User guide: BGS UK Geothermal Catalogue second digital release, new and legacy data

This guide accompanies the second digital release from the BGS of the UK digital geothermal catalogue of temperature measurements, thermal conductivity measurements and heat flow calculations.
This second release contains 1098 new sites alongside 36 sites from the legacy geothermal catalogue1. These 36 sites from the legacy catalogue were not included in the first digital release in 2024 due to IPR considerations. This is a 150% increase in the number of sites in the second digital geothermal catalogue release compared to first release (BGS, 2024; Fellgett and Monaghan, 2024).
The majority of the new sites are derived from three sources
•New thermal conductivity data collected by the BGS Thermal Conductivity Lab (BGS Thermal Conductivity Lab, 2025).
•Datasets synthesised in BGS publications on heat pumps (Busby, et al., 2009) and for subsurface temperature maps (Busby et al., 2011).
•Bottom hole temperature dataset compiled by the UK Onshore Geophysical Library (UKOGL, 2024).

In addition to the new sites, work has been undertaken to better attribute the data source (now called ‘data lineage’). The data lineage parameter indicates where the data came from, be it a report, personal communication, paper etc. In the first version of the catalogue, data lineage was attributed at site level (i.e. a borehole or location). Whilst this is valuable information there were two main issues with an attribution at site level:
1. If a site has multiple data types e.g. heat flow, conductivity and temperature, then each data type may be published in separate papers.
2. Sites are often revisited for work and if new data is collected then it is difficult to distinguish it from the legacy data

To address this problem in version 2 of the catalogue, data source is now attributed at ‘observation’ level, though for most of the catalogue a default value of “Legacy Geothermal Catalogue” is used (Section 2.3).

This second digital release contains data that has been: spatially located, assigned data lineage at observation / measurement level, IPR checked and assessed for release under version 3 of the Open Government Licence (OGL, https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/). The OGL is equivalent to a CC-BY licence establishing the data release to be suitable for commercial and non-commercial third-party use, provided the data source is acknowledged.

The guide describes the background and data sources used in this release, the methods used and limitations on data quality.
The main limitations on this dataset are:
• It contains both observation data (temperature and conductivity measurements) alongside interpreted (calculated) heat flow data.
• Data associated with the legacy geothermal catalogue is provided as it was listed. Values have not been individually validated, so there is a possibility that any errors made in the original reporting have been copied forward. This does not apply to some of the new datasets incorporated into the release.
• Some measures of data quality (e.g. equilibrated temperatures vs bottomhole temperatures) and error were included in the legacy dataset. These have been copied forward but vary by data lineage and have not been validated here.
• The heat flow calculations and corrections applied are detailed within the original data sources listed and vary between data sources. The heat flow values are reproduced from the legacy geothermal catalogue – subsequent publications (e.g. Busby 2010, Westaway and Younger 2013) document that the magnitude of paleoclimatic and topographic corrections have not been fully recognised, leading to an underestimation of temperatures at depth and heat flows for the UK geothermal resource. As a result, the heat flow dataset in this release should be used with caution and with understanding of these limitations.

Whilst every reasonable check has been made to ensure that these data are appropriate for release, given the challenges in verifying the IPR status of some of the datasets included in the UK digital geothermal catalogue, a take-down policy is in operation.