THE SOUTH DAKOTA ARTESIAN BASIN, 



A GEOLOGICAL STUDY. 



BY FRED F. B. COFFIN. 



THREE conditions must be present to 

 make any country a desirable place 

 to live: a good climate, a fertile soil and 

 an abundance of pure and wholesome 

 water. 



That South Dakota possesses the first 

 two conditions in an eminent degree is 

 past controversy. It is the purpose of 

 this article to demonstrate from known 

 facts that the third condition exists here in 

 quantity, in permanency and in purity sec- 

 ond to no State in the Union. As a fur- 

 ther preliminary I will state that it is ut- 

 terly impossible to treat this subject in its 

 entirety in an article designed for the pub- 

 lic press, hence, only the salient features 

 will be presented. 



South Dakota lies at the foot of one of 

 the largest catch basins in the United 

 States, being no less than the upper Mis- 

 souri Valley. The drainage area of this 

 valley from Sioux City, Iowa, northwest- 

 ward is 314,900 square miles. All the 

 drainage of this vast area, with slight ex- 

 ceptions, surface and phreatic, must pass 

 through South Dakota on its escape sea- 

 ward. This vast area seems to have been 

 carved out by the hand of nature with con- 

 summate design. 



A glance at a map will show that this 

 area embraces nearly all of North and 

 South Dakota, the north half of Wyoming 

 and the eastern portion of Montana. 



An examination of the topography of 

 this area discloses the cause of many con- 

 ditions. Starting at Sioux City, la., and 

 going northward along the course of the 

 Jim river, which is the lowest part of the 

 basin, we find the elevations above sea 

 levels as follows: Sioux City, 1,097 feet; 

 Huron, S. D., 1,285 feet; Columbia, S. D., 

 1.315; Jamestown, N. D., 1,406 ft; and 

 at Devil's Lake, 1,464 feet, showing a 

 gradual ascent northward of a little less 

 than one foot per mile. 



Going east from the Jim river, say at 

 Huron, we reach the "divide" between 

 the Missouri and the Mississippi valleys 

 at Lake Benton, Minn., at an elevation of 



about 1,900 feet, or 600 feet above the Jim 

 river. Again going westward from 

 Huron we reach the summit of the " co- 

 teaus," which is the dividing ridge be- 

 tween the Jim and the Missouri rivers, at 

 about the same elevation as at Lake Ben- 

 ton, Minn., or 600 feet above the Jim at 

 Huron. We then descend to the Missouri 

 river at Pierre, reaching an elevation of 

 1,440 feet. Crossing the Missouri we 

 reach the top of the bluffs on the west at 

 about 1 , 700 feet above sea level. The ascent 

 is then gradual till we reach the foot of the 

 Black Hills, say at Rapid City, where we 

 are at an elevation of 3,192 feet, about 

 150 miles west of Pierre, making an aver- 

 age ascent of about 9 feet to the mile. 

 The general elevation of the Black Hills is 

 about 7,000 feet. Harney's Peak being 

 8,020 feet. Going westward we find the 

 summit of the ranges of mountains divid- 

 ing the headwaters of the tributaries of 

 the Missouri and the Platte in Wyoming 

 to be about 10,000 feet. Going north- 

 ward we find the summit of the mountains 

 in Montana, dividing the headwaters of the 

 Missouri and Columbia rivers, to be about 

 7,000 feet. Or, in other words, that Mon- 

 tana is 3,000 feet lower than Wyoming, 

 Now, going eastward we find the dividing 

 ridge between the valleys of the Missouri 

 and the Assiniboine to be a little over 

 2,000 feet. 



This gives us the contour of this vast 

 catch basin and shows clearly why the 

 flood waters flow to a common center. Now 

 let us examine briefly the geological strucv 

 ture of this area and see if we can find a 

 receptacle for the storage of phreatic 

 waters. 



East of the Missouri river we have first 

 the drift or quarternary ranging from 50 

 to nearly 100 feet in thickness, with a gen.- 

 eral average of about 100 feet. First is 

 the soil or black loam ranging from 1 foot 

 .to 6 feet in thickness, ordinarily yellow 

 clay comes next, underlying the soil. Yet 

 in many places we find sand immediately 

 under the soil. The yellow clay is ordi. 



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