A digital groundwater model investigation of a Permo-Triassic aquifer in the West Midlands of England

Abstract

Increase in demand for potable water has led to a critical re-appraisal of water resources. Resource planning requires a systematic approach to the development of aquifer systems and, in order to maximise output, conjunctive use with surface reservoirs and rivers has to be considered ultimately. Therefore this can be implemented a complete understanding of the dynamic response of the system must be acquired. Analogue and digital simulation models have been developed for this purpose. A. digital finite difference approximation technique which utilises a backward difference formulation is considered to represent the linear partial differential equations of groundwater flow. A two dimensional model is formulated in which space and time are represented as discrete elements. The resultant simultaneous equations are solved iteratively by a Gauss- Siedal relaxation technique. A Permo-Triassic aquifer sited between the Coalbrookdale and South Staffordshire Coalfields of the West Midlands is studied. A considerable amount of data has to be processed and in order to secure maximum benefit several analytical techniques are developed. The extent and thickness of the aquifer is obtained from consideration of the depositional and sedimentological history of the associated sediments. This, togetb.er with field work exploration and an analysis of the tectonic history of the strata enables the geometrical configuration at'-d hydrogeological boundaries of the aquifer to be depicted. The hydraulic characteristics of the aquifer are determined from graphical and numerical analyses of in situ tests and from 1aboratory investigations. Additional information is obtained from least squares and linear programming solutions to groundwater flow equations compiled from historical records.