Groundwater
Groundwater occurs nearly everywhere below the surface of the Earth, where, as we have said before, it fills the pore spaces and fractures in rock at levels below the water table. The zone beneath the water table is called the saturated zone. Groundwater flows into the saturated zone by percolation downward from rainfall on the surface. Surface bodies of water, like streams, lakes, and swamps, are areas where the water table is exposed at the surface. Springs are also areas where the water table is exposed at the surface. If one digs or drills a well to intersect the water table, water will flow into the well and fill it to the level of the water table. The level of the water table can change as a result of changing amounts of input in the groundwater system (called recharge) and output from the groundwater system (called discharge). Recharge takes place by water infiltrating down from the surface. Discharge occurs as a result of outflow through surface bodies of water, springs, and wells. During the wet season the water table is generally higher because recharge exceeds discharge. During dry seasons the water table is depressed because discharge exceeds recharge. Likewise, during periods of drought the water will be lower.