APPLICATION OF THE TOP SPECIFIED BOUNDARY-LAYER (TSBL) APPROXIMATION TO INITIAL CHARACTERIZATION OF AN INLAND AQUIFER MINERALIZATION - 1 - DIRECT-CONTACT BETWEEN FRESH AND SALTWATER

This paper presents a basic study in generalized terms that originates from two needs: (1) to understand the major mechanisms involved in th e mineralization of groundwater of the Great Bend Prairie aquifer of K ansas by saltwater originating from a deeper Permian bedrock formation , and (2) to develop simple, robust tools that can readily be used for local assessment and management activities in the salt-affected regio n. A simplified basic conceptual model is adopted, incorporating two h orizontal layers of porous medium which come into contact at a specifi c location within the model domain. The top layer is saturated with fr eshwater, and the bottom layer is saturated with saltwater. The paper considers various stages of approximation which can be useful for simp lified simulation of the build-up of the transition zone (TZ) between the freshwater and the saltwater. The hierarchy of approximate approac hes leads to the development of the top specified boundary layer (TSBL ) method, which is the major tool used in this study for initial chara cterization of the development of the TZ. It is shown that the thickne ss of the TZ is mainly determined by the characteristic dispersivity. The build-up of the TZ is completed after a time period equal to the t ime needed to advect a fluid particle along the whole extent of the TZ . Potential applications and the effects of natural recharge and pumpa ge on salinity transport in the domain are discussed and evaluated in the context of demonstrating the practicality of the TSBL approach. (C ) 1998 Elsevier Science B.V. All rights reserved.