The movement of ground water, as influenced by geological factors, and its significance

Abstract

An analysis of ground-water movement based on the individual components of Darcy's Law has been undertaken with reference to aquifers in England˙ Variations in hydraulic gradient, in the parameters defining the physical and mechanical characteristics of an aquifer, in geological structure and in physical properties of ground water will modify fluid velocities. Although the hydraulic conductivity of porous media can be stated in terms of these parameters, complexities of geology prevent an adequate statement other than under restricted conditions Around a discharging or recharging well, non-steady and steady state flow has been analysed for the determination (in situ) of the formation constants of an aquifer, both real and apparent values being derived. Critical analysis of data in relationship to rate of abstraction, time since discharge commenced or ceased and distance to observation well has been carried out, variations in the formation constants usually occurring in defined trends. The inter-relationship of the formation constants and their importance in hydrological surveys has been discussed. Real variations in transmissibility have been determined and diagrams compiled to indicate regional trends. Analysis of yield-depression curves has led to the assemblage of type and breakaway curves" from which the formation constants of the aquifer can be derived within defined statistical probability levels. Factual data relating to ground-water movement have been analysed and the results presented on a probability basis, wherever possible. This method is considered to be important in hydrogeological studies, Particular emphasis has been placed on ground-water conditions in the Chalk due to its importance as a source of water supply. The significance of fluid movement in relationship to exploitation of ground-water resources and to problems of overdevelopment has been considered. Progressive changes in ground-water chemistry, under both natural and artificial conditions, have been established.