CHAPTER VIII. 

 ARTESIAN FLOWS. 



Requisites of Artesian Flows. A flowing well may be 

 obtained at any point where water is confined in the earth under 

 sufficient pressure to lift it to the surface, whether this be in 

 drift, in sandstone, in limestone or in granite, or whether the 

 water occupies the pores of the rocks or occurs in bedding planes, 

 joints, cleavage partings or in open solution passages. 



The first essential is a reservoir, which, in the scientific sense, 

 is any opening or series of openings in soils or rocks capable of 



FIG. 27. Section of an artesian basin. A, porous stratum; B, C, impervious beds 

 below and above A, acting as confining strata; F, height of water level in porous 

 bed A, or, in other words, height in reservoir or fountain head; D, E, flowing wells 

 springing from the porous water-filled bed A. (Chamberlin.) 



holding water. This must be filled with water, the escape of 

 which the second essential is prevented by an overlying im- 

 pervious bed or in some one of a dozen different ways. The third 

 essential is an adequate source of pressure. Usually this pressure 



FIG. 28. Section showing transition from porous to impervious bed. A , an open por- 

 ous bed inclosed between impervious beds B and C and grading into dense non- 

 water-bearing bed at E; F, original head; D, flowing well. (Chamberlin.) 



results from the fact that the catchment area of the water-bearing 

 reservoir is higher than the point at which it is tapped by the well. 

 Three of the simplest and most common artesian systems are 

 illustrated by Figures 17 (p. 41), 27 and 28. 



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