SourceThe following discussion on the source and occurrence of ground water has been adopted from Meinzer (1923, pp. 2-102) and the reader is referred to his report for a more complete discussion of the subject. A summary of groundwater conditions in Kansas has been made by Moore (1940).
Water that occurs in the pores or openings of the rocks and within the zone of saturation is called ground water. The amount of ground water that can occur below any region and the manner and rate of its movement to wells or springs is largely controlled by the character of the rocks.
In Thomas County, as in other parts of the High Plains, ground water is derived almost entirely from precipitation in the form of rain or snow. Part of the water that falls as rain or snow is carried away by surface runoff and is lost to streams, part of it may evaporate or be absorbed by vegetation and transpired into the atmosphere. The part that escapes surface runoff, evaporation, and transpiration percolates downward through the soil and underlying strata until its reaches the water table, where it joins the body of ground water in the zone of saturation. In the southern High Plains the average amount of rainfall entering the groundwater body each year has been determined by two different investigations as about one-fourth inch (Frye, 1942, p. 66) and as about one-half inch (Theis, Burleigh, and Waite, 1935, pp. 1-4). The geologic conditions in Thomas County are somewhat different from those in the two areas farther south, but the average annual rainfall is about the same and the amount of rainfall reaching the groundwater body in this area is probably of the same order of magnitude. Although this is a small percentage of the annual rainfall it should be noted that one-fourth inch of water entering the groundwater reservoir under 1 square mile amounts to 4,344,674 gallons or 13.3 acre feet, and one-half inch of rainfall over 1 square mile amounts to 8,689,348 gallons.
Ground water moves slowly through the rocks in directions determined by the shape and slope of the water table, which is controlled by topography, local variations in the quantity of recharge or discharge, and the stratigraphy and structure of the rocks. It is eventually discharged through springs or wells, through seeps into streams, or by evaporation or transpiration in bottom lands adjacent to streams. Most of the water obtained from wells in Thomas County comes from precipitation in the general vicinity and adjacent areas to the west.
Figure 5--Diagram showing several types of rock intensities and the relation of rock texture to porosity. A. Well-sorted sedimentary deposit having high porosity; B. poorly sorted sedimentary deposit having low porosity; C. Well-sorted sedimentary deposit consisting of pebbles that are themselves porous, so that the deposit as a whole has a very high porosity; D. well-sorted sedimentary deposit whose porosity has been diminished by the deposition of mineral matter in the interstices; E. rock rendered porous by solution; F. rock rendered porous by fracturing. (From O.E. Meinzer.)
Kansas Geological Survey, Thomas County Geohydrology|
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Web version Nov. 2001. Original publication date Dec. 1945.