ARTESIAN WELLS. 427 



author] gallons, which amount has (lowed or has been pumped from the wells in the 

 six years of existence of most of them, besides, of course, the amount supplied by 

 rainfall in these six years on the collecting area. 



It is more difficult to estimate the yearly supply on the collecting area with any 

 degree of accuracy. Accounts of the regular discharge of wells, either flowing in 

 1S86 or pumping in 1S90, could only be obtained in a few instances. Mr. Slack, who 

 collected the statistics for 1886, estimates that in February of that year the average 

 discharge of all the wells in the basin, in Denver and in the surrounding country, 

 was 2,900,000 gallons every twenty-four hours. The number of flowing wells was at 

 this time at a maximum. Since, the aggregate capacity of the wells lias yearly fallen 

 off, but how much can not be determined. Within wide limits the average pro- 

 duction during the last six years could perhaps be estimated in the following manner: 

 Accept that 25 per cent of the rainfall enters the earth, the balance being carried 

 away over the surf ice as visible streams, evaporated, and taken up by vegetation. 

 The yearly rainfall is about 14 inches. Twenty-live per cent of this amount is 1 g feet 

 n six years, which, sinking into a collecting area of 28,512,000 square feet, equals 

 49,896,000 cubic feet, or 374,220,000 [373,248,026: author] gallons, in two thousand 

 one hundred and ninety days, an average of 170,900 [170,433: author] gallons per 

 twenty-four hours. Adding to the above estimated amount of 49,896,000 cubic feet 

 collected in six years, the 349,272,000 [299,535,667: author] cubic feet of water 

 lowered or drained out of the originally saturated sandstone strata before wells 

 were bored makes 399,168,000 [349,431,067: author] cubic feet in two thousand one 

 hundred and ninety days, or 182,270 [159,557: author] cubic feet per day, equal to 

 1,367,025 [1,193,569: author] gallons average daily production of wells during the 

 last six years. 



Comparing this figure with the estimate of Mr. Slack and considering the falling 

 off in discharge since he made his estimate, it would seem that this daily average of 

 1,367,025 [1,193,569: author] gallons for the last six years might approximate the 

 truth. 



From the foregoing we may conclude with some degree of certainty that the 

 probable average amount of water permanently available from artesian wells in and 

 around Denver does not exceed 180,000 cubic feet daily, which is about 1^, cubic feet 

 per capita of Denver's population in 1890. We may also conclude that if all the 

 wells in Denver were plugged, it would take forty years before the water-bearing 

 strata of the Tertiary in the Denver Basin were again in the condition of saturation 

 existing when the first well was sunk. 



