418 GEOLOGY OF THE DENVER BASIN. 



narrower hands of the coal scries — available for collecting purposes for the 

 artesian supply of the Denver Basin is approximately 51,480,000 square 

 feet, based upon a width of 250 feet and a length of outcrop along the 

 foothills of 39 miles, from Wildcat Mountain, south of the Platte, to South 

 Boulder ('reck. The extensive exposures of this scries of sandstones in 

 the northwestern part of the field are unavailable tor the general artesian 



supply on account of intervening faults. The area of 51,480,000 square 

 feet covered to a depth of li inches, rhc available rainfall for absorption, 

 affords "_\">,7 1:0,000 cubic feet, or L92,548,585 gallons, of water to be taken 

 up l>v the underlying rocks each year. 



The area of the Arapahoe formation available for absorption, with 

 reference to the Denver artesian system, and which, therefore, excludes 

 the outlier northwest of Dry ('reck, is about L61| square miles, or 

 1,505,149,440 square feet. The amount of water falling upon this area for 

 the absorption by its strata is 2,252,574,720 cubic feet, or 16,850,480,244 

 gallons, per year. 



The area of the Denver formation, disregarding the covering of loess 

 which overlies it in many localities, is approximately 289 square miles, or 

 8,056,857,600 square feet, receiving upon it 4,028,428,800 cubic feet, or 

 30,134,7 12,207 gallons, of water per year, as the amount here available for 

 absorption. 



The total quantity of water falling annually upon the artesian strata 

 of the 1 >enver Basin and available for absorption bv them is 47, 1 7 7 . 7 _' 1 ,036 

 gallons. 



From water of irrigation. — Prof. P. II. Van Dicst, 1 of Denver, has also esti- 

 mated the quantity of water brought onto the absorbing areas l>v irrigation 

 ditches. He says: 



But rainfall is not the only source of water within this basin. The many 

 irrigation ditches bring a greal amou.n1 of stored-up water from rainfall outside of 

 the basin within its limits. It is estimated that of the amount of water brought in 

 at the upper part of the High Line ditch, not more than 60 per cent is utilized for 

 irrigation. This ditch has a flow of nearly 300 cubic feet per second during the 

 thirty maximum days; of one-third of that flow during the thirty days before 



The artesian wells of Denver: Scientific Society, Denver, Colo., June, 1884, pp. 37 and 38. 



