Modelling the hydrogeology and managed aquifer system of the Chalk across southern England
Published:January 01, 2012
R. W. N. Soley, T. Power, R. N. Mortimore, P. Shaw, J. Dottridge, G. Bryan, I. Colley, 2012. "Modelling the hydrogeology and managed aquifer system of the Chalk across southern England", Groundwater Resources Modelling: A Case Study from the UK, M. G. Shepley, M. I. Whiteman, P. J. Hulme, M. W. Grout
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Six regional recharge and groundwater models have been recently developed of the Chalk and Upper Greensand from Dorset to Kent. Updated Chalk stratigraphy and mapping have improved understanding of geological structure and the development of preferential groundwater flow pathways along hardground horizons. Where shallow dipping folds bring these into the zone of active groundwater flow, extensive ‘underdrainage’ may result in marked differences between surface and groundwater catchments. Hardgrounds and marls are also associated with spring discharges, as are some faults and the clay formations that underlie or confine the aquifer system. Higher specific yield within the Upper Greensand helps support summer baseflow, as do local groundwater discharges from augmentation schemes, watercress and fish farm operations. The aquifer system has been successfully modelled using the ‘variable hydraulic conductivity with depth’ version of MODFLOW. Depths of secondary permeability development have been distributed according to ground and groundwater level data. Interfluve–valley contrasts overlie a base hydraulic conductivity set according to the formation saturated at the water table and enhanced by active hardgrounds. Local parameter overrides may also be needed. The Wessex Basin conceptual and numerical model is described before summarizing similarities and contrasts from the other five regional model areas.
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Groundwater Resources Modelling: A Case Study from the UK
The UK is a country with over 150 years of widespread exploitation of its principal aquifers for public water supply. Increasing demands, greater awareness of environmental pressures and more exacting legislation has heightened the need for quantitative models to predict the impacts of groundwater use. In the UK this has culminated in a unique national, regulator-led programme for England and Wales to develop conceptual and numerical models of the principal bedrock aquifers.
The outcomes of this programme will be of interest to the international hydrogeological community, particularly as international legislation such as the European Water Framework Directive requires management of water issues across administrative boundaries with a varied cast of stakeholders.
The collection of papers provides a contrast between practitioner- and research-based approaches to assess and predict the anthropogenic impacts and environmental pressures. Many insights are provided on how the regular use of groundwater models may address the environmental challenges of the future.