The Environment Agency commissioned ESI, now part of Stantec, to develop a numerical groundwater model of the Bromsgrove Aquifer.
The Bromsgrove Aquifer is an important water resource public water supply. However, historic over-abstraction in some parts of the aquifer has resulted in falling groundwater levels and reductions in stream flows. This issue has been recognised for many years and several projects have been carried out by the Environment Agency and Severn Trent Water to development augmentation schemes to maintain stream flows during dry weather. However, there was still a concern that the aquifer as a whole was over abstracted and the Environment Agency needed a technically robust basis for assessing how much water could be sustainably abstracted.
Following a project to develop a conceptual model of the aquifer, the Environment Agency commissioned ESI to develop a regional groundwater model to implement this understanding of the aquifer. The main objective of this project is to produce a groundwater model that will significantly improve the Environment Agency’s ability to make abstraction licensing decisions on a sound scientific basis and, in doing so, manage groundwater levels and protect sensitive surface water features on the outcrop of the Bromsgrove Sherwood Sandstone aquifer.
ESI carefully reviewed the conceptualisation of the aquifer, particularly groundwater-surface water interaction and the way in which different sandstone formations overlapped along faults. From this review we built a layered MODFLOW model using an associated 4R runoff-recharge model.
The model was well calibrated to observed flows and groundwater levels and the Technical Review Panel recommended it as an appropriate tool for managing abstraction from the aquifer.
ESI was subsequently commissioned by the Environment Agency and Severn Trent Water to develop model scenarios to explore different groundwater abstraction scenarios and the implications of these for stream flows, ecology and the risk of groundwater flooding.
In 2017 ESI was commissioned by the Environment Agency to update the model and, where appropriate, re-calibrate it. The update of the model provided a useful validation of the original calibration although, the extensive additional data collected in the area by Severn Trent Water since 2012 allowed further refinement of the way in which groundwater-surface water interaction is modelled. The updated/refined model will now be used to assess further abstraction/augmentation scenarios.