Developments in modelling groundwater flow in the Chalk in London

Chalk has unique properties that affect how it stores and transmits groundwater. Understanding its dual porosity and dual permeability nature, the marked contrast between largely static water held in pore spaces and the more mobile water in fractures, has developed significantly over recent decades. More recently, the differing properties of the various formations within the Chalk Group have become more apparent, particularly on the back of detailed investigations in support of major tunnelling projects in London. This paper shows how recent developments in the conceptual understanding of the Chalk-Basal Sands aquifer in London (Streetly et al, 2018) were used as the basis of a new, detailed groundwater model of the aquifer. We discuss the challenges in developing this model and some of its subsequent uses in water resource management, climate change assessment and environmental impact assessment. The model was also the basis of more localised models developed to investigate the potential impacts of a significant increase in the exploitation of the Chalk -Basal Sands aquifer for heating and cooling in ground source energy schemes.