File:Water Supply and Irrigation Papers of the United States Geological Survey (1902) (14586385050).jpg

Identifier: watersupplyirrig6571unit (find matches)
Title: Water Supply and Irrigation Papers of the United States Geological Survey
Year: 1902 (1900s)
Authors: United States Geological Survey
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Contributing Library: Clemson University Libraries
Digitizing Sponsor: LYRASIS Members and Sloan Foundation

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dequate rain-fall to furnish this supply. VII. An absence of any (easy) escape for the water at a lower level than thesurface at the well. These seven prerequisites as stated by Chamberlin have been widelyquoted by various writers and have become classic. The writer hasmade no change in the statements except the substitution of the wordeasy for any in VII, which is undoubtedly in accord with themeaning intended by Professor Chamberlin. Of course the less oppor-tunity there is for the water of the water-bearing rock to escape at alevel below that of the well the higher will be the head of pressure at thewell, but the water-bearing stone is usually so fine that the frictionalresistance offered by it to the movement of the water is sufficient toestablish considerable pressure a few miles back from an outcrop.As water flows through a horizontal porous medium under a head at o Fifth Ann. Rept. U. S. Geol. Survey, 1885, pp. 131-173. U. S. GEOLOGICAL SURVEY WATER-SUPPLY PAPER NO. 67 PL. VIII
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LINES OF FLOW INTO A WELL IN A REGION IN WHICH THE GROUND WATERHAS A CONSTANT MOTION IN A GENERAL DIRECTION. ARTESIAN WELLS. 83 one end, the pressure gradually drops from the maximum value a1the end at which the water enters to nothing at the free end fromwhich the water flows. This is illustrated by fig. 45. If we shouldprevent the escape of water at K7 G2, it would rise to correspondingheights (H? IT, H) in all of the tubes. In spite of the free escapeat the right end of the sand column K7 G2, the pressure gradientHj H2 II. II4 H5 H,j is sufficient to produce a flow at any point alongthe tube K, K6 if the wall of the tube be punctured. In this case wemay imagine that the water-bearing sand and its confining tuberepresent, respectively, the water-bearing stratum and the upper andlower impervious strata of an artesian basin, the water column at theleft of the figure corresponding to the higher outcrop of the pervious

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