![\"Underground\"](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/09\/underground.jpg\")
<\/p>\nWith regard to existence of water at different depths in sub-surface regions, earth\u2019s crust can be divided into various zones, namely.<\/p>\n
There are various types of geological formation that would exists below the earth\u2019s surfaces but with regard to its water holding capacity (i.e. porosity) and its ability to allow the flow or water through interconnecting voids (i.e. yield), they are classified as:<\/p>\n
(a) Aquifers<\/strong><\/p>\n A permeable stratum or a geological formation of permeable material, which is capable of yielding appreciable quantities of ground water under gravity, is known as an aquifer. When an aquifer is overlain by a confined bed of impervious material, then this confined bed of impervious material is known as aquiclude. If a well is excavated through an aquifer, then amount of water yielded by it depends upon:<\/p>\n (i) Permeability of aquifer (b) Aquifuge<\/strong><\/p>\n The geological is that geological formation which is neither porous nor permeable and it neither contains nor yields ground water. Granite rock example of aquifuge.<\/p>\n (c) Aquitard<\/strong><\/p>\n The geological formation which does not yield freely to wells due to its lesser permeability, although seepage is possible thought it. The yield from such a formation is thus insignificant. Sandy clay is an example of aquitard.<\/p>\n (d) Aquiclude<\/strong><\/p>\n The geological formation which is highly porous, containing large quantities of water, but essential impervious, as not to yield water. A clay layer is an clay layer example of aquiclude.<\/p>\n
\n(ii) Thickness of aquifer<\/p>\n