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Ground Water, continued
Quality of Water
The chemical character of the ground waters in Morton County is shown by the analyses given in table 6. The analyses were made by Robert H. Hess in the Water and Sewage Laboratory of the Kansas State Board of Health. Thirty-eight samples of water were collected from representative wells distributed as uniformly as possible within the area and among the water-bearing formations. The analysis of the water supply at Elkhart (listed as well 138) is a composite analysis of the water from 5 wells.
The fluoride content of the waters was determined by the Modified Sanchis method, and the other constituents listed were measured by the methods used by the U. S. Geological Survey.
Chemical Constituents in Relation to Use
The following discussion of the chemical constituents of ground water has been adapted from publications of the United States Geological Survey.
Total dissolved solids--The residue left after a natural water has evaporated consists of rock materials, with which may be included some organic material and a small amount of water of crystallization. Water containing less than 500 parts per million of dissolved solids generally is entirely satisfactory for domestic use, except for the difficulties resulting from its hardness, and in some areas, because of excessive iron corrosiveness. Water having more than 1,000 parts per million is likely to contain enough of certain constituents to produce a noticeable taste or to make the water unsuitable in some other respects.
The total dissolved solids in samples of water collected in Morton County ranged from 201 to 2,627 parts per million. The samples from about two-thirds of the wells contained less than 500 parts per million, and such water is suitable for most ordinary purposes. About one-third of the samples contained between 500 and 1,000 parts per million, and the sample from two wells (43 and 70) contained more than 1,000 parts per million.
Hardness--The hardness of water, which is the property that receives the most attention as a general rule, is most commonly recognized by its effects when soap is used with the water in washing. Calcium and magnesium cause almost all the hardness of ordinary water. These constituents are also the active agents in the formation of the greater part of all the scale formed in steam boilers and in other vessels in which water is heated or evaporated.
In addition to the total hardness the table of analyses shows the carbonate hardness and the noncarbonate hardness. The carbonate hardness is that due to the presence of calcium and magnesium bicarbonates. It is almost entirely removed by boiling. In some reports this type of hardness is called temporary hardness. The non-carbonate hardness is due to the presence of sulphates or chlorides of calcium and magnesium, but it cannot be removed by boiling and has sometimes been called permanent hardness. With reference to use with soaps, there is no difference between the carbonate and noncarbonate hardness. In general the noncarbonate hardness forms harder scale in steam boilers.
Water having a hardness less than 50 parts per million is generally rated as soft, and its treatment for removal of hardness under ordinary circumstances is not necessary. Hardness between 50 and 150 parts per million does not seriously interfere with the use of water for most purposes, but it does slightly increase the consumption of soap, and its removal by a softening process is profitable for laundries or other industries using large quantities of soap. Waters in the upper part of this range of hardness will cause considerable scale in steam boilers. Hardness exceeding 150 parts per million can be noticed by anyone, and if the hardness is 200 or 300 parts per million it is common practice to soften water for household use or to install a cistern to collect soft rain water. Where municipal water supplies are softened, an attempt is generally made to reduce the hardness to 60 or 80 parts per million. The additional improvement from further softening of a whole public supply is not deemed worth the increase in cost.
The hardness of the samples of water from Morton County ranged from 179 to 1,935 parts per million. The softest water analyzed was from well 11 in the Cockrum sandstone, and the hardest water was obtained from well 43 in the Permian redbeds. Twenty-five of the samples analyzed had a hardness between 200 and 300 parts per million and seven had a hardness between 300 and 400 parts per million. The hardness of five samples exceeded 400 parts per million.
Iron--Next to hardness, iron is the constituent of natural waters that in general receives the most attention. The quantity of iron in ground waters may differ greatly from place to place, even though the waters are from the same formation. If a water contains much more than 0.1 part per million of iron the excess may separate out and settle as a reddish sediment. Iron, which may be present in sufficient quantity to give a disagreeable taste and to stain cooking utensils, may be removed from most waters by simple aeration and filtration, but a few waters require the addition of lime or some other substance.
Most of the water from wells in Morton County contained more than 0.1 part per million of iron. Five samples contained between 1.0 and 2.0 parts per million of iron and three samples (106, 136, and 15) contained between 2.0 and 3.0 parts per million.
Fluoride--Although determinable quantities of fluoride are not so common as fairly large quantities of the other constituents of natural water, it is desirable to know the amount of fluoride present in water that is likely to be used by children. Fluoride in water has been shown to be associated with the dental defect known as mottled enamel, which may appear on the teeth of children who, during the period of formation of the permanent teeth, drink water containing fluoride. It has been stated that waters containing 1 part per million or more of fluoride are likely to produce mottled enamel, although the effect of 1 part per million is not usually very serious (Dean, 1935, pp. 1269-1272). If the water contains as much as 4 parts per million of fluoride, 90 percent of the children exposed are likely to have mottled enamel, and 35 percent or more of the cases will be classified as moderate or worse.
More than half of the water samples collected in Morton County contained more than 1 part per million of fluoride. Four samples contained between 1 and 2 parts per million, 13 samples contained between 2 and 3 parts per million, and 4 samples contained more than 3 parts per million. The maximum fluoride content, 3.8 parts per million, was in a sample of water from well 52.
Water for irrigation--The suitability of water for use in irrigation is commonly believed to depend mainly on the total quantity of soluble salts and on the ratio of the quantity of sodium to the total quantity of sodium, calcium, and magnesium together. The quantity of chloride may be large enough to affect the use of the water and in some areas other constituents, such as boron, may be present in sufficient quantity to cause difficulty. In a discussion of the interpretation of analyses with reference to irrigation in southern California, Scofield (1933) states that if the total concentration of dissolved salts is less than 700 parts per million there is not much probability of harmful effects in irrigation use. If it exceeds 2,100 parts per million there is a strong probability of damage to either the crops or the land, or both. Water containing less than 50 percent sodium (the percentage being calculated as 100 times the ratio of the sodium to the total bases, in equivalents) is not likely to be injurious, but if it contains more than 60 percent its use is inadvisable. Similarly, a chloride content less than 142 parts per million is not objectionable, but more than 355 parts per million is undesirable. It is recognized that the harmfulness of irrigation water is so dependent on the nature of the land and the crops and on the manner of use and the drainage that no hard and fast limits can be adopted.
All but one of the samples of water collected in Morton County are well within the limits suggested by Scofield for safe waters for use in irrigation. Water from well 43 contained 2,627 parts per million of total dissolved solids and probably would not be suitable for irrigation.
Sanitary Considerations
The analyses of water given in the tables show only the amounts of dissolved mineral matter in the water and do not indicate the sanitary quality of the water. An abnormal amount of certain mineral matter such as nitrate, however, may indicate pollution of the water.
About 50 percent of the population of Morton County is dependent on private water supplies from wells, and every precaution should be taken to protect these supplies from pollution. A well should not be located where there are possible sources of pollution. Every well should be tightly cased to a level somewhat below the water table. As a general rule dug wells are more subject to contamination from surface water than are drilled wells, owing mainly to the fact that generally they are not effectively sealed at the surface.
Fortunately, more than 95 percent of the wells in Morton County are drilled wells.
Relation to Stratigraphy
The typical quality of water in the six principal water-bearing formations in Morton County is shown in figure 6, and is discussed below.
Figure 6--Analyses of typical waters from the six principal water-bearing formations in Morton County.
Permian redbeds--The artesian wells at Richfield penetrate the Permian redbeds. The water contains a large amount of calcium and sulphate and a relatively small quantity of iron. These beds are cemented by iron oxide but the water has a small iron content because the iron in the rock is ferric oxide, which is relatively insoluble. These beds yield water that contains more than 2 parts per million of fluoride, which might be injurious to the enamel of children's teeth.
Triassic (?) redbeds--Water from the Triassic (?) beds may be moderately hard or very hard, depending upon the zone from which the water is taken. The upper part of the Triassic (?) consists predominantly of buff and gray sandstones and yields moderately hard water to wells. The lower part is predominantly red siltstone and sandstone, but contains some gypsum, and yields strongly mineralized water under artesian pressure. An old artesian well (86) at the old town of Point of Rocks was reported to yield a "strong alkali water" (Parker, 1911, p. 144). Well 140 at Elkhart encountered strongly mineralized water at a depth of 460 feet in redbeds that are probably Triassic (?). The water from well 119, a zone near the top of the Triassic (?), has a total hardness of 202 parts per million and contains 2.8 parts per million of fluoride.
Cheyenne sandstone--Waters from wells in the Cheyenne sandstone have a moderate hardness and contain 1.5 to 2.3 parts per million of fluoride. The water from well 15 in this sandstone has a hardness of 237 parts per million and has a fluoride content of 2.0 parts per million. The quality of the water from the Cheyenne sandstone is very similar to that of water from the Cockrum sandstone.
Cockrum sandstone--Most of the wells in the northwestern part of the county get their water from the Cockrum sandstone. Most of the Cockrum water has a hardness of 200 to 300 parts per million and a fluoride content of 1.1 to 3.8 parts per million. The sample of water from well 11 in the Cockrum sandstone was the softest water of any of the 38 samples analyzed, 179 parts per million, and its fluoride content was only 0.6 part per million. The four samples from Morton County having the greatest fluoride content, however, were also from wells in the Cockrum sandstone. In general the Cockrum water is moderately hard and contains only a small amount of iron, but contains sufficient fluoride to be harmful to children's teeth.
Ogallala formation--The hardness of the water from wells in the Ogallala formation ranges from 201 to 645 parts per million, which averages slightly more than that of the water from the Cockrum sandstone.
In some respects the water from the Ogallala formation north of Cimarron River differs from the water from the Ogallala south of the river. Water from the Ogallala north of the river contains 1.9 to 2.8 parts per million of fluoride, whereas water from the Ogallala south of the river contains less than 1 part per million. The greater fluoride content north of the river is probably caused by recharge of the Ogallala formation by water from the Cockrum sandstone, whereas the Ogallala formation south of the river is probably recharged by precipitation on the sand dunes in southern Morton and Baca counties.
Water from the Ogallala formation south of the river contains more iron than water from the Ogallala north of the river or from the Cockrum.
Alluvium--Water from wells in the alluvium of Cimarron River is very hard. The sample from well 70 had a hardness of 795 parts per million and the sulphate and fluoride contents were 632 and 2.0 parts per million respectively. There are only a few wells in the alluvium in the Cimarron valley and most of these are stock wells. Supplies of softer water for domestic use are obtained in the valley from wells that penetrate the Triassic (?) redbeds or the Ogallala formation below the alluvium.
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Kansas Geological Survey, Morton County Geohydrology
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Web version Sept. 2004. Original publication date March 1942.
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