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Principles of Occurrence
The following discussion of the principles of the occurrence of ground water applies specifically to Elk County. For a more detailed discussion of the occurrence of ground water the reader is referred to Meinzer (1923). A discussion of the occurrence of ground water as applied to Kansas is given by Moore and others (1940).
The rocks that directly underlie the surface of Elk County include open spaces that contain gases or liquids. The number, size, shape, and arrangement of these openings are controlled by the character of the rock; thus, the occurrence of ground water is determined by the geology of the county. The openings range from microscopic pores to large solution channels. If the openings are connected, water may move from one to another. In general water moves freely in rocks having large openings, and such rocks yield more water to wells than do rocks having smaller openings.
In Elk County the source of ground water is precipitation that falls as rain or snow. A part of the precipitation percolates downward to the zone of saturation and becomes ground water. The rest of the precipitation runs off directly over the surface, evaporates, or is transpired from the soil by plants.
Where porous permeable rock extends some distance above the zone of saturation, the upper surface of the saturated zone is called the water table. In Elk County, the ground water in the alluvium of the stream valleys and parts of the upland areas is in the zone of saturation beneath the water table. If the upper surface of the zone of saturation is restricted beneath impermeable rock, the water table is absent, and the water is under artesian conditions, and in a well will rise above the top of the bed in which it is confined. The level to which the water would rise when under artesian conditions is called the piezometric surface. In Elk County the piezometric surface is above the land surface only in one area of about 160 acres in the valley of Painterhood Creek in sec. 1, T. 30 S., R. 12 E., near the community of Busby. Wells here obtain water from the Ireland sandstone member of the Lawrence shale at a depth of about 40 feet. Records were obtained on several of the wells, and the artesian head was measured. The maximum head measured was that of well 30-12-1ba, which was 4.60 feet above the land surface (Table 11).
Ground-water Recharge
Recharge is the addition of water to the underground reservoir and may be accomplished in several ways. In Elk County the principal source of recharge is local precipitation. Smaller amounts are contributed by infiltration from streams and ponds and by subsurface inflow from adjacent areas.
In Elk County the normal annual precipitation is 35.09 inches. Approximately 65 percent of the precipitation occurs in the growing season, from April through September. The normal annual precipitation amounts to about 2.9 acre-feet, or slightly less than 1 million gallons per acre.
A minimum value for the quantity of ground water recharged may be estimated from the amount discharged from ground-water bodies into streams, as the pumpage is probably nearly constant and is relatively small. The true value would be larger by the amount of ground water evaporated and transpired, but this amount was relatively small at the times when the analyses of surface flow were made.
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Kansas Geological Survey, Geology
Web version July 2002. Original publication date July 1958.
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