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Stanton County Geohydrology

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Ground Water

Principles of Occurrence

The following discussion on the occurrence of ground water has been adapted from Meinzer (1923, pp. 2-102), and the reader is referred to his report for a complete discussion of the subject. A summary of considerations on this subject is given also in State Geological Survey Bulletin 27 (Moore, 1940).

Ground water, or underground water, is the water that supplies springs and wells. The rocks that form the outer crust of the earth are at very few places solid throughout, but contain numerous open spaces, called voids or interstices. These open spaces are the receptacles that hold the water that is found below the surface of the land and is recovered in part through wells and springs. There are many kinds of rocks, and they differ greatly in the number, size, shape, and arrangement of their interstices and hence in their properties as containers of water. Therefore, the character, distribution, and structure of the rocks of any region determine the occurrence of water.

The amount of water that can be stored in any rock depends upon the volume of the rock that is occupied by open spaces, that is, the porosity of the rock. The porosity is expressed as the percentage of the total volume of the rock that is occupied by interstices. A rock is said to be saturated when all its interstices are filled with water. The porosity of a sedimentary rock is controlled by (1) the shape and arrangement of its constituents particles, (2) the degree of assortment of its particles, (3) the cementation and compaction to which it has been subjected since its deposition, (4) the removal of mineral matter through solution by percolating waters, and (5) the fracturing of the rock, resulting in joints and other openings. Well-sorted deposits of unconsolidated silt, sand, or gravel have a high porosity, regardless of the size of the grains. Poorly-sorted deposits have a much lower porosity because the small grains fill the voids between the large grains, thus reducing the amount of open space. The pore space in some well-sorted deposits of sand or gravel may gradually be filled with cementing material, thus gradually reducing the porosity.

The capacity of a rock to hold water is determined by its porosity, but its capacity to yield water is determined by its permeability. The permeability of a rock may be 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. Rocks that will not transmit water may be said to be impermeable. Some deposits, such as well-sorted silt or clay, may have a high porosity, but because of the minute size of the pores will transmit water only very slowly. Other deposits, such as well-sorted gravel containing large openings that communicate freely with one another, will transmit water very readily. If a force greater than the force of gravity were applied to the water in the silt or clay it would probably move more readily. Part of the water in any deposit is not available to wells because it is held against the force of gravity by molecular attraction-that is, by the cohesion of the water itself and by its adhesion to the walls of the pores.

Below a certain level, which in Stanton county ranges from less than 25 feet to about 250 feet below the surface, the permeable rocks are saturated with water under hydrostatic pressure. These saturated rocks are said to be in the zone of saturation, and the upper surface of this zone is called the water table. Wells dug or drilled into the zone of saturation will become filled with ground water to the level of the water table.

The permeable rocks that lie above the zone of saturation are said to be in the zone of aeration. As water from the surface percolates slowly downward to the zone of saturation part of it is held in the zone of aeration by the molecular attraction of the walls of the open spaces through which it passes. In fine-grained material there is invariably a moist belt in the zone of aeration just above the water table, and this moist belt is known as the capillary fringe. Although water in the zone of aeration is not available to wells, much of the water in the upper part of the zone may be withdrawn by the transpiration of plants and by evaporation from the soil.

Artesian Conditions

Ground water may be said to have normal pressure, subnormal pressure, or artesian pressure or pressure head. The static level of ground water under normal pressure is at the upper surface of the zone of saturation, and under subnormal pressure the static level is below this surface. Artesian water is ground water under sufficient pressure to rise above the zone of saturation. A well that flows at the land surface is known as a flowing artesian well.

Artesian conditions exist where a water-bearing bed is overlain by an impermeable or relatively impermeable bed that dips from its outcrop to the discharge area (Sayre, 1937, p. 22). Water enters the water-bearing bed at the outcrop and percolates slowly downward to be held in the water-bearing bed by the overlying confining bed. Down the dip from the outcrop area the water exerts considerable pressure against the confining bed. When a well is drilled through the confining bed into the water-bearing bed the pressure is released and the water rises in the well. If the water is under sufficient pressure, and if the altitude of the land surface is lower than the altitude of the outcrop of the water-bearing bed, the water may rise high enough to flow at the surface. In places where there are lenses or beds of relatively impermeable clay or silt at the level of the water table, the water encountered below, such lenses or beds will rise to the level of the surrounding water table, but such water is under normal pressure and is not artesian.

Although there are no known flowing wells in Stanton county, the water in the Cheyenne and Cockrum sandstones at many places in the western part of the county seems to be under slight artesian head. The water in the Ogallala formation, however, is in most places under normal pressure and therefore generally does not rise above the level at which it is first encountered. Cross section BB' in plate 4 shows the Cheyenne sandstone to be confined below the Kiowa shale and indicates that artesian water might be obtainable from the Cheyenne sandstone. The gas test well south of Johnson is the only well that has tapped the Cheyenne sandstone in the eastern part of the county, and the water in it was cased off so that the drilling could proceed to the possible gas-bearing zones. No other wells are known to have been drilled into the Cheyenne sandstone in the eastern part of the county.

Darton (1920, p. 9), in discussing the Dakota sandstone in the Syracuse and Lakin quadrangles, says—

This formation yields artesian flows from Coolidge westward up the Arkansas valley, but the head falls gradually and finally passes beneath the valley bottom a short distance east of Coolidge. Hence there is apparently no likelihood of finding flows within the area.

A well drilled in the SW sec. 34, T. 29 S., R. 43 W., in Stanton county, encountered two sandstones separated by a bed of shale. The first sandstone, Cockrum, carried only a meager supply of water and therefore was cased off. It is reported that when the drill penetrated the second sandstone (Cheyenne), at a depth of 175 feet below the surface, the water rose in the well within 85 feet of the surface. In a small area surrounding Blaine, Colo., about 12 miles west of Stanton county, wells drilled into the Dakota and Cheyenne sandstones flow at the surface. There are reported to be approximately 60 flowing wells in the Blaine area, ranging in depth from about 200 to 500 feet. The Cheyenne sandstone or its equivalent, also yields flowing artesian water in a few wells near Coolidge, in west-central Hamilton county.

Water in the Triassic (?) redbeds is probably under slight pressure in Stanton county, but so far as is known the pressure is not great enough to cause the water to flow at the surface. Only one well (101) in the county is known to penetrate the Triassic (?) beds, and the water level in it stands 211 feet below the surface. A well 460 feet deep and thought to end in Triassic (?) beds was drilled many years ago at Elkhart in southwestern Morton county, and is reported to have flowed at the surface, but the water was so highly mineralized that it was cased off. Three flowing wells at Richfield, in central Morton county, obtain water from Permian beds, but the water is highly mineralized and cannot be used for most purposes.

The Water Table and Movement of Ground Water

Shape and Slope

The water table is defined as the upper surface of the zone of saturation except where that surface is formed by an impermeable body (Meinzer, 1923a, p. 32). It may also be regarded as the boundary between the zone of saturation and the zone of aeration. The water table is not a static, level surface, but rather it is generally a sloping surface, which shows many irregularities caused by differences in permeability of the water-bearing materials or by unequal additions of water to the ground-water reservoir at different places.

The shape and slope of the water table in Stanton county are shown on plate 1, by means of contour lines drawn on the water table. Each point on the water table along a given contour line has the same altitude. These water-table contours show the configuration of the water surface just as topographic contours show the configuration of the land surface. The direction of movement of the ground water is at right angles to these water-table contour lines—in the direction of the greatest slope.

The map shows that the ground water beneath the plains moves through Stanton county in a general easterly direction, but that the direction of movement and the slope vary considerably in different places. The average gradient of the water table is about 18 feet to the mile, but as shown on the map the slope in the western part of the county is steep as compared with the more gentle slope in the eastern part. A short distance west of Manter the water table slopes as much as 60 feet to the mile, whereas southeast of Johnson the water table is nearly level, sloping as little as 4 feet to the mile.

Other things being equal, the slope of the water table in any area in general varies inversely with the permeability of the water-bearing material; that is, the water assumes a steeper gradient in flowing through fine material than through coarse material, providing the same quantity of water is moving through both types of material. This probably explains, at least in part, the great differences in the slope of the water table in eastern and western Stanton county. In the western part of the county, where the gradients are steep, the water in the upper part of the zone of saturation moves through the fine-grained Cockrum sandstone. As the water moves eastward it enters the coarser, more permeable sand and gravel of the Ogallala formation, and the gradient becomes greatly reduced. Some of the minor irregularities in the shape of the water table may be due to local differences in the permeability of the water-bearing formation.

Along Bear creek in the western part of the county the contour lines are flexed in a downstream direction, indicating the existence of a low ridge on the water table. Another, less discernible ridge on the water table is indicated by the downslope flexure of the contour lines in the northeastern part of the county. Influent seepage from Bear creek (p. 40) is the principal cause of these ridges on the water table. These ridges or areas are formed by water percolating downward because the frictional resistance offered by the small openings in the water-bearing material prevents the water from spreading out as rapidly as it would on the surface of a body of free water, such as a lake. As soon as the descending water reaches the water table it joins the main body of ground water and moves in an easterly direction to conform with the direction of movement of the ground water.

South of Manter a very prominent east-west trough or depression in the water table is indicated by the upslope flexure of the contour lines, and is the normal counterpart of the ridge to the north. On the south side of the ridge the water is moving in a southeasterly direction, whereas on the north side of the ridge it is moving in a northeasterly direction. East of Manter the waters gradually merge and move eastward in a common direction.

About 6 miles southeast of Johnson the downslope flexure of the 3,140-foot contour line indicates that a broad, relatively low mound has been built up on the water table. This is a low-lying area containing many shallow depressions that hold water after rains. Some of the water probably seeps downward to the underground reservoir, where it builds up a mound. A large part of the surface in Stanton county is mantled by loess—a very fine-grained, homogeneous material that resists the downward percolation of water because of its low permeability. The surface material in the relatively flat area southeast of Johnson, however, consists of sandy loam soils that allow the surface water to pass downward. Other minor irregularities in the shape of the water table also may be accounted for by the difference in the permeability of the soil—some taking in more water than others.

Relation to Topography

The water table and the land surface are similar in that they both slope in the same general direction and have approximately the same amount of total relief from west to east. On the map, plate 2, are shown the depths to the water level in Stanton county by the use of isobath lines—lines of equal depths to water level. In preparing this map the more general irregularities of the surface topography were taken into account by using aerial photographs and the available topographic maps. As shown on this map, the depth to water level ranges from less than 50 feet to 250 feet. Some inaccuracy has been introduced by small local irregularities on the land surface that are not shown on the topographic maps or aerial photographs. It will be noted on the map that the depth-to-water lines are flexed both upstream and downstream along Bear creek and Sand arroyo. This lack of analogy between the depth to water and the surface slope results from the combination of an almost uniform slope of the land and a water table whose slope in the western part of the county is much steeper than it is in the eastern part. (p. 30.) The relation between the water table and the land surface from west to east across the county is shown in figure 5. Thus it can be seen that the depth to the water table is greater at B in the middle of the county than at either A in the western part, or at C in the eastern part.

Figure 5—East-west section across Stanton county along the south side of T. 29 S. showing the relation between the land surface and the water table.

East-west section across Stanton county along the south side of T. 29 S. showing the relation between the land surface and the water table.

For purposes of detailed descriptions of the ground-water conditions, Stanton county may be divided into several areas based upon the depths to the water level: (1) shallow-water areas, (2) deepwater areas, and (3) the Johnson area of intermediate depth to water. The shallow-water areas may in turn be subdivided into the northeastern area, the southeastern areas, and the southwestern areas.

Northeastern shallow-water area

The northeastern shallow-water area is roughly triangular in shape and comprises parts of three townships, T. 27 S., R. 39 and 40 W., and T. 28 S., R. 39 W., which lie mainly south of Bear creek. In this area the depths measured ranged from 44 to 56 feet. All the wells in this area obtain water from sand and gravel of the Ogallala formation. In this area the zone of saturation ranges in thickness from 200 to 300 feet, and attains its greatest thickness in the southern part where the Ogallala formation occupies the pre-Tertiary trough described [earlier].

The relief of the surface is favorable for irrigation, and large quantities of water are available from wells. The possibilities of developing additional supplies for irrigation in this area are discussed [later].

Southeastern shallow-water areas

There are two small areas in the southeastern part of the county in which the water table is less than 50 feet below the surface. One area is along the valley of Sand arroyo and the other is along the valley of North Fork of Cimarron river. Both areas include only the stream valleys and are, therefore, narrow, and are delineated by the 50-foot lines on plate 2. No wells were found in either area, but the water levels in the wells adjacent to these areas are only slightly more than 50 feet below the surface. The alluvium in the valleys lies above the water table, and hence will not yield water to wells, but water probably can be obtained from the underlying Ogallala formation, which supplies water to wells in adjacent areas.

Southwestern shallow-water areas

There are two areas in the southwestern part of the county in which the water table is shallow. One of these areas comprises about 5 square miles along Sand arroyo in the southwestern corner of the county. The wells in this area (146) obtain water from the Cockrum sandstone and the water level in them is 50 feet or less below the surface.

The other area lies within the 50-foot line along Bear creek west of Manter. In the western part of this area Bear creek has cut through the Ogallala formation and exposed the Cockrum sandstone. Records of six wells in this area are given in the tables. Two of these wells (110 and 112) obtain water from the Cheyenne sandstone, two (109 and 113) obtain water from alluvium along Bear creek, one (98) obtains water from the Ogallala formation, and one (107) obtains water from the Cockrum sandstone. The depths of the wells range from 16 to 200 feet and the depths to water level in them range from about 12 feet to 40 feet.

Manter deep-water area

The Manter deep-water area includes the southeastern half of T. 29 S., R. 42 W., and the western part of T. 29 S., R. 41 W. The wells in the western part of this area obtain water from the Cockrum sandstone and those in the eastern part obtain water from the Ogallala formation. The depth to the water level is everywhere more than 200 feet and in the SE sec. 27, T. 29 S., R. 42 W., it is about 250 feet. The depths of most of the wells range from 215 to 256 feet, but the railroad well at Manter is 475 feet deep.

West-central deep-water area

The west-central deep-water area, in which the water level lies more than 200 feet below the surface, comprises about 7 square miles in the central part of T. 28 S., R. 42 W. Records were obtained for only two wells (64 and 67) in this area, both of which obtain water from the Ogallala formation. The depths of wells in this area range from about 225 feet to more than 250 feet, and the depth to the water level ranges from about 200 feet to 244 feet.

Northwestern deep-water area

The northwestern deep-water area is in the extreme northwestern corner of Stanton county and includes secs. 4, 5, 8, and 9 of T. 27 S., R. 43 W. The wells obtain water from the Cockrum sandstone and the depth to the water level ranges from about 200 feet to about 220 feet.

Johnson area of intermediate depth to water

The Johnson area comprises an arcuate belt that extends from the north county line through Johnson to the south county line, near the middle of the county. The depth to the water level in this area ranges from about 100 to 200 feet, and all the wells obtain water from the Ogallala formation except a few in the southern part that obtain water from the Cockrum sandstone. The thickness of the Ogallala formation (including undifferentiated Pleistocene) ranges from about 80 feet in the southern part to more than 400 feet in the vicinity of Johnson, where the Ogallala occupies the pre-Tertiary trough described on page 24. In the southern part of the Johnson area the Ogallala formation is above the water table and therefore is dry. In the central and northern parts of the area the thickness of the saturated part of the Ogallala ranges from about 100 feet to more than 250 feet.

Fluctuations

The water table does not remain in a stationary position, but fluctuates up and down much like the water in a surface reservoir. If the inflow to the underground reservoir exceeds the draft, the water table will rise; conversely, if the draft exceeds the inflow the water table will decline. Thus the rate and magnitude of fluctuation of the water table depend upon the net rate at which the underground reservoir is replenished or depleted.

The factors controlling the rise of the water table in Stanton county are the amount of rainfall within the county that passes through the soil and descends to the water table, the amount of seepage that reaches the underground reservoir from Bear creek and Sand arroyo, and the amount of water entering the county beneath the surface from areas farther west. All these factors depend upon precipitation either in or near the county. The relation between the amount of precipitation and the level at which the water stands in wells is complicated by several factors. After a long dry spell the soil moisture becomes depleted through evaporation and transpiration and when a rain does occur the soil moisture must be replenished before any water can descend to the water table. During the winter when the ground is frozen the water falling on the surface is hindered from reaching the water table, and during the hot summer some of the water that falls as rain is lost directly into the air by evaporation. Where the water table stands comparatively far below the surface, as it does in most of Stanton county, it fluctuates less in response to precipitation than it does where it is comparatively shallow.

The factors controlling the decline of the water table are the amount of water pumped from wells, the amount of water absorbed directly from the water table by plants (transpiration), the amount of water lost from the ground-water reservoir by evaporation, the loss of water from springs, and the amount of ground water passing beneath the surface into adjacent areas. The only escape of water from the ground-water reservoir in Stanton county seems to be through wells and by lateral movement out of the county. Owing to the deep-lying water table there is probably no loss of water from the ground-water reservoir through evaporation or transpiration in Stanton county, nor is there any discharge from springs. The last factor, the amount of ground water passing beneath the surface into adjacent areas, mayor may not cause the water table to decline. Assuming that no water is withdrawn from wells, then if the amount of water leaving the county beneath the surface to the east is equal to the amount of water entering the county at the west, there will be no decline of the water table; however, if the amount of water leaving the county becomes greater than the amount entering the county, there will be a resulting decline of the water table.

Change in the water level in wells records the fluctuation of the water table, which in turn records the recharge and discharge of the ground-water reservoir. In July, 1939, at strategic points in Stanton county 17 wells were selected and periodic measurements of the water levels in them were started, in order to determine the character and magnitude of fluctuations of the water table. The depths to water level in the wells were measured monthly beginning in August, 1939, and all measurements are given in table 2. All measurements prior to November 15, 1939, were made by me, those on and after that date were made by Richard B. Christy. The water levels in 13 of the 17 wells showed net gains of 0.01 foot to 0.84 foot from August, 1939, to July, 1940. The water levels in the other 5 wells showed net declines of 0.09 foot to 0.34 foot for the same period. In general, the water levels fluctuated very little during this period, and there seems to be no direct relation between the rainfall and the fluctuations in water level, owing to the lag between rainfall and recharge. The period of observation is too short to draw any conclusions regarding the trend of the water-table fluctuations. It is planned that the program of measuring water levels will be continued, for the longer the period of record the more reliable will be conclusions derived therefrom. All measurements through December acter and magnitude of fluctuations of the water table. The depths States Geological Survey for 1940, and additional measurements will be published annually in ensuing water-level reports.

Table 2—Water levels in observation wells in Stanton county, Kansas, in feet below the measuring point (For location of wells refer to plate 2; for descriptions, refer to well tables, pages 89-99.) The descriptions and 1939 water-level measurements are being published in "Water Levels and Artesian Pressures in Observation Wells in the United States in 1939": U. S. Geol. Survey Water-Supply Paper (in press). Subsequent water levels will be published in future papers of this series.

Well
No.
1939 1940
Aug. 8 Sept. 8 Oct. 9 Nov. 15 Dec. 15-16 Jan. 31 Feb. 20-21 Mar. 15 Apr. 22-23 May 14-15 June 17-18 July 17-18
4 55.92 55.87 55.89 55.82 55.86 55.81 55.81 55.79 55.79 55.77
13 51.53 51.60 52.44 52.45 52.57 52.65 52.67 52.72 52.83 52.82 52.82 52.52
29 100.34 100.33 100.43 100.41 100.38 100.43 100.45 100.44 100.44 100.44 100.44 100.43
35 179.07 179.03 179.12 178.98 179.00 178.84 179.04 178.92 178.99 178.94 178.89 178.80
47 70.91 70.91 70.92 70.94 70.91 70.92 70.91 70.92 70.88 70.10 70.91 70.89
48 78.25 78.29 78.28 78.34 78.29 78.28 78.30 78.30 78.30 78.27 78.28 78.38
54 102.55 102.44 102.58 102.51 102.51 102.48 102.53 102.52 102.52 102.52 102.49 102.68
57 150.49 150.39 150.52 150.34 ‡150.90 150.91 150.30 150.17 150.25 150.12 150.06 150.01
62 140.73 140.72 140.65 140.39 140.39 140.26 140.44 140.18 140.18 140.30 139.89 139.89
68 138.03 138.02 137.94 137.89 137.90 137.83 137.90 137.83 137.73 137.73 137.64 137.60
84 60.43 60.46 60.53 57.97 60.61 60.66 60.67 60.67 60.66 60.72 60.69 60.77
93   176.39 176.60 176.44 176.42 176.43 176.42 176.38 176.36 176.31 176.37 176.26
117 63.95 63.91 63.93 63.93 63.92 63.92 63.92 63.90 63.90 63.68 63.87 63.85
124 138.80 138.79 138.85 138.78 138.70 138.79 138.76 138.73 138.78 138.79 138.78 138.73
128 182.43 182.45 182.35 182.42 182.21 182.23 182.48 182.42 182.47 182.36 182.33 182.24
141 153.11 153.15 153.04 153.02 152.89 152.84 153.15 153.04 152.89 153.09 152.97 152.80
146 46.73 46.74 46.76 46.76 46.77 46.77 46.79 46.78 46.80 46.80 46.80 46.67
† Well pumping.
‡Well pumped just prior to measurement.

Recharge

Recharge is the addition of water to the underground reservoir and may be accomplished in several different ways. All ground water within a practicable drilling depth beneath Stanton county is derived from the water that falls as rain or snow either within the county or on near-by areas west of the county. Once the water becomes a part of the ground-water body it moves down the slope of the water table, later to be discharged at some point farther downstream.

The underground reservoir beneath Stanton county seems to be recharged by local rainfall within the county, by influent seepage from streams, and by subsurface inflow from areas west of the county.

Recharge from Local Rainfall

The average annual precipitation in Stanton county is about 17 inches, but probably only a very small percent of this amount reaches the zone of saturation, owing to several complicating factors. Of the total precipitation, part is lost by evaporation into the air, part is lost through runoff, and part is used by growing plants.

The amount of water lost through evaporation into the air varies from one season to the other, the rate of evaporation being the greatest in the summer when temperatures are highest. In an average year more than half the total precipitation in the county comes during the summer from May through August, when the rate of evaporation is greatest. Although no figures are available regarding the exact annual amount of evaporation in Stanton county, it seems reasonable to assume that a large proportion of the annual precipitation returns to the atmosphere through evaporation.

A part of the precipitation that falls is used by plants, and the amount consumed in this way is obviously greatest during the growing season, which closely coincides with the period of the maximum rainfall.

The amount of water leaving the county by runoff in streams is probably very small, even though the local runoff in some places is large, for much of the local runoff is respread over the area by streams and does not leave the county. The duration and intensity of the rainfall, the slope of the land surface, and the type of soil and vegetation principally determine the amount of local runoff from precipitation. The runoff from a gentle rain as a rule is much smaller than the runoff from a heavy downpour, hence the amount of ground-water recharge from a gentle rain of long duration generally is greater than the recharge from a heavy downpour of short duration, providing all other factors are equal.

The slope of the land is an important factor in determining the amount of runoff, and in general the steeper the slope the greater the runoff. The slope of the surface in most places in Stanton county is gentle, hence this factor tends to hold at a minimum the loss of precipitation through runoff.

Runoff is greater in places where the soil is tightly compacted and consists of fine, relatively impermeable material than in places where the soil is sandy and loosely compacted. The latter type of soil allows a part of the water to percolate into the ground, thus decreasing the amount of surface runoff.

Vegetation on the surface tends to decrease the velocity of the runoff, thereby offering a better opportunity for the water to seep into the ground.

From the foregoing it can be seen that the proportion of the precipitation that reaches the water table may be relatively small. Theis, Burleigh, and Waite (1935, pp. 2-3) believe that—

On the average over the High Plains only about half an inch of water a year escapes evaporation and absorption by the vegetation and percolates through the soil to the ground-water body.

The amount of recharge from precipitation in Stanton county is probably less than the average given for the entire High Plains, for about half the surface of the county is mantled by loess (plate 1), which greatly impedes if it does not prohibit the downward movement of water from the surface. The area of sand dunes south of Bear creek affords ample opportunity for a relatively large part of the precipitation to move readily downward beyond the influence of evaporation and the reach of plant roots. Other areas where the land lies low, the slopes are gentle, and the soils are sandy, are also favorable for recharge. Much of the rain that falls, particularly during heavy showers, will drain off into low places, or will stand on the surface for a time. A large proportion of the water will be lost through evaporation in either case, but some water will penetrate the soil and move downward toward the water table. The low area southeast of Johnson probably provides some recharge in this manner.

In many places the descending water will not recharge the underground reservoir directly beneath the area of intake, for the water, upon reaching a bed of impervious clay, silt, or caliche, must take a lateral course until it comes to an opening or pervious zone before continuing its downward course. In all probability the water follows a very irregular course from the surface to the water table.

Recharge from Streams

Two factors determine whether or not a stream is capable of supplying water to the underground reservoir; first, the water surface of the stream must be above the water table; and second, the material between the stream channel and the water table must be sufficiently permeable to permit water to percolate downward. If the water surface of the stream is lower than the water table and the material forming the sides of the channel are permeable, the process is reversed; that is, the ground-water reservoir will discharge water into the stream.

The ridges on the water-table contour map, described [earlier], indicate that along part of its course Bear creek is losing water to the ground-water reservoir. The channel of Bear creek lies above the water table throughout the county, and the deposits beneath the channel in most places allow the water to percolate downward. From a point in the SE1h sec. 12, T. 29 S., R. 43 W., northeastward the alluvium forming the bed of Bear creek consists of highly permeable sand and gravel that will readily allow water to percolate downward. Southwest of this point, where Bear creek has cut into the Cockrum sandstone, the stream bed in many places is floored by relatively impermeable shales that probably allow little or no percolation. Where the channel has cut into sandstone, however, water may seep downward and ultimately reach the water table.

During times of heavy rains in eastern Colorado and western Kansas, Bear creek carries a large volume of water. Although most of this water is emptied out upon the high plains of northern Grant county, where it generally disappears in a few days partly by evaporation and partly by seepage into the ground (Darton, 1920, p. 3), a large part also seeps into the ground before reaching Grant county. Residents of Stanton county report that sometimes after moderate rains the water that flows in Bear creek sinks before it reaches the county line.

No evidence for recharge from Sand arroyo is shown on the water-table contour map, but this stream probably supplies some water to the underground reservoir. The drainage area of Sand arroyo is considerably smaller than that of Bear creek, hence Sand arroyo carries a much smaller volume of water, which accounts in part for the smaller amount of recharge derived from it.

From the foregoing discussion it can be seen that during and after rains seepage from Bear creek and possibly Sand arroyo supplies a large quantity of water to the ground-water reservoir in Stanton county.

Recharge from Outside of County

A part of the water that falls on the surface in southeastern Colorado probably passes underground and eventually reaches the underground reservoir beneath Stanton county. The Dakota (Cockrum) sandstone is exposed over wide areas in western Las Animas county, Colorado, and adjacent areas, and undoubtedly absorbs water directly from rainfall and from streams that cross the outcrops. It is likely that a part of the water thus absorbed by the sandstone travels down the dip into Kansas, and probably migrates into the overlying Ogallala formation in Stanton county at places where the two formations are in contact and especially where the Cockrum thins. This method of recharge is illustrated in plate 5 by an east-west cross section from Trinidad, Colo., through Johnson, to the Stanton-Grant county line.

Plate 5—East-west cross section from Trinidad, Colo., through Johnson, to the Grant-Stanton county line, illustrating recharge of the Purgatoire (equivalent in part to the Cheyenne) formation and the Dakota sandstone (equivalent to Cockrum sandstone). In parts of Stanton county the Ogallala formation receives recharge from the Cockrum sandstone. (Geology in Colorado was taken from the Geologic map of Colorado [U. S. GeoI. Survey, 1935]; and elevations were taken from Darton [1906, pl. 6]). [A larger Acrobat PDF version of this figure is available.]

East-west cross section from Trinidad, Colo., through Johnson, to the Grant-Stanton county line.

West of Chacuaco creek the strata dip toward the west, and therefore any water absorbed by the Dakota sandstone west of Chacuaco creek probably travels westward and does not reach the underground reservoir in western Kansas. Water traveling down dip through the Dakota (Cockrum) sandstone does not migrate into the Ogallala formation until it reaches a line a few miles east of the ColoradoKansas boundary, for the Ogallala formation west of this line lies entirely above the zone of saturation (pl. 4, B-B'). At places where the Cockrum sandstone does not have a confining bed above it and where the pressure head of the water in the Cockrum is greater than the head in the Ogallala formation, the water can move from the Cockrum into the Ogallala. Downward migration of the water from the Cockrum is unlikely because the underlying Kiowa shale is relatively impervious and will not permit water to move through it into the underlying Cheyenne sandstone.

The amount of recharge received in this manner is necessarily limited by the small rainfall in southeastern Colorado and by the capacity of the sandstone to transmit water laterally. The average annual rainfall in the intake area is probably about the same as that in Stanton county, but the area of Dakota sandstone exposed east of Chacuaco creek is much larger than the total area of Stanton county. Therefore, although the average annual precipitation is relatively low, considerable recharge could occur in the area of outcrop. The amount of water discharged from the Dakota sandstone in southeastern Colorado through seepage into streams or by pumping from wells is not known, but it is thought to be relatively small compared to the total amount of water contained in the sandstone.

The Dakota dips beneath the Ogallala formation at about the Las Animas-Baca county line in Colorado, east of which the Dakota (Cockrum) is exposed only in the small stream valleys. Some of the water that falls on the surface of the Ogallala formation in Baca county probably passes underground and in part enters the Dakota sandstone. The amount of water entering the Dakota sandstone in this manner is thought to be small as compared with the amount entering the sandstone in the area of outcrop.

The recharge area for the Cheyenne sandstone must be sought outside of Stanton county, because the Cheyenne is not exposed to rainfall in the county and is everywhere overlain by the relatively impervious Kiowa shale. The Cheyenne sandstone is probably recharged in areas of outcrop west of Stanton county in the same manner as the Dakota sandstone. The Purgatoire formation in Colorado is equivalent to the Cheyenne sandstone and Kiowa shale in Stanton county. The amount of water added annually to the Cheyenne sandstone in this manner is probably small, owing to the scanty rainfall in southeastern Colorado and to the small area of outcrop.

Discharge

Transpiration and Evaporation

Water may be taken into the roots of plants directly from the zone of saturation or from the capillary fringe, and discharged from the plants by the process known as transpiration (Meinzer, 1923a, p. 48). The depth from which plants will lift ground water varies with different plant species and different types of soil. The limit of lift by ordinary grasses and field crops is not more than a few feet, but some types of desert plants have been known to send their roots 60 feet or more below the surface to reach the water table (Meinzer, 1923, p. 82).

The plant life in Stanton county consists mainly of short grasses and field crops and, as the water table nearly everywhere lies 50 feet or more below the surface, it is doubtful whether there is any great loss of water from the zone of saturation by the process of transpiration.

In areas where the water table is shallow some ground water from the zone of saturation evaporates directly into the atmosphere. In areas such as Stanton county, however, in which the zone of saturation and the capillary fringe lie at considerable depth, virtually no water is lost by evaporation from the zone of saturation.

Seepage into Streams

A stream that stands lower than the water table may receive water from the zone of saturation, but streams that stand above the water table, as do all the streams in Stanton county, cannot receive water from the zone of saturation. On the contrary, some of the streams in Stanton county contribute water to the ground-water reservoir, as described [earlier].

Springs

No springs that discharge water from the main zone of saturation were observed in Stanton county. The depth of the water table precludes the possibility of water-table springs, and artesian springs also are lacking. Many small seeps are found along Bear creek just east of the state line, but these seeps issue from small bodies of perched ground water rather than from the main ground-water reservoir. Here Bear creek has cut through the Ogallala formation, exposing shale and sandstone of the underlying Cockrum. Percolating ground water in the Ogallala formation encounters the impervious shale in the Cockrum, and as it cannot continue to move downward, it moves laterally and seeps out at places where the shale has been exposed by Bear creek.

Wells

From the foregoing discussion it can be seen that only a very insignificant amount of water, if any, is taken from the groundwater reservoir in Stanton county by natural processes, except the water that percolates slowly out of the county toward the east (earlier). All or virtually all the water taken from the underground reservoir within the county is discharged through wells, as discussed below.

Recovery

Principles of Recovery

The following discussion on the principles of recovery of ground water has been adapted in part from Lohman (1938, pp. 54-56).

When water is withdrawn from a well there is a difference in head between the water inside the well and the water in the surrounding material at some distance from the well. The water table in the vicinity of a well that is discharging water has a depression resembling in form an inverted cone, the apex of which is at the well. This depression of the water table is known as the cone of influence or cone of depression and the surface area affected by it is known as the area of influence. In any given well the greater the pumping rate the greater will be the draw-down (depression of the water level, commonly expressed in feet) and the greater will be the diameter of the cone of influence and of the area of influence.

The specific capacity of a well is its rate of yield per unit of draw-down and is usually stated in gallons a minute per foot of draw-down. For example, well 78 is reported to yield 650 gallons a minute with a draw-down of 13 feet. Its specific capacity is, therefore, 50 gallons a minute per foot of draw-down.

When a well is pumped the water level drops rapidly at first and then more slowly, but it may continue to drop for several hours or days. In testing the specific capacity of a well, therefore, it is important to continue pumping until the water level remains approximately stationary. When the pump is stopped the water level rises rapidly at first, then more slowly, and may continue to rise long after pumping has ceased.

The character and thickness of the water-bearing materials have a definite bearing on the yield and draw-down of a well, and in turn on the specific capacity of a well. Draw-down increases the height that the water must be lifted in pumping a well, thus increasing the cost of pumping (p. 49). If the water-bearing material is coarse and of a fairly uniform size it will readily yield large quantities of water to a well with a minimum draw-down, but if the water-bearing material is fine and poorly sorted it will offer more resistance to the flow of water into a well, thereby decreasing the yield and increasing the draw-down. Other things being equal, the draw-down of a well varies inversely with the permeability of the water-bearing material.

The specific capacity of wells, particularly in unconsolidated materials, generally can be greatly increased by the employment of special methods of well construction, as described [later].

In Stanton county ground water is recovered principally from drilled wells, but in part from dug wells. Descriptions of the types of wells employed in the county follow.

Dug Wells

Dug wells are wells that have been excavated by hand, generally with pick and shovel. In places where the walls will not stand alone, dug wells are cribbed with casings of wood, rock, concrete, or metal. As a rule dug wells are more subject to surface contamination than are properly constructed drilled wells. Moreover, as dug wells generally extend only a few feet below the water table, they are more likely to go dry during periods of drought than the deeper drilled wells.

There are only a few dug wells in Stanton county and they have all been abandoned in favor of drilled wells. Most of these wells were dug years ago by the early settlers of the county. The importance of water to these early settlers is illustrated by the time and hard labor they must have put into digging some of these wells. Several of the dug wells are more than 150 feet deep, are 3 to 5 feet in diameter, and are cribbed the entire depth.

Most of the dug wells in Stanton county have caved and are no longer in usable condition. Of the six dug wells found and inspected, only one (107) contained water and was equipped with a pump.

Drilled Wells

All the stock, domestic, railroad, municipal, and irrigation water supplies in Stanton county are obtained from drilled wells. Most of the wells were drilled by portable cable-tool drills mounted on trucks. This method of drilling consists in raising and lowering a heavy bit on the end of a steel cable, which is threaded over a sheave at the top of a tower or mast. The crushed material in the bottom of the hole is mixed with water and removed by means of a bailer.

Irrigation wells 19, 41, and 78 were drilled by the hydraulic-rotary method, the hole being made by the rapid rotation of a bit on the bottom of a string of drill pipe. In this method removal of the cuttings is accomplished by circulating mud-laden fluid down through the drill pipe and up through the annular space between the drill pipe and the hole. The cuttings are brought to the surface as fragments suspended in the mud. The mud also serves to plaster the materials around the hole, thereby preventing caving until the casing is installed. Wells 19 and 41 were drilled with a portable hydraulic-rotary drill rig (pl. 6A), which has all the drilling equipment except the derrick mounted on wheels. The derrick can be taken down joint by joint and transported to the next location by truck. Well 78 was drilled with a larger stationary drill rig (pl. 6B), of the type commonly used for drilling oil wells.

Plate 6—Rotary well-drilling rigs used in Stanton county to drill irrigation wells. A, Well 41 being drilled by a portable rig. B, Stationary derrick at well 78.

Two black and white photos; top is rotary well-drilling rigs; bottom is well 41 being drilled by a portable rig.

Most of the drilled wells in the county have galvanized-iron casing, but a few have wrought-iron casing. Wrought-iron casing is more expensive and more difficult to perforate, but will withstand more pressure and will last much longer than galvanized-iron casing. The diameter of the casing ranges from 5 or 6 inches in most domestic and stock wells to 18 inches or more in irrigation wells. Well 78 has 60-inch casing from the top to a depth of about 80 feet, and from there to the bottom it has 18-inch casing.

Wells in consolidated deposits

Most of the wells in the western and southwestern parts of Stanton county obtain water from consolidated deposits (Cockrum or Cheyenne sandstone) and have been drilled with portable cable-tool rigs. Many of the wells are open-end wells; that is, the hole is cased through the overlying Ogallala formation and a few feet into the consolidated rocks, but the lower part of the hole is not cased. Holes drilled into the bedrock formation below the Ogallala will as a rule stand open without casing. Well 112 was reported to have been drilled to a depth of 200 feet, but only the upper 30 feet was cased. Holes drilled into the consolidated formations will not always stand alone, so it becomes necessary in drilling some wells to case the holes from top to bottom. In such wells small perforations are sometimes cut in the casing opposite the water-bearing beds.

Wells in unconsolidated deposits

About 70 percent of the wells observed in Stanton county obtain water from unconsolidated sands and gravel of the Ogallala formation. It is necessary to case these wells the full depth of the hole in order to prevent caving of the walls. In some wells the casing has been perforated in the lower part; in other wells the casing is open only at the bottom. Perforating the casing greatly increases the area of intake, and thus the specific capacity of the well is increased and the entrance velocity of the water is reduced. Well screens are used in some wells to prevent fine sand from entering the well and to increase the intake area.

The public-supply well at Johnson City and all the irrigation wells in the county are gravel-packed wells. In constructing this type of well, a hole of large diameter (48 to 60 inches) is first drilled and temporarily cased. A well screen or perforated casing of a smaller diameter than the hole (12 to 25 inches) is then lowered into place and centered opposite the water-bearing beds. Blank casing extends from the screen to the surface. The annular space between the inner and outer casings then is filled with carefully sorted gravel—preferably of a grain-size just slightly larger than the openings in the screen or perforated casing, and also just slightly larger than that of the water-bearing material. The outer casing is then withdrawn in order to uncover the screen and allow the water to flow through the gravel packing from the water-bearing material.

The logs of some of the test holes drilled during the investigation reveal that in some places the water-bearing materials are sufficiently coarse and well sorted that gravel-packed wells are not required in order to obtain large yields. In such places less expensive wells employing well screens or slotted casings, but without gravel packing, may be used satisfactorily. In places where the water-bearing materials are fine-grained, however, the gravel-packed wells have several advantages that offset the greater initial cost. The envelope of selected gravel that surrounds the screen increases considerably the effective diameter of the well, and hence decreases the velocity of the water entering the well. This reduction in velocity prevents the movement of fine sand into the well and increases the production of sand-free water. Owing to the increased effective area offered by this type of construction, the entrance friction of the water is reduced and hence the draw-down may be reduced appreciably. As stated above, a reduction in draw-down, at a given yield, increases the specific capacity and reduces the cost of pumping.

Assuming that a well of the best possible construction is employed, then the maximum amount of water that can be withdrawn from the well is fixed by nature and nothing can be done to make the well yield more than the water-bearing material will provide. The problem for the driller then is to construct each individual well in such a manner as to obtain the greatest yield with the smallest amount of draw-down that is possible under the existing conditions.

According to McCall and Davison (1939, p. 29) draw-down can be kept to a minimum in several ways.

First, the well should be put down through all valuable water-bearing material. Secondly, the casing used should be properly perforated so as to admit water to the well as rapidly as the surrounding gravel will yield the water. Third, the well should be completely developed so that the water will flow freely into the well. … Increasing the depth of a well will have a greater effect on reducing the draw-down than will increasing the diameter, so long as additional water-bearing formations are encountered.

A report (Davison, 1939) containing a description of different types of pumping plants, the conditions for which each is best suited, construction methods, and a discussion of construction costs is available from the Kansas State Board of Agriculture, Topeka, Kan., and the reader is referred to this publication for details of well construction.

The most important question to the farmer who is contemplating the construction of an irrigation well is whether or not the ground water can be developed and pumped to the surface at a cost low enough to permit a profit from the crops produced. The depth to water level determines in part the original cost of the well and the cost of operation. The height a given quantity of water must be lifted is a prime factor in determining the cost of operating a well. The economic success of an irrigation project often hinges on this point, for the cost of lifting water to the surface increases in proportion to the total pumping lift. It is generally not possible to state the limit of economical pumping lift in a given locality, for it depends on such factors as the cost of fuel for operating the pump, efficiency of the pump, kind and price of the crops being irrigated, and the skill and management of the individual. In 1902 Johnson (1902, p. 668) made the following statement:

The economical pumping lift at Garden [Garden City, Kan.], under present conditions, can hardly be said to reach 20 feet. Under the more favorable conditions of future development and a local market this will probably not be increased by more than 50 percent. That is, 25 feet appears to be about the limit of height above the water plane at which irrigation farming from wells can profitably be conducted—at least on a commercial basis.

Since this statement was made the economical pumping lift in the vicinity of Garden City has increased more than 100 percent above the maximum figure given by Johnson, owing to modern developments in well construction, higher efficiency of modern pumps, type and increased price of crops being irrigated, and reduced cost of fuel for pumping.

The character and thickness of the water-bearing beds determine in part the original cost of constructing a well and the cost of operating the pumps after the well is completed. If the water-bearing beds are composed of somewhat fine materials it may be necessary to gravel-pack the well, and this increases the original cost. If the water-bearing materials are sufficiently coarse, less expensive wells employing well screens or perforated casings without gravel packing can be constructed.

Blowing wells

Several so-called blowing wells were observed in Stanton county. In wells of this type air is alternately blown out of or sucked into the casing. This phenomenon was observed in wells 35 and 96. Lugn and Wenzel (1938, p. 64) describe blowing and sucking wells in south-central Nebraska and state that they are caused by changes in atmospheric pressure. There may be unsaturated sand and gravel above the water table and below an impervious layer of loess or silt. This unsaturated material is filled with air that is confined between the impervious layer and the water table. According to Lugn and Wenzel this air is subjected to compression and expansion by changes in atmospheric pressure, and this pressure change causes a flow of air into or out of the unsaturated sand and gravel through the well casing.


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Kansas Geological Survey, Geology
Placed on web Oct. 5, 2018; originally published November 1941.
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