NRW’s water quality archive holds data from samples collected around Wales, including coastal, estuary, rivers, lakes, ponds, canals, sewage discharges, trade discharges, pollution investigation points and waste sites. 

Field measurements are taken in situ at the sampling station, but most parameters are analysed in laboratories to measure aspects of the water quality. Once samples have been analysed, the results must be processed and verified before they are added to the water quality archive. Therefore, there is a delay between samples being taken and the data being made available. Data may also be subject to change after publication, but the archive will be updated each month to include corrections.

NRW's water quality archive is a large dataset containing some potentially sensitive data and therefore some information has been redacted. The main sensitivities are around groundwaters, potable water supplies, third party data and investigation samples.

The GIS layer shows the site locations, the years in which they have been sampled and the WFD Management Catchment in which they are located. This can be used to help identify the files containing the data you require from the link below.

Link to download water quality data

Data Currency

NRW holds data going back to 1962 but the open data product contains data from 2000 onwards.  No samples will be included after the date the data quality review was last undertaken which at the time of writing was March 2021. A process is in development to enable more up to date results to be made available.

To find out when the individual files were last updated, see the index files within the download folders.

General: Data may be subject to change after publication with the archive being updated each month to include corrections. This may include flagging previously unflagged results as deviating or removing results that have been identified as invalid.

Deviating Samples: Natural Resources Wales Analytical Services (NRWAS) is required to have policies and procedures in place under the ISO/IEC 17025 accreditation standard to ensure that the integrity of reported results is maintained. Any sample that does not meet the set criteria when received or following analysis is described as deviating. We have highlighted the data readings that don’t meet these requirements in the “deviating_result” attribute. Deviating results may be affected by bias and/or imprecision of unknown magnitude. Hence caution should be exercised when interpreting these results and it is recommended that they are not used in statistical analysis.

Additional Help

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Attribution statement

Contains Natural Resources Wales information © Natural Resources Wales and Database Right. All rights Reserved. Contains Ordnance Survey Data. Ordnance Survey Licence number AC0000849444. Crown Copyright and Database Right.