1. Ground water moving slowly through the microfissure network of a limestone, most of which eventually joins a major cave conduit and flows more rapidly. In most environments percolation water enters the limestone through a soil cover. It is therefore high in carbon dioxide and has a major influence on limestone dissolution and later redeposition of calcite speleothems. Percolation water accounts for most of the storage in a limestone aquifer, responds slowly to flooding in comparison to sinkhole water, and is normally of high enough quality to provide a drinking-water supply . 2. The movement in laminar flow under hydrostatic pressure of water through the interconnected, saturated interstices of rock or soil, excluding movement through large openings such as caves and solution channels. 3. The downward movement of water through the unsaturated zone . 4.The downward flow of water in saturated or nearly saturated porous medium at hydraulic gradients of the order of 1.0 or less . 5. The movement of water through saturated interior pore space . Synonym: seepage water.