The groundwater circulation is limited in Sri Lanka because nine tenth area of the island is underlain by metamorphic hard rocks which are generally very impermeable. Therefore to satisfy the water demand some other possibilities of water resources should be explored before starting a groundwater investigation programme for a given area.
The water resources of a Miocene limestone aquifer in northwest Sri Lanka were investigated. The limestone aquifer receives recharge although it is buried beneath a thick sequence of Quaternary deposits of low permeability which cover the whole basin. Hydrochemical and pumping-test data show that this recharge occurs as leakage through the semi-permeable cover.