Principles of OccurrenceThe discussion of principles governing the occurrence of ground water that is given here takes account of conditions in Grant, Haskell, and Stevens Counties. Preparation of the discussion has been based chiefly on the authoritative and detailed treatment of the occurrence of ground water by Meinzer (1923), to which the reader is referred for more extended consideration. A general discussion of the principles of the occurrence of ground water with special reference to Kansas has been published by Moore (1940).
The rocks that make up the outer crust, of the earth generally are not entirely solid, but contain numerous openings, called voids or interstices, which may contain air, natural gas, oil, or water. The number, size, shape, and arrangement of the interstices in rocks depend upon the character of the rocks. The occurrence of water in any region, therefore, is determined by the geology.
The interstices or voids in rocks range in size from microscopic openings to the huge caverns found in some limestones. The open spaces generally are connected so that water may percolate from one to another, but in some rocks these open spaces are isolated and the water has little chance to percolate. In Grant, Haskell, and Stevens Counties the rocks from which ground water is obtained are poorly consolidated silt, sand, and gravel. Generally the sand and gravel of the Rexroad (?) and Meade formations contain many interstices and water percolates freely through them, but locally these interstices may be filled with calcium carbonate or other material, such as clay, that makes the rock almost impermeable. Some of the silt, sand, and gravel of the Rexroad and Meade formations is poorly sorted and the finer particles fill much of the space between the larger particles, thereby decreasing space available to ground water.
The porosity of a rock is the percentage of the volume of the rock that is occupied by the interstices. A rock is said to be saturated when all its interstices are filled with water or other liquid, and the porosity is then practically the percentage of the volume of rock that is occupied by water. The porosity of a rock determines only the amount of water a rock can hold, not the amount it may yield to wells. Some rocks may be moderately porous and yet will not yield an appreciable amount of water to a well. The permeability of a rock is defined as its capacity for transmitting water under pressure and is measured by the rate at which it will transmit water through a given cross section under a given difference of pressure per unit of distance. A rock containing very small interstices may be very porous but it would be difficult to force water through it, whereas a coarser-grained rock, although it may have less porosity, generally is much more permeable. Water may be held in rocks by the force of molecular attraction, which, in some fine-grained rocks, is sufficiently great to make the rock relatively impermeable.
Below a certain level in the earth's crust the permeable rocks generally are saturated with water and are said to be in the zone of saturation. The upper surface of the zone of saturation is called the ground-water table or simply the water table. All the rocks above the water table are in the zone of aeration, which ordinarily consists of three parts: the belt of soil water, the intermediate or vadose zone, and the capillary fringe.
The belt of soil water lies just below the land surface and contains a small amount of water held by molecular attraction. The soil zone must be saturated with water before any water can percolate downward to the water table. The thickness of the zone is dependent upon the character and thickness of the soil and upon the precipitation.
The intermediate or vadose zone lies between the belt of soil water and the capillary fringe. The interstices in the rocks in this zone generally are filled with air but may contain water for a short time while it is moving downward from the belt of soil water to the ground-water table. The vadose zone may be absent in places, such as some river valleys where the water table is near the surface, or it may be more than 200 feet thick, as in parts of Grant, Haskell, and Stevens Counties.
The capillary fringe lies directly above the water table and is formed by water rising from the zone of saturation by capillary action. The water in the capillary fringe is not available to wells, which must be deepened to the zone of saturation before water will enter them. The capillary fringe may be absent in coarse sediments, where the capillary attraction is negligible, but may be as much as 8 feet thick in very fine-grained sediments.
Water in Sand and GravelGrant, Haskell, and Stevens Counties are underlain by thick deposits of unconsolidated materials that were laid down by streams in Tertiary and Quaternary time. The sorting action of streams on these sediments caused the deposition of many distinct beds of gravel, sand, silt, and clay. Deposits of such uniform texture may have a relatively high porosity. Coarse, well-sorted gravel of this type has a relatively high specific yield and permeability, and properly constructed wells in this material yield large quantities of water. Some of the stream-laid material is poorly sorted and finer material occupies much of the pore space between the larger grains, reducing the porosity and specific yield.
In Grant, Haskell, and Stevens Counties, water is found in unconsolidated beds of sand and gravel in the Rexroad (?) and Meade formations and in the alluvium in the Cimarron River Valley. The Rexroad (?) and Meade formations are most important sources of ground water in the Grant-Haskell-Stevens area. Most of the domestic, stock, irrigation, industrial, and public-supply, wells in this area obtain water from these deposits. The yields of wells ending in the Rexroad (?) and Meade strata range from a few gallons a minute to more than 1,400 gallons a minute. The alluvium of the Cimarron River Valley probably would yield relatively large quantities of water to wells. The Cimarron River, however, has widened its channel and destroyed most of the bottom land, and as a result no irrigation has been developed in the valley area. The Laverne formation is an important potential source of ground water in this area but it is practically unexploited because of its great depth
Water in SandstoneThe particles comprising a sandstone generally are more even-grained and better sorted than those in unconsolidated sand and gravel. These particles are held together by cementing material which in some places may fill the interstices and prevent water from percolating through them. In this area, sandstone occurs in the Cheyenne and Dakota formations and locally in the Kiowa shale, but very few wells penetrate these beds because an adequate supply of potable water can be obtained in the overlying unconsolidated Tertiary and Quaternary deposits.
Water in ShaleShale is formed by the induration of clay or clayey mixtures; it generally has a relatively low specific yield and therefore yields little or no water to wells. In some areas the shale may have many open joints and bedding planes and consequently a higher permeability; in other areas it may contain sand grains in sufficient quantity to make it somewhat permeable. In this area shale occurs in the Kiowa and Dakota formations and does not yield water to wells.
Kansas Geological Survey, Grant, Haskell, and Stevens Geohydrology|
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Web version May 2002. Original publication date July 1946.