Usually when we talk about the water table we're describing the surface of local groundwater formations, or aquifers. Where the water table intersects the surface we find springs, rivers, ponds or lakes. People depend on fresh, unpolluted groundwater sources for drinking and for agricultural irrigation. Anything that affects the level of the water table or the quality of the water found in the aquifer is understood to have a water table impact.
Pollutants, chemicals that find their way into the groundwater, have a water table impact. A well can be rendered useless by pollution. Near the coasts there is a danger of salt water intrusion if the water table is over-pumped and drawn down faster than it is recharged by fresh water from rain, rivers, lakes, and streams. Over-pumping inland aquifers results in depletion and a lowered water table. Subsidence often occurs when the water table is drawn down and the rock and soil formations that were carrying the water dry up. Subsidence results in a permanent reduction of water volume in the aquifer, because no matter how much water may susequently be available for recharging, the rock formation has collapsed.
(Photo credit: the-tahoe-guy, Flickr)
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