Water table

Water table is the upper surface of the zone of saturation of water occurring in the ground. This is the level below which the soil and rock are saturated with water. The water table separates the groundwater zone that lies below it from the capillary fringe, or zone of aeration, that lies above it. The water table fluctuates both with the seasons and from year to year because it is affected by climatic variations and by the amount of precipitation used by vegetation. It also is affected by withdrawing excessive amounts of water from wells or by recharging them artificially.

Formation

The water table is formed by the infiltration of precipitation through the soil and its percolation downward to the zone of saturation. The rate of recharge of the water table can be influenced by the type of surface material (soil, rock, etc.), vegetation cover, and the amount and intensity of precipitation.

Measurement

The depth of the water table can be measured in a well that is not being pumped and is free to move up and down. The level at which water stands in this well is the same as the water table outside the well. The depth to the water table can also be determined indirectly by electrical resistivity and seismic refraction methods.

Importance

The water table is an important factor in agriculture, as it can significantly influence crop production. In areas where the water table is close to the surface, crops may benefit from the water supply. However, a high water table can also cause problems such as waterlogging of agricultural land, which can result in reduced crop yield or crop failure.

See also

• Aquifer
• Groundwater
• Hydrology
• Water cycle