Browsing by Subject "Rivers"
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Item American Eel in Texas – what we do, don’t, and need to, know(2016-01-22) Hendrickson, Dean A.; Cohen, Adam E.; Labay, Ben; Garrett, Gary P.; Casarez, Melissa; Martin, F. DouglasAmerican Eel is undoubtedly one of the most studied freshwater fishes of North America. Many recent discoveries have added new insights that re-write important aspects of the “text book” knowledge of the species’ complex life history in ways that could have significant impacts on management. Despite all of this new information, debate about the species’ conservation status continues, and new threats, such as continued habitat loss and major clandestine fisheries driven by extremely high value in the global market, have further complicated management. Though USFWS recently decided that the species does not merit listing as “Endangered,” in 2012 Canada changed that country’s assessment of the species’ status from “Special Concern” (since 2006) to “Threatened” and IUCN upped its classification in 2013 to “Endangered.” Ontario has considered it “Endangered” since 2007. All U.S. Atlantic states vowed to work together to produce, in 1999, the American Eel Benchmark Stock Assessment, which mandated each state conduct standardized monitoring of recruitment and later, mandatory catch and effort monitoring. Given all that activity and data generation, it is remarkable that still so little is known about the populations of the Gulf of Mexico (GOM) and its tributary rivers that making any management decisions in that large, neglected part of the species’ range is virtually impossible. The Fishes of Texas Project team has been collating and improving the limited and scattered data on occurrences of the species in the region and concludes it important to promote a broad scale (Gulf of Mexico) collaborative community effort to acquire and share data and carefully curated specimens and, hopefully, develop a GOM-wide collaborative research and management plan like that implemented by Atlantic states. Here we’ll review the literature and state of knowledge about the species in Texas and GOM, and suggest ways to begin work toward such an effort.Item Assessing Historical Fish Community Composition Using Surveys, Historical Collection Data, and Species Distribution Models(Public Library of Science, 2011-09-22) Labay, Ben J.; Cohen, Adam E.; Sissel, Blake; Hendrickson, Dean A.; Martin, F. Douglas; Sarkar, SahotraAccurate establishment of baseline conditions is critical to successful management and habitat restoration. We demonstrate the ability to robustly estimate historical fish community composition and assess the current status of the urbanized Barton Creek watershed in central Texas, U.S.A. Fish species were surveyed in 2008 and the resulting data compared to three sources of fish occurrence information: (i) historical records from a museum specimen database and literature searches; (ii) a nearly identical survey conducted 15 years earlier; and (iii) a modeled historical community constructed with species distribution models (SDMs). This holistic approach, and especially the application of SDMs, allowed us to discover that the fish community in Barton Creek was more diverse than the historical data and survey methods alone indicated. Sixteen native species with high modeled probability of occurrence within the watershed were not found in the 2008 survey, seven of these were not found in either survey or in any of the historical collection records. Our approach allowed us to more rigorously establish the true baseline for the pre-development fish fauna and then to more accurately assess trends and develop hypotheses regarding factors driving current fish community composition to better inform management decisions and future restoration efforts. Smaller, urbanized freshwater systems, like Barton Creek, typically have a relatively poor historical biodiversity inventory coupled with long histories of alteration, and thus there is a propensity for land managers and researchers to apply inaccurate baseline standards. Our methods provide a way around that limitation by using SDMs derived from larger and richer biodiversity databases of a broader geographic scope. Broadly applied, we propose that this technique has potential to overcome limitations of popular bioassessment metrics (e.g., IBI) to become a versatile and robust management tool for determining status of freshwater biotic communities.Item Assessing impacts of hydroelectric dams in the Amazon Fluvial Basin(2015-05) Wight, Charles Edward; Latrubesse, Edgardo; Arima, EugenioThe amount of water the Amazon River delivers to the Atlantic Ocean every day is enough to supply New York City's fresh water needs for 9 years. This is soon to change with the race to choke the Amazon Basin with large hydrologic dams. Although studies investigating single dams can provide great analysis on a couple key issues, they often fail to consider these effects on the systems entirety. Without linking the physical and social components, one fails to fully understand the impacts of hydroelectric dams and therefore the vulnerability of the basin. The focus of this study is based on three forms of investigation: 1. a comprehensive literature review including scholarship on hydroelectric dams, basis characteristics, protected areas, and political characteristics within the respective countries; 2. data procurement of the physical geography of 20 sub-basins, 1,100 tributaries, and land use-land change (LULC) data; and together 3. the creation of a multivariable database integrated with GIS (geographic information systems) in order to better interpret human/nature complexities. Combined, this database will be a powerful tool to assess vulnerability and risks associated with individual dams sites within a larger system. In addition, this database can be adjusted in the future such that when impacts of planned dams are actualized they can be recorded, and based of shared attributes of other dams in the database, this information can be correlated to make better predictions of new environmental and social impacts.Item Dissolved organic matter in major rivers across the Pan-Arctic from remote sensing(2016-05) Griffin, Claire Genevieve; McClelland, James W.; Frey, Karen E; Gardner, Wayne S; Liu, Zhanfei; Shank, Gerald CClimate-driven changes in Arctic hydrology and biogeochemistry are impacting transport of water and water-borne material from land to ocean. This includes massive amounts of organic matter that are mobilized and exported from the pan-Arctic watershed via rivers each year. Dissolved organic matter (DOM), an important part of the Arctic carbon cycle, has received growing attention in recent years, yet long-term studies of riverine biogeochemistry remain rare in these remote and logistically challenging regions. Remote sensing of chromophoric dissolved organic matter (CDOM, the portion of the DOM pool that absorbs light), provides a unique opportunity to investigate variations in DOM in major Arctic rivers over multiple decades. CDOM is a useful proxy for dissolved organic carbon (DOC) and is essential to photochemical processes in surface waters. This dissertation presents the development and application of remote sensing regression models across six major Arctic rivers: the Kolyma, Lena, Mackenzie, Ob', Yenisey and Yukon. Frozen, archival samples of CDOM were used to develop calibration data for remote sensing regressions. Remote sensing methods estimated CDOM with R² of 85% across all rivers, although individual rivers varied in their predictability in association with sediment loading and hydrology. As with previous studies of Arctic systems, concentrations and export of CDOM and DOC were highest during spring freshet in most of these rivers. Interannual variability in DOM export may be linked to the Arctic Oscillation. Within the Mackenzie, Ob', and Yenisey rivers, observations of DOM concentration and export were extended back to the 1980s, the first known empirical records of this length for Arctic rivers that span both continents. Although no pan-Arctic trends in CDOM export were detected, there is some evidence of long-term changes in riverine DOM. For example, discharge-specific CDOM concentrations decreased in the Yenisey River and increased in the Ob' River. Additionally, CDOM concentrations increased over the past ~30 years within the Mackenzie River. This dissertation also includes results from experiments used to quantify the effects of cryopreservation on CDOM analyses, and potential approaches for ameliorating freezing effects. These experiments showed that freezing for preservation introduces some error into CDOM measurements, although these effects vary between river systems. Sonication may improve CDOM measurements in some river systems, but the effects of both cryopreservation and sonication should be quantified on a case-by-case basis. Overall, this dissertation work demonstrates that 1) remote sensing of CDOM is a viable tool for tracking fluvial DOM in the major Arctic rivers, 2) only the Mackenzie River showed significant increases in CDOM concentration from the 1980s to present and 3) long-term changes in discharge-specific CDOM concentrations have occurred in the Yenisey and Ob' rivers. These long-term trends cannot be definitively linked to climate change, but may be related to effects of warming on permafrost, hydrology, and biogeochemistry within in Arctic watersheds with consequences for carbon cycling on both regional and global scales.Item Evaluating organic compound sorption to several materials to assess their potential as amendments to improve in-situ capping of contaminated sediments(2011-05) Dunlap, Patrick John; Reible, Danny D.; Liljestrand, HowardContaminated sediments represent a common environmental problem because they can sequester large quantities of contaminants which can remain long after the source of pollution has been removed. From the sediment these hazardous compounds are released into the sediment porewater where it can partition into organisms in the sediment and bioaccumulate up the food web; leading to an ecological and human health concern. The objective of this work is to investigate an emerging option in contaminated sediment remediation; specifically an option for in-situ treatment known as active capping. Conventional capping uses clean sediment or sands to separate contaminated sediment from overlying water and biota. Active capping is the use of a sorptive amendment to such a cap to improve its effectiveness. This work focuses on granular materials as direct amendments to conventional caps including; granular activated carbon (GAC), iron/palladium amended GAC, alumina pillared clay, rice husk char, and organically modified clays. All materials were investigated in batch sorption tests of benzene, chlorobenzene, and naphthalene in DI water. Additionally porewaters from three sites were extruded and the concentrations of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) were measured. At Manistique Harbor and Ottawa River PCBs were identified as the primary contaminant of concern while PAHs were the contaminant of concern at the Grand Calumet River. At these sites a solvent extraction method was used to analyze the sediment concentrations of the contaminants of concern. From the former batch tests activated carbon and a commercially available organoclay were chosen for further investigation. This includes PAHs in batch sorption tests using extruded sediment porewater to investigate matrix effects, and PCB sorption in distilled water.Item Influence of the composition and character of dissolved organic matter (DOM) on the removal of mercury from surface water in metal based-coagulation systems(2019-02-14) Diaz Arriaga, Farith Adilson; Lawler, Desmond F.; Katz, Lynn Ellen; Liljestrand , Howard M; Werth, Charles J; Eaton, David JAccording to The United Nations Environment Programme (UNEP), mercury pollution still represents a major threat to human health and the environment, mainly in regions where metallic mercury (Hg⁰) is used to extract gold or where coal burning increases the emissions of mercury in the atmosphere. In the particular case of the metallic mercury used in artisanal and small-scale gold mining (ASGM), there is substantial evidence about the direct impact of mercury on human health, mainly due to the inhalation of vapor mercury and the intake of fish with high levels of methylmercury (MeHg). Once metallic mercury is dumped into rivers and soils, this pollutant can react with sulfur reduced ligands in sediments or can be converted to Hg(II) and it will interact with dissolved organic matter (DOM) in aquatic environments. Such interaction will control the fate of this pollutant in water, as well as its toxicity and mobility downstream rivers. Accordingly, these Hg-DOM interactions will also control the ability to remove this pollutant during water treatment. This research shows that out, of the different functional groups present in dissolved organic matter, reduced sulfur ligands (S [subscript red] ) play a key role in removing mercury from waters with low Hg/DOM ratio. This trend is particularly evident in waters with low in aromatic content (which translate to low DOC removal) and high concentrations of S [subscript red] ligands. At much higher mercury concentrations, once the S [subscript red] ligands are saturated with mercury, the carboxylic ligands control the removal of mercury from solution. Under these conditions, the removal of mercury is proportional to the removal of carbon (∼1:1 ratio) as all the Hg(II) ions are bound to the all the functional groups available for Hg(II) complexation, even binding weak ligands such as carboxylic acids. In all cases, it is necessary to provide optimal coagulation conditions (pH and coagulant dose) to effectively remove dissolved organic matter, and therefore associated mercury, from solution.Item Movements of Diadromous Fish in Large Unregulated Tropical Rivers Inferred from Geochemical Tracers(Public Library of Science, 2011-04-06) Walther, Benjamin D.; Dempster, Tim; Letnic, Mike; McCulloch, Malcolm T.Patterns of migration and habitat use in diadromous fishes can be highly variable among individuals. Most investigations into diadromous movement patterns have been restricted to populations in regulated rivers, and little information exists for those in unregulated catchments. We quantified movements of migratory barramundi Lates calcarifer (Bloch) in two large unregulated rivers in northern Australia using both elemental (Sr/Ba) and isotope (87Sr/86Sr) ratios in aragonitic ear stones, or otoliths. Chemical life history profiles indicated significant individual variation in habitat use, particularly among chemically distinct freshwater habitats within a catchment. A global zoning algorithm was used to quantify distinct changes in chemical signatures across profiles. This algorithm identified between 2 and 6 distinct chemical habitats in individual profiles, indicating variable movement among habitats. Profiles of 87Sr/86Sr ratios were notably distinct among individuals, with highly radiogenic values recorded in some otoliths. This variation suggested that fish made full use of habitats across the entire catchment basin. Our results show that unrestricted movement among freshwater habitats is an important component of diadromous life histories for populations in unregulated systems.Item Review of the Geology of Texas(University of Texas at Austin, 1916-08-05) Udden, J.A.; Baker, C.L.; Bose, EmilItem Seasonal dynamics of organic matter and inorganic nitrogen in surface waters of Alaskan Arctic streams and rivers(2015-12) Khosh, Matthew Solomon; McClelland, James W.; Dunton, Kenneth H; Liu, Zhanfei; Shank, Gerald C; Townsend-Small, AmyClimate-linked changes in hydrology and biogeochemical processes within Arctic watersheds are likely already affecting fluvial export of waterborne materials, including organic matter (OM) and dissolved inorganic nitrogen (DIN). Our understanding of Arctic watershed OM and DIN export response to climate change is hampered by a lack of contemporary baselines, as well as a dearth of seasonally comprehensive studies. This work focuses on characterizing OM and DIN concentrations and sources in six streams/rivers on the North Slope of Alaska during the entirety of the hydrologic year (May through October) in 2009 and 2010. The highest OM concentrations occurred during spring snowmelt, with results indicating that terrestrial vegetation leachates are the major source of dissolved OM, while particulate OM originates from a degraded soil source. Over the hydrologic year, soils became a progressively increasing source of dissolved OM, while autochthonous production made up a sizeable proportion of particulate OM during base flow conditions. DIN concentrations were low throughout the spring and summer and increased markedly during the late summer and fall. Our findings suggest that penetration of water into thawed mineral soils, and a reduction in nitrogen assimilation relative to remineralization, may increase DIN export from Arctic watersheds during the late summer and fall. Although recent studies of Arctic rivers have emphasized the importance of the spring thaw period on OM export, our understanding of the mechanisms that control water chemistry observations during this time are still lacking. Experimental leaching results, from experiments conducted in 2014, suggest that aboveground plant biomass is a major source of dissolved OM in Arctic catchments during the spring, and that the timing of freezing and drying conditions during the fall may impact dissolved OM leaching dynamics on that same material the following snowmelt. Improved knowledge of OM and DIN temporal trends and the mechanisms that control seasonal concentrations is essential for understanding export dynamics of these water constituents in Arctic river systems. Perhaps more importantly, increased understanding of the seasonal controls on OM and DIN export in Arctic rivers is critical for predicting how these systems will respond under future climate change scenarios.Item Stratigraphic implications of the spatial and temporal variability in sediment transport in rivers, deltas and shelf margins(2010-05) Petter, Andrew Lucas, 1980-; Steel, R. J.; Mohrig, David; Fisher, William; Wood, Lesli; Olariu, CornelSediment delivery to a basin exerts a first-order control over sedimentation, and therefore study of sedimentary rocks can reveal information about the nature of sediment delivery in the past. This dissertation examines several aspects of this problem using experimental, outcrop, and subsurface data. Flume experiments were undertaken to test the combined effects of autogenic alluvial aggradation and forced regression on the development of fluviodeltaic stratigraphy. Alluvial aggradation occurred in response to steady relative sea-level fall, and eventually consumed the entire sediment budget as the river lengthened in response to forced regression. The Campanian Lower Castlegate Sandstone (Utah) was studied as a potential ancient analog resulting from similar autogenic behaviors as observed in the experiments. Extensive measurement of grain-size distributions and paleo-flow depths from outcrop were utilized to explore downstream changes in paleo-hydraulics of the ancient fluvial systems in the Lower Castlegate in response to extensive alluvial aggradation and consequent loss of sediment from transport. An interesting finding was the stratigraphic signature of backwater hydraulic conditions in the distal reaches of the Lower Castlegate paleo-rivers. Finally, a simple and novel inversion scheme was developed for estimating paleo-sediment flux from ancient shelf-margin successions. An advantage of the methodology is that it allows for both spatial and temporal reconstruction of paleo-sediment flux patterns. The inversion scheme was applied to shelf-margin successions in the Washakie-Sand Wash Basin of Wyoming, the New Jersey Atlantic margin, the North Slope of Alaska, and the Zambezi margin of East Africa using published subsurface datasets. The Neogene passive margins within the studied datasets were found to consistently deposit around one-third of their total sediment budget on the shelf-margin topset, and bypass two-thirds of their budget beyond the shelf edge. The implications of this finding on the flux of terrestrial-derived particulate organic carbon (POC) from rivers to the ocean were explored, and a long-term average flux of POC to deepwater storage was estimated. The sediment-flux inversion scheme was also applied to derive input parameters for stratigraphic modeling of the Ebro margin. The modeling results indicate that the autostratigraphic behavior of the margin may have been previously underestimated.Item Sustainable River Management on the US/Mexico Border: Recommendations for the Paso del Norte, PRP 202(LBJ School of Public Affairs, 2018) Schmandt, Jurgen; Stolp, ChandlerThe report examines emerging challenges to water supply in the Rio Grande, specifically in the river’s Paso del Norte sub-basin. Based on consultations with water stakeholders in New Mexico, Texas and Mexico we recommend ways for developing and implementing a plan for sustainable water management in the region. Our work contributes to an ongoing international project on sustainable management of engineered rivers in arid lands (SERIDAS).Item The uncertain future of global freshwater resources(2015-05) Ferré, Megan Dunleavy; Johnson, Joel P.; Mohrig, David; Pierce, SuzanneProjections regarding the future of conditions on Earth vary widely. Climate change, both human-induced and naturally-forced, is expected to have many far-reaching implications, including altering current global weather patterns and terrestrial freshwater supply. Already, terrestrial water fluxes have been affected by human demand and interventions. Examples of human-induced impacts include dam and reservoir building, water withdrawals from ground and surface water for agricultural, industrial, and municipal use, as well as environmental sanitation impacts. Since the 1970's, concurrent with rising global mean temperature, freshwater discharge from rivers to the world's oceans has been decreasing. In the United States, the Southwest (from the headwaters of the westernmost Colorado River to the Mexican border, encompassing California, Nevada, Utah, and Colorado) has experienced three extreme drought years since the start of the 21st century. Projections indicate that precipitation over the lower mid-latitude continental regions, including the southwestern United States, will continue to decrease as a result of continuing greenhouse gas emissions and increasing global mean temperature. Colorado River flow reached the ocean in mid-2014 as part of a restorative experiment agreed to by the United States and Mexico, but had not previously reached the ocean since 1998. Rivers in Australia, Africa, and Asia are experiencing the same phenomena, with human extraction impairing the river’s natural ability to meet the sea. There are political and technological techniques that could mediate regional decreases in freshwater supply. In particular, large changes in agricultural use are necessary to compensate for oncoming climate shifts and to ensure that the worldwide population has access to enough water for survival.