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A Model Study of Salt‐Water Intrusion to a River Using the Sharp Interface Approximation
Author(s) -
McElwee C. D.
Publication year - 1985
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.1985.tb01496.x
Subject(s) - alluvium , saltwater intrusion , geology , hydrology (agriculture) , aquifer , population , evaporite , stage (stratigraphy) , groundwater , salinity , saline water , water quality , geochemistry , geomorphology , geotechnical engineering , oceanography , paleontology , ecology , demography , sociology , biology , sedimentary rock
Between Salina and Enterprise, Kansas, the salinity of the Smoky Hill River increases sharply. As a result, the river downstream at various times exceeds the recommended drinking‐water‐quality standards for chloride. The Smoky Hill and Kansas Rivers are important sources of water for several population centers in eastern Kansas. Therefore, this problem has an impact on a significant part of the Kansas population. The source of the saline water is predominantly from ground‐water dissolution of the Hutchinson Salt Member of the Wellington Formation of Permian age. The dissolution of the salt has caused a north‐south trending collapsed zone called the Wellington aquifer to occur along the present eastern extent of the salt. A confining shale layer exists between the Smoky Hill alluvium and the Wellington aquifer in most areas. However, between New Cambria and Solomon, Kansas, the layer is thin and fractured, allowing the salt water to move up into the alluvium. The steady‐state model presented in this study indicates that the salt‐water layer of the alluvium in the Smoky Hill River valley should be in an unstable condition near the river. This indicates that unstable interface upconing should be a dominant mechanism for supplying salt water to the river system. The time‐varying model shows that the response of the chloride discharge to a flood event can be qualitatively explained by the unstable interface upconing mechanism. As the river stage rises, the salt‐water intrusion declines. As the river stage declines, the salt‐water intrusion increases beyond its normal value and subsides to the normal value over the period of a few months if no new flood events occur. During rising river stage, the river is supplying the ground‐water system, and the salt‐water intrusion or unstable upconing is shut off. During falling river stage, bank storage and perhaps an elevated water table cause the fresh ground‐water discharge to be greater than normal, which in turn causes greater than normal salt‐water intrusion. In addition, the time‐varying model shows that several years would elapse before significant benefit would be seen in the river system from a proposed Wellington aquifer relief‐well scheme.