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Timoner, Amer Xisca. "Stream biofilm responses to flow intermittency". Doctoral thesis, Universitat de Girona, 2014. http://hdl.handle.net/10803/283569.
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Streams experiencing a recurrent non-flow phase (i.e., flow intermittency) are characteristic of world regions with arid and semi-arid climates, where Mediterranean regions are part of. During non-flow streambed sediments, and consequently, microorganisms inhabiting these sediments are exposed to desiccation. These microorganisms, assembled in biofilms, lead a substantial part of the ecosystem processes. They recycle the carbon materials, intervene in the nutrient cycles and are on the base of the food web, fueling energy to the higher trophic levels. The aim of this tesis is to understand how biofilms respond to flow intermittency in order to unravel the consequences of the increasing spatial and temporal extent of flow intermittency, as a consequence of the global change, on the biogeochemical cycles and on the ecosystem functions in temporary streams. Structural and functional biofilm responses were analyzed at the cellular level (algae and bacteria), as well as at the whole biofilm responses (autotrophic vs heterotrophic processes) in two different field studiesEls rius que experimenten una fase sense cabal (intermitència fluvial) són característics de les regions del món amb climes àrids i semi-àrids, com ara les regions de la Mediterrànies. Durant la fase seca es produeix la dessecació de la llera del riu i conseqüentment els microorganismes que creixen sobre aquests sediments estan exposats a la dessecació. El conjunt d’aquests microorganismes es coneix com a biofilm, el qual juga un paper clau en el processament de la matèria orgànica i en els cicles del carboni i nutrients, A més són a la base de la xarxa tròfica aportant energia als nivells tròfics superiors. L'objectiu principal d'aquesta tesi és entendre el funcionament del biofilm quan es dona la fase seca, pas clau per entendre i predir les implicacions que tenen els períodes creixents sense cabal en els cicles biogeoquímics i en el funcionament de l’ecosistema. Les respostes estructurals i funcionals del biofilm des d’un punt de vista cel·lular (algues i bacteris), així com també en el conjunt del biofilm (processos autotròfics i heterotròfics) es van investigar mitjançant dos estudis de camp
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Edmunds, Matthew. "Stream surface seeding for flow visualisation". Thesis, Swansea University, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678585.
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Mitchem, Charles E. Jr. "A Comparative Study of Stream-Gaging Methods Employed in Nonpoint Source Pollution Studies in Small Streams". Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/9761.
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The U.S. Geological Survey started measuring stream flow in 1888 as part of a public land irrigation study. The demand for accurate stream flow measurement has increased with the rising concern about nonpoint source (NPS) pollution. NPS pollution studies, such as TMDL development, often involve quantification of flow in small first and second order streams. This application of technology intended for use in larger streams presents special problems that must be addressed by the user.
The goal of this study was to conduct a comparative analysis of the current technologies used to measure flow in small streams with respect to accuracy and cost. The analyses involved field investigations, laboratory experiments, and a cost analysis. The specific study objectives were: 1) Compare the accuracy of various methods for estimating stream discharge in small first and second order streams, 2) Compare the accuracy of various methods for estimating stream discharge in a controlled laboratory environment, and 3) Evaluate the costs associated with installation, operation, and maintenance of each of the systems investigated.
Ten stream-gaging methods were evaluated for their field performance, laboratory performance, and costs. Analysis of the field investigation data indicated that the Marsh McBirney current meter and the One-orange method were the most accurate among the methods studied. The results of the laboratory experiments imply that the Starflow acoustic Doppler and Valeport BFM001 current meter performed best among the ten methods. The Starflow acoustic Doppler device also proved to be the most cost-effective method. Overall, the Marsh McBirney and Valeport BFM001 current meters exhibited the best performance for both field and laboratory situations among the methods evaluated.Master of Science
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Frost, Carwyn. "Flow direction effects on tidal stream turbines". Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/98955/.
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This thesis investigated the non-dimensional performance characteristics of a tidal stream turbine and how they varied in response to changes in flow direction. The problem was considered from an industrial perspective and used the commercial software package ANSYS CFX and a 1:20th scale experimental turbine. Initial considerations analysed the performance of the turbine in an ‘upstream’ or ‘downstream’ configuration relative to the turbines support structure. The conclusions resulting from this were that up to a point by increasing separation between an upstream turbine and its support structure the greater average nondimensional performance characteristics became. Also, more significantly, it was identified that this orientation and clearance reduced the blade stanchion interaction considerably relative to the downstream orientation. The study made justification for the inclusion of a yaw mechanism to rotate the turbine to face the flow for flood and ebb phases of the tide. In an operational environment this would be expected to enhance the life of the turbine’s blades, thrust bearings, and gearbox - which are known to be prone to fatigue failure, due to highly dynamic loads. The thesis continued to expand into the potential uses of a yaw mechanism to address flow misalignment experienced throughout the tidal cycle. In order to justify this, the non-dimensional performance characteristics of the same turbine were compared for a series of flow misalignment cases. The CFD analysis showed that increased flow misalignment in either the positive and negative direction had the effect of reducing turbine torque and power performance characteristics, and also significantly increases the out-ofplane bending moments. A distinction between the positive yaw angles and negative yaw angles was identified in the turbine’s performance. The negative flow misalignment showed more favourable performance changes than the positive flow misalignment, this was due to the turbines rotational direction. The subsequent recommendations to industry were included making use of the turbines rotational direction and yaw mechanism, to experience lower performance reductions in the case of flow misalignment. Experimental results from tow tank testing at CNR-INSEAN using the 0.5 m diameter turbine validated the nondimensional performance characteristics of the CFD results. It was identified that steady state CFD results did not capture the performance characteristics of flow misalignment cases as well as the transient CFD results. The experimental turbine captured temporal features identified in the CFD analysis. Recommendations to industry include the careful consideration of steady state CFD analysis in non-idealised flow conditions.
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Hofstede, Coen Matthijs. "Ice Stream Dynamics: A Transition between Sheet Flow and Shelf Flow". Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/HofstedeCM2008.pdf.
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Stokes, Christopher Richard. "The geomorphology of palaeo-ice streams : identification, characterisation and implications for ice stream functioning". Thesis, University of Sheffield, 2001. http://etheses.whiterose.ac.uk/14815/.
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Ice streams are the dominant drainage pathways of contemporary ice sheets and their location and behaviour are viewed as key controls on ice sheet stability. Identifying palaeo-ice streams is of paramount importance if we are to produce accurate reconstructions of former ice sheets and examine their critical role in the oceanclimate system. Many workers have invoked palaeo-ice streams from a variety of former ice sheets, despite a limited understanding of their glacial geomorphology. This thesis addresses the problem by predicting several diagnostic geomorphological criteria indicative of ice stream activity. These are developed objectively from the known characteristics of contemporary ice streams and can be summarised as: large flow-set dimensions (>20 km wide and >150 km long), highly convergent flow patterns, highly attenuated subglacial bedforms (length:width >10: 1), Boothia-type dispersal plumes, abrupt lateral margins «2 km), ice stream marginal moraines, evidence of pervasively deformed till, and submarine sediment accumulations (marine-terminating ice streams only). Collectively, the criteria are used to construct conceptual landsystems of palaeo-ice stream tracks. Using satellite imagery and aerial photography to map glacial geomorphology, identification of the criteria is used to validate the location of a previously hypothesised ice stream and identify a hitherto undetected palaeo-ice stream from the former Laurentide Ice Sheet. Implications for ice stream basal processes are explored and their ice sheet-wide significance is assessed. On Victoria Island (Arctic Canada) five of the geomorphological criteria are identified and the extent of the marine-based M'Clintock Channel Ice Stream is reconstructed at 720 km in length and 140 km in width. The ice stream (operating between 10,400 and 10,000 yr BP) was located within a broad topographic trough, but internal glaciological processes, rather than properties of the bed controlled the margin locations. It eroded into pre-existing unconsolidated sediments and left a spectacular pattern of subglacially-produced landforms, recording a snapshot view of the bed prior to ice stream shut-down. Sediment availability appears critical to its functioning (deformable bed?) and the debris flux of the ice stream is inferred to have been high. Frictional shut-down occurred once down-cutting through sediments reached hard bedrock close to the terminus. The presence of four of the geomorphological criteria are used to identify a terrestrial ice stream which drained the Keewatin Sector of the Laurentide Ice Sheet between ca. 10,000 and 8,500 yr BP. Its size is reconstructed at over 450 km in length and 140 km in width, and it left behind a subglacial bedform pattern consisting of highly attenuated drumlins (length:width ratios up to 48: 1) displaying exceptional parallel conformity. This represents an isochronous bedform pattern and variations in lineament elongation ratio are thought to be a useful proxy for ice velocity. Highest elongation ratios occur immediately downstream of a topographic step where the ice stream entered a sedimentary basin. It is inferred that the ice stream was triggered by climatic warming which altered the ice sheet configuration and the thermal state of the bed. A switch from cold to warm-based conditions probably triggered rapid basal sliding. The ice stream (and a tributary) shut down when it ran out of ice, causing widespread thinning of the ice sheet and subsequent deglaciation. These ice streams denote considerable ice sheet instability over both hard and soft (deformable) beds and emphasise the enormous effects that ice streams had in controlling the deglaciation of the Laurentide Ice Sheet.
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Whitby, Benjamin. "Control of an axial flow tidal stream turbine". Thesis, Cardiff University, 2013. http://orca.cf.ac.uk/56450/.
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Tidal stream turbines have the potential to generate electricity from a renewable source that is highly predictable and non-polluting. The United Kingdom’s geographical location means that it has one of the most significant wave and tidal resources in the world. The implications of controlling horizontal axial flow, variable speed tidal stream turbines for the purpose of optimising energy capture, regulating power and reducing mechanical loads has been investigated. The research was separated into two main areas: control of the turbine in below rated flow speeds where the objective was to maximise energy capture, and control of the turbine in high flow speeds where the aim was to regulate power, shed load and ensure the survivability of the turbine. A control strategy that maximises the power output of a tidal stream turbine in below rated flow speeds, by allowing the rotor speed to be varied, was implemented. The performance of the control strategy was assessed in simulation and then implemented on a hardware in the loop test rig. In both cases the controller performed well and was able to maximise power output from the turbine by varying the rotor speed to maintain the optimum tip speed ratio. Two control strategies for regulating the output power from a tidal stream turbine in high flow speeds were investigated and compared. The first strategy relies on adjusting the pitch angle of the rotor blades to regulate power and the second assumes fixed pitch rotor blades and relies on the stall characteristic of the blades to regulate power. Models of both the pitch and stall regulated turbines were developed and simulated using the commercially available software GH Tidal Bladed®. The control system design behind both strategies was developed in Matlab. Following control implementation a comparison of each model was carried out in terms of performance under turbulent flows, loading and energy yield. Following the comparison it was concluded that the performance of the pitch regulated tidal stream turbine was superior to that of the stall regulated turbine. The research also revealed that the dynamics of each turbine model are significantly different for above rated flow speed operation. This has implications on controller design and loading experienced by each tidal stream turbine.
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Chan, Wing-yin Julia. "River channelization and flow regulation in Hong Kong /". Hong Kong : University of Hong Kong, 2002. http://sunzi.lib.hku.hk/hkuto/record.jsp?B25438918.
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Raina, Rajeev. "Development of a cell-based stream flow routing model". Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/2219.
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This study presents the development of a cell-based routing model. The model developed is a two parameter hydrological routing model that uses a coarse resolution stream network to route runoff from each cell in the watershed to the outlet. The watershed is divided into a number of equal cells, which are approximated as cascade of linear reservoirs or tanks. Water is routed from a cell downstream, depending on the flow direction of the cell, using the cascade of tanks. The routing model consists of two phases, first is the overland flow routing, which is followed by the channel flow routing. In this study, the cell-to-cell stream flow routing model is applied to the Brazos River Basin to demonstrate the impact of the cascade of tanks on the flow over a simple linear reservoir method. This watershed was tested with a uniform runoff depth in absence of observed runoff data. A case study on Waller Creek in Austin, Texas with observed runoff depths and stream flow is used to demonstrate the calibration and validation of model parameters.
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Nauditt, Alexandra. "Understanding stream flow generation in sparsely monitored montane catchments". Thesis, University of Aberdeen, 2017. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=233935.
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Hwang, Yeonsang. "Impact of input uncertainty in ensemble stream flow generation". Diss., Connect to online resource, 2005. http://wwwlib.umi.com/dissertations/fullcit/3178345.
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Melander, Lars. "Integrating Visual Data Flow Programming with Data Stream Management". Doctoral thesis, Uppsala universitet, Datalogi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-286536.
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Data stream management and data flow programming have many things in common. In both cases one wants to transfer possibly infinite sequences of data items from one place to another, while performing transformations to the data. This Thesis focuses on the integration of a visual programming language with a data stream management system (DSMS) to support the construction, configuration, and visualization of data stream applications. In the approach, analyses of data streams are expressed as continuous queries (CQs) that emit data in real-time. The LabVIEW visual programming platform has been adapted to support easy specification of continuous visualization of CQ results. LabVIEW has been integrated with the DSMS SVALI through a stream-oriented client-server API. Query programming is declarative, and it is desirable to make the stream visualization declarative as well, in order to raise the abstraction level and make programming more intuitive. This has been achieved by adding a set of visual data flow components (VDFCs) to LabVIEW, based on the LabVIEW actor framework. With actor-based data flows, visualization of data stream output becomes more manageable, avoiding the procedural control structures used in conventional LabVIEW programming while still utilizing the comprehensive, built-in LabVIEW visualization tools. The VDFCs are part of the Visual Data stream Monitor (VisDM), which is a client-server based platform for handling real-time data stream applications and visualizing stream output. VDFCs are based on a data flow framework that is constructed from the actor framework, and are divided into producers, operators, consumers, and controls. They allow a user to set up the interface environment, customize the visualization, and convert the streaming data to a format suitable for visualization. Furthermore, it is shown how LabVIEW can be used to graphically define interfaces to data streams and dynamically load them in SVALI through a general wrapper handler. As an illustration, an interface has been defined in LabVIEW for accessing data streams from a digital 3D antenna. VisDM has successfully been tested in two real-world applications, one at Sandvik Coromant and one at the Ångström Laboratory, Uppsala University. For the first case, VisDM was deployed as a portable system to provide direct visualization of machining data streams. The data streams can differ in many ways as do the various visualization tasks. For the second case, data streams are homogenous, high-rate, and query operations are much more computation-demanding. For both applications, data is visualized in real-time, and VisDM is capable of sufficiently high update frequencies for processing and visualizing the streaming data without obstructions. The uniqueness of VisDM is the combination of a powerful and versatile DSMS with visually programmed and completely customizable visualization, while maintaining the complete extensibility of both.
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Ari, Venkata Ramana. "Value Stream Mapping of Information Flow in Infrastructure Projects". Cleveland State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=csu1282252085.
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Stone, Mark Charles. "Natural stream flow fields measurements and implications for periphyton /". Online access for everyone, 2005. http://www.dissertations.wsu.edu/Dissertations/Spring2005/m%5Fstone%5F042705.pdf.
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O'Donnell, Brynn Marie. "The Flow Regime of Function: Influence of flow changes on biogeochemical processes in streams". Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/101660.
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Streams are ecosystems organized by disturbance. One of the most frequent disturbances within a stream is elevated flow. Elevated flow can both stimulate ecosystem processes and impede them. Consequently, flow plays a critical role in shifting the dominant stream function between biological transformation and physical transportation of materials. To garner further insight into the complex interactions of stream function and flow, I assessed the influence of elevated flow and flow disturbances on stream metabolism. To do so, I analyzed five years of dissolved oxygen data from an urban- and agriculturallyinfluenced stream to estimate metabolism. Stream metabolism is estimated from the production (gross primary production; GPP) and consumption (ecosystem respiration; ER) of dissolved oxygen. With these data, I evaluated how low and elevated flows differentially impact water quality (e.g., turbidity, conductivity) and metabolism using segmented metabolism- and concentration- discharge analyses. I found that GPP declined at varying rates across discharge, and ER decreased at lower flows but became constant at higher flows. Net ecosystem production (NEP; = GPP - ER) reflected the divergence of GPP and ER and was unchanging at lower flows, but declined at higher discharge. These C-Q patterns can consequently influence or be influenced by changes in metabolism. I coupled metabolism-Q and C-Q trends to examine linked flow-induced changes to physicochemical parameters and metabolism. Parameters related to metabolism (e.g., turbidity and GPP, pH and NEP) frequently followed coupled trends. To investigate metabolic recovery dynamics (i.e., resistance and resilience) following flow disturbances, I analyzed metabolic responses to 15 isolated flow events and identified the antecedent conditions or disturbance characteristics that most contributed to recovery dynamics. ER was both more resistant and resilient than GPP. GPP took longer to recover (1 to >9 days, mean = 2.5) than ER (1 to 2 days, mean = 1.1). ER resistance was strongly correlated with the intensity of the flow event, whereas GPP was not, suggesting that GPP responds similarly to flow disturbances, regardless of the magnitude of flow event. Flow may be the most frequent disturbance experienced by streams. However, streams are exposed to a multitude of other disturbances; here I also highlight how anthropogenic alterations to streams – namely, burying a stream underground – can change biogeochemical function. This thesis proposes novel frameworks to explore the nexus of flow, anthropogenic disturbances, and stream function, and thereby to further our understanding of the complex relationship between streams and disturbances.Master of Science
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Welderufael, W. A., i Y. E. Woyessa. "Stream flow analysis and comparison of methods for base flow separation : case study of the Modder River basin in central South Africa". Interim : Interdisciplinary Journal, Vol 8, Issue 2: Central University of Technology Free State Bloemfontein, 2009. http://hdl.handle.net/11462/375.
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Published ArticleA stream flow at an outlet of a catchment can be entirely a base flow or direct flow or a combination of both. The base flow component of a stream is mainly contributed from the ground water storage which often is an open aquifer whereas the direct flow component is mainly the result of a direct response of a rainfall event. The Upper Modder river basin catchment is considered to be the origin of the Modder River which supplies water to Rustfontein Dam, situated at the outlet of the C52A with an area of 928 km2. Nine years of daily stream flow showed a continuous none zero discharge throughout the year. During the rainy season the discharge of the stream increases significantly. Thus, it is necessary to separate the direct and base flow of the stream in order to understand the important component that is more likely to be affected by different land use changes in a catchment. The Modder river daily mean flow at the inlet of Rustfontein dam (in Central South Africa) was analysed using four base flow separation methods, the Nathan & McMahon (N&M), the Chapman, Smakhtin & Watkins (S&W) method and the frequency duration analysis. All the methods gave higher percentage of the low flow component, except for the S&W method which underestimated it. The N&M filtering equation gave base flow components greater than 66% in 1999 and increased to 84% in 2007 while the Chapman equation revealed 65% and 74% in 1999 and 2007, respectively. Similarly, the frequency duration analysis gave 62% in 1999 and increased to 79% in 2007. The frequency duration analysis gave up to 13% lower percentage than the N&M (1990) filtering equation. The nine year base flow averages are 69%, 69% and 75% for frequency duration analysis, Chapman (1999) and N&M (1990) filtering equations, respectively. The result revealed that the Modder River is largely supplied by the ground water discharge. The result seemed to concur with the fact that for a semi-arid catchment such as the Modder river basin, with an average annual runoff coefficient of approximately 6%, the contribution of annual rainfall to direct runoff is very minimal.
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Baudrit, Daniel 1957. "FLOW MEASUREMENT USING A SENSING DEVICE NEAR THE LIP OF A GATE (CANALS, OPEN CHANNEL FLOW)". Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/275569.
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Baker, Narelle Paula Marie. "The influence of subglacial hydrology on the flow of West Antarctic ice streams". Thesis, University of Cambridge, 2012. https://www.repository.cam.ac.uk/handle/1810/242375.
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Subglacial hydrology is known to influence the flow of ice. However, difficulty in accessing the base of large ice sheets has made determining the interaction between ice streams, basal sediment and water difficult to discern. The aim of this thesis is to determine the influence of subglacial hydrology on the flow of the West Antarctic ice streams. This is achieved through development of a numerical flowline model, the Hydrology, Ice and Till (HIT) model. Ice thermodynamics are coupled to a till layer of Coulomb plastic rheology. The porosity of the till changes with basal melt and freeze and can be augmented by water transported through a subglacial conduit system. Water availability strongly affects ice flow, as till porosity influences the till failure strength and thereby the basal resistance of the ice. The model was developed in four stages and a number of sensitivity tests were performed. It was then applied to Kamb Ice Stream (Ice Stream C) and Whillians Ice Stream (Ice Stream B), West Antarctica. Results confirm that ice streams are capable of oscillating between fast and slow velocity states. Cycles are generated at the grounding line of an ice stream and the speed of the transition from slow to fast flow is governed by water availability. The period of oscillation of the cycles for the West Antarctic ice streams was found to be several hundred years, which is in line with observations of stagnation and reactivation of these ice streams. This shows that subglacial hydrology has a role in modulating the flow variability of ice streams and that rather large changes in the flow of the West Antarctic ice streams are likely to occur this century.
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Heinrich, Roland Adolf Eberhard. "Flat-plate leading edge receptivity to various free-stream disturbance structures". Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184860.
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The receptivity process by which two-dimensional, time-harmonic freestream disturbances generate instability waves in the incompressible Blasius boundary layer is investigated analytically. The importance of the leading edge region and the linear nature of the receptivity process are discussed, and Goldstein's (1983a, 1983b) theoretical framework for the leading edge receptivity problem is reviewed. His approach utilizes asymptotic matching of a region close to the leading edge, which is governed by the linearized unsteady boundary layer equation, with a region further downstream, which is described by an Orr-Sommerfeld type equation. The linearized unsteady boundary layer equation is solved numerically, using the slip velocity and pressure gradient obtained from the inviscid interaction of the freestream disturbance with the semi-infinite plate. A new method is developed to extract the receptivity coefficient from this numerical solution. The receptivity coefficient determines the amplitude of the instability wave--a quantity not available from classical stability theory. The freestream disturbances investigated are oblique plane acoustic waves, vortical gusts of various orientations convected downstream with freestream speed U(∞), and a Karman vortex street passing above the plate surface with speed U(p). In addition, the case of a semi-infinite plate in a channel of finite width subject to an upstream traveling acoustic wave on the upper plate surface is considered. For oblique acoustic waves, the dominant receptivity mechanism is related to scattering of the waves by the leading edge. In contrast, for vortical gusts the receptivity produced by leading edge scattering is very small. The boundary layer receptivity to a Karman vortex street is found to be a strong function of the speed ratio U(p)/U(∞). A pronounced influence of channel walls, which is related to the alternate cut-on of higher modes in the upstream and downstream channel halves, is found. A comparison of the present results with available experiments shows good qualitative and quantitative agreement.
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Hellum, Aren. "Intermittency and the viscous superlayer in a single stream shear layer". Diss., Connect to online resource - MSU authorized users, 2006.
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McParland, Daniel. "Empirical in-stream flow assessment tools for British Columbian channels". Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/45054.
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Empirical hydraulic distribution equations have been proposed as simple and inexpensive alternatives to traditional data-intensive flow assessment methodologies. Two proposed depth and three proposed velocity empirical equations were compared to measured hdraulic distributions for two channels in the Interior Region of British Columbia. Empirical velocity distributions adequately reproduced the measured velocity distribution for both channels. An empirical depth distribution was able to replicate measured depth distributions at a relatively undisturbed channel (Harris Creek) but were unable to predict the measured depth distribution following morphological change at a channel recently disturbed by forest fire (Fishtrap Creek). Furthermore, the empirical distributions were compared to modelled depth and velocity distributions produced by a 2-dimensional hydrodynamic model (River2D). The empirical distributions provided reasonable representation of the hydraulic distributions for flows < 3 m³ s-¹. At flows approaching bankfull the empirical methods, in particular the velocity equations, were unable to adequately reproduce the distributions produced in River2D. Additionally, a joint frequency depth-velocity distribution was paired with habitat suitability indices to quantify available habitat across a range of flows at Harris Creek using reach average hydraulic conditions generated by River2D. The statistical habitat model produced similar habitat values to River2D at low flows and was able to recreate the general shape and trends of the habitat indices. As well, a proposed at-a-station hydraulic geometry simulator was used alongside a channel regime model to approximate reach average channel conditions at Harris Creek. The proposed hydraulic simulator was able to accurately predict reach average depth (mean error of 1.06 %) and velocity (4.47 %) for discharges ranging from daily low flow to bankfull flow. The hydraulic simulator was coupled with the statistical habitat model to generate hydraulic distributions and subsequently habitat indices for the modelled discharges. The incorporation of the regime models allows users to examine the influence of variable flow regimes and riparian vegetation (inherent of a changing climate) on available aquatic habitat. The proposed aquatic habitat model provides practitioners with a low-input, user-friendly flow assessment tool that can be used for preliminary habitat assessments and basin-wide habitat studies in British Columbia.
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Burke, Nicholas Allan. "Travel time and flow characteristics of a small stream system". Thesis, Heriot-Watt University, 2002. http://hdl.handle.net/10399/426.
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Radspinner, Robert Ryan. "Development of Design Guidelines for In-Stream Flow Control Structures". Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/32334.
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The use of in-stream flow control structures for channel stabilization has become increasingly popular due to its potential cost-effectiveness and ecological benefits. These structures help to protect the bank from erosion and lateral migration. However, a large number of these projects fail due to inadequate design guidelines. This study aims to create authoritative design guidelines which are based on hydraulic and physical criteria attributed to the channel reach. In this report, some of the most common types of in-stream structures have been reviewed and results from a practitioner experience survey have been analyzed. This research has allowed for the selection of the most promising structures which will be studied later in the project.Master of Science
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Imam, Bisher 1960. "Evaluation of disaggregation model in arid land stream flow generation". Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277033.
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A Disaggregation model was tested for arid land stream flow generating. The test was performed on data from Black River, near Fort Apache, Arizona. The model was tested in terms of preserving the relevant historical statistics on both monthly and daily levels, the monthly time series were disaggregated to a random observation of their daily components and the daily components were then reaggregated to yield monthly values. A computer model (DSGN) was developed to perform the model implementation. The model was written and executed on the Macintosh plus personal computer Data from two months were studied; the October data represented the low flow season, while the April data represented the high flow season. Twenty five years of data for each month was used. The generated data for the two months was compared with the historical data.
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Niu, Qian. "An empirical study of environmental flow determination in Hong Kong streams". Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B43224118.
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Horton, Nial. "Influence of a turbulent stream flow on the subsurface flow through a regular porous matrix". Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 2008. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=25938.
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Henry, Janell Christine. "Flow estimation for stream restoration and wetland projects in ungaged watersheds using continuous simulation modeling". Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/22021.
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More than a billion dollars are spent annually on stream restoration in the United States (Bernhardt et al., 2005), but the science remains immature. A promising technique for estimating a single or range of design discharges is the generalization of a parsimonious conceptual continuous simulation model. In this study the Probability Distributed Model (PDM), was generalized for the Maryland and Virginia Piedmont. Two hundred and sixty years of daily average flow data from fifteen watersheds were used to calibrate PDM. Because the application of the study is to stream restoration, the model was calibrated to discharges greater than two times baseflow and less than flows with a return period of ten years. The hydrologic calibration parameters were related to watershed characteristics through regression analysis, and these equations were used to calculate regional model parameters based on watershed characteristics for a single "ungaged" independent evaluation watershed in the region. Simulated flow was compared to observed flow; the model simulated discharges of lower return periods moderately well (e.g., within 13% of observed for a flow with a five year return period). These results indicate this technique may be useful for stream restoration and wetland design.Master of Science
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Kakouei, Karan [Verfasser]. "Predicting potential ecological effects of flow alterations using quantitative flow preferences of stream macroinvertebrates / Karan Kakouei". Berlin : Freie Universität Berlin, 2018. http://d-nb.info/117663450X/34.
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Ngan, Patricia. "Kalman filter and its application to flow forecasting". Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25948.
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The Kalman Filter has been applied to many fields of hydrology, particularly in the area of flood forecasting. This recursive estimation technique is based on a state-space approach which combines model description of a process with data information, and accounts for uncertainties in a hydrologic system. This thesis deals with applications of the Kalman Filter to ARMAX models in the context of streamflow prediction. Implementation of the Kalman Filter requires specification of the noise covariances (Q, R) and initial conditions of the state vector (x₀, P₀). Difficulties arise in streamflow applications because these quantities are often not known.
Forecasting performance of the Kalman Filter is examined using synthetic flow data, generated with chosen values for the initial state vector and the noise covariances. An ARMAX model is cast into state-space form with the coefficients as the state vector. Sensitivity of the flow forecasts to specification of x₀, P₀, Q, R, (which may be different from the generation values) is examined. The filter's forecasting performance is mainly affected by the combined specification of Q and R. When both noise covariances are unknown, they should be specified relatively large in order to achieve a reasonable forecasting performance. Specififying Q too small and R too large should be avoided as it results in poor flow forecasts. The filter's performance is also examined using actual flow data from a large river, whose behavior changes slowly with time. Three simple ARMAX models are used for this investigation. Although there are different ways of writing the ARMAX model in state-space form, it is found that the best forecasting scheme is to model the ARMAX coefficients as the state vector. Under this formulation, the Kalman Filter is used to give recursive estimates of the coefficients. Hence flow predictions can be revised at each time step with the latest state estimate. This formulation also has the feature that initial values of the ARMAX coefficients need not be known accurately.
The noise variances of each of the three models are estimated by the method of maximum likelihood, whereby the likelihood function is evaluated in terms of the innovations. Analyses of flow data for the stations considered in this thesis, indicate that the variance of the measurement error is proportional to the square of the flow.
In practice, flow predictions several time steps in advance are often required. For autoregressive processes, this involves unknown elements in the system matrix H of the Kalman model. The Kalman algorithm underestimates the variance of the forecast error if H and x are both unknown. For the AR(1) model, a general expression for the mean square error of the forecast is developed. It is shown that the formula reduces to the Kalman equation for the case where the system matrix is known. The importance of this formula is realized in forecasting situations where management decisions depend on the reliability of flow predictions, reflected by their mean square errors.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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Heise, R. "Implementation of a two-stream fan in the CIRSTEL system /". Thesis, Stellenbosch : University of Stellenbosch, 2006. http://hdl.handle.net/10019.1/1076.
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Bishop, Kevin Harold. "Episodic increases in stream acidity, catchment flow pathways and hydrograph separation". Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239601.
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Dudley, John Richard. "Channel form, flow and sediment transport in a step-pool stream". Thesis, Loughborough University, 2007. https://dspace.lboro.ac.uk/2134/11850.
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The influence of channel morphology and hydraulics on sediment transport within steep upland streams is investigated. Step-pools are the most common bedform in such streams. Bedload transport processes operating in a perennial step-pool stream in central England are established using magnetically-tagged particles and bedload pit samplers. Water-surface slope in two step-pool streams is monitored in detail. Water-surface slope measurements show that step-pool bedforms cause large spatial variations in flow depth during floods, and that the temporal variation of watersurface slope during a flood wave differs diametrically from the pattern found in lowgradient rivers that have little roughness. These results demonstrate that it is difficult to estimate the forces acting on the streambed in steep, rough streams and, therefore, conventionally established flow variables cannot be used to predict bedload transport . rates in step-pool channels. Particle tracing experiments are used to determine the control that step-pool morphology and flow hycfraulics have on particle displacements. Step-pool streams exhibit smaller particle travel distance per flood event than low-gradient rivers. This difference reflects the greater flow resistance and bed rugosity of step-pool streams. Bed morphology dictates flood particle displacement at step-pool bedform scale. It is shown that entrainment, pool export rates and transport distances of coarse sediment are dependent on downstream step dimensions, step permeability and pool form. Large variations in bedload transport rates at any given flow strength are associated with variable sediment supply, and particle tracing demonstrates that sediment availability is controlled at unit pool scale. Bedload consists of fine gravel moving over a stable bed surface at low discharges, while, at higher discharges, bedload coarsens, approaching the size of the pool bed material as the bed surface is partially mobilized. Step framework clasts are stable features of the streambed. Results from this study are incorporated into a descriptive model of discharge-related bedload transport phases in step-pool streams.
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Amoruso, Kenneth. "Independent control of a molten stream temperature and mass flow rate". Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/40008.
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Brogan, Connor O'Beirne. "A Dam Conundrum: The Role of Impoundments in Stream Flow Alteration". Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/85005.
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Over the past century, the world's rivers have become increasingly impounded to combat water scarcity and fossil-fuel reliance. Large dams have faded from popularity due to their adverse environmental effects, but small ponds and reservoirs continue to be constructed at high rates. Due to limited data regarding their size and flow, it has been difficult to assess how these smaller impoundments impact rivers. This study combined rainfall runoff data from the Chesapeake Bay Model with the unique routing framework of VA Hydro to create a simplistic hydrologic model capable of analyzing impoundment-induced flow alteration. Using standard design techniques and satellite imagery, a methodology was developed to build realistic stage-storage-discharge relationships for small and large impoundments. Eleven impoundments of the Difficult Run watershed were modeled within VA Hydro to assess their cumulative impact on downstream flow. Multiple models were created with different active impoundments and run for the full model period, 1984 - 2005. Flow alteration increased significantly with additional impoundments. Peak flows were attenuated as water was stored behind outlets, but median flows were increased as this water was slowly released. Average storm duration increased due to extended rising and falling limbs caused by impoundment outlets. Headwater channels increasingly ran dry, decreasing extreme low flows due to impoundment evaporation. Large reservoirs had a greater impact on median flows, but smaller ponds dominated low flow alteration. These results suggest that traditional hydrologic assumptions and metrics may be incapable of analyzing a changing flow regime without explicitly considering small and large impoundments upstream.Master of Science
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Dunn, Daniel D. "Attacker-Induced Traffic Flow Instability in a Stream of Automated Vehicles". DigitalCommons@USU, 2015. https://digitalcommons.usu.edu/etd/4455.
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Highway systems world wide continue to see an ever increased number of vehicles and subsequently a rise in congested traffic. This results in longer commute times, wasted energy as vehicles idle in stop and go traffic, and increases the risk of accidents. In short, increased congestion costs time and money. These issues have prompted much research into Automated Highway Systems (AHS). In AHS vehicles using computer algorithms can safely travel at much smaller inter-vehicle distances than human drivers are capable of. This increases the capacity of existing highway systems. Sensors aboard each vehicle make this possible by monitoring their surroundings. Vehicles equipped with Adaptive Cruise Control (ACC) are capable of this type of close proximity travel. ACC packages are becoming common as a standard package on many mid-priced vehicles.
Another form of automation, Cooperative Adaptive Cruise Control (CACC), which utilizes wireless communication between vehicles, has been proposed and will likely become available within the next couple decades. CACC allows each vehicle to communicate their intended speed or position changes to surrounding vehicles, further decreasing the possibility of collisions.
These automation methods are proposed to reduce driver stress, increase highway throughput, and decrease accident rates. However, the fact that vehicles are being automated creates new opportunities for malicious individuals to wreak havoc on society.
This research investigates the possibility that some vehicles on the highway might be under the control of malicious individuals who have modified their automated control systems to negatively affect vehicles around them. These malicious actors might also exploit the wireless communication of CACC vehicles and hack their control algorithms, causing them to become unstable. These hacked vehicles could become passive participants in the attack unbeknownst to the driver of the vehicle. The result of such attacks could be congested traffic, rapid changes in acceleration causing drivers discomfort, or multi-vehicle collisions. Such attacks could effectively negate the benefits of implementing AHS.
The goal of this work is to bring to light possible weaknesses in the proposed systems so they can be rectified before becoming an issue to the public at large.
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Halepoto, Imtiaz Ali. "Scheduling and flow control in CMT-SCTP". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/210189.
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Popa, Tiberiu. "Compiling Data Dependent Control Flow on SIMD GPUs". Thesis, University of Waterloo, 2004. http://hdl.handle.net/10012/1186.
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Current Graphic Processing Units (GPUs) (circa. 2003/2004) have programmable vertex and fragment units. Often these units are implemented as SIMD processors employing parallel pipelines. Data dependent conditional execution on SIMD architectures implemented using processor idling is inefficient. I propose a multi-pass approach based on conditional streams which allows dynamic load balancing of the fragment units of the GPU and better theoretical performance on programs using data dependent conditionals and loops. The proposed system can be used to turn the fragment unit of a SIMD GPU into a stream processor with data dependent control flow.
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Stewart, Rebecca M. "Land Cover Influences on Stream Nitrogen Dynamics During Storms". Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/76799.
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Previous studies on the effects of land cover influence on stream nitrogen have focused on base flow conditions or were conducted specifically within urbanized or primarily agricultural watersheds. While these studies have shown relationships between land cover and nitrogen, this relationship and the scale of influence could change during storms. The purpose of my study was to understand how land cover influences nitrogen in streams during storms. This was address using nine watersheds within the Little Tennessee Basin in North Carolina. While this basin is primarily forested, the nine watersheds have mixed agricultural, built, and forest land cover. Land cover influences were addressed through nitrogen concentration/discharge patterns, nitrogen concentration relationship to land cover, and comparison of storm and base flow nitrogen concentrations over time. Weekly base flow samples and samples from six storm were collected in 2010-2011. Total dissolved nitrogen (TDN), nitrate (NO??), dissolved organic nitrogen (DON), and ammonium (NH?⁺) concentrations were compared among sites. During most storms, DON peaked before the peak of the discharge while NO?? peaked after the peak of the storm. This suggest that DON could be coming from a near stream source or surface runoff while NO?? could be from longer pathways such as subsurface flow or from sources further away on the watershed. NO?? concentration varied among sites, while DON concentration varied more between base flow and storm samples. Examining the different landscape scales from 200-m local corridor, 200-m stream corridor, and entire watershed, watershed land cover was the best predictor for all the nitrogen concentrations. Agricultural and built combined best predicted TDN and NO??, while agricultural land cover was a better predictor of DON. For storms, nitrogen concentrations did not show seasonal patterns but was more related to discharge. Nitrogen concentration increased with discharge during storms and the more intense and longer storms had higher TDN and NO?? concentrations. However, conflicting seasonal trends were seen in monthly base flow. The more forested watersheds had high NO?? during the summer and low NO?? in the winter. For sites with higher NO??, the seasonality was reversed, with higher winter NO?? concentration. The least forested site had relatively constant nitrogen through the year at base flow and concentration decreased for most storms. Further studies on storms and nitrogen transport are needed to understand better the seasonal patterns of nitrogen input during storms.Master of Science
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Chadwick, Michael Andrew Joseph. "Effects of Nitrogen Deposition and Flow Permanence on Stream Organic Matter Dynamics". Fogler Library, University of Maine, 2003. http://www.library.umaine.edu/theses/pdf/ChadwickMAJ2003.pdf.
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Toften, Terje HaÌŠkon. "Effects of free-stream turbulence on a jet in a cross-flow". Thesis, University of Hertfordshire, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241571.
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bin, Ali Nauman. "Operationalization of lean thinking through value stream mapping with simulation and FLOW". Doctoral thesis, Blekinge Tekniska Högskola, Institutionen för programvaruteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-00614.
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Background: The continued success of Lean thinking beyond manufacturing has led to an increasing interest to utilize it in software engineering (SE). Value Stream Mapping (VSM) had a pivotal role in the operationalization of Lean thinking. However, this has not been recognized in SE adaptations of Lean. Furthermore, there are two main shortcomings in existing adaptations of VSM for an SE context. First, the assessments for the potential of the proposed improvements are based on idealistic assertions. Second, the current VSM notation and methodology are unable to capture the myriad of significant information flows, which in software development go beyond just the schedule information about the flow of a software artifact through a process. Objective: This thesis seeks to assess Software Process Simulation Modeling (SPSM) as a solution to the first shortcoming of VSM. In this regard, guidelines to perform simulation-based studies in industry are consolidated, and the usefulness of VSM supported with SPSM is evaluated. To overcome the second shortcoming of VSM, a suitable approach for capturing rich information flows in software development is identified and its usefulness to support VSM is evaluated. Overall, an attempt is made to supplement existing guidelines for conducting VSM to overcome its known shortcomings and support adoption of Lean thinking in SE. The usefulness and scalability of these proposals is evaluated in an industrial setting. Method: Three literature reviews, one systematic literature review, four industrial case studies, and a case study in an academic context were conducted as part of this research. Results: Little evidence to substantiate the claims of the usefulness of SPSM was found. Hence, prior to combining it with VSM, we consolidated the guidelines to conduct an SPSM based study and evaluated the use of SPSM in academic and industrial contexts. In education, it was found to be a useful complement to other teaching methods, and in the industry, it triggered useful discussions and was used to challenge practitioners’ perceptions about the impact of existing challenges and proposed improvements. The combination of VSM with FLOW (a method and notation to capture information flows, since existing VSM adaptions for SE are insufficient for this purpose) was successful in identifying challenges and improvements related to information needs in the process. Both proposals to support VSM with simulation and FLOW led to identification of waste and improvements (which would not have been possible with conventional VSM), generated more insightful discussions and resulted in more realistic improvements. Conclusion: This thesis characterizes the context and shows how SPSM was beneficial both in the industrial and academic context. FLOW was found to be a scalable, lightweight supplement to strengthen the information flow analysis in VSM. Through successful industrial application and uptake, this thesis provides evidence of the usefulness of the proposed improvements to the VSM activities.
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Kyrke-Smith, Teresa Marie. "Ice-stream dynamics : the coupled flow of ice sheets and subglacial meltwater". Thesis, University of Oxford, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.629515.
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Ice sheets are among the key controls on global climate and sea level. A detailed understanding of their dynamics is crucial to make accurate predictions of their future mass balance. Ice streams are the dominant negative component in this balance, accounting for up to 90% of the Antarctic ice flux into ice shelves and ultimately into the sea. Despite their importance, our understanding of ice-stream dynamics is far from complete. A range of observations associate ice streams with meltwater. Meltwater lubricates the ice at its bed, allowing it to slide with less internal deformation. It is believed that ice streams may appear due to a localisation feedback between ice flow, basal melting and water pressure in the underlying sediments. This thesis aims to address the instability of ice-stream formation by considering potential feedbacks between the basal boundary and ice flow. Chapter 2 considers ice-flow models, formulating a model that is capable of capturing the leading-order dynamics of both a slow-moving ice sheet and rapidly flowing ice streams. Chapter 3 investigates the consequences of applying different phenomenological sliding laws as the basal boundary condition in this ice-flow model. Chapter 4 presents a model of subglacial water flow below ice sheets, and particularly below ice streams. This provides a more physical representation of processes occurring at the bed. Chapter 5 then investigates the coupled behaviour of the water with the sediment, and Chapter 6 the coupled behaviour of the water with the ice flow. Under some conditions this coupled system gives rise to ice streams due to instability of the internal dynamics.
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Gillespie, Benjamin Robert. "Impacts of flow regulation and Artificial Floods in an upland stream ecosystem". Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/8017/.
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Mitigation of ecological impacts associated with stream regulation is now a legislative priority and Artificial Floods have been suggested as a potential tool to achieve this aim. However, understanding of the impacts of stream regulation and Artificial Floods on downstream ecology is currently limited. This thesis provides detailed reviews of both of these topics and identifies key contemporary research priorities. These priorities were subsequently addressed through assessment of the impact of stream regulation and Artificial Floods on downstream hydrology, physical chemistry, coarse sediment transport and benthic macroinvertebrates in an upland subcatchment of the River Humber, UK. Evidence that regulation was associated with significant impacts on hydrology (e.g. flood frequency, rate of change), physical chemistry (particularly flood pH and diurnal stream temperature range) and macroinvertebrates was identified, but impacts were found to vary spatially and temporally, indicating the importance of site specific and temporal factors. Control of hydrological characteristics was demonstrated during Artificial Floods which generally resulted in reductions of electrical conductivity, dissolved oxygen and pH and no change in stream temperature. Evidence for coarse sediment transport in line with overspill events prior to Artificial Floods was identified, but little evidence for change in macroinvertebrate assemblage was found. Evidence for the use of Artificial Floods as a management tool was greatest for coarse sediment transport and pH but overall, limited potential was demonstrated, bringing into question their validity as management techniques in some regulated streams and provoking requirement for further research. The findings of this thesis, methodological developments, conceptual advances and recommendations are therefore considered to have advanced the science and understanding of regulated stream management. Such progress is vital in this rapidly developing research field.
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Seraj, Hossein. "Detection of Solids in a Flow Stream Using Ultrasonics and Advanced Algorithms". Thesis, Curtin University, 2021. http://hdl.handle.net/20.500.11937/88097.
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Sand passing along gas production pipelines can cause major disruption to facilities and interrupt gas flow. This research focused on improving sand flow measurement in gas pipes. It provided an improved method to measure sand flow rate using commercial Acoustic Sand Detectors. Also it provided several methods to measure sand flow rate in gas pipes using ultrasonic sensors and various signal processing techniques which were more accurate than any other methods.
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Holmes, Rachel. "Disturbances to the uniform stream flow of a fluid with free surface". Thesis, Holmes, Rachel (2014) Disturbances to the uniform stream flow of a fluid with free surface. PhD thesis, Murdoch University, 2014. https://researchrepository.murdoch.edu.au/id/eprint/27338/.
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We consider two main problems involving disturbances to uniform stream flow. In the first part of the thesis we examine flow over topography with particular interest in obtaining subcritical solutions with no downstream waves. Solutions to the linearised, fully nonlinear and weakly nonlinear problem are computed for two different types of topography. An array of waveless solutions corresponding to one or more trapped waves are computed at a range of different Froude numbers and are shown to provide a rather elaborate mosaic of solution curves in parameter space. The free surface is shown to evolve into different shapes as we track these waveless contours through parameter space. In addition, for one type of bottom topography, certain values of the dimensionless flow rate and obstruction height are shown to have waveless solutions for almost all obstruction separation distances greater than some particular value. In the second part of the thesis we examine the flow past a line sink. We consider the fully nonlinear problem with the inclusion of surface tension and investigate the maximum sink strength for a given stream flow, before examining non-unique solutions. The addition of surface tension allows for a more thorough investigation into the characteristics of the solutions and produces some interesting results. The breakdown of steady solutions with surface tension appears to be caused by a curvature singularity as the flow rate approaches the maximum. The non-uniqueness in solutions is shown to occur for a range of parameter values in all cases with non-zero surface tension. The work involved in this thesis has application in design of submerged structures and water quality management in reservoirs.
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Anderman, Evan R. Poeter Eileen P. "Field verification of stream-aquifer interactions Colorado School of Mines survey field, Golden, Colorado /". Fort Collins, Colo. : Colorado Water Resources Research Institute, Colorado State University, 1993. http://hdl.handle.net/10176/co:4527_ucsu61410169internet.pdf.
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Thesis (M. Eng.)--Colorado School of Mines, 1993.Thesis advisor: Eileen Poeter, Dept. of Geology and Geological Engineering. Includes bibliographical references (leaves 93-97). Includes bibliographical references (p. 93-97). Also available in print version.
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Simkins, Richard M. "Response to Drought of a Stream Fish Assemblage in a High Elevation Stream in the Intermountain West". BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6901.
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One of the most influential disturbances for stream fish assemblages is large-scale declines in flow caused by periods of drought. Although stream characteristics are known to influence the response of stream fishes to drought, we asked if ecological traits of stream fishes determine, in part, their population level response to drought. To test for ecological trait-based responses to drought in a stream fish assemblage, we quantified species abundances over a period of 5 years that represented a wet to dry period. We sampled stream fishes in Yellow Creek, Wyoming, USA, a high elevation stream dependent on snow-storage for most of its flow. There were five regularly occurring species in the study site: redside shiner (Richardsonius balteatus), northern leatherside chub (Lepidomeda copei), mottled sculpin (Cottus bairdi), speckled dace (Rhinichthys osculus), and mountain sucker (Catostomus platyrhynchus). We used size class, species, and drought measures as predictors of abundance. Mean Palmer drought severity index over the growing season from the previous year (one year lag) provided the best predictor of stream fish abundances. Four of five species showed strong declines in abundance in response to drought conditions (mountain sucker abundance was not affected), but ecological traits of species were not good predictors of the magnitude of response to drought. Northern leatherside chub are most vulnerable to local extirpation during times of severe drought. Overall, juveniles showed a greater decline in abundance than adults in response to drought. Climate models predict that mountain streams will experience changes in flow regime, which may exacerbate effects of drought. Low flow refuge habitat may need to be incorporated into stream restoration designs to help increase recolonization in streams, especially for stream fishes that are most vulnerable to local extirpation and that have low recolonization rates.
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McEwen, Amiana Marie. "Abundance, Distribution, and Geometry of Naturally Occurring Macropores in Stream Banks". Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/95948.
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Preferential flow paths are areas of substantially higher permeability than surrounding media. Macropores and soil pipes are a type of preferential flow path where conduit-like voids in the subsurface are typically greater than three millimeters in diameter. They are known to occur in agricultural and forest soils, often as a result of biological and physical processes. Macropores also exist in stream banks and have the potential to enhance the exchange of water and solutes between the channel and riparian groundwater, yet the geographic distribution of bank macropores is unknown. Here we determined the abundance, distribution, and geometry of naturally occurring surface-connected macropores in the banks of 20 streams across five physiographic provinces in the Eastern United States. We identified a total of 1,748 macropores, which were present in all 20 streams, with 3.8 cm average width, 3.3 cm average height, 11.5 cm average depth, and 27.9 cm average height above water surface elevation. Macropore abundance, distribution and geometry were statistically different between physiographic provinces, stream orders, and soil textures, with the latter being the most important. Macropores tended to be larger and more abundant in soils with a high cohesiveness and a low hydraulic conductivity compared to soils with a low cohesiveness and high hydraulic conductivity. As a result, streams with greater longitudinal heterogeneity of soil texture also had greater heterogeneity of macropore density. However, macropore size and height above baseflow water surface elevation also increased with stream order and therefore stream size. This work represents the first attempt to characterize macropores across a variety of riverine systems and presents evidence that macropores may play an important role in hyporheic exchange within stream banks. These results may have water quality implications, where macropores may enhance hyporheic exchange yet reduce the filtering capacity of riparian buffer zones.MS
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Lockard, Brendan Corbett. "Long Term Hydrologic Effects on Stream Health from Residential Development Patterns". Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/34013.
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In this study eight residential development scenarios are created for the mostly undeveloped Back Creek Watershed outside Roanoke, Virginia. The development scenarios include low, medium (cluster), medium (conventional), and high density development with and without development restrictions. These scenarios represent a large range of development as the land use imperviousness varies from 1% for the baseline condition to 34% for the most developed scenario. The hydrologic model HSPF is used to generate overland and channel flows from 43 years of rainfall. Hydrologic output from HSPF of the various landuse patterns from the eight scenarios are evaluated using Post Processor, a Visual Basic program. The results show that increased development causes a reduction in Back Creek's baseflow and an increase in the occurrence of both high and low flow extreme events. Overall, these results indicate that increased development will increase the variability of flowrate in Back Creek.
Stream health impacts from flow variability were also analyzed with the Post Processor. First, hydrologic statistical variables with ecological relationships were used to gage the level of stream health impacts from flow variability. The averaged stream health index for the development scenarios was found to closely follow the amount of development, represented by the percent of impervious landuse. Second, the amount of velocity, depth, and both depth and velocity habitat available for three habitat guild representative species was evaluated for each scenario. The results indicated that increased development would lead to a substantial reduction in available riffle species habitat (represented by the fantail darter) and a moderate reduction in run and pool species habitat (represented by the central stoneroller and smallmouth bass, respectively).
Overall, increased development has been found to have a negative impact on stream health. This impact should be considered in any future expansion of the Roanoke suburbs into this watershed.
Master of Science
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Ahn, Taejin 1957. "A procedure for the determination of a flow duration curve at an ungaged basin". Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276585.
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The purpose of this study is to develop a method for predicting monthly flow duration curves for ungaged basins that are suitable for estimating average annual flow, and installed capacity and average annual energy generation at potential sites for hydropower development. The procedures were tested by developing monthly rainfall duration curves for five sample watersheds and then developing flow duration curves from the rainfall data. The methods were evaluated by comparing the predicted monthly flow duration curves to daily and monthly flow duration curves based on field data from the selected sites because a plant's potential energy output can be computed directly from a flow duration curve. The methods tested fit duration curves based on field data reasonably well and are suitable for preliminary evaluation of hydropower developments in ungaged basins.