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1,688 records · Page 14Linked to original sources
USGS1998

Design, revisions, and considerations for continued use of a ground-water-flow model of the coastal plain aquifer system in Virginia

A digital numerical model of the ground-water-flow system in the Virginia Coastal Plain was constructed as part of the Regional Aquifer System Analysis program of the U.S. Geological Survey and subsequently revised based on reinterpretations of the hydrogeologic framework. The revised model has been incorporated by the Virginia Department of Environmental Quality as a means to evaluate the effects of existing and proposed ground-water withdrawals. The revised model, which is documented here, includes many design features of the original model. Principal modifications are (1) reassignment of some model layers to represent different aquifers, (2) replacement of applied recharge and the uppermost surface-water layer by constant-head cells to represent the unconfined aquifer, and (3) revision of the lateral extents and transmissivity and vertical leakance values assigned to model layers. Ground-water levels simulated by the revised model under steady-state conditions, using withdrawal rates representing the period 1978-80, generally are similar to the water levels simulated by the original model under transient conditions using the same withdrawal rates. Differences probably result largely from changes in transmissivity and vertical leakance values. T he revised model enables the continued evaluation of development of the large and complex aquifer system. Improved information on parts of some aquifers has been incorporated. Only large, regional-scale trends in ground-water water levels, flow directions, and flow rates are simulated, however, and not local trends and (or) short-term changes in water level and flow. Changing hydraulic stresses, knowledge of hydrogeologic conditions, and resource-management needs require periodic revision of the model to maintain its usefulness for the management of ground-water resources in the Virginia Coastal Plain.

Virginia↗
USGS2025

To heal or not to heal?: 1. The effect of pore fluid pressure on the frictional healing behavior of lithologies in Oklahoma

The competition between fault healing (i.e., re-strengthening) and fault loading determines the timing and magnitude of fault failure within the seismic cycle. Repeating earthquakes can give observational estimates of fault healing rates, however, it is difficult to link laboratory studies of frictional healing and observed healing rates from repeating earthquakes in part because of uncertainty in lithology at depth. Due to well-constrained and relatively simple geology, earthquakes in Oklahoma can be linked to the granitic basement rock and to the Arbuckle Group, which is primarily composed of dolomite at earthquake depths. Here, we conduct friction experiments to measure healing rates of the two earthquake-bearing lithologies at confining pressures representative of earthquake depths and pore pressures ranging from 0% to 80% of the confining pressure. We measure frictional healing by executing slide-hold-slide tests with hold times ranging from 3 s to 3000 s. The friction experiments on the Troy Granite indicate that pore fluid pressure does not greatly affect healing rate. On the other hand, the dolomite of the Arbuckle Group exhibits decreased healing with increased pore fluid pressure, with weakening at the highest pore pressure. We hypothesize that this is due to an increase in dissolution of dolomite at high pore pressures/low effective normal stress. These healing rates are used in the companion paper to understand the moment-recurrence time behavior of repeating earthquakes in Prague, Oklahoma. This work has implications for possible enhanced dissolution and weakening behavior of the Arbuckle Group during wastewater injection activities.

Oklahoma↗
USGS1993

Hydraulic properties of the Madison aquifer system in the western Rapid City area, South Dakota

Available information on hydrogeology, data from borehole geophysical logs, and aquifer tests were used to determine the hydraulic properties of the Madison aquifer. From aquifer-test analysis, transmissivity and storage coefficient were determined for the Minnelusa and Madison aquifers, and vertical hydraulic conductivity (K v ') along with specific storage (Ss') for the Minnelusa confining bed. Borehole geophysical well logs were used to determine the thickness and location of the Minnelusa aquifer, the lower Minnelusa confining bed, and the Madison aquifer within the Madison Limestone. Porosity values determined from quantitative analysis of borehole geophysical well logs were used in analyzing the aquifer-test data. The average porosity at the two aquifer-test sites is about 10 percent in the Minnelusa aquifer, 5 percent in the lower Minnelusa confining bed, and 35 percent in the Madison aquifer. The first aquifer test, which was conducted at Rapid City production well #6, produced measured drawdown in the Minnelusa and Madison aquifers. Neuman and Witherspoon's method of determining the hydraulic properties of leaky two-aquifer systems was used to evaluate the aquifer-test data by assuming the fracture and solution-opening network is equivalent to a porous media. Analysis of the aquifer test for the Minnelusa aquifer yielded a transmissivity value of 12,000 feet squared per day and a storage coefficient of 3 x 10 -3 . The specific storage of the Minnelusa confining bed was 2 x 10 -7 per foot, and its vertical hydraulic conductivity was 0.3 foot per day. The transmissivity of the Madison aquifer at this site was 17,000 feet squared per day, and the storage coefficient was 2 x 10 -3 . The second aquifer test, which was conducted at Rapid City production well #5 (RC-5) produced measured drawdown only in the Madison aquifer. Hantush and Jacob's method of determining the hydraulic properties of leaky confined aquifers with no storage in the confining bed was used to evaluate the aquifer-test data by assuming the fracture and solution-opening network is equivalent to a porous media. The analysis of data from the RC-5 aquifer test showed that transmissivity was not equal in all directions. Hantush's method was used to determine the direction of radial anisotropy and magnitude of the major and minor axes of transmissivity. The major axis of transmissivity is at an angle of 42° east of north, and the transmissivity along this axis is about 56,000 feet squared per day. The minor axis of transmissivity is at an angle of 48° west of north, and the transmissivity along this axis is about 1,300 feet squared per day. The major axis of transmissivity intersects Cleghorn Springs, a large resurgent spring on the west edge of Rapid City. The shape of the potentiometric contours of the Madison aquifer near RC-5 agree with the orientation of the transmissivity ellipse. The average value of the storage coefficient from the isotropic analysis of the aquifer-test data was 3.5 x 10 -4 , and the average vertical hydraulic conductivity of the lower Minnelusa confining bed was 9.6 x 10 -3 foot per day.

South Dakota↗
USGS2025

A comprehensive geologic framework of the National Crustal Model for seismic hazard studies in the conterminous United States

A three-dimensional (3D) geologic framework has been developed for the conterminous United States (U.S.) as part of the U.S. Geological Survey National Crustal Model to enhance seismic hazard modeling. The geologic framework is created from geologic maps and multiple subsurface geologic unit boundaries including the base of the Miocene, Cenozoic, Phanerozoic, and the Mohorovičić discontinuity. Modifications are made to surficial geologic maps to remove discontinuities across state and country borders. The subsurface distribution of rock type and age is extrapolated from the surface, seeded with subsurface geologic information, and constrained by a map of basement geology. The framework provides the basis for estimates of subsurface seismic velocity and density that is needed to improve estimates of earthquake ground shaking and seismic hazard. The present framework greatly expands and updates a previously published 3D geologic framework of the western part of the U.S. that was itself a first-of-its-kind digital 3D portrayal of the nation.

conterminous United States↗
USGS2025

Geologic map of the Buckner 7.5-Minute quadrangle, Louisa County, Virginia

The Buckner 7.5-minute quadrangle straddles three terrane boundaries in the Piedmont Physiographic Province in central Virginia: the Chopawamsic terrane, the Elk Hill Complex, and the Goochland terrane. In much of the map area, the Elk Hill Complex separates the Chopawamsic and Goochland terranes. Rocks of the Chopawamsic terrane include Ordovician metavolcanic and metasedimentary rocks of the Chopawamsic Formation, Ordovician to Silurian granodiorite sheet intrusions, and Paleozoic mafic intrusions. Silurian to Devonian rocks of the Quantico Formation, mostly garnet-mica schist, crop out in the northwesternmost part of the map area, and are in unconformable contact with rocks of the Chopawamsic Formation on the southeastern limb of the Quantico synclinorium. The main map unit in the Elk Hill Complex is Neoproterozoic mica gneiss, which is in pre-metamorphic fault contact with rocks of the Chopawamsic Formation to the west. The main map unit of the Goochland terrane is the Maidens Gneiss. Except for Jurassic diabase dikes, all rocks on the Buckner 7.5-minute quadrangle were metamorphosed to amphibolite facies during the Alleghanian orogeny and preserve multiple compositional and phyllosilicate penetrative foliations. Evidence of amphibolite-facies metamorphism during the Taconic orogeny is preserved in rocks of the Elk Hill Complex. The entire width of the Maidens Gneiss on the Buckner 7.5-minute quadrangle is within the Spotsylvania high-strain zone and amphibolite-facies mylonitic textures are pervasive. Quartz veins and Jurassic diabase dikes crosscut all older rocks of the quadrangle. Multiple levels of terrace deposits are present along and near the major streams of the quadrangle. The lower terrace deposits are likely remnants of former positions of the Little River on the landscape, whereas higher deposits may be remnants of former deposits of the Atlantic Coastal Plain that covered this portion of the Piedmont Province. A linear cluster of aftershocks from the magnitude 5.8 earthquake that occurred near Mineral, Virginia, in 2011 defines the Fredericks Hall fault, which is at depth on the Buckner quadrangle. Most of the aftershocks occurred in the core of the Elk Creek antiform and have no relation to faults mapped at the surface. Several abandoned crushed stone and building stone quarries, as well as a mica prospect, exist in the quadrangle.

Virginia↗
USGS2026

Utilization of multiple geochronology techniques to constrain the age of laterization and mineralization of the world-class Mount Weld rare earth element deposit, Western Australia

Pervasive chemical weathering on stable cratons may form thick regoliths and elemental enrichment, but constraining the age of regolith formation is challenging. In this study we utilize multiple geochronological techniques on different minerals from the world-class Mount Weld rare earth element (REE) deposit, formed by lateritic weathering of a carbonatite, to constrain the age of formation and provide insight into landscape evolution. The oldest dates, ca. 100 to 38 Ma, are from Lu-Hf dating of churchite [HREE(PO 4 )·2(H 2 O)], a heavy REE phosphate mineral. Growth bands on individual minerals show a younging outwards. 40 Ar/ 39 Ar geochronology of cryptomelane [K(Mn 4+ ,Mn 2+ )₈O₁₆] yielded dates from ca. 40 to 27 Ma. Similarly, (U-Th)/He geochronology of goethite [FeO(OH)] yielded dates ranging from ca. 45 to 19 Ma. Integrating results into regional constraints, suggests 1) churchite formed by mineral saturation in a karst-like setting below the water table from ca. 100 to 40 Ma, 2) with minor uplift and erosion, cryptomelane and goethite formed at or near the water table between ca. 45 and 19 Ma, 3) after ca. 15 to 10 Ma chemical weathering within the profile had ended. Other studies document that the region experienced minimal uplift and a wet, warm climate from ca. 100 Ma to 15 Ma. These conditions and the high carbonate content of the carbonatite promote extensive chemical weathering, a deep weathering profile, and the preservation of the weathered section. This study highlights the use of multiple geochronological techniques utilizing different minerals to provide insight into how laterites form and to constrain the timing and history of the formation of this important mineral deposit.

Western Australia↗
USGS2024

The geometry of fault reactivation and uplift along the central part of the Maacama fault zone, northern California Coast Ranges (USA)

Fault reactivation of bedrock structures in active fault zones influences stress state and earthquake rupture phenomena through the introduction of weak slip surfaces that impact fault zone geometry and width. Yet, geometric relationships between modern faults and older reactivated faults are difficult to quantify in rocks that have experienced multiple deformation episodes. We used new geologic mapping, geomorphic tools, and structural modeling to quantify rock uplift and subsurface fault geometry of the central part of the Maacama Fault Zone near Ukiah, California, USA, and the surrounding area. Results suggest that the northern Mayacamas Mountains are in a tectonically driven disequilibrium, with differential rock uplift focused on the western side of the range. Steeply east-dipping fault surfaces and splays characterize the geometry of the Maacama Fault Zone. We mapped two newly identified faults to the east of the main Maacama Fault, the Cow Mountain–Mill Creek Fault, and Willow Creek Fault, which align with a moderately east-dipping cluster of microseismicity between 4–10 km depth beneath the Mayacamas Mountains. Static stress modeling on the Maacama Fault Zone and newly identified faults to the east quantify slip tendency values of 0.5–0.4, which suggests that the faults are moderately to poorly suited for slip in the modern stress field and may be weak. We infer that modern uplift is driven by oblique reverse, up-to-the-east, dip-slip motion on the reactivated Cenozoic Cow Mountain–Mill Creek and Willow Creek Faults as material is advected through a restraining bend on the Maacama Fault. This study shows that reactivated bedrock faults increase the fault zone width and introduce fault surfaces that contribute a component of vertical deformation and uplift in major strike-slip fault zones. Deformation is accommodated on an interconnected network of new and reactivated faults that delineate a complex seismic hazard.

California↗
USGS2025

Application of Hydrologic Simulation Program—FORTRAN (HSPF) as part of an integrated hydrologic model for the Salinas Valley, California

The U.S. Geological Survey (USGS), in cooperation with the Monterey County Water Resources Agency, conducted studies to help evaluate the surface-water and groundwater resources of the Salinas Valley study area, consisting of the entire Salinas River watershed and several smaller, adjacent coastal watersheds draining into Monterey Bay. The Salinas Valley study area is a highly productive agricultural region that depends on the coordinated use of surface water and groundwater to meet demand for irrigation and public water supply. To continue to meet these demands, a better understanding of the historical water balance and the effects of water-resource development on the long-term sustainability of water resources in the Salinas Valley study area is needed.

California↗
USGS1996

Hydrogeologic investigation and simulation of ground-water flow in the Upper Floridan Aquifer of north-central Florida and southwestern Georgia and delineation of contributing areas for selected city of Tallahassee, Florida, water-supply wells

A 4-year investigation of the Upper Floridan aquifer and ground-water flow system in Leon County, Florida, and surrounding counties of north-central Florida and southwestern Georgia began in 1990. The purpose of the investigation was to describe the ground-water flow system and to delineate the contributing areas to selected City of Tallahassee, Florida, water-supply wells. The investigation was prompted by the detection of low levels of tetrachloroethylene in ground-water samples collected from several of the city's water-supply wells. Hydrologic data and previous studies indicate that; ground-water flow within the Upper Floridan aquifer can be considered steady-state; the Upper Floridan aquifer is a single water-bearing unit; recharge is from precipitation; and that discharge occurs as spring flow, leakage to rivers, leakage to the Gulf of Mexico, and pumpage. Measured transmissivities of the aquifer ranged from 1,300 ft 2 /d (feet squared per day) to 1,300,000 ft2/d. Steady-state ground-water flow in the Upper Floridan aquifer was simulated using a three-dimensional ground- water flow model. Transmissivities ranging from less than 5,000 ft2/d to greater than 11,000,000 ft 2 /d were required to calibrate to observed conditions. Recharge rates used in the model ranged from 18.0 inches per year in areas where the aquifer was unconfined to less than 2 inches per year in broad areas where the aquifer was confined. Contributing areas to five Tallahassee water-supply wells were simulated by particle- tracking techniques. Particles were seeded in model cells containing pumping wells then tracked backwards in time toward recharge areas. The contributing area for each well was simulated twice, once assuming a porosity of 25 percent and once assuming a porosity of 5 percent. A porosity of 25 percent is considered a reasonable average value for the Upper Floridan aquifer; the 5 percent porosity simulated the movement of ground-water through only solution-enhanced bedding plains and fractures. The contributing areas were generally elliptical in shape, reflecting the influence of the sloping potentiometric surface. The contributing areas delineated for a 5 percent porosity were always much larger than those determined using a 25 percent porosity. The lowest average ground-water velocity computed within a contributing area, using a 25 percent porosity, was 1.0 ft/d (foot per day) and the highest velocity was 1.6 ft/d. The lowest average ground-water velocity, determined using a 5 percent porosity, was 2.4 ft/d and the highest was 7.4 ft/d. The contributing areas for each of the five wells was also determined analytically and compared to the model-derived areas. The upgradient width of the simulated contributing areas were larger than the upgradient width of the analytically determined contributing areas for four of the five wells. The model could more accurately delineate contributing areas because of the ability to simulate wells as partially penetrating and by incorporating complex, three-dimensional aquifer characteristics, which the analytical method could not.

Florida, Georgia↗
USGS2024

A seismic nodal deployment to understand magmatic structure in the vicinity of the Pahala earthquake swarm

In summer-fall 2022, 80 three-component SmartSolo IGU-BD3C-5 nodal seismometers were deployed surrounding the Pāhala seismic swarm on the Island of Hawaiʻi, with the goal of improving seismicity catalogs, and seismic velocity images of the crust and upper mantle in this region. The Pāhala swarm, located south of Mauna Loa and Kīlauea, has been the site of a multiyear sustained swarm of seismicity at depths of ~ 25 – 40 km, with order of magnitude increases in rate in 2015, and then again in 2019. This seismicity is possibly related to the input of magma from the mantle plume below, which may then be subsequently transported to volcanic edifices. However, these processes remain enigmatic, in part due to a lack of precise earthquake locations and seismic velocity models in this region. Here we provide an overview of the deployment, an assessment of the quality of the collected data, and discuss the viability of the dataset for local earthquake relocation, tomography, and teleseismic receiver functions. Through comparisons with proximal permanent broadband and short period instruments, we find that the nodes produce high quality data, particularly at periods shorter than 5 s, although we find, document, and correct discrepancies with the gain and polarities of the instruments. We successfully record signals from teleseismic earthquakes, even at periods longer than 5 s (the corner of the flat response of the nodes). We also record local earthquakes, including details related to source characteristics. This indicates that the data is likely to prove useful for investigations using both local and teleseismic earthquake signals to better understand the connections between the deep and shallow magmatic systems of Hawaiʻi. While this deployment provides a snapshot in time, its success may provide a useful benchmark for future studies as the volcanic systems of Hawaiʻi continue to evolve in the future.

Hawaii↗
USGS2024

Surficial geology and Quaternary fault map of the Las Vegas Valley, Clark County, Nevada

The Surficial Geology and Quaternary Fault Map of the Las Vegas Valley, Clark County, Nevada is a 1:50,000-scale compilation of published 1:24,000-scale geologic maps integrated with new field and desktop mapping. This geologic map compilation and GIS database are part of a broader study on the Quaternary faults in the Las Vegas Valley, the results of which are summarized in this report. The map compilation utilized a variety of digital base maps to evaluate the characteristics of surficial deposits and Quaternary fault scarps including lidar data in undeveloped parts of the valley and orthorectified historical aerial photos in the urbanized center of the valley. The map distinguishes twenty surficial map units including alluvial-fan and ephemeral-wash deposits, groundwater discharge deposits of the Las Vegas Formation, and alluvium deposits of Las Vegas Wash. Quaternary faults include the Quaternary Las Vegas Valley fault system in the center of the valley and the Frenchman Mountain fault system along the eastern margin. All Quaternary fault traces in the valley were evaluated, and the previously published fault mapping was modified as needed. The new mapping and uniform correlation of surficial deposits displaced by Quaternary faults yields a consistent valley-wide characterization of the recency of fault activity. The map and GIS database include a Quaternary geochronology compilation of 119 previously published surficial deposit ages of various types, 35 new luminescence ages, and 3 new radiocarbon ages. The new age data further bracket the ages of the Las Vegas basin Quaternary stratigraphy and provide new constraints on the timing of Quaternary fault activity.

Nevada↗
USGS2025

Using visualization science to inform the design of environmental decision-support tools—A case study of the U.S. Geological Survey Waterwatch

Environmental decision-support tools are increasingly being used to serve both expert and non-expert audiences. Many existing tools are primarily expert-focused, and redesigning them can be challenging because experts and non-experts interact with tools differently, existing users may be resistant to changes, and there is little guidance on how to prioritize redesign efforts and demonstrate their efficacy. In this report, we present a case study of a user-centered redesign of an established environmental decision-support tool—the U.S. Geological Survey WaterWatch. WaterWatch supports flood, drought, and other water resource management decisions through the display of water levels at gages across the United States. Using a participatory process, we identified a functional change (replacing the existing rainbow colormap), created an alternative design, and tested the alternative’s usability through two general public surveys. The results showed that replacing the rainbow colormap with a more intuitive diverging colormap improves usability, regardless of the audience’s subjective preference for the rainbow color scheme. In addition, we demonstrated the importance of using legends to improve the audience’s understanding of the map symbols. This study demonstrates how user-centered design approaches can be used to inform the design of high-profile products and tools.

Scientific Investigations Report↗
USGS2024

On the provenance of field reports of the 1886 Charleston, South Carolina, earthquake: A seismo-historical whodunnit

Much of what is known about the effects of the 1886 Charleston, South Carolina, earthquake throughout the epicentral region can be attributed to meticulous field investigations by an individual with training in geology and engineering, Earle Sloan ( Clendenin, 1926 ). In a recent study, Bilham and Hough (2024) undertook a detailed analysis of the effects of the earthquake on railroads in the Charleston region, drawing heavily from Sloan’s reports. This exercise identified several inconsistencies in Sloan’s field reports, including understandable measurement imprecision, inferred data entry mistakes, and transcription errors. The study also begged the question, where was Sloan at the time of the mainshock and over the following week? And to what extent did he draw from secondhand information in compiling his reports? On this question Sloan’s reports were sometimes enigmatic, lending themselves to misinterpretation in contemporaneous as well as modern interpretations. Beyond the details that were germane for, and briefly summarized by, the studies of Bilham and Hough (2023 , 2024) , in this report we don our historical seismologist caps to chronicle Sloan’s activities following the earthquake. We summarize our inferences here for the benefit of future scholars who might attempt to retrace either Sloan’s footsteps or our own. This study also serves to highlight Sloan’s singular contributions to earthquake science, which were never published separately.

South Carolina↗
USGS2025

The role of alkali bicarbonate-sulfate brines in the genesis of carbonatite REE resources at the Bear Lodge Alkaline Complex, Wyoming

Rare-earth element (REE) resources in the Bear Lodge Alkaline Complex, Wyoming, are hosted in a variably leached carbonatite dike swarm spatially related to bodies of diatreme breccia. This study examines fluid inclusions in carbonatite dikes, peripheral fluorite breccias, and smoky quartz veins to reconstruct the physiochemical conditions of REE mineralization. Results reveal a multi-stage evolution of carbonatitic fluids: 1) high-temperature (330–432°C), CO 2 -rich magmatic fluids, 2) REE-enriched alkali bicarbonate-sulfate brines, and 3) low-temperature meteoric (117–182°C) or diluted magmatic fluids. Multiphase inclusions (stage-2) contain burbankite, nahcolite, and alkali sulfate daughter crystals, linking the brines to early burbankite [(Na,Ca) 3 (Sr,Ba,REE) 3 (CO 3 ) 5 ] mineralization in carbonatite. REE mobility has been linked to the stability of aqueous complexes with ligands such as Cl-, SO 4 2- , and HCO 3 - . However, light REEs were not initially transported significant distances, rather they crystallized as burbankite from brines or brine-melts associated with the carbonatite magma. Crystallization of burbankite removed Na from the system, leaving residual fluids with high K/Na ratios and promoting potassic fenitization throughout the complex. Fractionation of light and heavy REEs and involvement of low temperature (<300°C), high K/Na bicarbonate brines may have facilitated transport and formation of peripheral occurrences that are more enriched in heavy REEs at Bear Lodge.

Wyoming↗
USGS2026

Widespread terrestrial ecosystem disruption at the onset of the Paleocene–Eocene Thermal Maximum

The Paleocene–Eocene Thermal Maximum (PETM, ~56 Mya) interval was marked by massive 13 C-depleted carbon emissions into the ocean/atmosphere system, manifested as a negative carbon isotope excursion (CIE) in sedimentary components, and ~5 °C global average warming. Episodes of hydrological perturbations and soil-erosion have been widely documented for the PETM but their link with vegetation- and carbon cycle changes remain poorly constrained. Here, we present organic microfossil evidence showing a strong increase in fern-dominated pioneer vegetation that replaced coniferous forests on the margin of the Norwegian Sea during the first millennia of the CIE. With the present stratigraphic constraints, the “fern spike” occurred simultaneously in terrestrial settings along the North Sea, Arctic Ocean, the US east coast and in southern Australia, indicating that pioneer vegetation persisted for several millennia following a partial collapse of previously stable terrestrial ecosystems. Both the ferns and influx of microcharcoal imply recurrent physical disturbance, including soil destabilization and erosion, potentially linked to droughts, wildfires, and strong hydrological forcing resulting from extreme climate change. Together with evidence for reworked clay minerals and ancient organic matter (kerogen), these findings show that highly disturbed terrestrial ecosystems were widespread across mid- and high-latitude regions globally. Carbon cycle model simulations suggest that a substantial loss of standing and buried biomass, along with oxidation of soil organic matter, acted as important positive feedbacks during the onset of the CIE. Additionally, enhanced kerogen weathering likely contributed as another major positive feedback throughout both the onset and main phase of the CIE.

Proceedings of the National Academy of Sciences↗
USGS2025

Hydrogeologic framework and conceptual model of the Red River alluvial aquifer east of Lake Texoma, southeastern Oklahoma, 1980–2022

The 1973 Oklahoma Groundwater Law (Oklahoma Statutes §82-1020.5) requires that the Oklahoma Water Resources Board conduct hydrologic investigations of the State’s groundwater basins to support a determination of the maximum annual yield for each groundwater basin. At present (2025), the Oklahoma Water Resources Board has not established a maximum annual yield for the Red River alluvial aquifer east of Lake Texoma. To support the evaluation and determination of a maximum annual yield, a hydrogeologic framework and conceptual groundwater-flow model were developed to assess groundwater availability in the Red River alluvial aquifer east of Lake Texoma. The scope of this hydrologic investigation is the alluvium and terrace containing the Red River alluvial aquifer in Oklahoma between Lake Texoma, the Texas State line, and the Arkansas State line, an extent referred to in this report as “the eastern part of the Red River alluvial aquifer.” Parts of the alluvium and terrace extent in Arkansas and Texas are included in some analyses to address hydrologic influences from outside the aquifer’s boundaries in Oklahoma. The eastern part of the Red River alluvial aquifer in southeastern Oklahoma consists of approximately 401,280 acres of Quaternary alluvium and terrace deposits associated with the Red River and its major tributaries. Mean annual recharge to the aquifer for the 1980–2022 study period was estimated to be 8.62 inches per year, or 17.98 percent of the mean annual precipitation over the same period (47.94 inches). This mean annual recharge rate is equivalent to an inflow of approximately 288,250 acre-feet per year for the eastern part of the Red River alluvial aquifer. Recharge estimated using the Soil-Water-Balance code accounts for 98.7 percent of the conceptual-model inflows to the eastern part of the Red River alluvial aquifer. Saturated-zone evapotranspiration accounts for 11.9 percent and net streambed seepage accounts for 87.4 percent of the outflows in the conceptual model.

Arkansas, Oklahoma, Texas↗
USGS2025

Methodology and technical input for the 2025 U.S. List of Critical Minerals—Assessing the potential effects of mineral commodity supply chain disruptions on the U.S. economy

The Secretary of the Interior, acting through the Director of the U.S. Geological Survey, is tasked by section 7002 (“Mineral Security”) of title VII (“Critical Minerals”) of the Energy Act of 2020 (Public Law 116–260, December 27, 2020, 116th Congress) with reviewing and revising the methodology used to evaluate mineral commodity supply risk and the U.S. List of Critical Minerals (LCM) no less than every 3 years. Following two previous LCM assessments, this analysis represents the latest technical input for evaluating each mineral commodity’s supply risk and determining their recommended status on the LCM. We evaluated mineral commodity supply risk using two criteria: (1) an economic effects assessment that quantified the potential effects of various trade disruption scenarios on the U.S. economy, and (2) an examination of whether the mineral commodity’s U.S. supply chain relied on a sole domestic producer that represented a single point of failure. For the first criterion, postdisruption equilibrium quantities and prices for each mineral commodity were calculated based on their price elasticities of supply and demand and the availability of excess production capacity for each yearlong foreign trade disruption scenario. Subsequently, a nonlinear optimization routine was used with detailed economic input-output tables to estimate the potential economic effects on the U.S. economy of over 1,200 scenarios for 84 mineral commodities. After accounting for the probability of each scenario’s occurrence, the overall results are presented in terms of changes in U.S. gross domestic product (GDP) by individual industry and the economy overall. The results, which ranged from a net decrease in U.S. GDP of nearly $4.5 billion to a net increase of $33 million, largely reflect U.S. import dependency and world production concentration. Using the Jenks natural breaks optimization method, a statistical classification technique, we categorized the mineral commodities into several classes based on this overall risk quantification. Mineral commodities with annualized probability-weighted net decreases in U.S. GDP greater than $2 million were recommended for inclusion on the LCM. If a mineral commodity did not meet the threshold for inclusion on the LCM under the first criterion, its domestic supply chain was examined under the second criterion, which recommended a mineral commodity for inclusion on the LCM if there was only a single domestic producer. Ultimately, the two criteria resulted in the recommendation of the addition of six mineral commodities (in descending risk order, potash, silicon, copper, silver, rhenium, and lead) to and the removal of two mineral commodities (arsenic and tellurium) from the LCM. By using an economic effects assessment, the results of this analysis provide a prioritization that can also be compared directly against other risk analyses and the cost of various risk mitigation strategies.

Open-File Report↗