HYDROGEOLOGIC COMPARISON BETWEEN FIRST-MAGNITUDE SPRINGS OF THE TERTIARY LIMESTONE AQUIFERS OF WEST-CENTRAL FLORIDA AND THE LATE CENOZOIC BASALT AQUIFERS OF THE SNAKE RIVER PLATEAU, IDAHO

Both Florida and Idaho are renowned for first-magnitude springs – springs that discharge more that 100 cfs. Springs in Florida collectively discharge billions of gallons every year from the Floridan Aquifer System, a Tertiary age (30-40 Ma) karstified limestone aquifer. A series of major springs in Idaho contribute more than 90% of the total flow of the Snake River along the old Oregon Trail. These Idaho springs release water from Late Cenozoic (3-5 Ma) flow basalts. Though large springs in Florida and Idaho are in disparate geological settings, our research indicates that their behavior is more similar than not.

Investigation into the architecture of both aquifers reveals that radically different formative processes – marine and coastal sedimentation in the case of Florida, volcanic eruptions and lava flows in Idaho – result in a convergence of aquifer properties. For instance, permeability is stratigraphically controlled in both aquifers. Analysis of time-series discharge measurements from several springs indicates that storage is large in both aquifers; therefore, the springs have a long memory, with a large lag-time between precipitation and discharge. Many springs in Florida and Idaho do not respond to individual storm events; however, seasonal, climatic, and anthropogenic effects are clear.

An understanding of aquifer behavior is essential to residents of Florida and Idaho as most residents of these two states depend upon water from their respective aquifers for domestic, industrial, and agricultural purposes. Further investigation into the similarities of these two aquifer systems will help us learn how to manage both more effectively.