Crossing boundaries, the influence of groundwater model boundaries and a method to join and split MODFLOW models
Published:January 01, 2012
A. D. Black, R. T. Lewis, M. W. Grout, W. R. Witterick, 2012. "Crossing boundaries, the influence of groundwater model boundaries and a method to join and split MODFLOW models", 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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Neighbouring groundwater models often have large areas of overlap to avoid boundary issues in hydrogeological assessments and such overlap or artificial boundaries can lead to inconsistent representations of aquifers and processes. This paper presents the aggregation of six adjacent models spanning East Anglia, England, into one model without internal boundaries. This study principally discusses the effect of, and difficulties arising from model edge boundaries. In addition, a review of conceptual and numerical discontinuities at model boundaries is included and a more consistent and robust modelling approach over the whole area is demonstrated. The large, joined model is used to delineate groundwater divides, assess their transient migration, review edge boundary implications for water balances and investigate abstraction impacts without the influence of internal static boundaries. Computer codes developed in conjunction with this study facilitate joining adjacent models and, conversely, splitting of the joined model back into models at the scale of the original component models using simulated groundwater divides, or to smaller submodels incorporating edge boundary conditions calculated from the parent model.
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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.