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Show OCCURRENCE OF UNDERGROUND WATER. 47 Decrease in flow and complete failure of some wells are reported throughout this area and are especially apparent in the vicinity of Murray. These results are directly traceable to the increased number of wells that have been sunk in recent years and to the fact that little economy is exercised in the use of the water. Well owners should more fully realize that the limited water supply comes from a common source, that the wastefulness of one counteracts the prudence of another, and that the common interest of all demands that the supply be conserved. Upland area.- The upland south of Salt Lake City includes the area lying between the base of the Wasatch and Traverse mountains and the area in which flowing wells can be obtained. This region is characterized topographically by the abundance and perfection of development of shore phenomena which mark different stages in the history of Lake Bonneville. As on the western side of the valley, the upland is in general a plain that rises toward the base of the mountains, but is interrupted by benches and escarpments and deeply cut by the creeks flowing from the Wasatch Mountains. The Bonneville terrace extends along the mountains like a narrow shelf, its horizontal lines contrasting strongly with the deep, vertical furrows on the mountains. Broad deltas formed by the larger creeks at the Provo stage extend down to the lowlands, and successive escarpments mark halting places in the retreat of Lake Bonneville. The most prominent of all the shore phenomena in the area covered by this report is the great embankment at the point of the mountains east of Jordan Narrows. Here the waves, gaining energy from the wide expanse of the old lake, carved a great sea cliff against the mountains and distributed the debris to form an enormous accumulation of sand and gravel. Prominent local features of this upland belt are the relics of glaciers adjacent to the mouth of Little Cottonwood Canyon and the evidences of recent faulting along the base of the mountains. Little Cottonwood Creek in Pleistocene time was occupied by a glacier which carved a broad U- shaped valley and deposited lateral and terminal moraines composed of a heterogeneous mass of coarse- and fine- textured debris. Along the entire front of the Wasatch Mountains Gilbert has found indications of recent dislocation associated with the great Wasatch fault. The evidence is varied, but escarpments in unconsolidated material breaking the even trend of alluvial slopes are conspicuous. The underlying deposits of the upland are mostly coarse textured, being near their origin, and consist chiefly of sand and gravel. The creeks, where they have cut deeply, expose good sections, but few deep- well records were obtained. This region in general is thinly populated, but where water is available there are settlements, and wherever the canals extend there are thriving farms. The contrast between the flourishing area which is supplied with water and the dry, barren region is striking. The map shows the distribution of the principal canal systems, which are supplied by the several creeks that flow from the Wasatch Mountains and by Jordan River. Underground water is used only to a limited extent. PI. VI and the list of wells illustrate conditions. Underground water is recovered chiefly in the lower ( western) part of the upland, where it lies at depths ranging from the surface to 50 feet below. In this productive area both dug and driven wells are used. The driven wells are commonly 50 to 200 feet in depth, and water is generally found beneath a bed of clay in sand or gravel under sufficient pressure to cause it to rise within pumping distance of the surface. In the eastern part of the upland area ground water generally lies at a greater depth than 50 feet below the surface, and in a number of places has not been found in test wells over 100 feet deep. In this ( eastern) division of the upland, where the greater part of the valley deposits are coarse textured, the ground water sinks deep before a relatively impervious bed is encountered, and then it tends to move to the lower part of the* valle3^. Away from the influence of seepage from the creeks little water is supplied to this area. Between the creeks the chief source of supply is seepage from the mountains. The most likely localities for sinking wells are along the courses of waterways, but over a large part of the upland the prospect is poor for obtaining underground water in quantity within easy reach of the surface. In the mouths of the canyons there is the chance of developing the underflow by |
