The relations of underground waters in this region present a variety of features. In many localities there are large supplies at moderate depths, and in other places the amount of waters in reach of the average farmer is so small as seriously to interfere with the settlement of areas of considerable extent. This has been particularly the case where large volumes of water were needed for cattle. The greatest difficulty in obtaining water has been in the area of the Brule clay back from the rivers and in the region underlain by Pierre clay. In the flats adjoining the river in Platte Valley and in Lodgepole Valley water supplies are usually obtained in wells from 10 to 40 feet in depth. On the table-lands on both sides of Lodgepole Valley waters are obtainable in large volume from wells from 150 to 300 feet deep, the depth increasing gradually westward. In Niobrara Valley supplies of water are obtained from shallow wells in the narrow strip of alluvial deposits near the river, and farther back on the table-land plenty of water is found at depths varying from 50 and 100 feet on the lower slopes to 300 feet in some of the highest areas to the northwest. In the sand hills water accumulates in basins at moderate distances below the surface, so that shallow wells ordinarily obtain satisfactory supplies.
Along the outer edge of the Brule clay area north of Pine Ridge water is usually found in the underlying Chadron sands. In Pl. XXXVII are shown the depths to water supplies in the western Nebraska region, based on observations of the water level in wells and springs and determinations of the geologic relations of the water bearing formations.
In the alluvial formations along Platte, Niobrara, and White rivers and Lodgepole, Pumpkinseed, Snake, and Hat creeks, and some of their branches, the water supply constitutes an underflow. Along the Platte this underflow is of large volume, but in some areas the water is somewhat alkaline. In the Pumpkinseed Valley at some localities, and in the greater portion of the White River and Hat Creek valleys, where they traverse the Pierre shales, these water supplies are often unsatisfactory both in quantity and in quality.
The next horizon is at the base of the Ogalalla formation, which supplies water for many wells on the table-lands on both sides of the Lodgepole Valley at depths varying from 100 to 300 feet. The volume of water appears to be large at nearly all localities. At some places the waters are obtained high up in the formation, but the principal supplies are in the basal beds. At many points along the northern margin of the table-land these waters flow out into the canyons as springs of greater or less force, of which the most noteworthy are those on Greenwood, Middle, Hackberry, and Bighorn creeks, in Lawrence Fork Canyon, and at Gabe, Long, and Duggers springs.
The Arikaree formation is a general reservoir for water, which is nearly everywhere available in the table-lands lying between the valley of North Platte River and the crest of Pine Ridge. In some areas it is necessary to sink wells to the base of the formation, where the materials are somewhat coarser than those higher up, but ordinarily the higher beds yield satisfactory supplies. These waters flow out at the surface in springs of greater or less magnitude in many canyons along the front of Pine Ridge; at a few widely scattered points in the Niobrara Valley, notably at Coyote Spring and at Royville; in the Snake Creek Valley, at Point of Rock Spring and Mud Spring; and along the north slope of the Platte Valley at the spring near the head of Sheep Creek and the springs near the heads of Red Willow and Indian creeks.
The Gering formation contains water throughout its area, but it does not appear to be reached by many wells. Numerous springs on the ridge south of North Platte River flow from this formation at the surface of the Brule clay. Along the front of Pine Ridge there are a number of springs which flow out of these beds, and possibly some of the deeper wells on the summit of Pine Ridge obtain their water from this horizon, but ordinarily ample supply is reached at a less depth in the overlying Arikaree formation.
The Brule clay immediately underlies a wide area of the high slopes of the North Platte and Pumpkinseed valleys and yields water supplies to many wells. It is known as "hardpan" to the well drillers. In most cases, however, the volume of the water is small, and its quality is often unsatisfactory. Numerous abandoned houses in these valleys usually indicate that prospective settlers have been unable to obtain water supplies at moderate depths from the Brule clay. Where water occurs it is in crevices and fissures, which traverse the clay at moderately frequent intervals, but the volume of water depends on many factors, and there is seldom a good chance to obtain a large supply. In the area north of Pine Ridge the wells usually penetrate through the Brule clay into the underlying Chadron sands, which almost invariably contain fairly large volumes of water. It is a source of supply to a number of farmers and ranches. The water is not always of satisfactory quality, and in the wells at Adelia and Crawford it has been found unsuitable for locomotives. This formation underlies the Brule clays in the Platte and Pumpkinseed valleys, and probably would often yield water there to wells a few hundred feet in depth. Some years ago a well was sunk at Gering to a depth of 331 feet, which obtained a promising flow of water, probably from the Laramie sandstone, which underlies the Chadron formation. Owing to the small size of the pipe and to accidents in boring, the well did not continue to flow, and clogged up so that it was a failure. As water supplies are particularly scant in the region about Gering and in the valleys to the south, it is very unfortunate that this boring was not given a fair trial. At Harrisburg, on the south slope of Pumpkinseed Valley, a boring has recently been made to a depth of 790 feet without obtaining a flow. Judging from the small samples of the borings which were seen, the well passed through the Chadron sands and entered the Laramie formation for several hundred feet, but it did not obtain a sufficient supply of water. It is known that the edge of the Laramie formation extends into southwestern Nebraska under the Chadron sands, and it should be expected to yield a water supply that would rise to an altitude of about 4,500 feet. In the underlying Pierre shale there are no chances for water. In the area in which this formation is at the surface, in northern Sioux and Dawes counties, great difficulty has been experienced in obtaining water supplies for local use, and the water found has generally proved to be of unsatisfactory quality.
In the older formations which underlie Nebraska there are widespread sheets of permeable deposits which carry large volumes of water. In the region to the west these deposits lie at great depth, and many of the higher lands are probably above the level to which the waters would rise to afford surface flows. Owing to the failure of any boring in the central and western portion of the State to reach the deep-seated water-bearing beds, there is lack of definite knowledge as to their depth, but there can be no doubt of their presence. The section constituting Pl. X illustrates the general relations of the two principal deep water-bearing formationsthe Dakota sandstone and the Carboniferous and underlying limestones. In eastern South Dakota the Dakota sandstone yields to many wells large volumes of excellent water under high pressure. In eastern Nebraska, where the formation approaches the surface, it is also the source of water supply, at first to wells of moderate depth and then to innumerable springs. The Carboniferous and underlying formations yield water to numerous wells between 650 and 1,500 feet deep in eastern Nebraska and Iowa. These waters pass into the formations along the foothills of the Black Hills and the Rocky Mountains at altitudes of from 3,000 to 6,000 feet in greater part, and have considerable pressure and head far to the east. This pressure and head, however, gradually decrease as the formations reach or approach the surface, the water then being free to escape. The waters in the Dakota sandstone lose their head entirely in eastern Nebraska, where the formation outcrops. The waters in the underlying Carboniferous limestones and older formations retain a moderate amount of head throughout Nebraska. Some of the factors bearing on the occurrence of these deep underground waters are shown in Pl. XXXVIII, and in Pl. XXXIX are shown some of the conditions of occurrence of the waters in the Carboniferous and underlying formations in the vicinity of Omaha, Nebr. It will be seen in Pl. XXXIX that the head is relatively constant near 1,100 feet above sea level over a wide area about Omaha, but there is a slight rise to the west even in a few miles. At Lincoln it is 1,210 feet above sea level. The increase of head and pressure to the west and northwest is gradual, for the distance is great, but the amount becomes large as the Black Hills and Rocky Mountain zones of intake are approached. In Pl. XXXVIII figures are given showing the altitudes along these zones and along the outcrop areas east, which will afford some idea of the head to be expected in the intermediate region. In the diagram, fig. 22, there is shown a piece of physical apparatus which illustrates the gradient of head between a leak on the one hand and the source of pressure on the other, representing closely the relations which have been found to exist in the South Dakota artesian basin and probably prevail in a measure also in central and eastern Nebraska, where the head of the deeper-seated waters diminishes eastward.
Data are not sufficiently definite as yet for a precise determination of this gradient of head across western Nebraska, but it is apparent that in some of the valleys westward the head is probably higher than the altitude of the land, so that there are prospects for surface flows.
In order to reach the deep-seated waters in western Nebraska it is necessary to penetrate the Tertiary formations, the Pierre clay, the Niobrara limestone, and the Benton shale, to the Dakota sandstone, which should be expected to yield a large supply of excellent water. An attempt was made to reach this horizon in a deep boring at Chadron some years ago. A depth of 1,100 feet was attained, when the boring was abandoned owing to great difficulty in penetrating the Pierre shale. More recently an attempt has been made at Ardmore by the Burlington and Missouri River Railroad, which attained a depth of 1,500 feet apparently without reaching the bottom of the Upper Cretaceous shales. These shales can be penetrated only by skillful well drillers, and it is necessary to begin with casing 12 or 14 inches in diameter at the top, as the size will have to be reduced occasionally as the boring progresses. The depth to the Dakota sandstone at Crawford will probably prove to be 2,000 feet, and in the valley of North Platte River the amount may be somewhat more. There is possibility of obtaining a flow in these localities, although the altitude is somewhat greater than that of the Dakota sandstone outcrops along the southern margin of the Black Hills. It is to be expected that the pressure of water in the Dakota sandstone will increase to the southwest, in the direction of the Rocky Mountains.
Underlying the Dakota sandstone, with a series of gray and red sandstones intervening, are the limestones of Carboniferous age, which contain water in considerable volume and with somewhat greater head than the waters in the Dakota sandstone. These are the same beds as those yielding flows in the Missouri Valley about Omaha, and there is fair reason to believe that they would prove a satisfactory source of water supply in other portions of Nebraska.
Last Updated: 24-Aug-2009