This is a picture of the San Joaquin Valley southwest of Mendota in the agricultural area of California. Years and years of pumping ground water for irrigation has caused the land to drop. The top sign shows where the land surface was back in 1925! Compare that to where the man is standing (about 1977).
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Ground-water pumping and land subsidenceCompaction of soils in some aquifer systems can accompany excessive ground-water pumping and it is by far the single largest cause of subsidence. Excessive pumping of such aquifer systems has resulted in permanent subsidence and related ground failures. In some systems, when large amounts of water are pumped, the subsoil compacts, thus reducing in size and number the open pore spaces in the soil the previously held water. This can result in a permanent reduction in the total storage capacity of the aquifer system. |
Earth's water
Water Science home page
USGS Water Resources The URL for this page is http://ga.water.usgs.gov/edu/earthgwlandsubside.html Comments? Contact Howard Perlman Last Modified: Apr 02, 2004 |