London and Water
Water data, with its context.
Explore water chemistry, river conditions and observed tides in and around London. Choose measurements, find their locations on the map, then examine the chart and records together.
What the map covers
The main selection is a 50 km radius around central London, centred on longitude −0.1278, latitude 51.5074. Nine named Thames and estuary tide gauges are also included. Southend and Sheerness are explicit station inclusions beyond that circle; they do not widen the selection for other sources.
Historical research collections sit alongside the regularly collected Environment Agency feeds. Their dates, locations and sampling frequency differ. A period between the first and last reading does not promise continuous coverage.
Reading the measurements
Check the units and metric variant before comparing values. Dissolved and total concentrations, different analytical methods, sample results and period averages remain separate. Tide heights retain their reported vertical datum; these are observations, not predicted tides.
A hollow mark identifies a reported limit or another qualified value. Hover for the source qualification. A missing value is not zero. A grid measurement's Details shows its source information, qualifiers and supporting fields.
Select Measurements offers measurement types with at least one located, timed, displayable result. Choose up to four, including distinct variants of the same chemical. Numeric values and reported outcomes, such as presence or absence, retain their meaning. Search dates find types with a reading in that range; choosing one still includes its full recorded date range. Search dates do not filter the map.
One map point represents a place. Its coloured sectors identify the selected measurements there, and its size reflects the reading count. Pick a point to open its measurement tabs; each tab has one chart, grid and CSV export. Dates are shared by the map and detail panel. Full date range beside the chart restores the selected measurements' initial date span. Show on map in the key includes one measurement; Show all on map restores the whole selection. Neither discards an open panel. Closing details also restores the initial date span. Removing a measurement is a separate action using its trash icon.
When the data changes
The underlying feeds are collected on a schedule. Your selected measurements establish a date span for browsing and drilling down. Later requests can see incoming data within the applied dates. Reload the page to fetch current coverage. If a request fails, the map retries and then offers Refresh if needed, retaining your choices. Publisher delays, gaps and revisions can affect what is available; the site does not promise minute-by-minute completeness.
Basemap credits
Ordnance Survey Open Zoomstack: contains OS data © Crown copyright and database right 2026, licensed under the Open Government Licence v3.0. The map uses the Open Zoomstack Light style.
Locally served map assets use Source Sans Pro fonts. Their notices are retained with the Source Sans licence and OS licence.
Measurement credits
Environment Agency, UK Centre for Ecology & Hydrology, the Harmonised Monitoring Scheme contributors, University of Bristol and Caravan-Qual contributors supply the displayed collections. Full source citations and dataset-specific reuse terms are listed on the Sources page. No single licence is asserted for every collection.