Artesian J Veils in North and South Dakota. 375 



Huron, the head is 1,948 feet above the sea; at Miller it has de- 

 clined 73 feet in a distance of twenty-two miles to the east; and 

 in the thirty-eight miles thence to Huron it falls 184 feet more. 

 Between Fort Randall and Yankton, in a distance of sixty miles 

 from west to east, this plane descends at least forty feet, but the 

 descent is more if the well at Fort Randall is at a considerable 

 height above the Missouri river. In the next twenty-two miles 

 eastward to Vermillion the descent is 140 feet. This feature of 

 the artesian water supply is caused, as before stated, by its out- 

 lets through springs in outcrops of the Dakota sandstone, which 

 begin thirty to forty miles southeast of Vermillion and extend 

 thence southeast and south. 



All of the eastern outcrops of the Dakota sandstone are lower 

 than the upper portion of the James river basin and the wells 

 farther west at Highmore and Harold. These outcrops therefore 

 cannot be the sources from which the sandstone receives its 

 artesian water, but, as we have seen, they are the avenues of 

 its natural outflow. We must look instead to the western out- 

 crops of this formation, where it skirts the Black Hills and ex- 

 poses its upturned edges along the base of the Rocky mountain 

 ranges, for the area upon which water is carried downward into 

 the sandstone. Thence we know this stratum to be continuous be- 

 neath the plains to the James river valley, for there are no nearer 

 nor other inlets from w^hich the copious supply of the artesian 

 wells can come. At a plane of greater or similar depth an artesian 

 reservoir exists beneath much, if not all, of the country westward 

 to the mountains. The gradients of the altitudes to which the 

 water of wells is capable of rising along east to west lines in 

 South Dakota, as at Huron, Miller, and at Highmore, are ap- 

 proximately the same as the average westward ascent of the 

 country, demonstrating this western origin of the water supply, 

 and indicating that such wells may be obtained upon an exten- 

 sive region of the arid plains. 



How far then can this artesian water be utilized for irriga- 

 tion ? Will it then be practicable to store the water in reservoirs 

 for use in the season of growing crops, and especially during se- 

 vere droughts, like that which so reduced or in some portions 

 entirely cut off the crops in North and South Dakota last year? 

 To this inquiry we may reply by computing the amount of water 

 needed for irrigating a given space, as a quarter section of 160 



