404 GEOLOGY OF THE DENVER BASIX. 



WELLS IN INTERMONTANE VALLEYS. 



Of the valleys in the mountains of Colorado the San Luis has long 

 since become prominent for its large supply of artesian water. Boring in 

 this valley commenced sometime in the year 1886, possibly not until 1887. 

 On December 1, 1888, there were recorded 1 twelve wells, from 85 to 235 

 feet deej), and flowing at the surface from 1 to 40 gallons per minute, one 

 reaching 400 gallons. Since then the industry has been vigorously prose- 

 cuted. In December, 1890, the flowing wells numbered 394, and at the 

 present day they largely exceed this figure even. The water is used not 

 only for domestic purposes, but in irrigation as well. The head of the wells 

 has materially diminished with the great increase in their number. 



More extended accounts of the San Luis wells may be found in the 

 several reports of the State engineer of Colorado, and in the volume of 

 the Eleventh Census on "Agriculture by irrigation," by Mr. F. 11. Newell. 



The yield of the San Luis wells is said to he derived from Quaternary 

 gravels, a source similar to that of the Utah wells. 



in the LTncompahgre Valley well boring began at about the same 

 time as in the San Luis. At Montrose- there were reported on December 

 1, L888, two flowing wells, yielding 27 and 35 gallons per minute, 

 respectively, from depths of 936 and 800 feet. 



On the confines of the Florence oil field between the years 1880 and 

 1890 artesian water was encountered in several instances in boring for 

 petroleum. The flows from the Dakota sandstone are invariably large and 

 usually quite strongly mineralized. 



ARTESIAN CONDITIONS OF THE DENVER BASIN. 



An artesian well is one that taps a subterranean body of water at a 

 point where it is under hydrostatic pressure sufficient to cause the water to 

 rise in the well and flow at the surface. "Wells which show a rise only, 

 without flowing at the surface, are not, in the proper use of the term, 



artesian. 



Colorado Stale Engineer's Report, 1887-88, p.299. 

 Idem, 11.355. 



