Under the action of gravity, surface water and groundwater always tend to d&:H&o)T!
flow from higher to lower elevations. Surface water will flow over solid and 71B3a
through permeable formations, and its volume and velocity are a function of YTY%#"
the available supply and the fluid head. Groundwater can move only 4YbC(f
through a pervious material (fractured or fissured rock or soils with e/e0d<(1
interconnected open voids), so its flow characteristic is also a function of dhRJg"vrQ
formation permeability. Groundwater elevation varies as the supply source `0BdMKjA
varies and can be raised or lowered locally by increasing or decreasing the SA6hbcYk
local supply (naturally by precipitation or artificially by pumping a well or FyD.>ot7M
irrigating). In general, over a large surface area, groundwater surface is a PB~_I=
subdued replica of ground surface.