Knowledge exchange project: karst aquifers

Duration: 2016–2019
Scheme: NERC Knowledge Exchange Fellowship

Chalk and Jurassic and Permian limestones in England

Overview

Karst results from the dissolution of rocks and is usually associated with cave systems and landscapes characterised by rocks sculpted by dissolution, large surface depressions, disappearing rivers and major springs. However, karst processes occur in all soluble rocks, and can result in rapid transport of pollutants into and through the ground, sometimes over distances of many kilometres.

This knowledge exchange project concerns the Chalk and Jurassic and Permian limestones of England. These are soluble-carbonate aquifers in which caves are uncommon and karst often not well-recognised.

The aquifers provide vital water supplies in many areas of England, and the groundwater within them also sustains many of our rivers and wetlands. Research shows that karst features can be widespread in these aquifers, and yet information on karst is not readily available for groundwater management and protection.

Chalk cave, Berkshire

The aims of this knowledge exchange are to bring together data and knowledge on karst in these aquifers from research and industry to develop a new understanding of the spatial distribution of karst, and to develop web-based resources with easy access to information on karst, to enable karst data to be used more easily in groundwater management and protection.

Participants include water companies, the Environment Agency, hydrogeological consultants and university academics.

UK karst aquifers

Carboniferous limestone cave, south Wales
Jurassic limestone cave, Yorkshire

There are different definitions of karst, but the term is generally applied to all soluble rocks in which fractures are enlarged by dissolution to form fissures and conduits, even if enterable caves are rare or absent (Worthington and Ford, 2009). In the UK, karst is usually associated with Carboniferous limestone, in which there is extensive cave development. The longest known cave is more than 80 km in length, and there are more than 170 explored caves that are more than 1 km in length.

In England, three of the major aquifers (the Chalk and the Jurassic and the Permian limestones) are carbonate aquifers in which caves are uncommon, although a few caves are known. The longest known cave in the Jurassic limestone is 2.8 km, whilst the longest known cave in the Chalk is 360 m, and that in the Permian limestone is 290 m. However, it appears that generally, these aquifers are characterised by more complex networks of smaller-scale dissolution voids, which form a conduit mesh rather than single, large cave passages.

In addition to caves, there are several types of evidence for karst in the Chalk and Jurassic and Permian limestone aquifers:

References

How to help: local evidence of karst

Chalk stream sink, Berkshire

The aim is to collate local indicators of karst/rapid flow in England in the Chalk, the Jurassic limestone and the Permian limestone.

If you can supply grid references for the features listed (either that can be used directly in open access web-based karst resources, or that can be used more generally in an overview of karst at a regional scale with the locality remaining confidential), please contact Lou Maurice.

Information being collated includes:

  • tracer tests indicating rapid groundwater flow
  • locations of hydrologically active stream sinks (swallow holes), i.e. surface karst features in which water is directly recharged into the ground at a particular point (information on discharge volume and whether they are perennial or ephemeral is also useful)
  • locations of springs with flows of more than 10 l/s and any information on their discharge
  • locations of caves, and any information on dimensions, lengths and cave hydrology
  • boreholes with images showing evidence of karstic cavities of more than 15 cm aperture

Karst information

Contact

Contact Lou Maurice for further information.