Date of this Version
Published in Geological Survey Water-Supply Paper 1360-H (1957) 134 pages.
The geology and ground-water resources of the upper Republican River valley west of the town of Alma, Nebr., to the Nebraska-Colorado State line and of the Frenchman River valley from its confluence with the Republican River to a point about 12 miles upstream from Wauneta, Nebr., were studied from January 1950 to April 1951. The purpose of the study was to relate the occurrence of ground water to irrigation and flood control and to aid in the evaluation of the effects of irrigation on the land in the area.
The area included in this study consists of 370 square miles of flat or gently sloping terraces and bottom land that border the Republican and Frenchman Rivers on either side. The Republican River is a comparatively shallow stream, ranging in width from about 150 feet at the western end of the area to about 300 feet at the eastern end. The channel banks are low, except where the river cuts into bordering terraces. In many places, natural levees of loose sand and gravel have been formed adjacent to the river banks.
The bedrock formations exposed in the area are the Niobrara formation and the Pierre shale of Cretaceous age and the Ogallala formation of Tertiary age. Deposits of sand and gravel, of early Pleistocene age, are present in the bottom of the ancestral Republican River valley and along the north side of the present valley. These coarse deposits are mantled by finer sediments of later Pleistocene and Recent age. Large quantities of ground water are available from the Pleistocene and Recent deposits throughout most of the Republican River valley. In the center of the valley as much as 40 to 60 feet of the deposits are saturated.
The ground-water reservoir is recharged principally by precipitation. Ground water also enters the Republican River valley by underflow through the fill of tributary valleys. Ground water is discharged by evaporation, transpiration, and effluent streams; ground water also is drawn upon extensively for irrigation, for municipal supplies, and for domestic and stock use in rural areas.