Determination of vertical hydraulic conductivity of aquitards in a multilayered leaky system using water-level signals in adjacent aquifers

•We apply harmonic analysis approach in a multilayered leaky system.•We apply coherence analysis to identify leakage-induced water-level changes.•Kv of aquitard is calculated using water-level fluctuations in the aquifers.•Correlation between frequencies and phases support robust estimate of Kv.