HYDROGEOLOGY OF A SUBSURFACE DAM IN AN INTERMITTENT STREAM BED, LAKOTA CREEK, HERMOSA, SD

Lakota Spring is a migrating, perennial spring under the influence of deep bedrock aquifers. The spring contributes approximately 15 cfs to Battle Creek, a tributary of the Cheyenne River. It is upwelling within the Triassic Spearfish Formation between Hermosa and Hayward located within the Black Hills of South Dakota. The spring and its migration pattern are the result of an intricate mix of ground and surface water resources. Surface water is channeled through shallow, younger deposits: Quaternary fluvial and alluvial fan sediments, Tertiary terrace deposits, and gypsum sinkholes. The surface water is mixed sub-aerially with water upwelling through fractures from deep bedrock aquifers contained within the Permian Minnelusa Formation and Mississippian Madison Limestone. The deep aquifers provide perennial stability for the spring, enabling it to flow during periods of severe drought. A prototype subsurface dam was installed within the dry stream bed upgradient from the spring in an attempt to create a perennial, useable ground water resource to stabilize riparian habitat and create a wetland. Due to non-representative sediment samples, the depth and extent of the aquifer was underestimated and the dam did not create a significant reservoir. A second attempt is currently underway to expand and modify the existing plans to create subsurface dams within this alluvial valley.