This report describes the geography, geology, and ground-water resources of a region that covers about 2,340 square miles in south-central Kansas comprising all of McPherson County, nearly all of Harvey County, and smaller parts of Sedgwick, Reno, and Marion counties. This large rectangular region was chosen for detailed study as it embraces the principal area of outcrop of the important Pleistocene water-bearing formation--the McPherson formation (the Equus beds of early reports)--which covers a broad area between the Smoky Hill and Arkansas River valleys. This formation had long been utilized as a source of public-water supply by most of the cities in the area except Wichita and had long been regarded as a possible new source of supply for Wichita--the largest city in the state--whose ground-water supply prior to 1940 was unsatisfactory because of the poor chemical quality of the water. As a result of this investigation it was apparent that an adequate supply for Wichita could be obtained from wells in the McPherson formation about 20 miles northwest of the city. The city developed a new well field, which has provided ample water of good quality since September 1, 1940. Saltwater intrusion into the water-bearing formations resulting from the improper disposal of oil-field brines in several oil fields in the area has ruined some well-water supplies, threatens others, and was given special attention during the course of the investigation--particularly in the location and development of the new Wichita well field.
The area is characterized by low topographic relief and includes large extremely flat sections; the total relief is only about 420 feet. It is drained largely by the Arkansas River and its tributaries--notably the Little Arkansas River - but parts of the area are drained by the Smoky Hill, Cottonwood, Walnut, and Ninnescah rivers. The climate is characterized by moderate precipitation, a wide range in temperature, moderately high average wind velocity, and comparatively rapid evaporation.
Although the area is dominantly agricultural, it includes 18 cities having public-water supplies. The principal crops are wheat, corn, sorghum, oats, alfalfa and hay, most of which are grown by dry farming methods as relatively little irrigation is practiced except in times of drought. Some areas are devoted principally to the raising of livestock. Natural gas and petroleum are produced from many oil fields and salt is mined at Hutchinson. Wichita is an important transportation and distribution center and also has important industries, especially the manufacture of aircraft.
The report includes a geologic map of the area and detailed descriptions of the geologic formations and their water-bearing properties based upon field mapping (partly on large scale aerial photos), the logs of 161 test holes drilled by the State Geological Survey, and the logs of 193 other wells and test holes. The formations mapped and described included the Permian Wellington, Ninnescah, and Stone Corral formations; the Cretaceous Kiowa shale; the Pliocene Delmore formation (formerly included in the now abandoned Emma Creek formation), which is described as a new formation; the Pleistocene McPherson formation (which includes the beds at the designated type locality of the Emma Creek formation); Pleistocene and Recent dune sand; and Recent alluvium. The Permian formations yield only meager supplies of highly mineralized water; the Delmore formation and sandstones of the Kiowa shale yield small supplies of relatively hard water to domestic and stock wells; and the sand dunes, though yielding only small supplies to wells, serve as important catchment areas for rainfall and hence help to recharge the adjacent McPherson formation and alluvium. Large supplies of moderately hard to hard water are obtainable from properly constructed wells in the McPherson formation and in the alluvium, which together underlie the larger part of the area. The larger supplies are obtained from the deposits of the deeply buried McPherson channel and the filled channel of the ancestral Arkansas River. These deposits yield adequate quantities of water for all public-supply, industrial, and irrigation wells in the area, and most of the domestic and stock wells. A description of the geologic history includes a discussion of the formation of the now buried McPherson channel that once united the ancestral Smoky Hill River with the ancestral Arkansas River. The McPherson channel was formed by an ancient stream, which was aided by subsidence of the Wellington formation through solution of its thick beds of salt. These and other features are shown by many cross sections based upon test drilling and by a contour map of the bed rock floor.
A large amount of hydrologic data presented in 35 plates, 31 figures, and 37 tables accompanied by descriptive text, including a water-table contour map of the area (superimposed on the geologic map); a map showing depths to water level and locations of all wells visited; cross sections of the area, based on test drilling; maps showing locations of test holes and bedrock contours; maps of the Wichita well-field area showing water-table contours and lines of equal change in water level on several dates from June 1940 to October 1944; a map showing distribution of chloride in ground waters; numerous hydrographs of wells under pumping, non-pumping, or special conditions; tabulated physical properties of water-bearing materials; tabulated records of 727 water wells and 229 chemical analyses of ground waters; and logs of 354 test holes and wells.
Descriptions of the 18 public water supplies in the area, including both the old and new sources of supply for the city of Wichita, and the history of the development of the new supply are given. The average daily consumption of water by these 18 cities aggregates about 25 million gallons, of which 71 percent or about 18 million gallons is used by the City of Wichita. A special section is devoted to the potential perennial yield of the Wichita well-field area. Records of precipitation, water levels, and pumpage over a period of 7 years were correlated and studied. During this period the average precipitation was greater than normal. However, it is concluded that the potential yield had not been reached at the end of 1944 because: (1) the water levels in wells affected by pumping in the well-field area seemingly had ceased declining at the pumping rate prevailing at the time; (2) only a part of the natural discharge in the area of pumping influence was being salvaged; and (3) the Little Arkansas River remains a gaining stream, but is a potential source of increased recharge in this area. It is further concluded that the potential yield of the present well-field area is about 40,000 acre-feet a year during years of normal precipitation, or about twice the present annual pumpage. Before this potential perennial yield can be achieved a total of about 200,000 acre-feet must be removed from storage (an amount equivalent to 10 years' pumpage at the present rate assuming no replenishment from precipitation). Recharge in the well-field area during the period of record is calculated to have been equivalent to at least 20 percent of the precipitation or about 7 inches per year. This gives a total of about 365 acre-feet per year per square mile or about 31,000 acre-feet per year in the 85 square mile well-field area. Assuming that the 20 percent proportion holds during years of normal precipitation, the total potential perennial yield would be about 27,000 acre-feet per year. If the potential perennial yield is ultimately reached, an additional 13,000 acre-feet a year will be derived from salvaged natural discharge and influent seepage from the Little Arkansas River.
The last section of the text describes ground-water conditions by localities and discusses the possibilities of developing additional large ground-water supplies. The most favorable areas for such future development are, in order of importance, the Arkansas Valley area, the McPherson channel area, and the Lindsborg (Smoky Hill River valley) area.
Kansas Geological Survey, South-central Kansas
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Web version April 2005. Original publication date July 1949.