Review of groundwater flow and contaminant transport modelling approaches for the Sherwood Sandstone aquifer, UK; insights from analogous successions worldwide

Sandstones are characterized by different hydraulic behaviours and need to be modelled in various ways to represent groundwater flow and contaminant transport. This review shows how sandstone aquifers within the UK Triassic Sherwood Sandstone Group, can be represented using three modelling approaches; the Conduit Network, Discrete Fracture Network and Equivalent Porous Medium. The Sherwood Sandstone aquifer is dominated by matrix flow in the Eastern England Shelf, Worcester, Needwood and Staffordshire basins. Here, the aquifers are modelled as Equivalent Porous Media at different spatial scales. Fractures represent the principal flow pathways in the Cheshire Basin. In this basin, Discrete Fracture Network models that account for diffusivity in the matrix can be used where the domain-scale is small. The Sherwood Sandstone aquifer across north-western England shows evidence of intense groundwater alteration and high flow velocities in solutionally-enlarged fractures. Turbulent flowing pipe-elements can be inserted in the modelling domain represented by Equivalent Porous Medium at specific sites. The review shows how the Sherwood Sandstone aquifer as well as other siliciclastic deposits across the world need to be represented using a range of modelling approaches, as they behave as matrix or fracture flow aquifers, or in specific cases show a karst-like behaviour.