Kansas Geological Survey, Open-file Report 1998-33
Hillel Rubin and Robert W. Buddemeier
KGS Open File Report 1998-33
September 16, 1998
This report describes techniques for analyzing the mineralization of groundwater resources due to horizontal penetration of saltwater into a freshwater aquifer. The methods were developed within the framework of a comprehensive research program concerning groundwater mineralization in south central Kansas. Previous studies addressed cases, in which a comparatively thin mineralized region represented by boundary layers (BLs) developed within the freshwater aquifer close to sources of salinity. However, at some distance downstream from the salinity source, the top of the mineralized region reaches the top of the aquifer. This is the location of the "attachment point", which comprises the entrance cross section of the domain evaluated by the present study. It is shown that downstream from the entrance cross section, a set of two BLs develop in the aquifer, termed inner and outer BLs. It is assumed that the evaluated domain, in which the salinity distribution gradually becomes uniform, can be divided into two sections, designated: (a) the restructuring section, and (b) the establishment section. In the restructuring section, the vertical salinity gradient leads to expansion of the inner BL at the expense of the outer BL, and there is almost no transfer of salinity between the two layers. In the establishment section, each of the BLs occupies half of the aquifer thickness, and the vertical salinity gradient leads to transfer of salinity from the inner to the outer BL. By use of BL approximations, changes of salinity distribution in the aquifer are calculated and evaluated. The establishment section ends at the uniformity point, downstream from which aquifer salinity is vertically uniform. The length of the restructuring section, as well as that of the establishment section, is approximately proportional to the aquifer thickness squared, and is inversely proportional to the transverse dispersivity.
The study provides a convenient set of definitions and terminology that are helpful in visualizing the gradual development of uniform salinity distribution in an aquifer subject to mineralization. The method developed in this study can be applied to a variety of problems associated with groundwater quality, such as initial evaluation of field data, design of field data collection, the identification of appropriate boundary conditions for numerical models, selection of appropriate numerical modeling approaches, interpretation and evaluation of field monitoring results, etc.
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Kansas Geological Survey, Geohydrology
Placed online Oct. 18, 2013
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