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Kansas Geological Survey, Open-file Report 1998-32


Approximate Analysis of Groundwater Mineralization Due to Discontinuity in an Impermeable Layer

Part 2: Seepage of Saltwater through a Semiconfining Discontinuity

by
Hillel Rubin and Robert W. Buddemeier

KGS Open File Report 1998-32
July 26, 1998

Abstract

This is the second report in a series of studies of groundwater mineralization in the Great Bend Prairie aquifer of Kansas by saltwater originating from a deeper Permian bedrock formation. Part 1 of this study addressed mineralization processes caused by direct contact between fresh and saltwater along local discontinuities in an impermeable layer that separates the freshwater aquifer from deep saltwater. However, field studies indicate that in various places the impermeable layer discontinuities expose subcrops of sandstone strata, which represent semipermeable strata within a matrix of low permeability siltstone layers. These exposed strata function as sources of saltwater seepage. This phenomenon is very similar to transmission of fluid through a semi-confining layer, in response to a local head differential. We have used this conceptual analogue as a basis for developing a simplified method for the simulation of salinity penetration through the discontinuity, and of the horizontal migration of the salinity to regions in the originally freshwater aquifer which are completely separated from the deep saltwater. Along the horizontal extent of the aquifer we have identified several regions. In all of them various types of regions of interest (ROI) were identified and top specified boundary layer (TSBL) simulations were applied.

The method developed in this paper can be useful as a simple but robust approach for the initial quantitative evaluation of mineralization processes typical of local semiconfining discontinuities in an impermeable layer separating a freshwater aquifer from a deep saltwater formation.

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Kansas Geological Survey, Geohydrology
Placed online Oct. 17, 2013
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