water table

Upper level of groundwater (water collected underground in porous rocks). Water that is above the water table will drain downwards; a spring forms where the water table meets the surface of the ground. The water table rises and falls in response to rainfall and the rate at which water is extracted, for example for irrigation and industry.

In many irrigated areas the water table is falling due to the extraction of water. Below northern China, for example, the water table is sinking at a rate of 1 m/3 ft a year. Regions with a high water table and dense industrialization have problems with pollution of the water table. In the USA, New Jersey, Florida, and Louisiana have water tables that are contaminated by both industrial wastes and saline seepage from the ocean.