Frequency Analysis of Shallow Water Tables for Drainage Applications

Abstract

In coastal areas with shallow aquifers, the minimum elevation of newly developed land is typically required to exceed the water-table elevation corresponding to a given return period. Determination of this regulatory water-table elevation usually requires a nonstationary frequency analysis of measured water-table elevations. In this paper, a simple and effective power-transform frequency-analysis procedure for extracting the requisite regulatory water-table elevation is presented and demonstrated. This procedure identifies the critical period yielding the maximum water-table elevation for a given return period, which is a robust regulatory elevation that might not need frequent updates. The assumptions underlying the proposed power-transform frequency-analysis procedure are shown to be valid at 23 of the 24 wells investigated in this study.