Editing Water table (section)

== Fluctuations ==
[[File:Water table-season fluctuation.svg|thumb|350px|Seasonal fluctuations in the water table may cause river beds to dry up during the dry season]]

=== Tidal ===
On low-lying [[Island#Oceanic islands|oceanic islands]] with porous soil, [[freshwater]] tends to collect in [[Lens (geology)|lenticular]] pools on top of the denser [[seawater]] intruding from the sides of the islands. Such an island's freshwater lens, and thus the water table, rises and falls with the tides.

=== Seasonal ===
In some regions, for example, [[Great Britain]] or [[California]], [[winter]] [[Precipitation (meteorology)|precipitation]] is often higher than [[summer]] precipitation and so the groundwater storage is not fully recharged in summer. Consequently, the water table is lower during the summer. This disparity between the level of the winter and summer water table is known as the "zone of intermittent saturation", wherein the water table will fluctuate in response to climatic conditions.

=== Long-term ===
[[Fossil water]] is groundwater that has remained in an aquifer for several millennia and occurs mainly in [[desert]]s. It is non-renewable by present-day [[rainfall]] due to its depth below the surface, and any extraction causes a permanent change in the water table in such regions.