Geology and ground-water resources of the Owl Creek area, Hot Springs County, Wyoming

Abstract

About 250 square miles is included in the project area, which consists of relatively broad valleys and flat terraces grading into rugged folded and faulted uplands. The project area lies at the southern end of the Bighorn structural basin. The climate is semiarid; the normal annual precipitation is about 13 inches. The exposed rocks range in age from Pennsylvanian to Recent; the younger deposits are exposed in and along the valleys, the older deposits in the uplands adjacent to the valleys. The alluvium and terrace deposits yield water to domestic and stock wells throughout the area and locally yield moderate to large quantities of water for irrigation. Large quantities of ground water can be obtained for only a short time, however, because recharge is not sufficient to sustain large yields for long periods. Some of the older formations that underlie the area (Madison limestone and Tensleep sandstone) yield large supplies of water to artesian springs. Other formations (the Cloverly and the Frontier formations and the Cody shale) can yield water under artesian pressure to domestic and stock wells. The depth to the water table ranges from only a few feet in the river flood plain to about 70 feet at the margins of the valleys. The water in the terrace and alluvial deposits moves generally eastward toward the Bighorn River. The ground-water reservoir is recharged principally by precipitation that falls either on the area or on adjacent areas and by percolation from irrigation water and streams. Ground water is discharged principally by evaporation and trangpiration, by seepage into streams, and through springs and wells. Most of the wells in the Owl Creek area were drilled, but some were dug and a few were bored or driven. Only eight wells in the area are used for irrigation. The yield of the irrigation wells ranges from about 50 to about 500 gallons per minute. Ground water for irrigation can be developed most practicably from the alluvium in the part of the valley that extends from the west side of Rose Dome to the vicinity of sec. 10, T. 43., R. 99 W., and from the terrace deposits north of Owl Creek in the central part of the area. The total amount of water that can be pumped from these aquifers is relatively small and depends on the amount of seepage from irrigation water applied to the land. The relatively few data obtained during this investigation indicate that ground water from the principal aquifers in the Owl Creek area the Chugwater and Frontier formations, the Cody shale, and the unconsolidated deposits is of poor chemical quality; all the ground water is highly mineralized, and that from the unconsolidated deposits is very hard. The water is unsuitable for irrigation and 2 GEOLOGY, GROUND-WATER RESOURCES, OWL CREEK AREA, WYO. is objectionable for domestic use because of large amounts of dissolved solids (more than 2,000 parts per million), mostly sodium sulfate. However, some water from unconsolidated deposits might be classified as safe for supplemental irrigation if applied under carefully controlled conditions. Conversely, the surface water, especially in the upstream part of the area, is of generally good quality for irrigation, although at some times and in some places it is unsuitable.