7. how much farming irrigation water comes from this underground water formation?

A lot through Aquifers

Explanation:

Groundwater is located in cracks and spaces in soil, sand and rock. It is stored and moves slowly through geologic formations of soil, sand and rocks called aquifers.

Precipitation from rainfall or other released water sources from dams, drainage onto the land surface to become groundwater. If the water meets the water table (below which the soil is saturated), it can move both vertically and horizontally. Water moving downward can also meet more dense and water-resistant non-porous rock and soil, which causes it to flow in a more horizontal fashion, generally towards streams, the ocean, or deeper into the ground.

The value of an aquifer as a source of groundwater is a function of the porosity of the geologic stratum, or layer, of which it is formed. Water is withdrawn from an aquifer by pumping it out of a well or infiltration gallery. An infiltration gallery typically includes several horizontal perforated pipes radiating outward from the bottom of a large-diameter vertical shaft.