To locate
groundwater accurately and to determine the depth, quantity, and quality of the
water, several techniques must be used, and a target area must be thoroughly
tested and studied to identify hydrologic and geologic features important to
the planning and management of the resource. The landscape may offer clues to
the hydrologist about the occurrence of shallow groundwater. Conditions for
large quantities of shallow groundwater are more favorable under valleys than
under hills. In some regions--in parts of the arid Southwest, for example--the
presence of "water-loving" plants, such as cottonwoods or willows,
indicates groundwater at shallow to moderate depth. Areas where water is at the
surface as springs, seeps, swamps, or lakes reflect the presence of
groundwater, although not necessarily in large quantities or of usable quality.
Geology is the key
Rocks are the most
valuable clues of all. As a first step in locating favorable conditions for
groundwater development, the hydrologist prepares geologic maps and cross
sections showing the distribution and positions of the different kinds of
rocks, both on the surface and underground. Some sedimentary rocks may extend
many miles as aquifers of fairly uniform permeability. Other types of rocks may
be cracked and broken and contain openings large enough to carry water. Types
and orientation of joints or other fractures may be clues to obtaining useful
amounts of groundwater. Some rocks may be so folded and displaced that it is
difficult to trace them underground.
Existing wells provide clues
Next, a
hydrologist obtains information on the wells in the target area. The locations,
depth to water, amount of water pumped, and types of rocks penetrated by wells
also provide information on groundwater. Wells are tested to determine the
amount of water moving through the aquifer, the volume of water that can enter
a well, and the effects of pumping on water levels in the area. Chemical
analysis of water from wells provides information on quality of water in the
aquifer.
How groundwater occurs in rocks
Groundwater is
simply the subsurface water that fully saturates pores or cracks in soils and
rocks. Aquifers are replenished by the seepage of precipitation that falls on
the land, although they can be artificially replenished by people, also. There
are many geologic, meteorologic, topographic, and human factors that determine
the extent and rate to which aquifers are refilled with water.
Water dowsing?
Do
you recognize this? It is a dowsing stick, one of a number of items
that some people use in an attempt to locate underground water. Find out
how these methods are used.
Sources and more information
- Water Dowsing, USGS General Information publication
- Appraising the Nation's Ground-Water Resources, USGS General Information publication
SOURCE:
http://water.usgs.gov/edu/gwhowtofind.html
How Dowsing Works -
A Youtube Documentary Video from
The British College of Dowsing
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