9 research outputs found
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Hydrogeology and Hydrochemistry of the Ogallala Aquifer, Southern High Plains
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.Bureau of Economic Geolog
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Characterization Study of the Ogallala Aquifer, Northwest Texas
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.Bureau of Economic Geolog
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Siting a Low-Level Radioactive Waste Disposal Facility in Texas Volume Four- Geologic and Hydrologic Investigations of State of Texas and University of Texas Lands
The Bureau of Economic Geology, The University of Texas at Austin, conducted preliminary investigations of the geology and hydrology of 5 areas in Culberson and Hudspeth Counties, Texas, selected by the Texas Low-Level Radioactive Waste Disposal Authority as potential sites for a low-level radioactive waste repository. This report discusses the results of those studies.
Two areas in Culberson County, Texas, Site S-15 and Block 46 and adjacent regions, were investigated. The Permian Castile Formation underlies all of Site S-15 and the eastern half of Block 46. The Castile Formation displays evidence of extensive solution and local collapse and appears to contain a complex system of karst features and underground solution channels. The western half of Block 46 is underlain by the Permian Bell Canyon Formation, consisting of interbeds of sandstone and limestone. Both the Castile and subjacent Bell Canyon Formations contain prominent joint systems and local areas of normal faults. Surficial deposits are commonly composed of detritus derived from local formations and appear to be both porous and permeable.
The groundwater flow in both areas is governed by karst dissolution and collapse features. The chemical and isotopic composition of groundwater indicates active recharge through the thin unsaturated zone combined with older water flowing from the west. Residence time of groundwater in the aquifers is relatively short, and numerous springs discharge from the shallow groundwater table.Bureau of Economic Geolog
Seed treatments with essential oils protect radish seedlings against drought
Establishment of seedlings of economic crops is often reduced if there is not a steady supply of water. Essential oils (EO) from plants are increasingly used instead of synthetic chemicals to protect plant and animal products against biotic and abiotic stresses. We investigated priming radish seeds by soaking or by matriconditioning with synthetic or natural compounds as a means of inducing resistance to drought stress, thus maintaining crop yield. Priming radish seeds for two hours in solutions of essential oils (EO) thymol and carvacrol derived from Origanum syriacum, with “oregano natural product” (ONP; a solution of the residue remaining after EO extraction), or with the gibberellin synthesis inhibitor trinexapac ethyl (TE), was much more effective in inducing drought resistance than was matriconditioning with the same compounds in sawdust for two days. The latter treatment induced considerable fungal and bacterial infection in treated seeds if the substrate-matrix was not heat-treated beforehand. The increase in specific leaf area in plants from treated seeds was mostly consistent with an increase in leaf water content. Seed treatments with EO, ONP, and especially TE led to a three-fold increase in radish seedling survival compared with water-treated controls, when 21 day-old seedlings were irrigated after 6 days of drought. Under drought conditions, seedlings from treated seeds had a 2–3-fold increase in relative water content increased 2–3-fold, while membrane permeability decreased 20–50-fold as a result of the treatments. However, the physical benefits of the treatments often did not correlate with treatment-induced increases in physiological parameters such as pigments (chlorophyll, carotenoid, anthocyanin), pigment ratios (chlorophyll a/b, carotenoid/chlorophyll), or antioxidant activity. Seed treatments with biostimulants can be as effective as treatments with synthetic compounds in inducing drought resistance in seedlings