1,721,051 research outputs found
Evolution of Edwards-Trinity Aquifer biodiversity: Insights from phylogeography
No full textThe exceptional groundwater community inhabiting the karstic Edwards-Trinity Aquifer system in central Texas has inspired generations of biologists seeking to understand diversification in an extreme environment. Since the late 1990s, molecular genetic tools have increasingly been used to uncover hidden diversity and infer the evolutionary history of groundwater species inhabiting the Edwards-Trinity system. The field of phylogeography—the study of the spatial distribution of genealogical lineages within and among intraspecific populations and closely related species—has provided unparalleled insight into patterns of Edwards-Trinity groundwater biodiversity. Similar to other global groundwater biodiversity hotspots, phylogeographic studies in the Edwards-Trinity Aquifer system have documented exceptionally high levels of endemism and strong population structure due to isolation across naturally fragmented habitat. Cryptic species (two or more morphologically similar but genetically distinct species) have been discovered in a number of phylogeographic investigations, including Eurycea salamanders, Dionda minnows, and Stygobromus amphipods. A number of these species are threatened or endangered with extinction due to habitat loss and degradation resulting from urbanization. Accurately delimiting species boundaries has had significant implications for biodiversity and groundwater conservation in the Edwards-Trinity region because the Endangered Species Act has been used to regulate unrestricted groundwater withdrawal in the eastern Edwards Aquifer where listed species are found. New developments in deoxyribonucleic acid (DNA) sequencing technology coupled with advancements in model-based inference will provide powerful tools for furthering our understanding of Edwards-Trinity biodiversity and predicting its response to a rapidly changing environment
Recommended from our members
Oil Production and Groundwater Quality in the Edwards-Trinity Plateau Aquifer, Texas
Full text linkThis article suggests that evaporite dissolution and oilfield brine locally impact the Edwards-Trinity Plateau Aquifer, but the problem is not regionally pervasive
A Multiphased Approach to Groundwater Assessments for the Edwards-Trinity and Related Aquifers in the Pecos County Region, Texas
No full textThe Edwards-Trinity aquifer, a major aquifer in the Pecos County region of western Texas, is a vital groundwater resource for agricultural, industrial, and public supply uses. Resource managers would like to better understand the future availability of water in the Edwards-Trinity aquifer in the Pecos County region and the effects of the possible increase or temporal redistribution of groundwater withdrawals. To that end, the U.S. Geological Survey (USGS), in cooperation with the Middle Pecos Groundwater Conservation District, Pecos County, City of Fort Stockton, Brewster County, and Pecos County Water Control and Improvement District No. 1, completed a comprehensive, integrated analysis of available hydrogeologic data to develop a groundwater-flow model of the Edwards-Trinity and related aquifers in parts of Brewster, Jeff Davis, Pecos, and Reeves Counties. Following calibration, the model was used to evaluate the sustainability of recent (2008) and projected water-use demands on groundwater resources in the study area
Hydrogeology and Ground-Water Flow in the Edwards-Trinity Aquifer System, West-Central Texas
No full textTwo finite-element ground-water flow models were developed for the Edwards–Trinity aquifer system, west-central Texas, to gain a better understanding of the flow system; one ground-water flow model was developed at a large scale to simulate the regional system and contiguous, hydraulically connected units, and one model was constructed at a smaller more detailed scale to simulate the most active areas of the system. The study area is divided into four geographic subareas: the Trans-Pecos (9,750 square miles), the Edwards Plateau (23,750 square miles), the Hill Country (5,500 square miles), and the Balcones fault zone (3,000 square miles). The major aquifers within the study area are the Edwards–Trinity aquifer underlying the Trans-Pecos and Edwards Plateau, the Trinity aquifer underlying the Hill Country, and the Edwards aquifer in the Balcones fault zone. Hydraulically connected aquifers include the High Plains aquifer north of the Edwards Plateau, and the Cenozoic Pecos alluvium aquifer adjacent to both the Trans-Pecos and the Edwards Plateau along the Pecos River. Minor contiguous aquifers include the Dockum, Ellenburger–San Saba, Marble Falls, Hickory, and Lipan, which is adjacent to the Colorado River in Tom Green and Concho Counties, Texas. The ground-water flow equations solved by the finite-element method are based on conservation of mass and energy. The equation for ground-water flow assumes laminar flow through a porous media. In places, the Edwards–Trinity aquifer system is a fractured karst system in which ground water flows through caverns and other features of secondary porosity development. The regional and subregional models were constructed to synthesize the known hydrologic boundaries and geologic structures into a heterogeneous continuum model of the karst ground-water flow system, rather than simulate the flow through specific fractures and caverns. A heterogeneous continuum or equivalent porous media approach uses an effective transmissivity and anisotropy for each element of the models. Th
A Conceptual Model of the Hydrogeologic Framework, Geochemistry, and Groundwater-Flow System of the Edwards-Trinity and Related Aquifers in the Pecos County Region, Texas
No full textA conceptual model of the hydrogeologic framework, geochemistry, and groundwater-flow system of the Edwards-Trinity and related aquifers, which include the Pecos Valley, Igneous, Dockum, Rustler, and Capitan Reef aquifers, was developed as the second phase of a groundwater availability study in the Pecos County region in west Texas. The first phase of the study was to collect and compile groundwater, surface-water, water-quality, geophysical, and geologic data in the area. The third phase of the study involves a numerical groundwater-flow model of the Edwards-Trinity aquifer in order to simulate groundwater conditions based on various groundwater-withdrawal scenarios. Resource managers plan to use the results of the study to establish management strategies for the groundwater system. The hydrogeologic framework is composed of the hydrostratigraphy, structural features, and hydraulic properties of the groundwater system. Well and geophysical logs were interpreted to define the top and base surfaces of the Edwards-Trinity aquifer units. Elevations of the top and base of the Edwards-Trinity aquifer generally decrease from the southwestern part of the study area to the northeast. The thicknesses of the Edwards-Trinity aquifer units were calculated using the interpolated top and base surfaces of the hydrostratigraphic units. Some of the thinnest sections of the aquifer were in the eastern part of the study area and some of the thickest sections were in the Pecos, Monument Draw, and Belding-Coyanosa trough areas. Normal-fault zones, which formed as growth and collapse features as sediments were deposited along the margins of more resistant rocks and as overlying sediments collapsed into the voids created by the dissolution of Permian-age evaporite deposits, were delineated based on the interpretation of hydrostratigraphic cross sections. The lowest aquifer transmissivity values were measured in the eastern part of the study area; the highest transmissivity values were measured in a faulted area of the Monument Draw t
Configuration of the base of the Edwards-Trinity aquifer system and hydrogeology of the underlying pre-Cretaceous rocks, west-central Texas
No full textThe Edwards-Trinity aquifer system is underlain by an extensive complex of rocks, ranging from Late Cambrian through Late Triassic in age, that are typically about 10 to perhaps 1,000 times less permeable than those composing the aquifer system. The Cretaceous rocks of the aquifer system are separated from the pre-Cretaceous rocks by an unconformity that spans about 60 million years of erosion during the Jurassic Period. The upper surface of the pre-Cretaceous rock complex forms the base of the Edwards-Trinity aquifer system. The configuration of the base reflects the original topography of the eroded pre-Cretaceous land surface plus the effects of subsequent deformation
Oil Production and Groundwater Quality in the Edwards-Trinity Plateau Aquifer, Texas
Full text linkChloride concentrations and chloride/bromide ratios from 198 water wells in the Edwards-Trinity Plateau Aquifer were compiled, mapped, and evaluated within the context of regional geology and land use. The study area occupies eight counties in west-central Texas, within which oil production and agriculture are predominant land uses. Samples from 49 wells had chloride concentrations above the 250 mg/l secondary drinking water standard, 22 samples had greater than 500 mg/l chloride, and 9 samples exceeded 1000 mg/l chloride. Of the 22 samples above 500 mg/l chloride, 10 had relatively low chloride/bromide ratios of less than 300, consistent with oilfield brine, and 2 had ratios above 2000, consistent with groundwater impacted by evaporite dissolution. The remaining ten samples had chloride/bromide ratios ranging from 300 to 2000, consistent with partial mixing of unimpaired groundwater with evaporite-laden water. There were no significant correlations between chloride concentration and well depth, inconsistent with contaminants originating at the land surface. Results of this study suggest that evaporite dissolution and oilfield brine locally impact the Edwards-Trinity Plateau Aquifer, but the problem is not regionally pervasive
Description of a New Genus and Species of Stygobiontic Diving Beetle, Psychopomporus felipi Jean, Telles, and Miller (Coleoptera: Dytiscidae: Hydroporinae), from the Edwards-Trinity Aquifer System of Texas, USA
No full textPsychopomporus felipi Jean, Telles, and Miller, new genus and new species (Coleoptera: Dytiscidae), is described from San Felipe Springs, Val Verde County, Texas, USA, which emerges from the Edwards-Trinity aquifer system. Psychopomporus felipi shows several features typical of subterranean diving beetles, such as depigmentation, compound eyes reduced, elytra fused, and flight wings absent. Psychopomporus differs from other hydroporine genera in having a broad elytral epipleuron, the prosternal process small and with a medial, strongly produced prominence, and the meso- and (to a lesser extent) protibia apically broadly expanded and medially distinctly curved. This is the fourth stygobiontic diving beetle described from the Edwards-Trinity aquifer system in south-central Texas, USA
Fracking en el Acuífero Transfronterizo Edwards-Trinity-El Burro: implicaciones y daños ambientales transfronterizos
No full textEn México, la Secretaría de Energía (Sener), a través de la Comisión Nacional de Hidrocarburos (CNH), proyecta en lo inmediato la extracción de gas de lutitas o shale gas por medio del fracturamiento hidráulico o fracking en el área fronteriza de Coahuila con Texas. Se prevé que la principal fuente de abastecimiento hídrica será la subterránea, subyacente en el Sistema Acuífero Transfronterizo Edwards-Trinity-El Burro. No obstante, la literatura especializada advierte de los vacíos de conocimiento con relación al funcionamiento hidrogeológico, sociotécnico y ambiental de ese sistema acuífero compartido. De acuerdo con la metodología de evaluación de los Acuíferos Transfronterizos del Programa ISARM/Américas (UNESCO, 2015), este trabajo efectuó un diagnóstico inicial del conjunto de información relativa al Sistema Acuífero Transfronterizo Edwards-Trinity-El Burro, identificado previamente por este Programa, para demostrar que poco se ha estudiado y relacionado el fracking con la perspectiva y gestión de manejo de los sistemas de flujo del agua subterránea transfronteriza, en función de la demanda de agua que implica dicha técnica de fracturamiento. Se consideró, además, que la unidad hidrogeológica en cuestión es un curso hídrico internacional. Asimismo, se llevó a cabo un análisis comparativo entre los marcos jurídicos e institucionales existentes entre Texas y México aplicables a la protección y conservación del agua subterránea con relación al fracking, y se advirtió la existencia de importantes asimetrías en el conocimiento, la evaluación y la gestión de estos cursos de agua compartidos. Los resultados de la presente investigación sugieren que en México existe poco conocimiento e interés en la evaluación sistémica de los acuíferos transfronterizos y, en consecuencia, se observa la falta de un esquema conjunto para la prevención y el control de daños ambientales transfronterizos derivados del fracking
Edwards-Trinity (Plateau) and Pecos Valley Aquifers: One Layer Groundwater Flow Model
No full textThe Texas Water Development Board improved the calibration of the Edwards-Trinity (Plateau) and Pecos Valley Aquifers GAM by converting the model from a two-layer to a one-layer model and by adjusting many of the input parameters including the model boundaries, model base and top elevations, recharge, hydraulic conductivity, anisotropy, and storage. The updated model was also calibrated for a longer period of time, 1930 through 2005, than the original model which was calibrated for the period 1980 through 2000. The updated model was constructed and run using a newer version of MODFLOW: MODFLOW-2000 versus MODFLOW-96 in the original model. Additionally, calibration was achieved using parameter estimation software, PEST, along with FORTRAN pre-processors
- …
