Figure: 09-12PE-B Title: Mean annual ground temperatures at Bonanza Creek, Fairbanks, Alaska from 1930 to 2003. Caption: (NOAA/Vladimir E. Romanovsky, University of Alaska, Fairbanks) Keywords: ice, permafrost, global warming, climates, greenhouse gases
Figure: 09-25PE-E Title: Subsidence around Las Vegas. Caption: InSAR-derived maps showing ground subsidence due to groundwater pumping in the Las Vegas Valley between April 1992 and December 1997. (From USGS Fact Sheet 165-00, Land Subsidence in the United States, 2000.) Keywords: groundwater, aquifers, water tables
Title Page Photo “ Water is the one substance from which the earth can conceal nothing; it sucks out its innermost secrets and brings them to our very lips. ”—Jean Giraudoux (U.S.G.S. Water Quotes, http://ct.water.usgs.gov/EDUCATION/morewater.htm)
Vocabulary thermohaline circulation (p. 269) tidal bore (p. 268) tidal range (p. 267) tides (p. 267) waterless zone (p. 283) water table (p. 281) zone of aeration (p. 281) zone of confined water (p. 282) zone of saturation (p. 281) lake (p. 273) marsh (p. 278) permafrost (p. 273) permeability (p. 280) porosity (p. 280) runoff (p. 263) salinity (p. 266) subartesian (well) (p. 283) swamp (p. 278) aquifers (p. 281) artesian well (p. 283) global conveyer-belt circulation (p. 269) groundwater (p. 281) hydrologic cycle (p. 261) iceberg (p. 271) ice floe (p. 271) ice pack (p. 271) ice shelf (p. 271)
Aquifer—where underground water is stored; a permeable subsurface rock layer that can store, transmit, and supply water.
Aquiclude—an impermeable rock layer that hinders or prevents water movements. Excludes water because of high density, or as in case of clay, because interstices are many but too small to transmit water.
Zone of saturation—the second hydrologic zone below the surface of the ground, whose uppermost boundary is the water table. The pore spaces and cracks in the bedrock and the regolith of this zone are fully saturated .
Groundwater—water found in the zone of saturation.
Water table—the top of the zone of saturation within the ground.
Where water table intersects Earth’s surface, water flows out.
A lake, swamp , marsh, or permanent stream is almost always an indication that the water table reaches the surface there.
Perched water table—occurs when a localized zone of saturation develops above an aquiclude.
Cone of depression—occurs when water is removed from well faster than underground water can replace it; this lowers the water table, which becomes the approximate shape of an inverted cone in the immediate vicinity of well.
Zone of confined water—the third hydrologic zone below the surface of the ground, separated from zone of saturation by impermeable rock.
Occurs in many, but not most parts of world.
It contains one or more permeable rock layers (aquifers) into which water can infiltrate.
If drilled into, confining pressure will force water to rise in the well.
Piezometric surface—the elevation to which water will rise under natural confining pressure in a well.
Artesian well —the free flow that results when a well is drilled from the surface down into a zone of confined water and the confining pressure is sufficient to force the water to the surface without artificial pumping.
Subartesian well —the free flow that results when a well is drilled from the surface down into a confined aquifer but which requires artificial pumping to raise the water to the surface because the confining pressure forces the water only part way up the well shaft.
Waterless zone —the lowermost hydrologic zone that generally begins several kilometers or miles beneath the land surface and is characterized by the lack of water in pore spaces due to the great pressure and density of the rock.