Browsing by Subject "aquifers"

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Carbon Dioxide Storage in Deltaic Saline Aquifers: Invasion Percolation and Compositional Simulation
(2021) Tavassoli, Shayan; Krishnamurthy Prasanna; Beckham, Emily; Meckel, Tip A.; Sepehrnoori, Kamy
Characterization Study of the Ogallala Aquifer, Northwest Texas
(1985) Nativ, Ronit; Smith, D. Anderson
The Ogallala aquifer, which is the main water supply in the High Plains of Texas, is being severely depleted by extensive pumpage for irrigation. The aquifer overlies the Permian evaporites that are being considered as a potential repository for the disposal of high-level nuclear wastes. Potential contamination of the aquifer by these wastes and further depletion of the limited water resources are major concerns of the people in the area. The purpose of this work is to develop a general hydrogeologic characterization of the aquifer that will serve as a firm basis for accurate evaluation of aquifer recharge mechanisms relevant to problems stemming from accidental spills of radionuclides at the land surface and possible interactions of the radionuclides with deeper hydrologic units. Aquifer hydraulics relevant to problems that may be encountered in shaft construction were studied as well. The existing geologic, hydrologic, geochemical, and isotopic data are integrated into a regional hydrogeologic model for water and solutes. The model enables (1) an understanding of recharge/discharge relationships, ages of water, and rock-water interactions, and (2) the tracing of cross-formational flow between the Ogallala and the underlying aquifers. This report presents preliminary conclusions of research conducted from August 1984 through August 1985.
Declines and Losses of Spring/Ciénega Ecosystems in the Chihuahuan Desert of Texas
(2017-07-15) Garrett, Gary; Bean, Megan; Edwards, Robert; Hendrickson, Dean A.
Desert ecosystems are particularly susceptible to anthropogenic influences. This is especially true for desert aquatic systems where limited water resources can be easily impaired by excessive water mining depleting the underlying aquifers. Although the aquatic environments and their associated native fishes are declining throughout the Chihuahuan Desert, we will focus on examples from the Big Bend region, the Balmorhea Springs Complex, the Pecos River region, and the Devils River region. Ongoing and impending land use and water consumption patterns suggest even further reductions in the near future. Even though numerous conservation activities are underway, archaic Texas water laws must be revisited and reformulated if the desert aquatic systems are to be truly conserved for more than the immediate future.
Discovery of the Mexican Blindcat, Prietella phreatophila, in the U.S., and an update on its rangewide conservation status
(2017-03-03) Hendrickson, Dean A.; Johnson, Jack; Sprouse, Peter; Howard, Sarah; Garrett, Gary P.; Krejca, Jean K.; Gluesenkamp, Andrew; Dávila Paulín, José Antonio; Dugan, Laura; Cohen, Adam E.; Hernández Espriú, Antonio; Sullivan, John P.; Fenolio, Danté B.; Karges, John; Smith, Ryan; García De León, Francisco J.; Wolaver, Brad; Reddell, James
Mexican blindcat, Prietella phreatophila, was described in 1954 from a single locality in Northern Coahuila, México. Long listed as endangered by the Mexican federal government, it was listed by the U.S. Fish and Wildlife Service as a foreign endangered species in 1970, and the most recent (1996) update of its assessment for the IUCN Red List considers it endangered as well. Explorations in the late 1990s discovered many new localities extending nearly to the international border, and a captive population established provided insights into the species’ basic biology and behavior. In 2016 the species was discovered in a cave in the Amistad National Recreation Area (ANRA), just north of the Río Grande in Texas. The 1970 listing instantly gave the TX population full protection under the U.S. Endangered Species Act. The species’ subterranean and mostly inaccessible habitat endows it with extremely low detectability and its actual range is likely broader than physical sampling of specimens has revealed. We review all prior and new knowledge of the species and its habitat to provide an updated international reassessment of its overall conservation status and threats, which most notably include aquifer depletion and contamination in both the Mexican and U.S. portions of its known range. A live captive population of two specimens collected in 1997 in Coahuila and one Texas specimen is now at the San Antonio Zoo, we are working with NPS to further explore ANRA caves and hope eventually to return to Coahuila to more fully update the species’ conservation status.
Edwards Aquifer Storage Assessment, Kinney County to Hays County, Texas
(1993) Hovorka, Susan D.; Ruppel, Stephen C.; Dutton, Alan R.; Yeh, Joseph S.
The distribution of water in the Edwards aquifer was assessed using a core- and log-based stratigraphic study that included 200 neutron and resistivity logs and 300 porosity and permeability plug analyses. The Kainer, Person, Devils River, West Nueces, McKnight, and Salmon Peak Formations of the Edwards Group were investigated during this study. The aquifer extends over 3,111 mi^2 (8,004 km^2) and thickens toward the south from approximately 500 to 780 ft (150 to 240 m). In the Edwards outcrop, the aquifer thins northward because of erosion and decreased saturated thickness. Porosity data were interpolated between wells to create a three-dimensional cell-based model of porosity. Porosity distribution reflects both the depositional rock fabric and later diagenesis. Small-scale vertical variations in porosity are the result of facies changes caused by high-frequency cyclicity in the depositional environment. Vertical facies stacking influences the amount of dolomitization and diagenetic enhancement of porosity. Subtidal facies deposited during major sea-level highstands are generally undolomitized and exhibit low porosity (4- to 12-percent porosity). Grainstones at cycle tops in the Kainer, Person, and Devils River Formations are typically high-porosity intervals with high depositional porosity that may have additional solution enlargement of pores and pore throats (20- to 42-percent porosity). Dolomitized subtidal facies have very high porosity in intervals with stacked tidal-flat cycles because of preferential dolomite dissolution.
Epigenetic Zonation and Fluid Flow History of Uranium-Bearing Fluvial Aquifer Systems, South Texas Uranium Province
(1981) Galloway, William E.
The coastal plain of Texas is becoming increasingly important as a producer of epigenetic sandstone uranium resources. The rapidly expanding database generated by both exploration and mining has, within the past decade, led to the development and refinement of exploration concepts that are, in some respects, unique to the province. Initially, models applied were based on attributes of the well-studied epigenetic uranium deposits of the Wyoming Tertiary basins. The roll-front model and its implicit epigenetic oxidation-reduction zonation proved successful to a point because Gulf Coast deposits do exhibit many features of their Wyoming counterparts. However, deeper exploration and more sophisticated description of known deposits reveal fundamental differences between the depositionally active Gulf Coastal Plain and the interior Tertiary basins. Interior basins have been depositionally inactive since the mid-Tertiary, and the total sediment pile above uranium-bearing aquifers is decreasing as older Tertiary strata continue to erode. In contrast, basinward stratigraphic equivalents of principal Gulf Coast fluvial uranium hosts, such as the Catahoula and Oakville Formations, have been buried deeper than 15,000 ft (4,500 m), and burial has continued throughout the late Tertiary and Quaternary. Additionally, Gulf basin host sands overlie thick sequences of underconsolidated older Tertiary and Mesozoic sediments, which have not yet attained hydrostatic equilibrium with the surface. The result is a hydrologically active basin in which counterflow of geochemically different water masses has existed since the deposition of the host fluvial systems and continues to exist.
Evaluation of Groundwater Nitrate Contamination in Aquifers in Texas
(2017) Reedy, R. C.; Scanlon, Bridget R.
Nitrate is the most widespread groundwater contaminant in Texas and the U.S. Elevated levels of groundwater nitrate can have serious health implications, including methemoglobinemia and increased cancer risks. Sources of nitrate contamination include both natural and anthropogenic sources such as inorganic and organic fertilizers (including manure), output from concentrated animal feeding operations (CAFOs), septic tanks, and leaking sewer systems. Natural sources of nitrate arise from nitrogen fixation by legumes, mineralization of organic matter (nitrification), and natural geological processes. Numerous previous studies have investigated groundwater nitrate contamination in Texas. Early studies focused on identifying sources using nitrogen isotopes, particularly distinguishing between nitrate from fertilizers and septic tanks. While groundwater nitrate levels were anticipated to be high in the Ogallala Aquifer beneath playas adjacent to CAFOs, many studies found that nitrate levels were reduced due to denitrification facilitated by high levels of organic matter. Recent research suggests that nitrate contamination has been increasing in Texas over the past few decades, with the Seymour aquifer in the Rolling Plains identified as a hotspot of groundwater nitrate contamination. Studies have also assessed the factors influencing groundwater nitrate contamination, with logistic regression indicating that precipitation, percentage of agricultural land, low-density residential land, and soil organic matter are significant explanatory variables. Unsaturated zone sampling has helped link land surface processes to groundwater nitrate levels, suggesting that much of the elevated nitrate in the Ogallala and Seymour aquifers may be attributed to high levels of natural nitrate prior to cultivation, which was oxidized during cultivation and subsequently mobilized into the underlying aquifer.
Evaluation of Groundwater Nitrate Contamination in Major Aquifers in Texas
(2016) Reedy, R. C.; Scanlon, Bridget R.
Nitrate is the most widespread groundwater contaminant in Texas and in the U.S. There are many potential adverse health implications of elevated groundwater nitrate, including methemoglobinemia and cancer risks. There are a variety of sources of nitrate, including natural sources, inorganic and organic fertilizers (manure), output from concentrated animal feeding operations (CAFOs), septic tanks, and leaking sewer systems. Natural sources result from nitrogen fixation by legumes, mineralization of organic matter (nitrification), and natural geologic sources. Many previous studies have been conducted on groundwater nitrate contamination in Texas. The early studies focused on source identification using nitrogen isotopes, mainly distinguishing between nitrate from fertilizers and septic tanks. Groundwater nitrate levels were expected to be high in the Ogallala Aquifer beneath playas adjacent to concentrated animal feeding operations; however, many studies showed that nitrate levels were reduced by denitrification attributed to high levels of organic matter. A recent study suggested that nitrate contamination has been increasing in the state over the past several decades and identified the Seymour aquifer in the Rolling Plains as a hotspot of groundwater nitrate contamination. A study evaluated controls on groundwater nitrate contamination using logistic regression, indicating that precipitation, percent of agricultural land, low-density residential land, and soil organic matter were the dominant explanatory variables. Unsaturated zone sampling was used to link land surface processes to groundwater nitrate levels and suggested that much of the elevated nitrate levels in the Ogallala and Seymour aquifers could be attributed to high levels of natural nitrate prior to cultivation that was oxidized during cultivation and mobilized into the underlying aquifer. The current study examined the distribution of groundwater nitrate in major and minor aquifers in the state using approximately 10,000 analyses from major aquifers and approximately 2,000 analyses from minor aquifers. Approximately 70% of the samples in the major and minor aquifers exceeded the detection levels for nitrate. The majority of the samples are from rural domestic and irrigation wells. A total of 5.5% of the samples from the major aquifers exceeded the MCL, with the highest level of contamination in the Seymour Aquifer (61% of sampled > MCL), followed by the Pecos Valley Aquifer (11%), Ogallala Aquifer (9%), Edwards Trinity High Plains (6%), and the remaining major aquifers < 2%. Groundwater nitrate concentrations generally decreased with depth.
Evaluation of Nitrate Contamination in Major Porous Media Aquifers in Texas
(2003) Scanlon, Bridget R.; Reedy, R. C.; Kier, Katherine S.
This study aimed to evaluate the factors influencing nitrate contamination in major porous media aquifers across Texas by analyzing groundwater nitrate concentration data alongside nitrogen loading and aquifer susceptibility parameters. Attributes related to nitrogen loading included atmospheric deposition, fertilizers, land use, sewage and septic input proxies, population density, precipitation, and irrigation. Aquifer susceptibility attributes included land surface slope, soil drainage, clay content, and organic matter content. Multivariate logistic regression was employed to assess the probability of nitrate concentrations exceeding 4 mg/L nitrate-N in shallow wells (≤ 30 m) based on these variables. The final regression model incorporated precipitation, percentage of agricultural land, low-density residential land, and soil organic matter. Observed and predicted probabilities of elevated nitrate concentrations showed strong correlation in both calibration and validation datasets. The inverse relationship between precipitation and nitrate concentration may indicate dilution in high precipitation areas and possible evapoconcentration in low precipitation areas. While nitrate loading was not explicitly included in the model, agricultural land percentage served as a proxy for nitrogen loading from agricultural sources, and low-density residential land use served as a proxy for septic tank effluent. The percentage of organic matter may reflect denitrification in certain regions. This GIS and logistic regression analysis offers valuable insights into the factors influencing nitrate concentrations in groundwater. Future studies should complement this analysis with field sampling to validate the GIS and logistic regression findings and assess the impact of processes like dilution and denitrification on nitrate concentrations.
Exploration and Production Program for Locating and Producing Prospective Aquifers Containing Solution Gas and Free Gas Texas Gulf Coast - Annual Report
(1982) Gregory, A. R. (Alvin Ray), 1915-; Lin, Zsay-Shing; Reed, Roneá S.; Morton, Robert A.
The Port Arthur field in Jefferson County, Texas, has been identified as a promising candidate for secondary enhanced gas recovery methods due to its multiple watered-out gas reservoirs, thick aquifers, and gas stringer sandstones at depths ranging from 10,850 to 11,700 feet. Sidewall core data indicate an average porosity of 30 percent and average permeability of 60 millidarcies (md). Reservoir simulation studies suggest that approximately 3.91 billion standard cubic feet of unconventional gas can be recovered through natural flow from the 11 C" sandstone over a 10-year period, by reducing reservoir pressure from 6,500 to 4,018 pounds per square inch gauge (psig). The break-even gas price is estimated to be $3.45 per thousand standard cubic feet for a 15-percent rate of return. Additional gas recovery opportunities exist through co-production from other sandstones and by further reducing reservoir pressure using artificial lift methods. It is recommended to drill a design test well to a depth of 11,650 feet at a location near the Meredith No. 2 Doornbos (Well No. 14). This test well will help evaluate the feasibility and effectiveness of secondary enhanced gas recovery techniques in the Port Arthur field.
Exploration and Production Program for Locating and Producing Prospective Aquifers Containing Solution Gas and Free Gas- Texas Gulf Coast
(1983) Gregory, A. R. (Alvin Ray), 1915-; Lin, Zsay-Shing; Reed, Roneá S.
This project was designed to locate and evaluate a prospective watered-out gas reservoir in the Texas Gulf Coast inland area. The prospective reservoir was to be suitable for application of enhanced gas recovery methods for producing the unconventional gas that remained in the reservoir after primary gas production ceased. A test well site would be located within a favorable prospect area. Previous work conducted by the Bureau of Economic Geology for the U.S. Department of Energy focused on the selection of test well sites in the Frio Formation and Wilcox Group of the Texas Gulf Coast. These studies were intended to make use of thermal energy, mechanical energy, and gas dissolved in formation waters by producing large volumes of hot water from deep, highly pressured formations. In this project, funded by the Gas Research Institute, interest shifted to locating prospective reservoirs containing significant quantities of free gas in addition to the gas dissolved in the water. Abandoned watered-out reservoirs and wet zones where large amounts of water must be produced to obtain the gas by co-production were identified. The present project, funded by the Gas Research Institute, shows their continuing interest in unconventional gas and in developing prospects that are favorable for co-production of gas and water from watered-out gas reservoirs. Guidelines used to screen gas fields along the Texas Gulf Coast resulted in the selection of the Port Arthur field, Jefferson County, Texas, as a suitable prospect for application of enhanced gas recovery methods. Several watered-out gas sandstones in this field have excellent reservoir characteristics. All 18 wells in the field have been plugged and abandoned by previous operators; hence, leasing problems should be simplified. Abundant shallow Miocene sands in the area are available for salt-water disposal. The "C" reservoir interval, located at an average depth of 11,130 ft, received the most extensive evaluation. Predicted gas recovery by natural flow is 5.1 billion standard cubic feet as reservoir pressure declines from 6,632 to 4,309 psig. A sample economic analysis showed a net present worth of $968,000 and a payout time of 3 years. This prospect has the potential to be economically profitable in addition to being a good research and development test for evaluating co-production techniques. It is recommended that a co-production well be drilled and tested on a site near the Meredith No. 2 Doornbos (Well 14).
Geologic and Hydrogeologic Framework of Regional Aquifers in the Twin Mountains, Paluxy, and Woodbine Formations Near the SSC Site, North-Central Texas
(1996) Dutton, Alan R.; Mace, Robert E. (Robert Earl), 1967-; Nance, Hardie Seay, 1948-; Blum, Martina U.
Water-utility districts and many municipalities in North-Central Texas recently obtained as much as 100 percent of their water supply from deep regional aquifers in Cretaceous formations. Use of groundwater from the aquifers during the past century has resulted in water-level declines of as much as 850 ft (259 m), especially in Dallas and Tarrant Counties. Future water-level changes will depend on the amount of groundwater produced to help meet growing water-supply needs for municipalities, industries, and agriculture throughout North-Central Texas. It is probable that a significant part of the increased water demand will be met by groundwater although at less than historic rates. The objective of this study was to develop a predictive tool for studying the effect of future groundwater production from regional aquifers in North-Central Texas. To do this, we reviewed the history of groundwater development, hydrogeology of the regional aquifers, and constructed numerical models of groundwater flow. A cross-sectional model of both aquifers and confining layers was used to evaluate model boundary conditions and the vertical hydrologic properties of the confining layers. Results and insights from the cross-sectional model were used in a three-dimensional simulation of groundwater flow in the deep aquifers. The layers of the regional confining system were not explicitly included in the three-dimensional model. Hydrogeologic properties were assigned on the basis of aquifer test results and stratigraphic mapping of sandstone distribution in the aquifer units.
Geologic and Hydrogeologic Framework of Regional Aquifers in the Twin Mountains, Paluxy, and Woodbine Formations Near the SSC Site, North-Central Texas (Draft)
(1994) Mace, Robert E. (Robert Earl), 1967-; Nance, Hardie Seay, 1948-; Dutton, Alan R.
Water-utility districts and municipalities in North-Central Texas recently obtained as much as 100 percent of their water supply from deep regional aquifers in Cretaceous formations. Use of groundwater from the aquifers during the past century has resulted in water-level declines of as much as 800 ft (243.8 m) in Dallas and Tarrant Counties. Future continued water-level decline throughout North-Central Texas will depend on the amount of groundwater produced to help meet increased water-supply needs for municipal, industrial, and agricultural growth. It is probable that a significant part of the increased water demand will be met by groundwater. The objectives of this study were to develop a hydrologic model of the complex interrelations among aquifer stratigraphy, hydrologic properties, and groundwater availability and, given expected patterns of future groundwater demand, to predict water-level changes in the regional aquifers that underlie North-Central Texas. A cross-sectional model of both aquifers and confining layers was used to evaluate model boundary conditions and the vertical hydrologic properties of the confining layers. Results and insights from the cross-sectional model were used in a three-dimensional simulation of groundwater flow in the deep aquifers. The layers of a regional confining system were not explicitly included in the three-dimensional model. Hydrogeologic properties were assigned based on aquifer test results and stratigraphic mapping of sandstone distribution in the aquifer units.
Hydrochemical Characterization of Saline Aquifers of the Texas Gulf Coast Used for Disposal of Industrial Waste
(1986) Kreitler, Charles W.; Richter, Brend C.
Disposal of toxic chemical wastes into geologic formations in the deep subsurface and the number of disposal wells used have increased sharply during the last 30 years. In Texas, permits for more than 200 waste disposal wells, which accept approximately 16 percent of the chemical wastes generated in the United States, were issued by the Texas Department of Water Resources (TDWR) during this period (Knape, 1984). Most waste disposal wells use porous, saline sandstone aquifers along the Texas Gulf Coast (fig. 1). Simultaneously, fresh groundwater is recovered from shallower, updip sections of these aquifers. Therefore, integrity of disposal zones is of importance both on a statewide and on a nationwide level. Waste injected into subsurface formations may react with formation fluid or formation material, depending on the chemical and physical nature of the phases involved. Aquifer material may dissolve or mineral matter may precipitate, thus changing original compositions of disposal zones. It is desirable to predict these changes to assure successful operation of injection practices. To satisfactorily evaluate the suitability of deep-well injection into Gulf Coast formations, hydrochemical and hydrogeological parameters of these aquifers are currently under study by the Bureau of Economic Geology, The University of Texas at Austin. This report represents the first stage of the characterization of saline aquifers in the Gulf Coast that are used for industrial waste disposal and summarizes geochemical parameters of disposal zones.
Hydrogeologic Characterization of the Saline Aquifers, East Texas Basin- Implications to Nuclear Waste Storage in East Texas salt Domes
(1983) Kreitler, Charles W.; Collins, Edward W.; Fogg, Graham E.; Jackson, M. P. A.; Seni, Steven J.
Groundwaters in the deep aquifers (Nacatoch to Travis Peak) range in salinity from 20,000 to over 200,000 mg/L. Based on their isotopic compositions, they were originally recharged as continental meteoric waters. Recharge probably occurred predominantly during the Cretaceous time; therefore, the waters are very old. Because the basin has not been uplifted, there are no extensive recharge or discharge zones. The flanks of domes and radial faults associated with domes may function as localized discharge points. Both the water chemistry and the hydraulic pressures for the aquifers suggest that the basin can be subdivided into two major aquifer systems: (1) the upper Cretaceous aquifers (Woodbine and shallower) which are hydrostatic and (2) the deep lower Cretaceous and deeper formations (Glen Rose, Travis Peak, and older units), which are slightly overpressured. The source of sodium and chloride in the saline waters is considered to be from salt dome dissolution. Most of the dissolution occurred during the Cretaceous. Chlorine-36 analyses suggest that dome solution is not presently occurring. Salinity cross sections across individual domes do not indicate that ongoing solution is an important process. The major chemical reactions in the saline aquifers are dome dissolution, albitization, and dedolomitization. Albitization and dedolomitization are important only in the deeper formations. The high Na concentrations in the deeper aquifer system result in the alteration of plagioclase to albite and the release of Ca into solution. The increase in Ca concentrations causes a shift in the calcite/dolomite equilibrium. The increase in Mg results from dissolution of dolomite.
Hydrogeologic Characterization of the Saline Aquifers, East Texas Basin-Implications to Nuclear Waste Storage in East Texas Salt Domes
(1987) Kreitler, Charles W.; Collins, Edward W.; Fogg, Graham E.
Groundwaters in the deep aquifers (Nacatoch to Travis Peak) range in salinity from 20,000 to over 200,000 mg/l. Based on their isotopic compositions, they were originally recharged as continental meteoric waters. Recharge probably occurred predominantly during Cretaceous time; therefore, the waters are very old. Because the basin has not been uplifted and faulting of the northern and western sides, there are no extensive recharge or discharge zones. The flanks of domes and radial faults associated with domes may function as localized discharge points. Both the water chemistry and the hydraulic pressures for the aquifers suggest that the basin can be subdivided into two major aquifer systems: (1) the upper Cretaceous aquifers (Woodbine and shallower) which are hydrostatic to subhydrostatic and (2) the deep lower Cretaceous and deeper formations (Glen Rose, Travis Peak, and older units), which are slightly overpressured. The source of sodium and chloride in the saline waters is considered to be from salt dome dissolution. Most of the dissolution occurred during the Cretaceous. Chlorine-36 analyses suggest that dome solution is not presently occurring. Salinity cross sections across individual domes do not indicate that ongoing solution is an important process. The major chemical reactions in the saline aquifers are dome dissolution, albitization, and dedolomitization. Albitization and dedolomitization are important only in the deeper formations. The high Na concentrations in the deeper aquifers system result in the alteration of plagioclase to albite and the release of Ca into solution. The increase in Ca concentrations causes a shift in the calcite/dolomite equilibrium. The increase in Mg results from dissolution of dolomite. The critical hydrologic factors in the utilization of salt domes for disposal of high-level nuclear waste are whether the wastes could leak from a candidate dome and where they would migrate. The following conclusions are applicable to the problem of waste isolation in salt domes: (1) Salt domes in the East Texas Basin have extensively dissolved. The NaCl in the saline aquifers is primarily from this process. Major dissolution, however, probably occurred in the Cretaceous time. There is little evidence for ongoing salt dome dissolution in the saline aquifers. (2) If there was a release to a saline aquifer, waste migration would either be along the dome flanks or laterally away from the dome. If there is a permeability conduit along the dome flanks, then contaminants could migrate to the fresh-water aquifers, provided an upward hydraulic gradient exists. Calculation of performance assessment scenarios must take into account whether there is potential for upward flow between saline aquifers at repository level and the fresh water aquifers. If an upward flow potential exists, upward leakage along the dome flanks should be used as the worst-case scenario.
Hydrogeology and Hydrochemistry of the Ogallala Aquifer, Southern High Plains
(1987) Nativ, Ronit
The Ogallala aquifer, which underlies the Southern High Plains, consists of the saturated sediments of the Ogallala Formation (Neogene). It serves as the main source of water for the High Plains of Texas and New Mexico but has been severely depleted due to extensive pumpage. The hydrology and hydrochemistry of the aquifer are influenced by the surface topography of the underlying formations and the thickness and permeability of formation deposits. Two distinct hydrogeologic provinces were observed. The first province, located along paleo valleys filled with coarse fluvial sediments, exhibits increased formation thickness and saturated section, as well as higher porosities and hydraulic conductivities. Ground-water flow lines within this province follow the orientation of the paleo valleys. The hydrochemical composition in this province remains relatively constant, characterized by Ca-HCO3 to mixed-HCO3 water, depleted in 0180, δD, and tritium. In contrast, the second hydrogeologic province features thinner and less permeable formations, primarily composed of fine-grained eolian elastics. Ground-water discharge from aquifers in the Cretaceous contributes to the hydrochemical facies, resulting in isotopic compositions different from those of the first province. Cross-formational movement of water and low permeability in the Ogallala Formation in these areas lead to varying hydrochemical facies and isotopic compositions. Secondary factors influencing the chemical composition of Ogallala Formation ground water include contamination from evaporating saline lakes, agricultural chemicals and fertilizers, and oil field brines. The impact of these chemicals may increase in the future as contaminants continue to move through the unsaturated zone toward the water table.
Hydrology of Gulf Coast Aquifers, Houston-Galveston Area, Texas
(1977) Kreitler, Charles W.; Guevara, Edgar H.; Granata, G.; McKalips, Dawn G.
Aquifers in the Houston-Galveston area are composed principally of fluvial-deltaic sediments. The Alta Loma Sand is a complexly faulted, high-sand-percent unit that represents a seaward progression of fluvial, delta-plain, and delta-front facies. The Beaumont Formation, overlying the Alta Loma Sand, is a high-mud-percent unit that represents a coastal progression of delta-plain to delta-front facies. Four arbitrarily defined intervals from land surface to 2000 ft indicate the superposition of dip-oriented and strike-oriented high-sand-percent trends. Aquifer geology partly controls short-term and long-term aquifer hydrology. Dip-oriented high-sand-percent trends are optimum locations for ground-water development. Growth faults act as partial hydrologic barriers to ground-water production. Faults between Harris and Galveston Counties have partly isolated the aquifers into two subsystems. In Harris County, groundwater of low dissolved solids is meteoric in origin, whereas in Galveston County, groundwater of low dissolved solids is a mixture of meteoric and saline waters.
Letter to H.B. Stenzel from Robert Soyer on 1947-06-13
(1947-06-13) Soyer, Robert
The Mexican Blindcat Project: new discoveries and future efforts
(2017-03) Gluesenkamp, Andrew; Hendrickson, Dean A.; Sprouse, Peter
The endangered Mexican blindcat (Prietella phreatophila, Carranza 1954) is one of only four stygobitic ictalurid catfish in North America. Members of two monotypic genera (Satan eurystomus and Trogloglanis pattersoni) are known from the Edwards Aquifer in Texas and, until recently, Prietella (represented by P. lundbergi and P. phreatophila) was only known to occur in Mexico (northern Coahuila to southern Tamaulipas). The recent discovery of P. phreatophila in a cave on the Amistad National Recreation Area in Val Verde County, Texas is the result of decades of sporadic effort on both sides of the US/Mexican border and has stimulated a renewed effort to investigate the distribution, ecology, evolutionary history, and conservation status of this species. Collaborative efforts among The San Antonio Zoo, The University of Texas at Austin, Zara Environmental and The National Park Service are currently focused on habitat surveys in Texas as well as captive husbandry and propagation. Future efforts will include collaborators from the Comisión Nacional de Áreas Naturales Protegidas, Área de Protección de Recursos Naturales Sabinas, and the Laboratorio de Genética para la Conservación, Centro de Investigaciones Biológicas del Noroeste, La Paz to conduct expanded fieldwork in Mexico, hydrogeologic studies, and surveys using environmental DNA.