Question

How does water flow underground?

Answer 1

Within pore volume

Explanation:

From higher elevations to lower elevations groundwater flow occurs due to gravity. However, only the porous space allow water molecules to move. In groundwater movement, porosity (volume of porous space out of volume of total space underground) is an important factor along with type of subsurface (silt, clay or sand) and hydraulic gradient (slope).

See the figure below