Date of Award


Document Type


Degree Name

Master of Science (MS)



First Advisor

P.J. Gerla


The rapid growth of the city of Sioux Falls, South Dakota, has created a great demand for additional sources of ground water. Due to limited information on the buried, confined Split Rock Creek aquifer near Sioux Falls, a detailed hydrogeologic assessment of the aquifer was conducted to determine the mechanism of recharge to the aquifer.

A four-fold plan was earned out to gather the necessary data. . This plan involved determining the general hydrostratigraphy of the study area by reviewing available data and by drilling test holes where data were limited, collecting water-level data over an extended period, collecting water samples for major inorganic, radionuclide, and stable isotope analyses, and determining the hydraulic characteristics of the aquifer and confining layers through aquifer and baildown tests.

Results indicate that the Split Rock Creek aquifer exists in paleo-valleys in the highly fractured Precambrian Sioux Quartzite. Aquifer materials are comprised of weathered and eroded Sioux Quartzite. The main portion of the aquifer lies to the east of Sioux Falls, between Brandon and Valley Springs, with aquifer thickness in this area exceeding 200 feet. Total dissolved solids in aquifer water collected from this area are less than 500 parts per million (ppm).

Water levels in the aquifer increase during years of above normal precipitation, indicating recharge of the aquifer. Recharge has been great enough to sustain the approximately 292 million gallons of annual municipal pumping by Sioux Falls and Brandon. Water-chemistry data indicate post-depositional water present in the aquifer. Radiocarbon data indicate the age of the aquifer water ranges from approximately 3,000 to 10,000 years, and stable isotope data indicate the waters are meteoric in origin.

Low permeability, unfractured till overlies the majority of the aquifer, eliminating the possibility of significant recharge in those areas. Ground-water flow directions indicate the main source of recharge is the Sioux Quartzite aquifer. Induced recharge from surficial outwash and alluviwn is possible in localized areas of river valleys.

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