by Warren G. Hodson
Originally published in 1963 as Kansas Geological Survey Bulletin 161. This is, in general, the original text as published in 1963. The information has not been updated.
Wallace County is a 910-square mile area in the High Plains section of west-central Kansas. Chalk and shale beds of Late Cretaceous age are the oldest rocks cropping out in the county. The Ogallala Formation of Tertiary age (Pliocene) unconformably overlies the Cretaceous rocks in most of the county and consists of fluviatile deposits that in places exceed 400 feet in thickness. As much as 50 feet of loess and 70 feet of alluvium constitute the youngest deposits and are Late Pleistocene in age.
In Wallace County, the number of irrigation wells has been increasing about 6 percent per year in recent years. Yields of most irrigation wells range from about 400 gpm (gallons per minute) to more than 2,000 gpm. Most ground water is obtained from the Ogallala Formation, which contains about 4 million acre-feat in storage. Aquifer tests in the Ogallala indicate transmissibilities of about 150,000 gpd (gallons per day) per foot and permeabilities of about 1,000 gpd per square foot. Movement of ground water is eastward at about 0.9 foot per day.
Alluvial deposits along the principal valley yield moderate quantities of water, but the deposits are narrow and confined to the inner valleys. In areas of Cretaceous outcrops, ground-water supplies are meager and where available are obtained from thin surficial deposits and weathered zones.
Kansas Geological Survey, Geology
Placed on web July 9, 2007; originally published November 1963.
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