Natural and anthropogenic halite karst subsidence in north Cheshire, UK; comparison of Rostherne Mere, Melchett Mere, Tatton Mere and their surroundings

Most of the north Cheshire - Knutsford Group - of meres (lakes) in the UK formed naturally by dissolution of Triassic halite after the Devensian glaciation. Anthropogenic brine extraction in the 19th and 20th Centuries produced further subsidence that enlarged some meres and formed the new lake of Melchett Mere. The characteristic features of three meres, Rostherne, Melchett and Tatton are compared here by historical surveys, maps, photographs and LiDAR interpretations. These illustrate the similarities of the natural and anthropogenic subsidence features, which can only be separated by temporal evidence of their formation. Rostherne Mere and Tatton Mere are mainly natural, though deepened or made larger by anthropogenic salt dissolution; Melchett Mere is completely anthropogenic and mainly formed between 1927 and 2003. All three meres are surrounded by landslip scars related to the subsidence. Former brine pumping at Northwich, Plumley and possibly Agden is implicated in the formation of Melchett Mere and the reactivation of natural subsidence at Rostherne and Tatton meres plus The Mere along with Tabley, Pickmere and Budworth meres to the south west. The brine run linkages between these abstraction areas and the subsidence crosses the route of the proposed HS2 railway.