16-19 Tracing Groundwater Flow in Karst Aquifers: The Hydrogeology of Sinking Valley, PA

Session: From Thin Section to Outcrop: Exploration of Undergraduate Research (Posters)

Poster Booth No.: 19

Presenting Author:

Taylor Steinhilber

Authors:

Steinhilber, Taylor Ansley¹, Pirhalla, Kathryn Rose², Ahne, Daniel W³, Hurd, Todd Michael⁴, Behr, Rose-Anna⁵, Crowell, Bryan⁶, Walsh, Talor⁷

(1) Millersville University Earth Sciences, Millersville, , (2) Millersville University Earth Sciences, Downingtown, , (3) Millersville University Earth Sciences, Millersville, , (4) Shippensburg University, Shippensburg, , (5) PA Geological Survey, Middletown, , (6) Etters, , (7) Millersville University Earth Sciences, Millersville, ,

Abstract:

Groundwater flow in karst aquifers can be difficult to delineate, yet essential to understand, as these aquifers provide nearly 40% of the drinking water in the Unites States and support ecologically important springs.  Sinking Valley, located in Blair County, PA, is a carbonate valley hosting a variety of karst features including sinkholes, springs, and sinking streams including Sinking Run. Sinking Run is a tributary of the Little Juniata River and it flows west from Arch Spring through Sinking Valley. During drier periods, Sinking Run completely enters the subsurface through a swallow hole located 8 kilometers west of its confluence with the Little Juniata River. Sinking Run typically continues downstream of the swallow hole as a dry stream. Eventually, this dry stream is recharged by springs downstream of the swallow hole and often flows into the Little Juniata River.

Here, we present the results of a fluorescent dye trace that was conducted to characterize the hydrogeology of this karst system. Sodium Fluorescein dye was injected into the furthest downstream swallow hole found within Sinking Run, and water samples were collected at 6 – hour intervals for 2.5 days in the adjacent Little Juniata River. Analysis of dye intensities at the ten sampling locations using a spectrofluorophotometer revealed discharge from a riparian spring on the Little Juniata River, located within the Bellefonte Dolomite and upgradient of Sinking Run. Dye was not detected within the lower reaches of Sinking Run, indicating that the lower reaches of Sinking Run are hydrologically disconnected from the upper reaches of the stream. The short storage time and localized discharge of the dye indicates conduit flow influence along bedding planes, dependent on geologic structure rather than surface topography.  This study seeks to locate and provide insight into fluid flow to potentially vulnerable springs, which are particularly important for managing the ecologically valuable trout fisheries of the Little Juniata River. 

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