A new study of Byrds Mill Spring (BMS), Oklahoma’s largest spring and an important drinking-water source, by John Richins, Aestus’ Dr. Todd Halihan, and Ndubuisi Igwebuike, provides new insight into how hydraulic siphons and rapid recharge pathways can influence groundwater quality during extreme precipitation.
BMS discharges from the Arbuckle-Simpson aquifer, which is located within the heavily karstified Arbuckle Group. Under normal conditions, BMS maintains remarkably stable electrical conductivity (EC) of around 520 µS/cm. But during the extreme rainfall of May 2015, EC repeatedly dropped to nearly 10 µS/cm—close to rainwater levels—even while the spring discharge rate remained relatively stable.
Using precipitation, groundwater-level, discharge, and continuous EC data, researchers developed a hydraulic siphon and groundwater-mixing model to explain the oscillations in EC. The model indicated a siphon-controlled recharge pathway approximately 100 meters upgradient of the spring. Electrical resistivity imaging provided independent evidence of a fault-related structure at roughly the same location, see the graphic below.
The results also point to two nearby intermittent losing streams as likely rapid recharge pathways during major storms.
The practical takeaway is significant: changes in water quality can occur without obvious changes in spring discharge. Karst aquifers contain fractures, conduits, and other preferential pathways that can rapidly connect surface water with groundwater, particularly during extreme storms. This study demonstrates how even small, intermittent losing streams can become significant recharge pathways, potentially influencing spring water quality without producing obvious changes in discharge. Monitoring flow alone may therefore miss important storm-driven inputs to karst groundwater systems.
