Browsing by Subject "Rio Grande"
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Item Cave and cliff swallows as indicators of exposure and effects of environmental contaminants on birds from the Rio Grande, Texas(Texas A&M University, 2004-11-15) Musquiz, DanielCave (Petrochelidon fulva) and cliff swallows (Petrochelidon pyrrhonota) were collected along the Rio Grande and evaluated as potential indicators of environmental contamination. The Rio Grande receives toxic substances from agricultural, industrial, municipal, and non-point sources; consequently, high levels of contaminants have been detected in birds, mammals, fishes and sediments. Swallows were obtained from 8 sites between Brownsville and El Paso, as well as from a reference site in Burleson County, 320 miles north of the nearest site of the Rio Grande. Blood samples were analyzed by flow cytometry, a technique that allows the detection of DNA damage in blood and other tissues. Plasma samples were analyzed for thyroid hormones using a radioimmunoassay technique. Organochlorines and trace metal analysis was limited to a few samples. DDE and PCB levels were below levels known to cause reduced hatching, embryo mortality, and deformities, Hg, Pb, and As were below detection, and Se, Ni and Cr concentrations were lower than levels known to cause harm in birds. Neither species showed sex-related differences in chromosome damage. Cave swallows from the Del Rio area had the highest levels of DNA variation, which may be indicative of DNA damage, possibly from PAHs exposure. Previous studies indicate that sediment samples from tributaries near Del Rio have high levels of chromium compared to other sites along the Rio Grande. A significant increase in DNA variation between sampling years was detected in cave swallows from Llano Grande Lake. Wildlife samples collected from Llano Grande Lake have recorded high levels of DDE and PCBs; in addition, this urban/agricultural contaminant sink appears to be affected by PAH exposure. T3 levels were below the detection limit of the radioimmunoassay. There were no gender related differences in T4 levels in cave swallows. Cave swallows sampled from Laredo had significantly higher T4 levels than those from birds at other sites during 1999. It was not possible to determine thyroid hormone disruption in plasma samples. Thyroid hormone and flow cytometry data were useful in establishing baseline data. Areas of concern based on genotoxic data include Llano Grande Lake, Del Rio, and El Paso.Item Cottonwood distributions across the Rolling Plains of Texas and Kansas(2007-12) Walker, Ryan Nicholas; Wallace, Mark C.; Ballard, Warren B.; Janis, Michael W.; Rahman, A. FaizThe presence of trees is a limiting factor for wild turkeys (Meleagris gallopavo) throughout the arid and semiarid portions of their range. Any long-term changes that occur to local tree populations will likely impact local wild turkey populations. Cottonwoods (Populus spp.) are the primary riparian tree of western North America and are linked to the flow regime of the river system. From 2000 through 2006, we measured 3,832 Plains cottonwoods (P. deltoides ssp. monilifera) at four sites in the Rolling Plains of Texas and Kansas. Only 132 (3.4%) of these cottonwoods were <10 cm in diameter at breast height. We documented large declines in daily flow following dam completion along the Canadian River, Texas. We documented small declines in daily flow following dam completion along the Salt Fork of the Red River, Texas. We documented low or intermittent flows along the Cimarron River, Kansas. The large declines in flow rate along the Canadian River have led to channel narrowing and vegetation encroachment throughout the floodplain. The small declines in flow rate along the Salt Fork of the Red River did not alter the meandering status of the river, sheltering it from the changes that occurred along the Canadian River. The sporadic flow along the Cimarron River suggested this river was more unstable than the other rivers. Regardless of river flow status, we failed to detect large quantities of cottonwood regeneration across the study area. This leaves the future unclear for cottonwoods and wild turkeys in this region. We were concerned by the limited regeneration of riparian cottonwoods and wanted to examine a period >7 years. We used Landsat satellite imagery to identify changes, from 1973 to 2005, in riparian trees that may have occurred concurrently with changes in local wild turkey populations. Our supervised classification accuracies ranged from 0.9 to 64.0%, which were insufficient for us to complete our objectives. Landsat imagery was not sufficient to identify changes in riparian trees in our study area. Other satellite-based systems provide improved spatial resolution, but currently lack the necessary temporal resolution to be effective. We suggest aerial photography and ground-based surveys remain the most useful tools for documenting changes in riparian trees.Item Crustal xenoliths from Potrillo Maar: implications for evolution of continental crust beneath the southern Rio Grande rift(Texas Tech University, 2003-08) Chattopadhyay, IndraniThe mid-crustal xenoliths from Potrillo maar record a petrologic and geochemical history that has until now been unknown from the Potrillo volcanic field. The igneous and meta-igneous xenoliths are samples of one or more plutonic bodies that crystallized at depths from 7-14 km (middle to upper crust). The rock unit ranges in composition from hornblende biotite diorite to quartz monzonite and monzogranite; it is broadly alkalicalcic The initial Sr87Sr86 suggests that the source region is heterogeneous or that the parental magmas were contaminated by crustal material. At least three geochemical groups can be identified, primarily on the basis of silica content. There is considerable overlap between groups 1 and 2, and the boundary between these two groups cannot be distinguished graphically. The third group is granitic and is geochemically distinct from groups 1 and 2. A dioritic composition is thought to represent mafic parental magma. Its calculated liquidus temperature at 2% H2O and 4 Mpa pressure is 1172°C. The presence of fossiliferous limestone xenoliths indicates that the Potrillo maar eruption sampled rocks of late Paleozoic age. However, the age of marble and quartzite xenoliths are not known. The quartzite xenoliths are relatively undeformed, but isoclinal folding in some of the marble xenoliths suggests subsurface deformation that has not been observed in local surface exposures of metasedimentary rocks. One model proposed for the crust under the southern Rio Grande rift assumes that the marble is late Paleozoic in age. The fossiliferous limestones are late Paleozoic in age and are older than the plutonic rocks. The relative age of the deformed marbles in this model is not clear, it can be deformed with the plutonic rocks or due to an earlier regional extensional event. In the second model, marble is proposed to result from contact metamorphism in the aureole of a plutonic rock body at a depth of 7-14 km. The presence of marble and calc-silicate xenoliths in dioritic blocks is consistent with a correlation of the marble with surface exposures of the Castner Marble in the Franklin MountainsItem Dividing the water at Fort Quitman : a discussion of binational allocation and dynamic treaty interpretations(2016-05) Henley, Marion Hope; Eaton, David J.; Rubinstein, Carlos; Niemeyer, SteveThis report discusses the binational water allocation of the Rio Grande between the United States (U.S.) and Mexico. The International Boundary and Water Commission, United States and Mexico (IBWC) is charged with the administration and enforcement of treaties and other international agreements governing this watercourse, including but not limited to the Convention of 1906 and the Treaty of 1944. These two treaties establish an upper and lower segment of the Rio Grande. The 1906 Convention allocates water to Mexico and the U.S. in the transboundary segment from El Paso to Fort Quitman, about 90 miles away. The 1944 Treaty governs the watercourse from Fort Quitman to the Gulf of Mexico. Water allocation at Fort Quitman is indefinite in these treaties because the location represents a “terminus” point of the two segments. A plain-language interpretation of the treaties indicates the flows reaching this gage actually belong 100 percent to U.S., and therefore to Texas water rights holders, due to a waiver of rights by Mexico in the 1906 Convention for all flows in the upper segment. However, the established practice of the IBWC since the 1950s is to allocate those waters equally between Mexico and the U.S. (“50/50”). Research into IBWC materials reveals that this 50/50 allocation practice was established ad-hoc. There is no diplomatic evidence of agreement between the nations to justify the 50/50 allocation. Indeed, the current allocation practice at Fort Quitman contradicts the actual treaty text. The IBWC has not exercised its authority to establish the 50/50 allocation lawfully. Recommendations to remedy the matter include returning all the flows at Fort Quitman to the U.S. and Texas, to mandate the 50/50 practice through legal and diplomatic policy-making mechanisms. Another issue is whether Mexico ought to compensate the U.S. for the 2.1 million acre-feet it has received since the informal water allocation began in 1958 in contradiction to the treaties.Item Dynamics of water use and responses to herbivory in the invasive reed, Arundo donax (L.)(2010-07-14) Watts, David A.The first objective of this study was to investigate the role of an invasive grass species, Arundo donax (L.), on the hydrologic cycle. At a site on the Rio Grande in South Texas, we measured the gas exchange of carbon dioxide and water vapor at the leaf scale and structural characteristics, such as leaf area and shoot density, at the stand scale. In order to assess the effect of water availability, this study was conducted along transects perpendicular to the edge of the river along a potential moisture gradient. The second objective was to quantify the effect of two herbivores, an armored scale, Rhizaspidiotus donacis (Leonardi), and a stem-galling wasp, Tetramesa romana (Walker),on the photosynthetic and transpiration rates of A. donax. Leaf gas exchange measurements were made to determine the direction and magnitude of the effect on physiological processes and by what mechanisms any effects arose. Stands of A. donax used approximately 9.1 ? 1.1 mm of water per day. This rate of water use was at the high end of the spectrum for plants. The major controls on stand scale transpiration were evaporative demand, leaf area index, and water availability. During two summer seasons, stand scale transpiration varied greatly, following the pattern of variability in precipitation, suggesting that recent rainfall constituted a significant proportion of the water taken up by this species. Herbivory by a stem-galling wasp and a sap-feeding scale, both separately and together, reduced the rates of leaf scale physiological processes in A. donax. The efficacy of the wasp was density dependent, and this herbivore reduced the carboxylation rate of Rubisco. The effect of the scale took approximately five months to manifest, which coincided with generation time. Scale reduced photosynthesis by decreasing the maximum rate of electron transport. When the two insects were both present, the effect of their herbivory seemed to be additive. These results will assist the responsible management agencies in evaluating the propriety of using one or both of the insect herbivores as biological control agents.Item Sedimentary, structural, and provenance record of the Cianzo basin, Puna plateau-Eastern Cordillera boundary, NW Argentina(2011-05) Siks, Benjamin Charles; Horton, Brian K., 1970-; Steel, Ronald J.; Milliken, Kitty L.The fault-bounded Cianzo basin represents a Cenozoic intermontane depocenter between the Puna plateau and Eastern Cordillera of the central Andean fold-thrust belt in northern Argentina. New characterizations of fold-thrust structure, nonmarine sedimentation, and sediment provenance for the shortening-induced Cianzo basin at 23°S help constrain the origin, interconnectedness, and subsequent uplift and exhumation of the basin, which may serve as an analogue for other intermontane hinterland basins in the Andes. Structural mapping of the Cianzo basin reveals SW and NE-plunging synclines within the >6000 m-thick, upsection coarsening Cenozoic clastic succession in the shared footwall of the N-striking, E-directed Cianzo thrust fault and transverse, NE-striking Hornocal fault. Growth stratal relationships within upper Miocene levels of the succession indicate syncontractional sedimentation directly adjacent to the Hornocal fault. Measured stratigraphic sections and clastic sedimentary lithofacies of Cenozoic basin-fill deposits show upsection changes from (1) a distal fluvial system recorded by vi fine-grained, paleosol-rich, heavily bioturbated sandstones and mudstones (Paleocene‒Eocene Santa Bárbara Subgroup, ~400 m), to (2) a braided fluvial system represented by cross-stratified sandstones and interbedded mudstones with 0.3 to 8 m upsection-fining sequences (Upper Eocene–Oligocene Casa Grande Formation, ~1400 m), to (3) a distributary fluvial system in the distal sectors of a distributary fluvial megafan represented by structureless sheetflood sandstones, stratified pebble conglomerates and sandstones, and interbedded overbank mudstones (Miocene Río Grande Formation, ~3300 m), to (4) a proximal alluvial fan system with thick conglomerates interbedded with thin discontinuous sandstone lenses (upper Miocene Pisungo Formation, ~1600 m). New 40Ar/39Ar geochronological results for five interbedded volcanic tuffs indicate distributary fluvial deposition of the uppermost Río Grande Formation from 16.31 ± 0.6 Ma to 9.69 ± 0.05 Ma. Sandstone petrographic results show distinct upsection trends in lithic and feldspar content in the Casa Grande, Río Grande, and Pisungo formations, potentially distinguishing western magmatic arc (Western Cordillera) sediment sources from evolving eastern thrust-belt sources (Puna‒Eastern Cordillera). In addition to growth stratal relationships and 40Ar/39Ar constraints, conglomerate clast compositions reflect distinct lithologic differences, constraining the activation of the Cianzo thrust and coeval movement on the reactivated Hornocal fault. Finally, U-Pb geochronological analyses of sandstone detrital zircon populations in conjunction with paleocurrent data and depositional facies patterns help distinguish localized sources from more distal sources west of the basin, revealing a systematic eastward advance of Eocene to Miocene fold-thrust deformation in the central Andes of northern Argentina.Item Systematization of water allocation systems: an engineering approach(Texas A&M University, 2007-04-25) Santos Roman, Deborah MatildeThe allocation of water resources is typically accomplished within the framework of water allocation systems (WAS). In general, a WAS sets priorities, applies rules, and organizes responses to a range of water allocation scenarios. This research presents a comprehensive study of water allocation strategies and provides a conceptual framework of principles and guidelines for designing, assessing, implementing and supporting WAS. The voluminous compilation of international treaties and conventions, interstate compacts, intrastate administrative documentation, and scientific/engineering literature was researched in order to identify different water allocation strategies and mechanisms. From this analysis eight fundamental areas of WAS were identified: water rights, determination of water allotment, administrative systems, reservoir storage considerations, system reliability, multiple uses, instream flow requirements, and drought management. The systematic scrutiny of these eight areas at the international, interstate, and intrastate levels defined the conceptual framework for assessing WAS. The Texas experience with regard to its Water Availability Modeling system is also reviewed with particular emphasis on the application of the Water Rights Analysis Package (WRAP) model in supporting water allocation efforts. The Lower Rio Grande WAS was used as a case study to demonstrate how the principles presented in the conceptual framework can be used to assess water allocation issues and identify alternative strategies. Three WRAP simulation studies utilizing several components of the conceptual framework were performed in order to assess the Lower Rio Grande WAS. The simulations focused on three of the major water allocation issues of the Texas Rio Grande: reallocation among uses, instream flow requirements, and drought management. The simulations showed several deficiencies in the Lower Rio Grande WAS, particularly regarding the size of the domestic-municipal-industrial (DMI) reserve and its effect on the reliability of other uses. The simulation results suggest that water from the DMI can be liberated to be used by irrigators and to support environmental flows without affecting the reliability to municipal users. Several strategies were proposed that can potentially improve the overall efficiency of the system. Nonetheless, implementing new strategies and water allocation policies in the Lower Rio Grande WAS would require considerable changes in regulation policies.Item Understanding and Predicting Changes in Precipitation and Water Availability Under the Influence of Large-Scale Circulation Patterns: Rio Grande and Texas(2012-12-11) Khedun, Chundun 1977-Large-scale circulation patterns have a significant modulating influence on local hydro-meteorological variables, and consequently on water availability. An understanding of the influence of these patterns on the hydrological cycle, and the ability to timely predict their impacts, is crucial for water resources planning and management. This dissertation focusses on the influence of two major large-scale circulation patterns, the El Ni?o Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO), on the Rio Grande basin and the state of Texas, US. Both study areas are subject to a varying climate, and are extremely vulnerable to droughts, which can have devastating socio-economic impacts. The strength and spatial correlation structure of the climate indices on gauged precipitation was first established. Precipitation is not linearly related to water availability; therefore a land surface model (LSM), with land use land cover constant, was used to create naturalized flow, as it incorporates all necessary hydro-meteorological factors. As not all ENSO events are created equal, the influence of individual El Ni?o and La Ni?a events, classified using four different metrics, on water availability was examined. A general increase (decrease) in runoff during El Ni?os (La Ni?as) was noted, but some individual events actually caused a decrease (increase) in water availability. Long duration El Ni?os have more influence on water availability than short duration high intensity events. Positive PDO enhances the effect of El Ni?o, and dampens the negative effect of La Ni?a, but when it is in its neutral or transition phase, La Ni?a tends to dominate climatic conditions and reduce water availability. LSM derived runoffs were converted into 3-month Standardized Runoff Indices (SRI 3) from which water deficit durations and severities were extracted. Conditional probability models of duration and severity were developed and compared with that based on observed precipitations. It was found that model derived information can be used in regions having limited ground observation data, or can be used in tandem with observation driven conditional probabilities for more efficient water resources planning and management. Finally a multidimensional model was developed, using copulas, to predict precipitation based on the phase of ENSO and PDO. A bivariate model, with ENSO and precipitation, was compared to a trivariate model, which incorporates PDO, and it was found that information on the state of PDO is important for efficient precipitation predictions.