Studies on groundwater recharge characteristics at a reclaimed land site with an equatorial climate using time‐series and spectral analyses

Groundwater recharge studies are essential for investigating the feasibility of using the reclaimed lands in Singapore for subsurface storage and recovery of water. Through time‐series and spectral analyses, net recharge percentages and stress‐filtering characteristics at the reclaimed land were found to depend strongly on the stress transfer velocity, which was a combined function of rainfall pattern and vadose zone thickness. Based on stress transfer velocity, a theory was established to provide logical explanations for the rainfall–recharge relationship, the observed stress‐filtering characteristics and the recharge percentage characteristics at the unconfined sandy aquifer. Although the reclaimed land site has a lithollogically homogeneous soil profile, a non‐uniform recharge pattern was observed to be influenced pronouncedly by the uneven density distribution of bush grasses. Under a bare soil condition, significantly lower recharge percentages were observed for areas under the influence of offshore tides. The unconfined sandy aquifer appears to dampen out the wave propagation of offshore tides rapidly within a short distance from the tidal source, though it has a fairly straight shoreline and is created from highly compacted sand fills. Copyright © 2006 John Wiley & Sons, Ltd.