Water Supply and Irrigation Papers of the United States Geological Survey . probable that withincreased numbers of wells and long-continued flow the availableartesian supply will eventually be materially diminished. The area in which flows may be expected from the Dakota andassociated sandstones is shown on the map (PL XI), which also showsthe depths to the sandstone, the location and depths of wells whichhave been sunk, and the altitude of the head of the water. Thelast-named item has been determined from the altitude of the outcropin the Black Hills and the observed pressures in wells. These
Water Supply and Irrigation Papers of the United States Geological Survey . probable that withincreased numbers of wells and long-continued flow the availableartesian supply will eventually be materially diminished. The area in which flows may be expected from the Dakota andassociated sandstones is shown on the map (PL XI), which also showsthe depths to the sandstone, the location and depths of wells whichhave been sunk, and the altitude of the head of the water. Thelast-named item has been determined from the altitude of the outcropin the Black Hills and the observed pressures in wells. These pres-sures are converted into head by multiplying the number of poundsto the square inch by (the height in feet represented by the pressureof 1 pound) and adding the altitude of the land. This gives thealtitude above sea level to which the water would rise in pipes or upthe slopes of adjacent higher lands. Lines are drawn on the mapfor every 100 feet of altitude of head and show a regular down gradefrom the Black Hills to the southeast corner of the State, V/herever. f I AURORA COUNTY. 65 data are lacking lines have been introduced on the assumption thatthe gradient Is regular. Where the altitude of the head is greaterthan the altitude of the surface the wells will flow, and the (low area,represented in Plate XI has been deduced in this manner from theheadlines and the topographic contour lines. As the precise gradientof head is not everywhere accurately ascertained, and as some of thetopographic data arc only approximate, the flow area can he indicatedonly approximately in some portions of the State. There is, more-over, considerable variation in pressure in the different Hows atvarious depths, and in many wells where the water in the uppersandstones will not have sufficient head to How. a deeper water willrise to the surface. The data are sufficient to indicate that flowsmay be expected in a, large area in which no wells have yet been sunkin (he many valleys of the centr
Size: 1309px × 1908px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorunitedstatesgeologica, bookcentury1900, bookdecade1900
