate-river`	Sulphate in river water Concentration of sulphate in river water.	mg/l as SO₄	monitoring-station
`sodium-dissolved`	Sodium, dissolved Concentration of sodium in river water.	mg/l	monitoring-station
`calcium-dissolved`	Calcium, dissolved Concentration of calcium in river water.	mg/l	monitoring-station
`magnesium-dissolved`	Magnesium, dissolved Concentration of magnesium in river water.	mg/l	monitoring-station
`potassium-dissolved`	Potassium, dissolved Concentration of potassium in river water.	mg/l	monitoring-station

Rights and access

Licence position

Open with attribution. Derivative use true; redistribution true; commercial reuse true.

Permitted uses

Public display
Derived analysis
API delivery
Bulk download
Commercial use

Available to: Public, Developer, Research, Professional, Enterprise. These follow from the rights of the contributing publishers, not from a Hydrionis pricing decision — no access tier can widen what a publisher withheld.

Contributing sources

Environment Agency — Water Quality Archive (WIMS) (Open Government Licence v3.0)

Attribution and citation

Cite and reuse →

Two different obligations, deliberately kept apart. One is a condition of somebody else's licence; the other is a request Hydrionis has no standing to enforce.

Attribution you are required to give

These are conditions of the licences the underlying data is published under. They are obligations to the publishers, not to Hydrionis, and they apply to you directly whether or not you mention Hydrionis at all.

Contains public sector information licensed under the Open Government Licence v3.0.

Environment Agency — Open Government Licence v3.0 (licence text)

Suggested citation for Hydrionis

Hydrionis (2026), England River Water Quality Dataset, version 1.0.0, accessed 2026-10-05, hydrionis.com/data/datasets/england-river-water-quality/

Cite Hydrionis where you rely on the compilation, the normalisation, the eligibility judgements or a chart. Where you use an unmodified published value, the publisher’s attribution is the one that is required; crediting Hydrionis as well is welcome and is not something Hydrionis can require of you.

Recommended, not required. Hydrionis does not claim rights over unmodified public data it relayed, and doing arithmetic on somebody else’s measurements does not make them Hydrionis’s. Cite the version and the access date: England River Water Quality Dataset changes as publishers release and as methods are revised, and a citation without both cannot be checked later. Full guidance is on cite and reuse.

Changelog

Version 1.0.0 — 2026-08-24

First release.

Additions

Annual values for six determinands at 4,846 English river monitoring points.

Version 1.1.0 — 2026-08-28

Expanded from six determinands to twenty-eight, and every series now carries its sample count, censored share and detection-limit history.

Additions

Chemistry: water temperature, conductivity, alkalinity, turbidity, suspended solids, biochemical oxygen demand and dissolved organic carbon.
Nutrients: total oxidised nitrogen, nitrite as N and total phosphorus as P, each kept apart from the determinand it resembles.
Eleven dissolved metals, including the Water Framework Directive priority substances lead, cadmium, mercury and nickel.
Six major ions describing catchment geology: chloride, sulphate, sodium, calcium, magnesium and potassium.

Use this data

Download quality observations from EA (471,154 rows) (CSV)
Download chemistry observations from EA (227,540 rows) (CSV)
Download contaminant observations from EA (60,193 rows) (CSV)
Machine-readable JSON /api/v1/datasets/england-river-water-quality.json
How to cite this, and who you must credit
How these figures were produced
Request this at a different scale, format or geography

Every bulk extract ships with a companion metadata file carrying this dataset’s version, its sources, their licences, the attribution you are required to give and the suggested citation — so the terms travel with the file rather than staying on this page.

About this data

The fields a professional user needs to judge whether this is fit for a particular purpose. Deliberately not a score.

About this data

Everything below is a property of the data rather than a rating of it. There is deliberately no single confidence score: how much a gap matters depends on what you are about to do with the series, and only you know that.

Source	Environment Agency — Water Quality Archive (WIMS) · Open Government Licence v3.0
How the values came to exist	Mixed across the series — the basis is recorded on every individual value.
Period held	2000–2025
Known gaps	The archive’s public interface begins in 2000. The large improvement in English river chemistry that followed the Urban Waste Water Treatment Directive largely predates this and is not visible here. Sampling frequency has fallen at many points over the period, so a national average computed year by year would partly measure which points were still being sampled rather than what was in the rivers. These are river samples, not treated drinking water. Comparison against a drinking-water standard is a comparison between different things.
Continuity	Version 1.0.0, released 2026-08-24. 2 recorded versions; breaking changes and corrections are listed in the changelog above.
Last read from the publisher	2026-08-28 · publisher updates annually
Redistribution	Permitted by the upstream licences
Commercial reuse	Permitted by the upstream licences. No Hydrionis access tier can widen this.
Methodology	How this was produced