interface parameters between ground and surface water in a fault-controlled
A perennial spring forming a tributary to Battle Creek in the Black Hills
was studied to determine controls on both shallow and deep water sources.
Characteristics defining the interface between these sources are
poorly understood but are integral to development of a tenable water supply.
Seismic reflection has indicated a large fault extending to the
basement, potentially cutting the Mississippian Madison Group aquifer.
Alluvial deposits consist of interbedded gravel and silt and overlie
the Triassic Spearfish formation.
Gypsum beds in the upper Spearfish formation dissolve forming
conduits for surface runoff to infiltrate into coarse-grained alluvial beds
that are in hydraulic connection with the stream channel.
Thus, a mixed spring source seems likely.
Six piezometers were installed up- and downstream of the spring and
monthly water table measurements have been made.
Observed water levels have remained steady at each location and are
unaffected by precipitation. Shallowing
of the water table proceeds southward from five to zero meters at the spring
representing the decrease in surface elevation in the down valley direction.
The subsurface water table gradient is low, much less than the land
surface, and the intersection of these 2 features results in the spring.
Analysis of these data have suggested that deep-sourced water rises
through the brecciated rock along the fault to the surface due to artesian
pressure within the underlying aquifers.
This deep source provides a continuous supply that is enhanced by
flow through the dissolution features and shallow gravels in wet
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