As the Maltese rock strata are sedimentary type, the local rocks tend to have pores in them, therefore being permeable, that is they allow liquids and fluids to pass through them. In fact only the Blue Clay is impermeable therefore donít allow liquids and fluids to pass through. This scenario results into providing what is known as Groundwater that is water stored in the rock strata. Such zone is also known as Zone of Saturation.
Rainwater passes through permeable rock. When it meets impermeable rock it stops there and fill the pores of the above rock with water. This is called an aquifer which is the layer which holds groundwater. The boundary between the Zone of Saturation and Zone of Aeration is called Water Table. Water table resembles the topography and its level depends on:
When there is impermeable rock which interferes in the Aeration Zone, it will make it possible for the formation of another water table known as Perched Aquifer.
In Malta the largest aquifer is known as the Main Sea Level Aquifer. Here we have fresh water floating over less denser saline ground water. The water table is therefore to be found at sea level.