Geochemistry at a Karst Spring Reveals Complex Stormflow Dynamics in an Eogenetic Karst Aquifer

Area of Science:

• Hydrogeology
• Environmental Science
• Karst Geomorphology

Background:

• The Floridan Aquifer System (FAS) is a complex, eogenetic karst aquifer with unique porosity and cave networks.
• Understanding flow dynamics and residence times is crucial for water resource management in the FAS.
• Stormflow in eogenetic karst aquifers, particularly after extreme weather events, remains understudied.

Purpose of the Study:

• To investigate stormflow dynamics in the eogenetic FAS following Hurricane Idalia.
• To analyze the geochemical and hydrological responses to hurricane-induced rainfall.
• To assess the impact of karst characteristics on stormflow chemistry and residence times.

Main Methods:

• In-situ sensor data (NO3-N, specific conductance, discharge) collected at 15-min intervals.
• Grab sampling for water isotopes and major element chemistry.
• Analysis of stormflow pulses and their geochemical signatures.

Main Results:

• At least two distinct stormflow pulses were identified through NO3-N and geochemical analysis.
• One pulse showed dilution of NO3-N, while another mobilized NO3-N, persisting for at least 19 days.
• Stormflow pulses amplified existing seasonal NO3-N trends, indicating complex interactions.

Conclusions:

• Eogenetic karst characteristics significantly influence stormflow dynamics and residence times in the FAS.
• The carbonate bedrock matrix plays a critical role in controlling stormflow behavior.
• Findings are vital for refining water resource strategies in karst aquifer systems.