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Abstract
The report describes the geography, geology, and ground-water resources of Pawnee and Edwards counties in central Kansas. These counties have an area of about 1,368 square miles and had a population of 14,042 in 1945. The area consists of gently rolling upland plains together with large areas of sand hills and relatively flat flood plains and terraces. The climate is subhumid, the average annual precipitation being between 20 and 24 inches. Farming and the raising of livestock are the principal occupations in the area. Irrigation from Pawnee River and from wells has been practiced extensively in Pawnee Valley and irrigation from wells has been developed to a lesser extent in Arkansas Valley and in the dune-sand areas south of the valley.
The rocks that crop out in this area range in age from Cretaceous to Recent. The Cretaceous rocks are exposed in the upland areas in northern Pawnee County and in the area between Pawnee and Arkansas Rivers in southwestern Pawnee County and northwestern Edwards County. The Ogallala formation crops out only in small areas in northwestern Edwards County and southwestern Pawnee County. The alluvium and terrace deposits underlie the principal valleys and the adjacent areas and dune sand covers the large area lying south of the Arkansas Valley. The alluvium in Pawnee and Arkansas Valleys and the Meade formation, which underlies the dune-sand area, yield large quantities of water to wells. Other formations generally yield only small to moderate quantities of water to wells. The report contains a map showing the areas of outcrop of the rock formations and a diagrammatic cross section of the area showing the distribution of the formations that lie above the Permian redbeds, as determined by extensive test drilling.
The report contains a map of the area showing the locations of wells for which records were obtained and the depths to water level. The depth to water level in areas of Tertiary and Quaternary rocks generally is less than 50 feet. In other areas the depth to water may be only a few feet or may be as much as 200 feet, depending upon which bedrock formation supplies water to the well. A map showing by means of contours the shape and slope of the water table is also included in this report. The map shows that ground water moves eastward to northeastward through a large part of the area.
The ground-water reservoir is recharged principally from rain and snow that fall within the area, by percolation from streams and depressions, and by underflow from adjacent areas. Ground water is discharged from the groundwater reservoir by seepage into perennial streams, by transpiration and evaporation, by movement into adjacent areas, and by wells.
Most of the wells in the area are drilled or driven, but a few are dug or bored. Of the 360 wells listed in the report, 127 are irrigation wells. In 1943, 76 of these wells were used to irrigate about 3,380 acres of land, and about 3,400 acre-feet of ground water was pumped for this purpose. The areas most favorable for the development of large supplies of water for irrigation and industrial use are the Arkansas Valley, the Pawnee Valley, and the dune-sand area south of the Arkansas Valley.
Ground water in the Pawnee-Edwards area generally is hard, but is suitable for most uses. Waters from the Dakota formation generally contain a large amount of dissolved solids, but may be only moderately hard owing to natural softening. These waters generally are high in fluoride. Water from the alluvium is hard, but it is of slightly better quality in the Pawnee Valley than in the Arkansas Valley. The formation that yields the largest quantities of the most suitable water is the Meade formation, which underlies the area south of the Arkansas Valley.
The report contains a section in which the character, distribution and thickness, age and correlation, and water supply of the rock formations are described. This discussion deals with all formations down to and including the Permian redbeds.
The field data upon which this report is based are given in tables; they include records of 360 wells, chemical analyses of water from 71 representative wells, and logs of 144 wells, including 131 test holes put down as a part of this investigation and two test holes put down at the Edwards-Kiowa county line as a part of the investigation of the geology and ground-water resources of Kiowa County.
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Kansas Geological Survey, Pawnee and Edwards Geology and Groundwater
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Web version June 2004. Original publication date March 1949.
URL=http://www.kgs.ku.edu/General/Geology/Pawnee/02_abstract.html