Determination of hydraulic diffusivity of aquifers by spectral analysis

This study uses the cyclical frequency to develop the mathematical relation ship between hydraulic diffusivity and spectral density functions calculate d from groundwater level variation. Such relationship can be applied to (1) unsteady state, one-dimensional confined aquifer with time-dependent water level on both end boundaries, and (2) linearized unconfined aquifer with o r without vertical recharge. The spectral density functions of groundwater fluctuations are largely affected by the spectral density functions obtaine d from time-dependent end boundaries and their cross-spectral density funct ions. Hydraulic diffusivity of an aquifer can be solved by type-curve match ing technique at a specified frequency band under the conditions of (1) con fined aquifer having equal time-dependent boundaries on both ends, (2) unco nfined aquifer having equal time-dependent boundaries on both ends with sur face recharge, and (3) unconfined aquifer subjected to surface recharge but neglecting the water table fluctuations on both end boundaries.