Under the action of gravity, surface water and groundwater always tend to Q\#{2!I
flow from higher to lower elevations. Surface water will flow over solid and yj'' \
through permeable formations, and its volume and velocity are a function of ef}E.Bl
the available supply and the fluid head. Groundwater can move only )_*a7N!
through a pervious material (fractured or fissured rock or soils with QYfAf3te
interconnected open voids), so its flow characteristic is also a function of eH%L?"J~:
formation permeability. Groundwater elevation varies as the supply source c4> s E[]
varies and can be raised or lowered locally by increasing or decreasing the ?lDcaI>+n
local supply (naturally by precipitation or artificially by pumping a well or .xkV#ol
irrigating). In general, over a large surface area, groundwater surface is a V/}>>4
subdued replica of ground surface.
