Evaluation of ground-water-level changes near Gillette, northeastern Wyoming
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Water-Resources Investigations Report↗
Geology topics
Marvin A. Crist
Publications and source records attributed to Marvin A. Crist.
Geohydrology of the High Plains aquifer system, Cheyenne urban area, Wyoming
The Cheyenne area is on broad tablelands that form part of the High Plains aquifer. Surficial deposits, along with the Ogallala Formation and the White River Group, are included in the High Plains aquifer in the study area, and both unconfined and confined ground-water conditions exist within 100 feet of land surface. During wet years, shallow ground-water problems affect urban development. The High Plains aquifer is considered an aquifer system in the Cheyenne area. Water-yielding sandstone and conglomerate units are surrounded by sequences of clay and silt; although the water-yielding units under confined conditions may be areally extensive, they are not easily identified. Urban development has modified the High Plains aquifer system locally as indicated by the mapped potentiometric surfaces, the perched water zones, and the surface-drainage patterns. That part of the system in the shallow zones is affected by excavations and by structures that penetrate the saturated zones.
Wyoming↗
Effect of pumpage on ground-water levels as modeled in Laramie County, Wyoming
Groundwater is being extensively developed for domestic, agricultural, and industrial use in a 2,320-square mile area in Laramie County, WY., bounded approximately by Horse Creek on the north, Nebraska on the east, Colorado on the south, and pre-Tertiary outcrops on the west. Currently (1977) about 47,300 acres of land are irrigated with groundwater. Groundwater levels are declining in some areas as much as 4 feet per year. The investigation was made to provide State water administrators with data on water-level changes resulting from present (1977) groundwater withdrawals and to provide a means of predicting the future effect of groundwater development. A digital model was developed of the hydrologic system in the post-Cretaceous rocks. The ability of the model to simulate the hydrologic system was determined by comparing the water-level changes measured at 37 observation wells located in areas of irrigation pumping with the water-level changes calculated by the model for 1971-77. Comparison of the measured and calculated changes showed agreement with a root-mean-square deviation of + or - 3.6 feet with 8 feet as the maximum deviation. It is concluded that the model adequately simulates present hydrologic conditions in the post-Cretaceous rocks and may be used to predict the effect of applied stress to the system. (USGS)
Open-File Report↗
Hydrologic analysis of the valley-fill aquifer, North Platte River Valley, Goshen County, Wyoming
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Water-Resources Investigations Report↗
Selenium in waters in and adjacent to the Kendrick Project, Natrona County, Wyoming
Selenium in concentrations exceeding the maximum limit, 0.01 milligrams per liter or 10 micrograms per liter, recommended by the U.S. Public Health Service in 'Drinking-Water Standards, 1962,' Public Health Pub. 956, is present in waters in areas near Casper, Wyo. Some streams containing selenium flow into the North Platte River upstream from several municipalities that obtain water from the river and the alluvium along the river. The area of this investigation includes about 725 square miles in Natrona County in central Wyoming. Study effort was most intensive within the area bounded by the North Platte River, Casper Creek, and Casper Canal, the approximate boundaries of the Kendrick irrigation project. Geologic formations in the area contain selenium that may have been derived from deposits of seleniferous material or from volcanic emanations brought down by rain. Formations older than Cretaceous age were not considered as important sources of selenium in waters of the area, because no irrigation water is applied to areas underlain by these rocks. The selenium concentration in 82 samples of Cretaceous rocks ranged from less than 10 to 4,200 ?g/kg (micrograms per kilogram of sample); no correlation was found between selenium concentration and the depth at which the sample was collected. Of four samples of Tertiary rocks analyzed, three contained no selenium and one had a selenium concentration of 40 ?g/kg. The selenium concentration in 93 samples of Quaternary rocks ranged from less than 10 to 52.0 ?g/kg, and the highest selenium concentration was generally found at depths less than 4 feet. No geologic formation has consistently high concentrations of selenium, but high concentrations were found at points throughout the study area. Probably the rocks in any locality could be the source of selenium in the water in the surrounding vicinity. The selenium concentration in water from some wells fluctuates widely. It is concluded that the selenium concentrations in the ground water in these areas have not reached a state of equilibrium in the aquifer. It is possible that such nonequilibrium conditions exist in aquifers throughout much of the area. If so, statements in this report concerning- trends of selenium concentration in ground water are somewhat speculative.Poison Spring Creek, Poison Spider Creek, Oregon Trail Drain, and Casper Creek are the principal tributaries that contribute selenium to the North Platte River. The selenium load, expressed in pounds per day, in Poison Spring Creek and Poison Spider Creek decreased slightly during the first year of sampling and increased slightly during the second year of sampling. The selenium load in Oregon Trail Drain is greatest in late winter and early spring during the period of low flow; the selenium load in Casper Creek varies, but shows no correlation with season and little correlation with stream discharge. The North Platte River above and below the irrigation project had consistently low selenium concentrations, 10 ?g/l (micrograms per liter) or less, in the period April 1968 through June 1969. The total selenium load contributed to the North Platte River from tributaries in the study area is almost undetectable after mixing with the river water. From the fall of 1968 .to the spring of 1969, results of water sampling in areas influenced by irrigation show that the selenium concentration increased at 29 percent of the locations (average net increase of 64 ?g/l), decreased at 34 percent of the locations (average net decrease of 80 ?g/l), and had little (10 ?g/l or .less) or no change at 37 percent of the locations. As a comparison, results of water sampling in areas not influenced by irrigation showed that the selenium concentration increased at 2 percent of the locations (average net increase of 30 ?g/l), decreased at 26 percent of the locations (average net decrease of 30?g/l), and had little or no change at 72 percent of the locations. It is not possible to
Water Supply Paper↗
The ground-water system in southeastern Laramie County, Wyoming
Increased development of irrigation wells in southeastern Laramie County, Wyo., has caused concern about the quantity of water available. Ground water from approximately 230 large-capacity wells is used to irrigate most of the 18,165 acres under irrigation. The purpose of this study is to provide more knowledge about the character of the aquifers, quantity of water in storage, rate of withdrawal, and the effect of withdrawals on streamflow. The area studied consists of about 400 square miles in southeastern Laramie County in the extreme southeast corner of Wyoming. The White River Formation of Oligocene age and alluvium of Quaternary age are the principal aquifers. The White River Formation is made up primarily of clay, silt, and fine sand. Secondary permeability in the White River Formation accounts for it being an important aquifer. The alluvium, which Includes terrace and flood-plain deposits, consists of sand and gravel that contain some lenses of silt and clay. Existence of secondary permeability in the White River Formation has been accepted for some time although the nature of the secondary permeability has been disputed. Examination of downhole conditions with a television camera during this study revealed openings in the formation that appeared to be similar to tubes or caverns. The openings were of various sizes and shapes but only a few appeared to be associated with fracturing. Solution activity in the formation probably is an important factor in the development of secondary permeability. The study area was divided into the Pine Bluffs-Egbert area and the Carpenter area. Ground-water movement in the Pine Bluffs-Egbert area is generally eastward into Nebraska; in the Carpenter area, movement is generally southward into Colorado. Pumpage from large-capacity wells in the Pine Bluffs-Egbert area was estimated to be about 21,790 acre-feet in 1971. Water levels exhibited a declining trend annually in some areas during the period of record. Data indicate that pumpage in the Pine Bluffs-Egbert area probably is the cause of decreased base flow in Lodgepole Creek since approximately 1961. Increased pumpage, above that in 1971, will result in further reduction of discharge of Lodgepole Creek into Nebraska. In the Carpenter area, it was estimated that the terrace deposit contained about 1 million acre-feet of saturated sediments in March 1971. The amount of ground water in storage in the White River Formation in this area is unknown. Pumpage from large-capacity wells in the Carpenter area was estimated to be about 7,090 acre-feet in 1971. Recharge to the area was not estimated but there was no indication of a net decline in water levels between September 1970 and September 1971.
Open-File Report↗
Ground-water resources of Natrona County, Wyoming
Natrona County covers an area of 5.369 square miles in central Wyoming. The climate is arid except in the mountainous areas. The county includes parts of the Great Plains, Middle Rocky Mountains, Wyoming Basin, and Southern Rocky Mountains physiographic provinces. There is wide variation of topography. More than 30 geologic formations are exposed in the county, 28 of which are known to yield water to wells and springs. The formations range in age from Precambrian to Holocene. Ground water in approximately 40 percent of the county contains more than 1.000 mg/l (milligrams per liter) of dissolved solids. Water chemically suitable for livestock can be developed at depths of less than 1,000 feet throughout most of the area. Many of the geologic formations were deposited under similar conditions and have similar water-bearing properties; also. water from these rocks deposited under similar conditions tends to have similar chemical characteristics. For this report, the stratigraphic section has been arbitrarily divided into six rock units based on similarity of deposition. The igneous and metamorphic rock unit includes rocks of Precambrian age and igneous intrusives and extrusives of Tertiary age. These rocks probably would not yield more than about 5 gpm (gallons per minute) to wells. The water is usually calcium bicarbonate type and contains less than 500 mg/l of dissolved solids. The marine rock unit includes formations of Cambrian, Mississippian, and Pennsylvanian and Permian age, having a maximum total thickness of about 1,900 feet. The Madison Limestone of Mississippian age and the Tensleep Sandstone and the Casper Formation of Pennsylvanian and Permian age supply the largest yields to wells and springs in the county. In the northeastern part of the county, flow from each of three wells in the Madison reportedly is more than 4.000 gpm. Each of three wells in the Tensleep in the same area flows more than 400 gpm. Yields of springs in the Casper Formation near Casper Mountain range from about 1.0 to 17 cubic feet per second. Ground water from near the outcrop of all these formations usually contains less than 500 rag/l of dissolved solids. The dissolved-solids content increases with distance from the outcrop and in places is more than 3.200 mg/l. Several types of water were found in this unit including sodium sulfate, calcium sodium sulfate, calcium sulfate, sodium calcium sulfate, sodium chloride, and calcium bicarbonate.
Water Supply Paper↗
Geology and ground-water resources of Laramie County, Wyoming
Laramie County, an area of 2,709 square miles, is in the southeast corner of Wyoming. Rocks exposed there range in age from Precambrian to Recent. The most extensive aquifers in the county are the White River Formation of Oligocene age, which is as much as 500 feet thick and consists predominantly of siltstone ; the Arikaree Formation of Miocene age, which consists of as much as 450 feet of very fine grained to fine-grained sandstone; and the Ogallala Formation of Miocene and Pliocene age, which consists ,of as much as 330 feet of gravel, sand, silt, and some cobbles and boulders. These formations are capable of yielding large ,supplies of water locally. Terrace deposits of Quaternary age yield moderate .to large supplies of water in the southeastern and northeastern parts of the county. In the Federal well field, large yields of water from the White River Formation are obtained from gravel lenses. In the eastern part of the county near Pine Bluffs, large yields are obtained from openings in .the siltstone of the White River. Previous investigators reported that the large yields were obtained in areas where the formation is fractured and fissured. The authors of this report believe that .the large yields from siltstone in the White River Formation are from pipes, sometimes called natural tunnels, rather than from fractures ,or fissures. Little is known about the water-bearing properties of the pro-Tertiary aquifers in the county, but water derived from the pro-Tertiary formations would probably be of poor quality, except in the vicinity of the outcrop near the western edge of the county. Precipitation is the principal source of recharge to the ground-water reservoirs. About 5 percent of the annual precipitation, or about 108,400 acre-feet per year, is estimated to be recharged. Only a small amount of additional recharge is from streams. The general movement of ground water is eastward, and the average gradient of the water table is about 40 feet per mile. The total amount ,of ground water pumped from wells in Laramie County during 1964 is estimated to be 28,000 acre-feet; about 6,000 acre-feet was used for municipal and industrial supplies, about 17,000 acre-feet was used for irrigation in the Pine Bluffs-Carpenter area, and about 5,000 acre-feet was used for other purposes. The balance of the recharge (80,400 acre-feet) is estimated to be discharged by the following means: 20 percent by underflow, 20 percent by streamflow, and 60 percent by evapotranspiration. The coefficient of transmissibility of the Ogallala Formation, determined by averaging data from 28 pumping tests made in the Cheyenne municipal well field, is about 16,000 gallons per day per foot. However, this figure is an average of the more permeable zones, and the average coefficient of transmissibility of the Ogallala in the county is probably much less because of the heterogeneous character of the formation. A coefficient of transmissibility of 3,800 gallons per day per foot was calculated for the Ogallala, in the same vicinity that the pumping tests were made, by using a regional method of analysis. Although the average transmissibility of the Ogallala is considered to be low, large yields are obtained from gravel stringers and lenses in the formation. The maximum perennial yield from the Cheyenne well field is estimated to be about 1.6 billion gallons per year. Moderate to large yields of water can be obtained in the north-central part of the county where the saturated thickness of the Arikaree Formation, or combined Arikaree and Ogallala Formations, is 200 feet or more. Ground water has been developed throughout the county, but development has been intensive only in the Cheyenne municipal well fields near Cheyenne and Federal and in the Pine Bluffs lowland. The water level has been lowered as much as 40 feet in the Cheyenne well field and somewhat less in the Federal well field.
Wyoming↗