A personal perspective of 20 years of regional groundwater resource modelling of the Permo-Triassic Sandstone aquifers in England

In 1998, the Permo-Triassic Sandstone aquifer of the West Midlands-Worfe (WMW) area became the subject of one of the first major groundwater modelling project initiated under the Environment Agency of England's national groundwater modelling framework. The 4R runoff-recharge code that allowed these models to apply a semi-integrated approach to simulating catchment hydrology was developed and trialled in parallel with the WMW project. This combined groundwater and surface water modelling approach has enabled the Environment Agency of England to make complex water resource management decisions in a wide range of aquifers and catchments based, in part, on outputs from such models. Since that time, the Environment Agency has used the framework to develop around a dozen further models of Permo-Triassic Sandstone aquifers, of varying levels of complexity. Many of the older models have subsequently been through one or more cycles of updating and/or recalibration. This paper provides a high level review of these models based on the personal experience of the author and compares and contrasts their implementation in the USGS groundwater modelling code MODFLOW. This includes a discussion of key conceptual issues that are common across the models, or unique to particular models, and the uses to which the models have been put. The paper concludes with a discussion of future opportunities and challenges for the programme. Thematic collection: This article is part of the Hydrogeology of Sandstone collection available at: https://www.lyellcollection.org/topic/collections/hydrogeology-of-sandstone