Browsing by Subject "Rivers"
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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 Long-term forward hydrologic fluvial system evolution model(Texas Tech University, 1997-05) Vining, Mark RichardThis work presents a computer model of river sediment transport and the morphologic evolution of the river system, on the scale of thousands to millions of years, with the influence of geologic processes. The computer program runs under Windows '95 or 3.x. Code is written in Borland C++ 5.01. Data input is from eight editable files. The code, sample data, and user instructions are provided. The model is a 1-D finite-difference scheme of longterm average flow conditions. The simulation is discretized into time steps, length cells, sediment grain size classes, and fluvial environments within each cell. The cell landscape is composed of three fluvial environments (channel, alluvial ridge, and floodplain) and the watershed drainage area. Time steps are divided into four steadystate domains which characterize short-term variations in discharge. A time dilation procedure characterizes the varying shape of discharge event hydrographs downstream.Item 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 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.