Stream Temperature as a Tracer of Interactions Amongst Hydrological Processes, Atmospheric Exchange, and Human Activity

The water temperature of global river networks (also referred to as ‘stream temperature’ or ‘river temperature’) is an influential control on numerous aspects of water quality and riverine ecology, impacting rates of solute processing, dissolved oxygen content, and habitat viability for aquatic ecosystems. River water temperatures arise from the complex interplay of hydrological processes, atmospheric forcings, anthropogenic disturbances, making river thermal regimes challenging to understand and predict at the reach, regional, and global scale. In the absence of widespread water temperature observations, models are commonly used to simulate aspects of water temperature variability by integrating the influence of basin-specific controls and heat fluxes into and out of river systems. In addition to their role as a critical water quality parameter, water temperatures can also be leveraged as a practical tool to probe hydrologic interactions between stream channels and the underlying subsurface. This dissertation explores three diverse applications of water temperature modeling: 1) tracing groundwater-surface water interactions around stream restoration structures using water temperature observations; 2) leveraging machine learning to infer continental-scale drivers of river thermal behavior; and 3) predicting water temperatures at high spatial and temporal resolutions with coupled temperature-hydrologic models.The first chapter of this dissertation uses water temperature heat tracing methods, in combination with other field observations, to characterize hyporheic exchange induced by beaver dam analogue restoration structures. Beaver dam analogues are process-based restoration structures designed to mimic the effects of natural beaver dams and stabilize degraded and incised river reaches. Despite their frequent application, the influence of these structures on groundwater-surface water hydrology remains unclear. Vertical heat tracing, measurements of hydraulic head, and analyses of porewater biogeochemistry were used to investigate hydrologic behavior associated with three beaver dam analogues installed on Red Canyon Creek, WY, USA. These analyses demonstrated that while the restoration structures had a negligible effect on overall stream chemistry, beaver dam analogues were capable of producing heterogeneous and localized regions of hyporheic exchange. These results highlight the effectiveness of using water temperatures to trace vertical heat flow and related groundwater-surface water interactions in tandem with other field-based observations. Given the demonstrated impacts of water temperatures on river water quality, it is critical to better understand how the dominant controls on river thermal regimes vary in time and across broad spatial scales in order to design more effective watershed management strategies. Machine learning models are well suited to this objective, as they can generate accurate predictions of environmental processes while revealing key interactions between variables in large datasets. In the second chapter of this dissertation, a suite of random forest models was used to predict metrics of river temperature variability across the conterminous US using watershed characteristics extracted from a publicly-available dataset. Variable importance metrics were then interpreted to infer the underlying controls on river temperatures. Regional climate forcings tended to most closely control river temperature magnitude, though those forcings were mediated by the influence of hydrological processes, watershed characteristics, and anthropogenic disturbances. Results from the random forest models underscored the challenge in predicting aspects of water temperature variability at continental scales, particularly when river thermal regimes are disrupted by dams and reservoirs. The presented machine learning approach to river temperature prediction illustrates how large environmental datasets can be leveraged to provide discerning insight into the drivers of hydrologic and thermal processes. To supplement predictions of water temperatures at point locations along the river network, deterministic energy balance models are often applied to provide spatially distributed and temporally continuous water temperature simulations. Deterministic water temperature models function by quantifying radiative, turbulent, and advective heat fluxes into and out of a river at the air-water and water-streambed interfaces. While such water temperature models are often applied within single catchments, many watershed management applications require high resolution predictions of temperatures at a broader spatial extent. The third chapter of this dissertation focuses on the development of a coupled hydrological-water temperature energy balance model in a single test basin with the potential for expansion to the full conterminous US. Using forcings and outputs from the National Water Model, a continental-scale hydrologic model implemented by NOAA and NCAR, several water temperature model configurations of increasing complexity were tested to evaluate tradeoffs between performance and computational efficiency. Modeling efforts demonstrated that the National Water Model can be effectively leveraged to provide high-quality predictions of hourly water temperatures throughout a river network, though critical challenges remain in expanding coupled water temperature models to continental scales

The impact of national culture upon the customer value hierarchy : a comparison between French and American consumers

The general objective of this dissertation is to investigate how culture impacts upon customer value. Specifically, by examining consumers\u27 cognitive means-end structures, propositions are developed in terms of how culture influences the perception and importance of the content and structure of the customer value hierarchy. The propositions are tested utilizing data from in-depth laddering interviews with a matched sample of 30 French consumers and 30 American consumers on the subject of wine consumption in a restaurant usage situation. The data are analyzed in two simultaneous stages: 1) a quantitative independent coding analysis of implication matrices and centrality statistics, and 2) a qualitative coding analysis of the meaning, valence, and linkages of customer value hierarchy dimensions. The findings indicate that culture does influence the content and structure of the customer value hierarchy. The data appear to provide empirical evidence that cultural value dimensions can be utilized to theoretically predict similarities and differences in customer value. Interestingly, the perception and importance of consumption consequences appear to be more sensitive to cultural differences than do the pereception and importance of product and service attributes and evoked end-states. Moreover, cultural values alone are not the only influence upon consumer perceptions. In addition to personal characteristics and use situation, other cultural factors are shown to be influential, most notably social norms. This research extends existing customer value theory and means-end theory by demonstrating that culture is intertwined throughout all of the levels of meanings that consumers construct for products and services rather than just at the end-state level, and by testing a priori propositions regarding the influence of culture. This research indicates that future conceptualizations of value should consider the inclusion of culture, in addition to person, product, and situation. Additional refinements may include the categorization of specific attribute, consequence, and end-state subtypes, the expansion of the situation to include occasion, the inclusion of valence into value dimension linkages, and application to the study of perception (i.e., meaning) and preference (i.e., importance). Finally, by identifying both cultural similarities and differences, this research provides partial support for the strategic concept of intermarket segmentation based upon customer value segments. Large-scale verification of these findings would further strengthen the conclusions. Future research should also focus upon factors that moderate the influence of culture upon customer value, along with possible antecedents and consequences for both consumers and marketers

Contaminants in Unionid Mussels from the Confluence of the Mississippi and Illinois Rivers

Unionid mussels were collected from three mussel beds near the confluence of the Mississippi and Illinois rivers in 2003 to evaluate concentrations of selected elements and organic compounds in three abundant species and to preliminarily investigate the relative contribution of these waterways to observed contaminant burdens. Copper (Cu), selenium (Se), and zinc (Zn) concentrations were higher and lead (Pb) concentrations were lower in Amblema plicata collected downstream of the confluence than in those collected upstream. Mean concentrations of nickel (Ni), total mercury (Hg), methylmercury (MeHg), Pb, and Zn varied by species. Concentrations of cadmium (Cd) decreased with age in A. plicata from two of three sites. Tissue concentrations of some elements, e.g., arsenic (As), Cd, Cu, Pb, Se, and Zn, were similar to or higher than those previously reported for unionid mussels from areas of contaminated sediment. Concentrations of Cd, Cu, and Zn in A. plicata were comparable to those collected from the Mississippi River approximately 450 and 900 km upstream from our study sites (Naimo et al. 1992). Although total Hg concentrations we observed were an order of magnitude lower than in that study, MeHg concentrations were above those associated with reductions in soft tissue mass in a study of Elliptio complanata (Salazar et al. 1995). A number of polychlorinated biphenyl (PCB) congeners were detected in A. plicata tissues, with 85% of detections occurring in mussels from downstream of the confluence. Concentrations of individual PCB congeners were ???33 ng/g ww and the maximum summed PCB congener concentration was 100.2 ng/g ww. Although few persistent pesticides were detected, -hexachlorocyclohexane (HCH) was detected in each of the species collected from below the confluence of the two rivers, and in A. plicata collected above it on both the Mississippi and Illinois rivers, at a maximum concentration of 103.5 ng/g ww. Aldrin, ??-HCH and dichlorodiphenyltrichloroethane (DDT) were detected in few of the specimens collected. The findings of this preliminary investigation suggest that unionid mussels from near the confluence of the Mississippi and Illinois rivers may be at risk of negative health effects of elevated exposure to certain environmental contaminants. Studies examining the health and productivity of unionid mussels from this area appear warranted.published or submitted for publicationis peer reviewe

Unattended Underground Energy Harvesting Sensor

The team designed an underground energy harvesting sensor that utilizes the ambient energy from its surroundings to provide low power telecommunications to a remote host. The scope of this project is to analyze the feasibility of such system and explore the capabilities of available energy harvesting techniques that utilize the environment, feasibility of operation, and creating a design. Some of the most common methods that have been proven to function on certain environments are thermoelectric and solar energy. Thermoelectricity uses a temperature gradient and solar uses the energy of the sun. To provide a remote vibration signal an accelerometer was suggested. Based on the requirements the Monnit wireless accelerometer was selected. The wireless accelerometer is a (1.775x1.040x0.785”) high frequency device that collects readings of motion vibrations from nearby objects from underground requiring at max 0.126W of power at 3.6V that is countered by 2-4 (1.580x1.760x0.139”) RC12-8-01LS thermoelectric coolers. These coolers utilize the temperature difference between the underground earth and the surface to generate 0.156W of power at 0.5V to continuously recharge a lithium ion battery. The accelerometer takes the readings and sends them to the Gateway aboveground. The (5.004x3.800x1.510”) Monnit 3G International gateway takes the readings from the sensor and sends it to the host through cellular data using 13.75W of power at 5.5V countered by one 6W (13.100x14.000x0.500”) solar panal to continuously recharge the lithium ion battery. A max 36W 12V (5.710x3.350x1.100”) lithium ion battery is used because it surpasses all competitors in rechargeability, lifetime, and strength. Upon completion the concept of energy generation for low power telecommunications is feasible.https://scholarscompass.vcu.edu/capstone/1207/thumbnail.jp

Characterization of LOCOS and oxidized mesa isolation in deep-sub micrometer SOI NMOS processes

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (leaves 76-77).by Jeffrey Wade Thomas.M.S