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Surface fissures in the Hueco Bolson and adjacent basins, West Texas
No full textBureau Publication GC9202 - to purchase a print copy please go to: https://store.beg.utexas.edu/geologic-circulars/520-gc9202.html Research funded by the Texas Low-Level Radioactive Waste Disposal Authority under Interagency Contract Number IAC(90-91)0268Surface fissures have been observed in many desert basins in the western United States. These surface-collapse features are usually discovered after a normally dry surface has been covered with water, either by runoff from intense rainfall, by flooding, or by irrigation. Their sudden appearance attracts the attention of local residents, especially when the fissures render unpaved roads impassable. Collapse features begin as near-surface tension fractures that are enlarged by erosion and piping. Uneroded tension fractures are typically 0.1 to 7.6 cm wide and are filled with fine-grained sediment. Surface-collapse features may coalesce to form fissures, some up to 15 km long. Maximum reported depth of fissures or fractures is 25 m. Most tension fractures have formed where ground water has been pumped and water levels have dropped significantly (30 to 140 m). However, some fractures exist where no substantial pumping has occurred and no corresponding drop in water tables has been recorded. These features may have formed as a result of the lowering of ground water over geologic time. Tensional stress leading to fracture formation may result from differential compaction of unconsolidated sediments over bedrock irregularities or abrupt sedimentary facies boundaries or from desiccation. Seismic activity, although not a prerequisite for formation of collapse features, in some instances may trigger the development of tension fractures. Near-surface tension fractures may remain undetected until they are enlarged by piping and the surface above them collapses. Polygonal and branching patterns of fissures suggest desiccation as a cause of fracture genesis, but this origin remains unproven.
Fissures at the Hueco Bolson study area in western Texas are located on a flat-lying alluvial slope on Cenozoic sediments that fill a small basin in Cretaceous bedrock. The basin is separated from the main part of the Hueco Bolson by the Campo Grande fault. All three fissures at the Hueco Bolson study area are in topographic lows, indicating that overland flow is important to their development. The conditions necessary for piping to occur probably exist in the study area only in topographic lows during and after heavy rains.
Detailed study of fractures reveals that walls of fractures that underlie fissures match across each fracture's midline, evidence of simple tensional separation. These fractures are filled with silty, clayey sediment that contains vertical, clayey laminae, suggesting multiple periods of filling or fracturing or both. Fracture fill conducts water more readily than surrounding sediments, as seen at fissure 1. Low chloride concentrations down to 4.6 m below the surface near this fissure indicate that relatively high moisture fluxes occur there, compared with moisture fluxes in sediments in ephemeral stream channels and on low-lying interfluves. Unlike in fissured areas elsewhere in the desert Southwest, there has been no significant ground-water pumping in the vicinity of the study area. However, four factors have led to lower ground-water levels in the study area over geologic time: incision of the Rio Grande, change to a warmer, drier climate, fault movement on the Campo Grande fault, and preferential drainage of relatively permeable basin fill beneath the study area. These fissures and those that form where ground water has not been pumped are natural geomorphic features of the desert Southwest.Bureau of Economic GeologyUT Librarie
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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Dissolved noble gases in groundwater
Get PDFtextAtmospheric noble gases (He, Ne, Ar, Kr, and Xe) dissolved in groundwater are a valuable tool in hydrology. Numerous studies have relied on groundwater recharge temperatures calculated from dissolved noble gas data (noble gas temperatures, NGT) to infer paleoclimate conditions. This research investigated gas dissolution during groundwater recharge and critically examined the use of dissolved noble gas data in groundwater research. A detailed investigation of an agriculturally impacted shallow aquifer allowed comparison of measured water table temperatures (WTT) with calculated NGT. Results suggest that NGT calculated from widely used noble gas interpretive models do reflect measured WTT, supporting the use of dissolved noble gases to deduce recharge temperatures. Samples having dissolved gas concentrations below the equilibrium concentration with respect to atmospheric pressure were attributed to denitrification induced gas stripping in the saturated zone. Modeling indicated that minor degassing (<10% [Delta]Ne) may cause underestimation of groundwater recharge temperature by up to 2 °C. In another study a large dissolved noble gas data set (905 samples) from California was analyzed. Noble gas modeling using the same interpretive models indicates that multiple models may fit measured data within measurement uncertainty, suggesting that goodness-of-fit is not a robust indicator of model appropriateness. A unique aspect of this study was the high Ne and excess air concentrations associated with surficial artificial recharge facilities. A final study examined whether climatic/hydrologic changes occurring over glacial-interglacial time periods could impact the accuracy of NGT used in paleoclimate studies. Numerical modeling experiments estimated WTT sensitivity to changes in: 1) precipitation amount, 2) water table depth, and 3) air temperature. Precipitation and water table depth had a minor impact on WTT (~0.2 °C). In contrast, the impact of air temperature changes on WTT was more pronounced. Results suggest that air temperatures inferred from NGT data may underestimate actual air temperature change since the last glacial maximum by ~1 °C at sites having seasonal snowcover. These results suggest despite uncertainty in the exact physical processes controlling gas dissolution during groundwater recharge, NGT do reflect WTT. However, inferring paleo-air temperatures from NGT are subject to error, especially locations with seasonal snowcover.Earth and Planetary Science
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Optimal electrification planning in Sub-Saharan African countries
Get PDFAccess to reliable, sustainable, and affordable electricity services is essential for quality of life and economic development. However, ~53% of the population in Sub-Saharan Africa (SSA) live without access to electricity. Due to its rapid population growth and accelerated urbanization, Africa is a key driver of global energy demand growth. However, to meet the United Nations Sustainable Development Goal 7, which aims to achieve 100% electricity access by 2030, the region is faced with dual challenges of providing access to the 600 million people who currently lack electricity access while reaching the millions born every year in areas without access to electricity. A variety of local and national studies have been undertaken in recent years to provide feasible electrification solutions. This study first investigates the historical evolution and the current situation of electricity supply and demand, in order to reveal the links between electrification and socio-economic factors as well as energy resources exploration. Next, utilizing an open-source Spatial Electrification Tool (OnSSET), this study seeks the least cost electrification options for SSA countries, including grid-connection, mini-grid, and stand-alone systems, and analyzed the sensitivity of the results to projected population, energy targets, grid generation costs, diesel prices, and solar costs, etc. The results show that electrification rates vary spatially across SSA. Large electrification gaps exist between urban and rural areas in SSA, with 78% of the urban population and 27% of the rural population in SSA having electricity access in 2018. Electrification increased substantially in SSA from 25% in 2000 to 47% in 2018. East African countries, such as Ethiopia and Kenya, were leading the increase. The OnSSET model results suggest that, in urban areas with most of the population and close to transmission lines, grid extension is usually the least cost option, while stand-alone or mini-grid options are more economical in rural areas with less population and electricity demand. Detailed analysis of Angola and Senegal using the OnSSET model shows that for a certain level of access, the projected population connected to the grid ranges from ~70% in Angola to ~90% in Senegal by 2030. Considering a scenario with emission costs and renewable subsidies, with higher grid generation costs and lower solar cost, mini-grid solar or stand-alone solar options are favorable for more areas than grid extensionEnergy and Earth Resource
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Assessing linkages between climate teleconnections and freshwater inflows to Texas bays and estuaries
Get PDFUnderstanding spatiotemporal variability in freshwater inflows to the bays and estuaries along the Gulf of Mexico is critical for water resources management to maintain the health of the ecosystem and marine life. The objective of this study was to assess linkages between climate teleconnections (e.g. El Nino Southern Oscillation [ENSO], North Atlantic Oscillation [NAO], and Pacific Decadal Oscillation [PDO]), precipitation, and freshwater inflows to the Gulf of Mexico. Seasonal Trend Decomposition using LOESS (STL) analysis was used to decompose monthly precipitation and freshwater inflows (1941-2015) to each bay and estuary, isolating long-term variability, and comparing it to ENSO during warm and cool PDO phases and NAO. Results show that there are moderately strong positive correlations between ENSO and precipitation (R = 0.37 to 0.7) with mostly higher precipitation during El Nino and lower precipitation during La Nina. These correlations were weakened during PDO warm phase (R = 0.16 to 0.41) and amplified during PDO cool phase (R = 0.66 to 0.8). Temporal variability in precipitation was linked to bay and estuary freshwater inflows, showing high flows during El Nino and low flows during La Nina. Additionally, there are moderately strong positive correlations between NAO and freshwater inflows to two of the 10 bays/estuaries in the northeast (Sabine-Neches and Trinity San Jacinto, R = 0.45 and 0.41). These correlations tend to occur within the year of the driving conditions in the Pacific and Atlantic oceans. Identifying these linkages and the corresponding response times can help predict and manage the hydrologic response to wet and dry climate cycles linked to climate teleconnections along the Texas Gulf Coast to help protect and maintain the health of the vital estuarine environmentsEnergy and Earth Resource
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Energy and water production trends in the Powder River Basin
Get PDFEnergy extraction and water are intrinsically linked. Quantifying this relationship is critical to develop effective management strategies that minimize adverse environmental impacts and potentially reduce production costs. The objective of this study was to assess the spatiotemporal variability in water use and water production through hydrocarbon extraction from conventional and unconventional reservoirs using data from the Powder River Basin in Wyoming as a case study. Field level and detailed well-by-well analyses were conducted to quantify the spatiotemporal variability of oil and gas volumes and the corresponding co-produced water from conventional oil reservoirs and coal bed methane (CBM) reservoirs, and additional water used for hydraulic fracturing in unconventional shale reservoirs. Results show that conventional oil and CBM gas production has markedly declined along with produced water. The water demands of unconventional oil and gas development in the last decade have increased with increasing unconventional oil production, however water use per unit of energy produced has increased. Produced water from unconventional oil wells does not meet hydraulic fracturing water demands. CBM wells in proximity to new unconventional well development may be a source of water needing minimal treatment for growing hydraulic fracturing water demands.Energy and Earth Resource
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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Cost of desalinating brackish groundwater using stochastic estimates of groundwater storage volumes and salinity
Get PDFStrategic water planning in Texas is an important way to ensure Texans have enough water. With increasing climate extremes (droughts and floods) and climate change, new drought resistant supplies, such as brackish groundwater desalination, will become more important in the overall water portfolio in Texas. Current brackish groundwater studies produced by the state provide deterministic estimates of brackish groundwater storage volumes and groundwater salinity estimates. These estimates have high uncertainties; however, these uncertainties are not quantified or communicated. In this thesis two stochastic workflows were developed to reevaluate results of a deterministic brackish groundwater study: Monte Carlo simulation to produce stochastic storage estimates and ensemble learning to produce stochastic groundwater salinity estimates. These workflows were tested against the results of deterministic estimates, showing that the stochastic P50 storage estimate was about two times greater than the deterministic storage estimate when a lithologically appropriate specific yield distribution was sampled. The stochastic analysis also revealed that the aquifer storage estimates are highly uncertain due to a lack of measured data in the brackish aquifers. In reprocessing data from the original deterministic analysis, uncertainty in salinity estimates was found to increase with increasing salinity, which is expected due to the limited number of brackish and saline water quality samples in the public record. Finally, the stochastic estimates of storage and salinity were used to assess the cost of desalinating groundwater from a San Antonio Water System project in the 2022 State Water Plan. Results show that brackish groundwater salinity uncertainties had a greater effect on the cost of desalinated groundwater than the uncertainties in the storage volume estimates. Overall, by developing stochastic workflows and estimates, stakeholders can target specific data to acquire to reduce uncertainties for specific projects. The additional context provided by uncertainty analysis could greatly benefit stakeholdersEnergy and Earth Resource
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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