396211 - The Effect of the Vertical Hydraulic Conductivity on the Salt Transport from an Estuary into the Underlying Aquifer
Thursday, June 7
10:30 AM - 12:00 PM
Location: Lakeshore B
Ashok PAndit, 150 W Florida – Florida Institute of Technology; Howell Heck, 150 W Florida – Florida Institute of Technology
Heavier saltwater overlies fresh groundwater in many estuaries. It has been shown in the case of the Swan-Canning Estuary in Australia that unstable conditions occur if the anisotropy ratio is relatively small. An unstable condition causes salt fingers to migrate from the estuary into the underlying aquifer which can result in significant salt transport from the estuary into the aquifer. This study examines the effect of the anisotropy ratio on the transport of salt from the Indian River Lagoon (IRL), an estuary on the east-central coast of Florida, into the unconfined aquifer. The coupled model SEAWAT was used to examine the salt transport from the IRL to the underlying unconfined aquifer at two transects, Eau Gallie and River Walk. The model runs included a calibrated model using spatially varying anisotropy ratios, and others with uniform anisotropy ratios. The lateral hydraulic conductivity at the two transects was 20 m/d, and 13 m/d, respectively. Results showed that the condition remained stable and no fingering occurred in either transect when the anisotropy ratio was 150 or higher. The magnitude of fingering increased significantly as the anisotropy ratio decreased. An anisotropy ratio of 10, which is typically used in numerical models, showed considerable fingering. The condition was stable for the calibrated model. A key conclusion is that it is important to know the correct anisotropy ratio prior to modeling as arbitrarily selected anisotropy ratios can lead to highly erroneous results related to salt transport.