Determination of Hydraulic Diffusivity of a Limestone Aquifer Using Spectral Analysis Techniques
In a tidally influenced aquifer system, hydraulic diffusivity of the aquifer is proportional to the speed and amplitude at which a finite pressure pulse of the tide propagates through the aquifer system. This pressure pulse results in a spectral signature in observed groundwater wells. Frequency domain analysis of the tidally impacted groundwater wells and tides provides a meaningful and non-invasive approach to determination of hydraulic diffusivity of an aquifer.
Hydraulic diffusivity was estimated for a prolific aquifer in South Florida based on identification of tidally influenced spectral signature, lag time, and amplitude in groundwater wells and tides. An analytical solution of sea-aquifer model with a leaky semi-confining layer separating an overly unconfined aquifer from an underlying semiconfined aquifer was applied to estimate hydraulic diffusivity; based on the parameter values obtained from the spectral analysis technique. The hydraulic diffusivity values for the aquifer obtained from the spectral analysis techniques was within the same order of magnitude as that obtained from pumping tests.