Under the action of gravity, surface water and groundwater always tend to BD}%RTeWKq
flow from higher to lower elevations. Surface water will flow over solid and J(maJuY
through permeable formations, and its volume and velocity are a function of |8[!`T*s
the available supply and the fluid head. Groundwater can move only bj 8pqw|;
through a pervious material (fractured or fissured rock or soils with gW4fwE^
interconnected open voids), so its flow characteristic is also a function of aaN/HE_
formation permeability. Groundwater elevation varies as the supply source Y8IC4:EO
varies and can be raised or lowered locally by increasing or decreasing the PNo:vRtsq
local supply (naturally by precipitation or artificially by pumping a well or L]"$dF
irrigating). In general, over a large surface area, groundwater surface is a
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subdued replica of ground surface.