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Digital data sets that describe aquifer characteristics of the Enid isolated terrace aquifer in northwestern Oklahoma

ARC/INFO export and nonproprietary format files The data sets in this report include digitized aquifer boundaries and maps of hydraulic conductivity, recharge, and ground-water level elevation contours for the Enid isolated terrace aquifer in northwestern Oklahoma. The Enid isolated terrace aquifer covers approximately 82 square miles and supplies water for irrigation, domestic, municipal, and industrial use for the City of Enid and western Garfield County. The Quaternary-age Enid isolated terrace aquifer is composed of terrace deposits that consist of discontinuous layers of clay, sandy clay, sand, and gravel. The aquifer is unconfined and is bounded by the underlying Permian-age Hennessey Group on the east and the Cedar Hills Sandstone Formation of the Permian-age El Reno Group on the west. The Cedar Hills Sandstone Formation fills a channel beneath the thickest section of the Enid isolated terrace aquifer in the midwestern part of the aquifer. All of the data sets were digitized and created from information and maps in a ground-water modeling thesis and report of the Enid isolated terrace aquifer. The maps digitized were published at a scale of 1:62,500. Ground-water flow models are numerical representations that simplify and aggregate natural systems. Models are not unique; different combinations of aquifer characteristics may produce similar results. Therefore, values of hydraulic conductivity and recharge used in the model and presented in this data set are not precise, but are within a reasonable range when compared to independently collected data.

Oklahoma↗

Digital data sets that describe aquifer characteristics of the High Plains aquifer in western Oklahoma

ARC/INFO export files This diskette contains digitized aquifer boundaries and maps of hydraulic conductivity, recharge, and ground-water level elevation contours for the High Plains aquifer in western Oklahoma. This area encompasses the panhandle counties of Cimarron, Texas, and Beaver, and the western counties of Harper, Ellis, Woodward, Dewey, and Roger Mills. The High Plains aquifer underlies approximately 7,000 square miles of Oklahoma and is used extensively for irrigation. The High Plains aquifer is a water-table aquifer and consists predominately of the Tertiary-age Ogallala Formation and overlying Quaternary-age alluvial and terrace deposits. In some areas the aquifer is absent and the underlying Triassic, Jurassic, or Cretaceous-age rocks are exposed at the surface. These rocks are hydraulically connected with the aquifer in some areas. The High Plains aquifer is composed of interbedded sand, siltstone, clay, gravel, thin limestones, and caliche. The proportion of various lithological materials changes rapidly from place to place, but poorly sorted sand and gravel predominate. The rocks are poorly to moderately well cemented by calcium carbonate. The aquifer boundaries, hydraulic conductivity, and recharge data sets were created by extracting geologic contact lines from published digital surficial geology maps based on a scale of 1:125,000 for the panhandle counties and 1:250,000 for the western counties. The water-level elevation contours and some boundary lines were digitized from maps in a published water-level elevation map for 1980 based on a scale of 1:250,000. The hydraulic conductivity and recharge values in this report were used as input to the ground-water flow model on the High Plains aquifer. Ground-water flow models are numerical representations that simplify and aggregate natural systems. Models are not unique; different combinations of aquifer characteristics may produce similar results. Therefore, values of hydraulic conductivity and recharge used in the model and presented in this data set are not precise, but are within a reasonable range when compared to independently collected data.

Oklahoma↗

Geology and ground-water conditions of Clark County, Washington, with a description of a major alluvial aquifer along the Columbia River

This report presents the results of an investigation of the ground-water resources of the populated parts of Clark County. Yields adequate for irrigation can be obtained from wells inmost farmed areas in Clark County, Wash. The total available supply is sufficient for all foreseeable irrigation developments. In a few local areas aquifers are fine-grained, and yields of individual wells are low. An enormous ground-water supply is available from a major alluvial aquifer underlying the flood plain of the Columbia River in the vicinity of Vancouver, Camas, and Washougal, where the aquifer is recharged, in part, by infiltration from the river. Yields of individual wells are large, ranging to as much as 4,000 gpm (gallons per minute). Clark County lies along the western flank of the Cascade Range. in the structural lowland (Willamette-Puget trough) between those mountains and the Coast Ranges to the west. The area covered by the report includes the urban, the suburban, and most of the agricultural lands in the county. These lands lie on a Series of nearly fiat plains and benches which rise steplike from the level of the Columbia River (a few feet above sea level) to about 800 feet above sea level. Clark County is-drained by the Columbia River (the trunk stream of the Pacific Northwest) and its tributaries. The Columbia River forms the southern and western boundaries of the county. Although the climate of the county is considered to be humid, the precipitation ranging from about 37 to more than 110 inches annually in various parts of the county, the unequal seasonal distribution (about 1.5 inches total for ;July and August in the agricultural area) makes irrigation highly desirable for most .crops and essential for some specialized crops. Consolidated rocks of Eocene to Miocene age, chiefly volcanic lava flows and pyroclastics but including some sedimentary strata, crop out in the foothills of the Cascades in the eastern part of the county and underlie the younger, unconsolidated rocks in the lowlands to the west At most places small to moderate quantities of water can be obtained from fractures in the older consolidated rocks. However, in the populated parts of the county, these rocks generally are overlain by considerable thicknesses of more permeable materials, and few wells have been drilled in them. Springs and dug wells yield an ample domestic supply at a number of outlying farms in the foothills. The younger (Pliocene to Recent) unconsolidated materials were deposited chiefly by streams in the basin formed by downwarping of the older rocks. However, some lake deposits and glacial drift also are included. The oldest unit of this group, the lower member of the Troutdale formation of Pliocene age, consists chiefly of clay, silt, and fine sand but includes lenses of coarser sand and, rarely, gravel. The maximum known thickness of the lower member of the Troutdale formation is about 660 feet. This unit is not a good aquifer because most of the strata are fine grained. However, at a few places drilled wells have penetrated lenses of coarser grained materials in these deposits and have obtained small to moderate amounts of water from them. The upper member of the Troutdale formation consists almost entirely of lightly to moderately cemented gravel, of which the most striking feature is the presence of a considerable percentage of quartzite pebbles. The average thickness of the upper member of the Troutdale may originally have been 300 to 400 feet. The member crops out over considerable areas in the county and, where conditions of topography and exposure are optimum, has beer very deeply weathered. It is suggested that the upper member of the Troutdale formation may prove to be of early Pleistocene age.

Washington↗

Proposed artificial recharge studies in northern Qatar

The aquifer system in northern Qatar comprises a water-table aquifer in the Rus Formation which is separated by an aquitard from a partially confined aquifer in the top of the overlying Umm er Radhuma Formation. These two aquifers are composed of limestone and dolomite of Eocene and Paleocene age and contain a fragile lens of freshwater which is heavily exploited as a source of water for agricultural irrigation. Net withdrawals are greatly in excess of total recharge, and quality of ground water is declining. Use of desalinated seawater for artificial recharge has been proposed for the area. Artificial recharge, on a large scale, could stabilize the decline in ground-water quality while allowing increased withdrawals for irrigation. The proposal appears technically feasible. Recharge should be by injection to the Umm er Radhuma aquifer whose average transmissivity is about 2,000 meters squared per day (as compared to an average of about 200 meters squared per day for the Rus aquifer). Implementation of artificial recharge should be preceded by a hydrogeologic appraisal. These studies should include test drilling, conventional aquifer tests, and recharge-recovery tests at four sites in northern Qatar. (USGS)

Open-File Report↗

Geology and ground-water resources of the lower Lodgepole Creek drainage basin, Nebraska, with a section on chemical quality of the water

The area described is almost wholly in Nebraska and is the drainage basin of Lodgepole Creek from the Wyoming State line to the Colorado State line, a distance along the stream valley of about 95 miles. It covers about 1,950 square miles. The purposes of the study were to ascertain the characteristics, thickness, and extent of the water-bearing formations and to obtain and interpret data on the origin, quality, quantity, movement, availability, and use of ground water in the area. The rocks exposed in the drainage basin are the Brule formation of Oligocene (Tertiary) age, the Ogallala formation of Pliocene (Tertiary) age, and alluvium of Pleistocene and Recent (Quaternary) age. The Brule formation is mainly a siltstone, which yields an average of 950 gallons per minute (gpm) to irrigation wells tapping its fractured zones or reworked material; the maximum reported discharge is 2,200 gpm. The Ogallala formation underlies most of the area. It consists of lenticular beds of clayey, silty, sandy, and gravelly materials and supplies water to all wells on the upland, including a few large-discharge wells, and to many irrigation and public-supply wells in the valley of Lodgepole Creek. The yield of irrigation wells tapping the Ogallala formation ranges from 90 to 1,600 gpm and averages about 860 gpm. The alluvium is present in the valleys of Lodgepole Creek and its tributaries and consists mainly of heterogeneous . mixtures of silt, sand, and gravel, and lenticular bodies of these materials. Between the Colorado State line and Chappell, Nebr., irrigation wells derive most of their water from the alluvium. However, between Chappell and Sidney most of the irrigation wells tap both the alluvium and permeable zones in the underlying Brule formation, and in much of the valley west of Sidney, where the water table is beneath the bottom of the alluvium, irrigation wells derive water from the underlying Brule or Ogallala formations. Irrigation wells obtaining water chiefly from the alluvium have a yield ranging from 130 to 1,200 gpm, averaging about 770 gpm. In the Lodgepole Creek valley below Sidney the depth to water generally is less than 20 feet and, in many places, less than 10. In much of this part of the area the water table extends to the land surface or to the root zone of the vegetation, and discharge by evapotranspiration is high. In the valley of Lodgepole Creek between Sidney and the Wyoming State line, the depth to water generally ranges from less than 10 feet near the stream to more than 100 along the edge of the valley. In the upland the depth to water ranges from about 80 to about 300 feet. Recharge to the ground-water reservoir is derived chiefly from precipitation; other sources are seepage from irrigation systems and streams, and subsurface inflow of ground water. Water that infiltrates to the water table generally moves toward Lodgepole Creek in a downstream direction and is discharged into the stream through springs and seeps. However, within an area of at least 400 square miles in the northern part of the lower Lodgepole Creek drainage basin, ground water moves toward the valley of the North Platte River. Water is discharged from the ground-water reservoir into streams, by evapotranspiration, through wells, and by subsurface outflow. During the 1951-52 water year about 13,000 acre-feet of ground water left the area as streamflow. An estimated 20,000 acre-feet of water annually is discharged by the transpiration of grasses and trees growing along the creek bottom, and about 1,000 acre-feet of water leaves as subsurface outflow. During the period 1950-51 about 68,000 acre-feet of water was pumped from wells in the area for all uses. Of this amount; about 35,000 acre-feet in 1950 and 23,300 acre-feet in 1951 were used to irrigate about 15,560 and 15,790 acres. Nearly one-fourth of this water percolated back to the ground-water reservoir. These acreages, however, included about 2,100 acres irrigated in p

Water Supply Paper↗

Geohydrology of the Albin and La Grange areas, aoutheastern Wyoming

The Albin and La Grange areas in southeastern Wyoming are two adjoining different hydrologic areas. Since ground water is the only source of water for irrigation in the Albin area, 34 irrigation wells have been drilled since 1968 and developed in conjunction mostly with center-pivot sprinkler systems that in 1974 irrigated about 6,980 acres. Most irrigation wells are developed in channel deposits of the Ogallala Formation of late Miocene. Water levels in parts of these channel deposits have declined about 4 to 7 feet since pumping began in 1968. In the La Grange area, lands are irrigated by surface water, ground water or a combination of both. The best producing wells are those completed in both the Brule Formation of Oligocene age and the alluvium. Secondary porosity was located and elevated in the Brule using caliper logs, an Acoustic Borehole Televiewer and geophysical logs. From the spring of 1970 to the spring of 1974, hydrographs of wells in parts of the La Grange area show water-level rises of about 5 feet resulting from the net effect of surface-water recharge and groundwater pumpage. Throughout the La Grange area no significant annual water-table declines have occurred. It is unlikely that irrigation wells pumping near Horse Creek have caused significant direct streamflow depletion.

Wyoming↗

Ground-water geology and pump irrigation in Frenchman Creek Basin above Palisade, Nebraska

This report describes the geography, geology, and ground-water resources of that part of the Frenchman Creek basin upstream from Palisade, Nebr., an area of about 4,900 square miles. The basin includes all of Phillips County, Colo., and Chase County, Nebr., and parts of Logan, Sedgwick, Washington, and Yuma Counties, Colo., and Dundy, Hayes, Hitchcock, and Perkins Counties, Nebr. The land surface ranges from nearly flat to rolling; choppy hills and interdune saddles are common in the areas of dune sand, and steep bluffs and gullies cut the edges of the relatively flat loess plateaus. Most of the basin is drained by tributaries of Frenchman Creek, but parts of the sandhills are undrained. Farming and livestock raising are the principal industries. Irrigation with ground water has expanded rapidly since 1934. The rocks exposed in the basin are largely unconsolidated and range in age from Pliocene to Recent. They comprise the Ogallala formation (Pliocene), the Sanborn formation (Pleistocene and Recent?), dune sand (Pleistocene and Recent), and alluvium (Recent). The rocks underlying the Ogallala are the Pierre shale (Late Cretaceous) and the White River group (Oligocene). The Pierre shale is relatively impermeable and yields little or no water to wells. The White River group also is relatively impermeable and yields little or no water to wells; however, small to moderate quantities of water possibly may be obtained from wells that penetrate fractured or 'porous' zones in the upper part of the White River group or permeable channel deposits within the group. The Ogallala formation is the main aquifer in the basin and yields moderate to large quantities of water to wells. The Sanborn formation and the dune sand generally lie above the water table, but in areas of high water table the dune sand yields small quantities of water to wells for domestic and stock supplies. The alluvium, which includes the low terrace deposits bordering the major streams, yields small to large quantities of water to wells. The ground-water reservoir is recharged only from precipitation on the basin. Of the average annual precipitation of 19.5 inches, about 0.9 inch infiltrates to the water table, thereby contributing about 220,000 acre-feet of water annually to the ground-water reservoir. About 81 million acre-feet of water that could drain under gravity, and thus theoretically is available to wells, is held in groundwater storage in the basin. Water is discharged from the ground-water reservoir by wells, evaporation and transpiration, springs, seepage into streams, and movement into adjacent areas to the east and southeast. Most of the domestic, stock, and irrigation water supplies and all the public supplies are pumped from wells. During 1953, 96 wells were used to irrigate 10,000 acres of land with 19,000 acre-feet of water. About 34,000 acre-feet of water is evaporated and transpired annually in the valleys of the main streams and in areas of shallow water table in the sandhills. From the projection of base-flow measurements made during 1952, it was estimated that the average annual flow of Frenchman Creek into the reservoir above Enders Dam is about 57,000 acre-feet. By similar determinations, the average annual flow of Frenchman Creek at the gaging station at Palisade, Nebr., about 22 miles downstream from Enders Dam, is about 76,000 acre-feet, and the flow of Stinking Water Creek at the gaging station near Palisade is about 22,000 acre-feet. The combined flow of Frenchman and Stinking Water Creeks at their confluence near Palisade thus is about 98,000 acre-feet per year. About 90,000 acre-feet of ground water is estimated to move eastward each year across the Colorado-Nebraska State line within the basin. Additional irrigation wells that will tap the Ogallala formation and the alluvium in the major valleys undoubtedly will be drilled. On the basis of current estimates of future irrigation.withdrawals, it is concluded that by the

Water Supply Paper↗

Water movement through the unsaturated zone of the High Plains Aquifer in the Central Platte Natural Resources District, Nebraska, 2008-12

Uncertainty about the effects of land use and climate on water movement in the unsaturated zone and on groundwater recharge rates can lead to uncertainty in water budgets used for groundwater-flow models. To better understand these effects, a cooperative study between the U.S. Geological Survey and the Central Platte Natural Resources District was initiated in 2007 to determine field-based estimates of recharge rates in selected land-use areas of the Central Platte Natural Resources District in Nebraska. Measured total water potential and unsaturated-zone profiles of tritium, chloride, nitrate as nitrogen, and bromide, along with groundwater-age dates, were used to evaluate water movement in the unsaturated zone and groundwater recharge rates in the central Platte River study area. Eight study sites represented an east-west precipitation contrast across the study area—four beneath groundwater-irrigated cropland (sites 2, 5, and 6 were irrigated corn and site 7 was irrigated alfalfa/corn rotation), three beneath rangeland (sites 1, 4, and 8), and one beneath nonirrigated cropland, or dryland (site 3). Measurements of transient vertical gradients in total water potential indicated that periodic wetting fronts reached greater mean maximum depths beneath the irrigated sites than beneath the rangeland sites, in part, because of the presence of greater and constant antecedent moisture. Beneath the rangeland sites, greater temporal variation in antecedent moisture and total water potential existed and was, in part, likely a result of local precipitation and evapotranspiration. Moreover, greater variability was noticed in the total water potential profiles beneath the western sites than the corresponding eastern sites, which was attributed to less mean annual precipitation in the west. The depth of the peak post-bomb tritium concentration or the interface between the pre-bomb/post-bomb tritium, along with a tritium mass balance, within sampled soil profiles were used to estimate water fluxes in the unsaturated zone at three of the eight study sites: site 2 (irrigated), site 3 (dryland), and site 8 (rangeland). Estimates for recharge were about 68 millimeters per year [(mm/yr), post-bomb peak], 133 to 159 mm/yr (tritium interface), and 137 mm/yr (mass balance) at site 2 (irrigated); about 63 mm/yr (tritium interface) and 12 mm/yr (mass balance) at site 3 (dryland); and about 53 mm/yr (tritium interface) and 10 mm/yr (mass balance) at site 8 (rangeland). Recharge values from the mass balance at site 2 were more than an order of magnitude greater than recharge values at site 3, suggesting irrigation is an important control on water movement through the unsaturated zone. For the remaining five sites, the post-bomb tritium had flushed through the system and recharge was considered modern (within 10 years of sampling). The chloride mass-balance method was used to determine water fluxes below the root zone (less than 2 meters below land surface) at the rangeland sites: sites 1, 4, and 8. At these rangeland sites, water fluxes ranged from 1.8 to 96 mm/yr at site 1, 1.1 to 9.6 mm/yr at site 4, and 1.1 to 68 mm/yr at site 8, with mean rates of 21, 4.3, and 13 mm/yr, respectively. Site 1 had a greater mean water flux, which was consistent with the greater precipitation in the east than at site 8 in the west. Chloride mass balance was not calculated at the irrigated and dryland sites because of uncertainty about additional sources of chloride. Concentrations of nitrate as nitrogen in pore water in the unsaturated zone were larger beneath the irrigated and dryland (agricultural) sites compared with the rangeland sites. The larger concentrations at the agricultural sites are consistent with the application of nitrogen fertilizer at the agricultural sites and no substantial accumulation at the rangeland sites. The shape of the nitrate as nitrogen and chloride concentration profiles at site 1 (rangeland) indicate a reasonably larger and more consistent water flux in the UZ than beneath the other two rangeland sites (sites 4 or 8). Excluding site 7, the general shape of the nitrate as nitrogen profiles was similar beneath the agricultural sites and supports the estimates of water movement and recharge rates determined from the tritium and chloride methods. Movement of bromide through the unsaturated zone indicated greater water fluxes are found beneath irrigated lands than beneath rangeland. Bromide profiles in the unsaturated zone, determined from center of mass and peak displacement methods, document water fluxes ranged from 58 to 394 mm/yr beneath irrigated sites and 9 to 201 mm/yr beneath rangeland sites. Water-flux estimates from the potassium bromide tests at most sites did not represent overall recharge rates because the bromide remained primarily in the root zone. Apparent groundwater age was used to determine the groundwater residence time at the eight sites and to estimate recharge rates. Groundwater ages in the study area ranged from old water (defined here as groundwater that was recharged more than 50 years ago) to modern (defined here as groundwater that has recharged within the past 10 years). Groundwater ages indicated that the shallow monitoring wells generally had younger residence times, whereas the deeper monitoring wells generally had the older residence times. Groundwater dates from the shallowest monitoring wells were used to determine recharge rates at the water table. These rates generally were similar to recharge rates determined from tritium and chloride mass-balance methods. Groundwater recharge rates generally increased with well depth, and the deeper monitoring wells likely do not represent local recharge conditions but recharge from a regional flow system that receives recharge from distant sources. Overall, these data generally indicate that water movement within the unsaturated zone primarily is affected by spatial contrasts in mean annual precipitation and by the land use or land cover. The eight unsaturated-zone sites each generated unique, valuable datasets that likely will improve the understanding of water movement and recharge rates in the central Platte River valley.

Nebraska↗

Ground-water resources of the Rogue River Basin, Oregon

The Rogue River basin, as area of about 5,060 square miles, comprises much of the southwestern corner of the State of Oregon. It is mountainous and its arable lands are largely confined to the valley floors along the middle reaches of the Rogue River and its main tributaries, the Applegate and Illinois Rivers and Bear Creek. In these valleys, level farming lands and an equable climate afford hospitable localities to a moderate population. Although mainly an agricultural economy, lumbering, mining, and tourist trade are also economic mainstays of the inhabitants. The average annual precipitation on the valley floor is about 21 inches, but it is progressively greater with higher altitudes and reaches 87 inches in the Coast Range to the west and 60 inches in the Cascade Range to the east. The frost-free season averages 176 days in the valleys with frosts seldom occurring later than May or earlier than October. The principal farm crop of the basin is soft fruit, mainly fancy pears. Beef and dairy herds are important in the Applegate and Illinois River valleys. The rocks which underlie the basin range from Paleozoic to Recent in age. The best water-yielding rocks are the alluvial deposits of Pleistocene and Recent age and the weathered parts of several granitic masses. Of 1,035 wells visited, only 52 were drilled exclusively for irrigation. Due to the inadequate yield, a number of these wells were not in use at the time of the field investigation. The quality of the shallow ground waters is generally good, but the deeper ground waters in many places are too saline for common use. The boron and fluorine content of the ground water from some of the deep wells in the Umpqua and Chico formations is sufficient to render it unsuitable for some uses. Properly constructed and developed wells in the Agate Desert gravels and in the older alluvium of the Illinois River valley will yield small and moderate supplies of ground water for irrigation. The younger alluvium in places will yield moderate amounts of water to large open wells, locally called "sumps." The weathered part of the granite rock underlying the Grants Pass and Tolo localities yields water sufficiently for small and moderate irrigation and industrial supplies. The other rock formation of the basin commonly yield water sufficiently only for domestic supplies. In many places these rocks are so lacking in permeability that many drilled wells have failed to obtain even adequate yields for household supply.

Oregon↗

Map of water table in Graham County, northwestern Kansas, March 1979

A map of the water table in Graham County, prepared in collaboration with the U.S. Bureau of Reclamation, provides current (1980) information on water levels in the unconsolidated deposits. Graham County, an area of 900 square miles in northwestern Kansas, is within the rolling, moderately to well-dissected terrain on the eastern edge of the High Plains. The eastward-flowing South Fork Solomon River separates the county into nearly equal parts. The principal source of water for domestic, stock, municipal, and irrigation use if from wells in the shallow unconsolidated deposits. The aquifers occur chiefly in the Ogallala Formation of Miocene age and in deposits of Quaternary age.

Kansas↗

Fluvial sediment dynamics in the Shoshone River and tributaries around Willwood Dam, Park County, Wyoming

Sedimentation affects many of the aging reservoirs in the United States. Dams and water diversions from rivers have been central elements of infrastructure supporting agricultural irrigation in the arid and semiarid regions of the Western United States for more than a century. The Willwood Irrigation District diversion dam (hereafter referred to as “Willwood Dam”) in Park County, Wyoming, is approximately 12 miles northeast of Cody, Wyo.; has a structural height of 70 feet; and impounds the Shoshone River for diversion into the Willwood Canal. Willwood Dam is part of a larger irrigation scheme supported by water storage in the much larger Buffalo Bill Dam, which is approximately 20 miles upstream. In October 2016, renovation construction activities at Willwood Dam and the Willwood Canal caused an unplanned evacuation of nearly 96,000 cubic yards of fine sediment. The fine sediment release in 2016 raised concerns that ongoing sediment management at Willwood Dam could impose limits on the long-term health of the aquatic ecosystem and fish populations. The U.S. Geological Survey, in cooperation with Wyoming Department of Environmental Quality and Willwood Work Groups 2 and 3, initiated an investigation of the dynamics of sediment transport in the Shoshone River and selected tributaries between Buffalo Bill Dam and Willwood Dam. The goal of the study was to quantify sediment transport into and out of Willwood Dam on an annual, seasonal, and event basis to better understand the relative quantities of sediment coming from natural sources and human activities on the landscape. The study ran from March 2019 through October 2021 and used observations of streamflow, turbidity, and acoustic backscatter collected at streamgages upstream and downstream from Willwood Dam to quantify suspended-sediment loads into and out of the dam during irrigation and fallow seasons, precipitation-runoff events, and deliberate sediment releases. Each tributary’s relative contribution to the sediment load upstream from Willwood Dam was examined using discrete measurements of suspended-sediment concentration and bedload during irrigation and fallow seasons, precipitation events, and stable conditions. Analysis of daily precipitation and temperature data indicated that conditions in the study area during the 2019 agricultural year were wetter and colder than period of record normal, and drier and near normal temperatures for the 2020 and 2021 agricultural years. Not all sediment load records between 2019 and 2021 are complete because of rejected observations (outliers), instrument failures or fouling, and instrument removal for calibrations. Statistical modeling of suspended-sediment concentration using paired values of turbidity and acoustic backscatter produced four models that, after refinement, had coefficients of determination indicating that more than 84 percent of the variance was explained by either turbidity or acoustic backscatter. A system of rules was developed to select the model predictions based on the seasonal operations of Willwood Dam, assumptions about the grain sizes mobilized during these operations, and assumed accuracy of the models at the downstream streamgage (Shoshone River below Willwood Dam, near Ralston, Wyo. [streamgage 06284010]) under different operational conditions. The sediment budget between upstream and downstream estimates of loads was interpreted using the mean predicted values bound by their respective model prediction intervals. When mean predicted loads of one streamgage were contained in the prediction intervals of the other streamgage, and vice-versa, difference in the sediment budget were interpreted as “indeterminate.” Modeled sediment load balances demonstrated the depositional and erosional behaviors expected from the conceptual model of dam operations whereby sediment tends to accumulate during irrigation seasons when the dam is spilling over the top, and sediment tends to evacuate during the fallow seasons when it is flowing through the sluice gates at the base of the dam. The sediment load calculations using the rules-based model criteria indicated that between 14,200 and 380,000 tons of suspended sediment moved through the Shoshone River around Willwood Dam during the irrigation seasons of 2019, 2020, and 2021; 380,000 tons of suspended sediment were transported during the cool, wet year of 2019, and 14,200 tons of suspended sediment were transported in 2020, which was relatively dry. During fallow seasons 2019, 2020, and 2021, which had fewer complete records, between 1,140 and 106,000 tons of suspended sediment was estimated to have moved through the river. For all seasons except fallow season 2022, the models estimated that more sediment was released from the dam than entered the dam, but the modeled mean loads at each streamgage were nearly always within the prediction intervals of each other, making the sediment balance indeterminant. Examination of suspended-sediment loads during irrigation seasons indicated that between 65 and 85 percent of fine sediment was transported during annual high flows and storm events, with the remainder transported during steady, lower streamflows. Examination of suspended loads during fallow seasons indicated that deliberate sediment releases through Willwood Dam accounted for between 39 and 67 percent of the total sediment moved during the fallow seasons. Deliberate sediment releases from Willwood Dam had estimated net exports of between 1,360 and 22,400 tons. Between August 2017 and July 2023, suspended-sediment concentration and bedload sediment samples were collected from 9 tributaries to the Shoshone River during 137 sampling events, including stable and precipitation-runoff conditions. During irrigation season precipitation events, the mean total sediment yields ranged from 0.33 to 9.51 tons per day per square mile; during fallow season precipitation events, the mean total yields ranged from 0.04 to 0.95 ton per day per square mile. The mean total sediment yield per unit area across all samples at each tributary site ranged from 0.26 to 3.08 tons per day per square mile. Bedload was a minor fraction of the total load, constituting a mean of 4 percent across all samples; 3 and 6 percent for events and nonevents, respectively, during irrigation season; and 3 and 1 percent for events and nonevents, respectively, during the fallow season. With the exception of one tributary, Dry Creek, these mean yield values were within the range of watershed-scale background sediment yield values estimated from reservoir surveys and previous suspended-sediment studies. Imagery from irrigation seasons 2012, 2015, 2017, 2019, and 2022 was used to determine the planimetric backwater extent of the pool area in the Shoshone River behind Willwood Dam to identify any changes in sediment storage. Active river channel widths in the Shoshone River upstream from Willwood Dam were all similar between years except 2015, which was determined to be statistically different from all other years. Bathymetric data taken in the pool behind Willwood Dam during three different surveys between November 2017 and April 2022 indicated no statistically significant differences in bed elevations between the years. Results from the planimetric and bathymetric survey data provide multiple lines of evidence indicating that sediment did not accumulate behind the dam within the error of the methods used. Examination of how precipitation affects sediment transport in the Shoshone River upstream from Willwood Dam indicated that accumulated rainfall from the natural runoff events captured during the study period varied from a trace to as much as 4.26 inches, with associated predicted suspended-sediment loads varying from 112 to 232,000 tons of suspended sediment. The behavior of the sediment loads relative to accumulated precipitation did not appear to change depending on irrigation or fallow season. A model of suspended-sediment concentrations relative to the 2-day accumulated precipitation indicated that suspended-sediment concentrations in the Shoshone River upstream from Willwood Dam increased exponentially for accumulations of 0.3 inch or more; such storms accounted for 10 percent or less of precipitation events observed during the 1981 to 2018 period of record. The gaps in records, precision of the instrumentation, and large variation in grain sizes in suspended-sediment mixtures downstream from the dam made closing the sediment budgets for most seasons unattainable. The biggest recent change in sediment storage measured using the planimetric area of deposits behind Willwood Dam took place between 2015 and 2017. The main event between these two measurements was the installation of new Willwood Canal gates in October 2016, which resulted in the large unplanned sediment release. Because the sediment budgets were nearly always indeterminate and the planimetric and bathymetric data indicated little change in the bed and bank material, it is likely that the change in sediment storage behind the dam during the study period was small relative to the precision of the statistical models and other uncertainties. This body of evidence suggests that, averaged during the 3-year study period, no major changes in storage took place, and that the current operations may be keeping storage at near-equilibrium. This condition could have been initiated because the middle sluice gate has now been operational since 2014, and the sediment release in October 2016 evacuated a large amount of legacy sediment from storage. Although the uncertainties are large, sluicing events allow for controlled releases of sediment that contributed to the near equilibrium conditions observed over an annual basis during this study.

Wyoming↗

Hydrology of the Estancia Basin, central New Mexico

The Estancia Basin of central New Mexico is a topographically closed basin that ranges in altitude from 6,000 feet to more than 10,000 feet above sea level. In the center of the basin a valley-fill aquifer of Quaternary age is as much as 400 feet thick. Limestone of the Madera Group of Pennsylvanian and Permian age crops out over most of the southwestern part of the basin. Large-scale ground-water withdrawals for irrigation began about 1950. Between 1950 and 1985, water levels declined 50 to 60 feet in a number of places. From 1985 to the present (1989), however, a small rise in water level has been measured in a number of wells; this rise can be attributed to decreased ground-water withdrawals resulting from a government crop- reduction program and also to several years of heavy winter snowfall. Continuous water-level recorders were placed on three wells from 1986 to 1988. Two of these wells showed short-term water-level changes characteristic of unconfined aquifers, whereas the other showed changes characteristic of confined aquifers. All three wells showed water-level changes caused by barometric-pressure changes. Six series of miscellaneous measurements and two gain-and-loss (seepage) studies were made in streams in the south- western part of the basin. These measurements showed an extreme variability in discharge under different climatic conditions. The specific conductance of water in much of the southwestern part of the basin ranges from 350 to 550 microsiemens per centimeter at 25 degrees Celsius. East of State Highway 41 in the area of the salt lakes, water quality is highly dependent on depth in the aquifer. Specific- conductance values ranging from about 4,000 to 6,000 microsiemens were measured in water samples from wells in the center of the basin during this study, but previous studies have identified water samples having specific-conductance values of as much as 187,000 microsiemens. A comparison of specific- conductance measurements and laboratory analyses of well water shows that water quality has changed in the past several decades. In many places, increases in spedtic conductance can be correlated with deelines in water level.

Water-Resources Investigations Report↗

Hydrogeology, Water Chemistry, and Factors Affecting the Transport of Contaminants in the Zone of Contribution of a Public-Supply Well in Modesto, Eastern San Joaquin Valley, California

Ground-water chemistry in the zone of contribution of a public-supply well in Modesto, California, was studied by the U.S. Geological Survey National Water Quality Assessment (NAWQA) Program's topical team for Transport of Anthropogenic and Natural Contaminants (TANC) to supply wells. Twenty-three monitoring wells were installed in Modesto to record baseline hydraulic information and to collect water-quality samples. The monitoring wells were divided into four categories that represent the chemistry of different depths and volumes of the aquifer: (1) water-table wells were screened between 8.5 and 11.7 m (meter) (28 and 38.5 ft [foot]) below land surface (bls) and were within 5 m (16 ft) of the water table; (2) shallow wells were screened between 29 and 35 m (95 and 115 ft) bls; (3) intermediate wells were screened between 50.6 and 65.5 m (166 and 215 ft) bls; and (4) deep wells are screened between 100 to 106 m (328 and 348 ft) bls. Inorganic, organic, isotope, and age-dating tracers were used to characterize the geochemical conditions in the aquifer and understand the mechanisms of mobilization and movement of selected constituents from source areas to a public-supply well. The ground-water system within the study area has been significantly altered by human activities. Water levels in monitoring wells indicated that horizontal movement of ground water was generally from the agricultural areas in the northeast towards a regional water-level depression within the city in the southwest. However, intensive pumping and irrigation recharge in the study area has caused large quantities of ground water to move vertically downward within the regional and local flow systems. Analysis of age tracers indicated that ground-water age varied from recent recharge at the water table to more than 1,000 years in the deep part of the aquifer. The mean age of shallow ground water was determined to be between 30 and 40 years. Intermediate ground water was determined to be a mixture of modern (Post-1950) and old (Pre-1950) ground water. As a result, concentrations of age tracers were detectable but diluted by older ground water. Deep ground water generally represented water that was recharged under natural conditions and therefore had much older ages. Ground water reaching the public-supply well was a mixture of older intermediate and deep ground water and young shallow ground water that has been anthropogenically-influenced to a greater extent than intermediate ground water. Uranium and nitrate pose the most significant threat to the quality of water discharged from the public-supply well. Although pesticides and VOCs were present in ground water from the public-supply well and monitoring wells, currently concentrations of these contaminants are generally less than one-hundredth the concentration of drinking water standards. In contrast, both uranium and nitrate were above half the concentration of drinking water standards for public-supply well samples, and were above drinking water standards for several water-table and shallow monitoring wells. Shallow ground water contributes roughly 20 percent of the total flow to the public-supply well and was the entry point of most contaminants reaching the public-supply well. Naturally-occurring uranium, which is commonly adsorbed to aquifer sediments, was mobilized by oxygen-rich, high-alkalinity water, causing concentrations in some monitoring wells to be above the drinking-water standard of 30 ug/L (microgram per liter). Adsorption experiments, sediment extractions, and uranium isotopes indicated uranium in water-table and shallow ground water was leached from aquifer sediments. Uranium is strongly correlated to bicarbonate concentrations (as measured by alkalinity) in ground water. Bicarbonate can effectively limit uranium adsorption to sediments. As a result, continued downward movement of high-alkalinity, oxygen-rich ground water will likely lead to larger portions of the aquifer having

Scientific Investigations Report↗

Water resources of the Santa Rosa Indian Reservation and vicinity, Riverside County, California

The Santa Rosa Indian Reservation is a 17-square-mile area located between the Santa Rosa and San Jacinto Mountains in south-central Riverside County, Calif. The source of water in most of the study area is precipitation on the three topographic subbasins that nearly surround the reservation. Precipitation averages about 12 inches annually (18,000 acre-feet per year), with 10 inches (15,000 acre-feet per year) of it returning to the air by evapotranspiration, 1 inch (1,500 acre-feet per year) running off from the area, and 1 inch (1,500 acre-feet per year) going to ground-water recharge. Local geology and the shape of the ground-water basin, as defined by a gravity survey, indicate that the area receives no ground-water inflow from outside the study area. Production of a dry-farm crop is planned for the 800-acre area west of Vandeventer Flat on the reservation's main section. Additional water supplies are needed for crop irrigation. At present (1979), water is obtained from a supply well that taps the saturated section of the sandy material overlying the basement complex of Cretaceous age or older. Existing data indicate that the aquifer may not yield large volumes of water to individual wells. A specific capacity of about 0.4 gallon per minute per foot of drawdown was measured at the supply well. Estimates of specific yield for the material encountered during the drilling of three wells and a test hole were 5 to 10 percent. The thickest section of the aquifer in the Vandeventer Flat area was outlined by a gravity survey. Test wells should provide information on thickness of the aquifer, aquifer properties, and potential well yield. Damming of area streams could also supply irrigation water. Average runoff totals about 1,500 acre-feet per year, with greater volumes lost during periods of heavy precipitation and flooding. Peak discharge from the central and southern subbasins totaled about 160 acre-feet per hour during the January-March period of 1978. Water-quality analyses for the supply well and five major springs indicate that the ground water is suitable for irrigation everywhere except at Sulphur Spring, where the percent sodium of 97 is above recommended maximum levels, and at Bull Canyon Spring, where water of 1,300 micromhos specific conductance is considered a high salinity hazard. The sulfate concentration of 290 milligrams per liter in Bull Canyon Spring is above the recommended maximum level for drinking water.

California↗

Concentrations, distribution, and sources of selenium from irrigated lands in western United States

Concentrations, distribution, and sources of selenium from irrigated lands were studied between 1986 and 1990 at 20 reconnaissance project areas in 17 western states under the Department of Interior's National Irrigation Water Quality Program. Samples of water, bottom sediment, whole‐body fish, and bird livers for analysis of selenium concentrations were collected before, during, and after irrigation season from streams, canals, lakes, and ground water in each project area. Selenium concentrations in water ranged from less than the detection limit of 1 μg/L in 42% of the 586 samples collected to 4,800 μg/L from a well in the Pine River Area, in southern Colorado. Selenium concentrations in 223 samples of bottom sediment ranged from less than the detection limit of 0.1 μg/g to 85 μg/g in a sample from the Middle Green River Basin, in Utah. Selenium concentrations in whole‐body fish (all species) ranged from 0.1 μg to 50 μg per gram dry weight, with the maximum concentration observed in a carp from the Gunnison River Basin, in western Colorado. Selenium concentrations in bird livers (all species) ranged from less than 0.32 μg to 170 μg per gram dry weight with the maximum concentration observed in the liver of an avocet from the Kendrick Reclamation Project, in Wyoming. Cretaceous‐age marine shales probably are the original sources for selenium in 16 of the 20 areas studied. In several areas, evaporative concentration of applied irrigation water and drainage of this water to wetlands, canals, streams, and lakes appears to be responsible for elevated concentrations of selenium.

Colorado, Utah, Wyoming↗

Groundwater residence time estimates obscured by anthropogenic carbonate

Groundwater is an important source of drinking and irrigation water. Dating groundwater informs its vulnerability to contamination and aids in calibrating flow models. Here, we report measurements of multiple age tracers ( 14 C, 3 H, 39 Ar, and 85 Kr) and parameters relevant to dissolved inorganic carbon (DIC) from 17 wells in California’s San Joaquin Valley (SJV), an agricultural region that is heavily reliant on groundwater. We find evidence for a major mid-20th century shift in groundwater DIC input from mostly closed- to mostly open-system carbonate dissolution, which we suggest is driven by input of anthropogenic carbonate soil amendments. Crucially, enhanced open-system dissolution, in which DIC equilibrates with soil CO 2 , fundamentally affects the initial 14 C activity of recently recharged groundwater. Conventional 14 C dating of deeper SJV groundwater, assuming an open system, substantially overestimates residence time and thereby underestimates susceptibility to modern contamination. Because carbonate soil amendments are ubiquitous, other groundwater-reliant agricultural regions may be similarly affected.

California↗

Selective annotated bibliography of geology and ground-water resources for the Montana part of the Northern Great Plains regional aquifer-system analysis

Increasing demand for water to meet needs for energy, industry, irrigation, domestic, and municipal uses has resulted in a study of the geology and hydrology of rocks of Mesozoic and Cenozoic age. This report presents the results of a literature search for the part of the study area in Montana. It consists of an annotated listing of pertinent published reports, a partial subject and area index of the reports, and a correlation chart of geologic and aquifer units listed in the annotations. (USGS)

Open-File Report↗

Hydrologic conditions in the Wheatland Flats area, Platte County, Wyoming

The area includes about 260 square miles in central Platte County that consists of Wheatland Flats and a border region. Wheatland Flats is an area of about 100 square miles that is bounded by Chugwater Creek on the east, the Laramie River on the north, and Sybille Creek on the west. The southern boundary is approximately the southernmost limit of alluvial terrace deposits. Surface water diverted from the Laramie River along with ground water from wells is used to irrigate about 57,000 acres most of which are on and adjacent to Wheatland Flats. More than 200 wells are used for irrigation, industrial, and municipal supplies. The wells are completed in an upper aquifer consisting primarily of shallow alluvial deposits of Quaternary age and a lower aquifer, the Arikaree Formation of early Miocene age. Net water-level decline after approximately 20 years (1958-60 to 1979) generally is less than 10 feet in each aquifer , although declines of as much as 13 feet have occurred in the Airkaree Formation at specific locations. A digital model was used to simulate hydrologic conditions in the Wheatland Flats area. The model indicated that ground-water discharge to streams decreased by 10 percent from 1971 to 1978. Stream-discharge measurements are not available to verify the loss. However, it is reasonable to assume, on the basis of hydraulic-head decline in the aquifers, that there has been some ground-water contribution to the stream. (USGS)

Water-Resources Investigations Report↗