Under the action of gravity, surface water and groundwater always tend to LN!e_b
flow from higher to lower elevations. Surface water will flow over solid and V:Z}cfR .7
through permeable formations, and its volume and velocity are a function of )P|&o%E
the available supply and the fluid head. Groundwater can move only %]U'
through a pervious material (fractured or fissured rock or soils with Pjvzefp
interconnected open voids), so its flow characteristic is also a function of 2*[Gm e
formation permeability. Groundwater elevation varies as the supply source =PQMd
varies and can be raised or lowered locally by increasing or decreasing the 8x,{rS qq
local supply (naturally by precipitation or artificially by pumping a well or T l/!Dn
irrigating). In general, over a large surface area, groundwater surface is a ; 5cN
o&
subdued replica of ground surface.
