Cloud County may be divided into two general categories, the upland area and the valley area. In the upland area, ground water is obtained from consolidated Cretaceous rocks. The Dakota Formation is the chief aquifer, although a few shallow wells obtain meager supplies of water from the Greenhorn Limestone. The Dakota Formation generally yields water of good quality in adequate quantity for stock and domestic use, but in a region in north-central and northwestern Cloud County salt water may be encountered. Over most of the region in which the water is salty, the upper part of the Dakota Formation yields water of good quality in quantity sufficient for domestic use, but the salinity increases with depth. South of Buffalo Creek, in western Cloud County, in an area several square miles in extent, the water in the entire Dakota Formation is salty. In this area shallow wells in the Greenhorn Limestone yield small supplies of water to wells.
The valley area in Cloud County contains deposits of two general classes, the alluvium and low terrace deposits (Wisconsinan and Recent) and the high terrace deposits (Illinoian). The alluvium and low terrace deposits although not covering the largest area in the county, are the most important aquifer. All irrigation wells obtain water from these deposits, and yields may be as much as 1,500 gpm. Much water for future development of irrigation is in storage in these beds, but overdevelopment probably would result in a lowering of the water table in the area and would diminish to some extent the flow of the river. Lowering the water table to any great extent would upset the hydrologic balance in the valley, which at present tends to hold back a part of the salt water that enters the valley where water in the Dakota Formation is salty. Upsetting this balance by overpumping might result in a serious saltwater problem in the valley area.
The second, or high-terrace, area includes the Illinoian terraces along the valley walls of Buffalo Creek and Republican River. These deposits are composed principally of silt, but some sand is interbedded and a few feet of sand and gravel lies near the base. These high-terrace deposits yield enough water for domestic or stock use but not enough for irrigation. Illinoian deposits bordering the valley of Solomon River contain sand and gravel composed of transported arkosic material and also pebbles of limestone and sandstone of local origin, but they lie principally above the water table and are not important as an aquifer.
Kansas Geological Survey, Geology
Placed on web June 29, 2009; originally published May 1959.
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