Answer to Question 1
The best aquifers are those materials that have high porosity and permeability. These include sediments of sand or gravel, poorly cemented sandstone or conglomerate, porous limestones. Highly fractured rocks also make good aquifers.
Answer to Question 2
An aquifer is a body of rock or regolith with sufficient porosity and permeability to provide water in useful quantities to wells or springs. It is contained by confining beds of low permeability. Good aquifers have both high porosity and high permeability, which allows high volumes of water into the aquifer. Sands and gravels are very good aquifers, and some rocks such as limestone make good aquifers.
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