428 GEOLOGY OF THE DENVER BASIN. 



THE LIFE OK THE WELLS. 



The wells of the city of Denver and its suburbs range in date of sink- 

 ing from March, 1883, to the present day, although in the past six years 

 operations have been at a minimum. Well statistics gathered in February, 

 1886, and again in December, 1890, show for the intervening period a 

 gradual but pronounced diminution in yield, appearing first as a decrease 

 in the strength of flow and in the discharge for a particular area, followed 

 by an increased influence of one well upon another and a not infrequent 

 failure to flow at the surface, this gradually extending throughout the entire 

 district; finally, there appears under the heavy overdraft by pumping 

 an actual lowering of the water-table to a considerable depth beneath the 

 surface. It is difficult to formulate a more detailed statement than this 

 regarding the action of the wells, on account of their interrelations, the 

 silting up of the tubes, leakage, and the imperfect methods of packing, 

 casing, and drilling. 



The period of 1885-1887 was one of special activity in well-boring, 

 and during this time the effects of over-development, which in later times 

 increased to an actual drain on the total water supply, gradually became 

 evident. Between the years 1888 and 1890 but few of the wells yielded 

 flows at the surface, and these only for a short time. In December, 1890, 

 from the long and heavy overdraft, there were but six flowing wells, and, 

 with these exceptions, the water-levels had sunk to between 1 "> and 200 feet 

 beneath the surface. The surface of the water-table of 1890 is found to 

 be undulating, approximately with the surface of the ground. The plane 

 is naturally somewhat broken, for the relative positions of the wells and 

 the character and texture of the strata are not without their influence, and 

 in special instances of heavy drain, as at the well of the Union Depot, the 

 water has lowered a considerable distance beyond the general level. 



The life of individual wells has varied greatly, ranging from two 

 months to six years and over, though in the latter case the flows have 

 materially diminished in quantity. In regard to the wells sunk most 

 recently, a small number flowed tor a few days or weeks, when the water 

 then fell beneath the surface and in time assumed a level, the further 

 lowering of which became evident only after considerable lapse of time. 



