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Geohydrology of Trego County

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Geology and Ground-Water Resources of Trego County, Kansas

By Warren G. Hodson

Cover of the book; beige paper with black text; small logo of Kansas outline with rock pick.

Originally published in 1965 as Kansas Geological Survey Bulletin 174. This is, in general, the original text as published. The information has not been updated.

You may also wish to visit our web site on the Trego County geologic map.


Trego County is a 900-square-mile area in the High Plains section of west-central Kansas. The altitude ranges from about 2,000 to 2,600 feet above sea level. The climate is semiarid, and the mean annual rainfall is 21.40 inches. The population of the county in 1960 was 5,473. Farming and livestock raising are the chief occupations.

The Carlile Shale of late Cretaceous age is the oldest rock formation cropping out in the county. The Carlile is overlain by the Niobrara Chalk, the dominant bedrock formation in the county. The Ogallala Formation of Neogene (Pliocene) age unconformably overlies Cretaceous rocks in much of the county and consists principally of fluviatile deposits of sand, gravel, and silt. Terrace deposits of Pleistocene age occur along the principal valleys. Eolian silts that mantle the uplands and alluvium along stream valleys constitute the youngest deposits and are late Pleistocene in age.

The Ogallala Formation is the most widespread aquifer and yields water to many domestic and stock wells. Alluvium and terrace deposits yield moderate quantities of water, but these deposits are not of wide areal extent. In areas of Cretaceous outcrops, small quantities of ground water are obtained from the Dakota Formation of early (?) Cretaceous age and from the Codell Sandstone Member of the Carlile Shale of late Cretaceous age.

Hydrologic data are given in tables and include records of 280 wells, logs of 176 test holes and wells, and chemical analyses of 59 samples of water from wells.

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Kansas Geological Survey, Geology
Placed on web Dec. 12, 2008; originally published June 1965.
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