STORM HYSTERESIS AS IN INDICATOR OF MATRIX FLOW PATHS IN A CONDUIT-DOMINATED SPRING

Studying how the chemistry of karst springs reacts to periods of increased discharge can provide insights into how these systems store and transmit water. A new spring classification system updating the classic 1971 work of Shuster and White will be based on these storm responses. Preliminary data show that high frequency storm data yield additional information on recharge and flow patterns. A clockwise hysteresis occurs in water samples taken from Smullton Sinks, a karst spring in Centre County, PA, over the course of rainstorm events. The Mg:Ca ratio plotted against water depth suggests that Mg-rich water stored in the matrix is being forced out by rainfall event water entering the system. This was not expected from Smullton, a conduit spring by Shuster and White’s classification, because low Mg conduit water would be expected to arrive before any matrix water being forced out and into the spring. High Mg:Ca ratios are also indicative of diffuse recharge.

Depth measurements recorded at Smullton, Springhouse, and Weaver springs (all in Centre County, PA) show similar reaction times in response to increased recharge, though Smullton was classified as a conduit spring and Springhouse and Weaver were classified as having predominantly diffuse flow. Therefore, Smullton would be expected to have faster reaction time than Springhouse or Weaver. Increased sampling frequency will allow for springs to be placed more precisely along the continuum stretching from diffuse to conduit flow and from diffuse to focused recharge as will the hysteresis patterns generated by the springs.

Understanding how water flows through karst systems is crucial for water supply and contamination protection. Changes in concentration of dissolved species in spring water over the course of a storm are key to developing a new classification system. This system once developed will be put to use predicting how complex karst environments react to storm events.