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Cloran, Christina Elizabeth. "Investigating Nickel Flux and Toxicity in Clay Sediments with Batch and Stream Recirculating Flume Experiments." Wright State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=wright1229973400.
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Bernard, David P. "Impact of stream acidification on invertebrates : drift response to in situ experiments augmenting aluminum ion concentrations." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/24478.
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Recent evidence strongly suggests that aluminum toxicity is important in determining the structural and functional characteristics of freshwater communities affected by acid precipitation. To determine the effect dissolved aluminum has on lotic invertebrates previously unexposed to anthropogenic acidification, experiments were carried out in a second-order headwater stream 50 km east of Vancouver, British Columbia during August 1982. In three separate experiments, HC1 and/or A1C1₃ were added to Mayfly Creek during daylight hours, increasing acidity from pH 6.9 - 7.0 to pH 5.8 - 6.0 and total aluminum from < 0.1 mg/L to > 1.0 mg/L. Biological response was monitored by sampling invertebrate drift with 86 Mm nets.
Relative to an unmanipulated, upstream control site, drift density doubled in response to added H⁺ alone (pH 5.9). When Al₃⁺ was added (pH 5.9) drift density increased fourfold. Following 48 h continuous dosing with HC1 (pH 5.9) there was an even greater response to added Al₃⁺.
Ephemeroptera were able to detect dissolved aluminum and responded almost immediately (within 45 min). Similarly, Trichoptera and Chironomidae detected increased H⁺ concentrations and responded immediately. Response to
augmented Al₃⁺ by Trichoptera, Hydracarina, and Chironomidae was delayed 6 h. However, pre-exposing animals to 48 h HC1 resulted in enhanced aluminum sensitivity for Chironomidae and for Simulium and Plecoptera, which had not responded within 10 h to H⁺ or Al₃⁺ alone. It is proposed that rapid increases in drift density are due to behavioral escape responses, while delayed responses are probably associated with physiological impairment. Evidence was also obtained suggesting that during early stages of morphological development Ephemeroptera and Chironomidae are more sensitive to increased Al₃⁺ and H⁺ concentrations than during later developmental stages.
In laboratory experiments using artificial stream channels, Chironomidae larvae and Ephemeroptera nymphs were exposed to CI⁻ and H⁺ concentrations, equal to those during field experiments. Results showed that drift behavior in these animals is not stimulated by mildly elevated chloride concentrations.
These studies demonstrate that increased dissolved aluminum concentrations intensify biological response to acidification, and confirm acid sensitivity patterns for Ephemeroptera and Chironomidae reported by others. The observed acid
insensitivity of Plecoptera, simuliids, and Trichoptera also conforms to previously described patterns.
Experimentally manipulating this community produced results closely resembling those obtained in similar studies for areas currently affected by acid precipitation. The major difference in results between studies is that invertebrate communities previously unexposed to acidification contain more species sensitive to mild acidification. These latter animals are particularly sensitive to the presence of elevated dissolved aluminum concentrations.Science, Faculty of
Zoology, Department of
Graduate
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Blasch, Kyle William. "Streamflow timing and estimation of infiltration rates in an ephemeral stream channel using variably saturated heat and fluid transport methods." Diss., The University of Arizona, 2003. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_2003_253_sip1_w.pdf&type=application/pdf.
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Brown, Glen, and n/a. "Towards an in situ technique for investigating the role nutrients play in epilithon growth in an Australian upland stream." University of Canberra. School of Resource, Environmental & Heritage Sciences, 2001. http://erl.canberra.edu.au./public/adt-AUC20060614.171246.
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There is limited knowledge and understanding of the role of nutrients and effect of
herbivore grazing on epilithon production in Australian upland rivers. Before
investigating these processes, a method was required that will allow the study of factors
(physical, chemical and biological) that affect epilithon abundance and distribution in
lotic systems. The Thredbo River, Kosciusko National Park, New South Wales,
provided an opportunity to conduct this investigation because it: is relatively
undisturbed; has been intensely studied; is easily accessed; and is of appropriate width
and depth to conduct in-stream experiments.
The specific goals of this research were the: (1) validation of the nutrient-diffusing
substrate method for investigating epilithon responses to nutrients; (2) development of
experimental channels in which to investigate nutrient/epilithon dynamics in an upland
stream; (3) development of a method to inhibit macroinvertebrate grazing from in situ
experimental channels, so that epilithon responses to nutrients with and without grazing
pressure can be studied; and (4) assessment of the ecological implications of nutrient/
epilithon/macroinvertebrate interactions assessed from in-stream experiments.
Major achievements of my research, that advance the study of stream ecology, are as
follows:
· The investigation of the features of nutrient release from terracotta nutrientdiffusing
substrates showed that phosphorus does not readily diffuse through
terracotta clay, probably because terracotta contains known binding agents for
phosphorus, such as iron, and because pores are easily blocked. I concluded that
this type of substrate is inappropriate for studying nutrient dynamics and epilithon
responses to the nutrient(s) limiting growth. The outcomes of this research has
implications for future research using nutrient-diffusing substrates, and of how
nutrient limitation information is interpreted from past research using terracotta
nutrient-diffusing substrates.
· I designed and tested in-stream experimental channels that were functional and
provided near natural conditions for studying the interactions between nutrients/
epilithon/macroinvertebrates, without affecting physical variables not tested for.
The in situ method developed was successful in simulating 'real world'
complexities. Clay paving bricks were used as standardized common surface for
community development because their colour, size and surface texture are similar
to those of natural stones.
· I developed a technique for successfully inhibiting macroinvertebrate grazing from
designated areas, using electricity, without affecting flow and light. This technique
will enable in-stream herbivory studies to assess the effects of macroinvertebrate
grazing pressure on epilithon under natural conditions, including variability in
flow, temperature, light and nutrients. It will allow the vexed question of whether
epilithon biomass is controlled by bottom-up or top-down processes to be
objectively addressed.
The construction of in situ experimental channels that simulate natural conditions,
combined with the non-intrusive methods of macroinvertebrate exclusion and nutrient
addition, resulted in a study design that will facilitate the investigation of biotic
responses to nutrients in Australian upland streams. Using the method developed, I
showed that variable flows in the upper Thredbo River appear high enough to slough
epilithon, but not high enough to dislodge macroinvertebrates. This may mean that in
systems such as the Thredbo River that experience frequent low level disturbance, the
epilithon is unable to reach equilibrium. There is strong top-down control of epilithon
in this stream, with nutrients, temperature and light playing a secondary role. I
concluded that natural variability may be more important than previously considered
and perhaps this, rather than constancy, should be studied.
This thesis adds support to the continuance of multiple factor investigations, and
advocates that such studies be conducted under natural conditions so that the results
are more relevant to natural systems than from studies conducted in controlled
laboratory and outdoor artificial streams. Clearly, the in-stream channels, developed as
part of the current research, will allow research that contributes to our understanding of
community responses to the physical, chemical and biological processes operating in
lotic environments.
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Grubh, Archis R. "Effects of anthropogenic disturbances and biotic interactions on stream biota in gulf coastal plain streams." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1155753270.
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Shelton, Jeremy Mark. "Impacts of non-native rainbow trout on stream food webs in the Cape Floristic Region, South Africa integrating evidence from surveys and experiments." Doctoral thesis, University of Cape Town, 2013. http://hdl.handle.net/11427/6189.
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Includes abstract.Includes bibliographical references.
Impacts of invasive predators may be influenced by whether or not native predators which function in the same way as the invasive predator exist in the recipient system. Impacts are expected to be strong in isolated systems lacking functionally similar predators because native species will be naïve to the foraging behaviour of the introduced predator, and because the invasion is likely to change the role which the native predator assemblage performs. In this thesis I studied how the introduction of a functionally novel predatory fish, rainbow trout Oncorhynchus mykiss, has affected native fish, and how changes in the functioning of the predator assemblage have influenced lower trophic levels, in headwater streams in a catchment area within the Cape Floristic Region, South Africa. Fish populations, benthic invertebrate assemblages, benthic algae and particulate organic matter were surveyed in each of 24 minimally-disturbed headwater streams in the upper Breede River catchment, and relevant environmental variables in each stream measured, over one summer.
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Bernal, Berenguer Susana. "Nitrogen storm responses in an intermittent Meditterranean stream." Doctoral thesis, Universitat de Barcelona, 2006. http://hdl.handle.net/10803/1436.
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The amount of dissolved inorganic nitrogen delivered to streams and groundwater has substantially increased in the last decades due to anthropogenic impacts. This fact has stimulated research on processes related to the nitrogen cycling in order to elucidate the ability of terrestrial and aquatic ecosystems in controlling nitrogen loads. Some of these studies pointed out during storms streamwater chemistry is significantly altered. However, because of the inherent difficulty of an extensive field experimental setting for dealing with episodic storms, studies focused on hydrological processes or stream solute dynamics during storms rely on a very limited number of events. Hydrobiogeochemical processes have been mainly studied in temperate experimental catchments and little attention has been paid to Mediterranean catchments. Recent studies have stressed the fragility of Mediterranean regions in front of the global change and because of that Mediterranean regions should become hot spots for present and future studies.The main goal of the present thesis was to study the variability of nutrient dynamics, in particular nitrogen, during stormflow in relation to baseflow conditions in Fuirosos, an intermittent stream draining a small Mediterranean catchment (Part I). As a secondary objective (Part II), solute dynamics in Fuirosos were compared with those measured at one of its main tributaries, the Grimola stream. Biotitic granodiorite was an important fraction of the Fuirosos catchment, whereas the Grimola catchment was underlain by leucogranite. The Fuirosos stream had an alluvial zone and it was flanked by a well developed riparian forest, whereas the Grimola stream had not a significant alluvial zone, neither a well developed riparian area. Thereby, the effect of (i) catchment size, (ii) lithology and (iii) the presence of an alluvial-riparian zone on stream hydrogrochemistry were assessed by comparing the Fuirosos and Grimola streams.
The Fuirosos Stream Watershed, a relatively undisturbed Mediterranean ecosystem that can not be considered a N-saturated catchment, leaks to the stream most of the nitrogen loss in the form of nitrate (57 %). This figure contrast with that reported for other pristine tropical and humid catchments where nitrogen export is mainly in the form of dissolved organic nitrogen. In particular, nitrate is mainly mobilized during stormflow conditions (from 52 % to 80 % of the annual yield). Contrastingly, most of the dissolved organic carbon export occurs during baseflow conditions (from 40 to 70 % of the annual yield). These results point to a decoupling between soil nitrification and nutrient uptake by biota, which brings about the leaking of nitrate to the stream. Hydrochemistry in this Mediterranean intermittent stream is highly variable within and in between years. The antecedent moisture conditions and the magnitude of storm events are key factors on shaping the hydrological responses to storm events. However, storm episodes that occur during similar climatological and hydrological conditions produce different streamwater chemistry depending upon the time of the year. This is so, mainly because of the influence of the summer drought period on streamwater chemistry. Both, the mixing model (EMMA) and the spectral analysis approaches, point out that groundwater is the most important contributor to stormflow in Fuirosos. Nonetheless, the EMMA approach emphasizes how stream water and nitrate sources vary throughout the year. Our results stress the importance of sampling storms during all seasons to draw general conclusions about watershed processes. The mixing model shows that nitrate is retained by biota in the Fuirosos alluvial zone only when streamflow is lower than 80 l/s. Above this threshold, the system is not efficient in retaining nitrate arriving from the catchment. This result might be keep on mind when establishing the importance of near- and in-stream processes for regulating catchment nitrate loads since a major fraction of the annual nitrate export usually occurs during stormflow conditions in many catchments. The spectral analysis also shows that the variability of stream nitrate concentrations is more damped in Fuirosos than in Grimola. This is attributed to the buffer effect that biota has on nitrate concentrations in the Fuirosos alluvial zone, which retards its delivery in relation to the Grimola catchment.
"Efecte de les pluges en la dinàmica del nitrogen en una riera intermitent i mediterrània"
La quantitat de nitrogen dissolt que arriba avui dia als nostres rius i aqüífers és substancialment major a la de fa un parell de dècades a resultes de l'activitat antròpica. Aquest fet ha estimulat força la recerca dels processos relacionats amb el ciclatge del nitrogen, amb la intenció d'esbrinar la capacitat que tenen els ecosistemas terrestres i aquàtics per controlar les càrregues de nitrat que els hi arriben. Alguns d'aquests estudis indiquen que durant les tempestes s'altera de forma substancial la química de l'aigua del riu. Això no obstant, la major part dels treballs realitzats es recolzen en un nombre limitat d'episodis, donada la dificultat inherent al mostreig intensiu de camp a l'hora d'estudiar les respostes hidrològiques i la dinàmica dels soluts durant les crescudes. Tradicionalment, la comunitat científica s'ha dedicat a l'estudi dels processos hidrobiogeoquímics de regions temperades i tropicals, i desafortunadament, les conques Mediterrànies no han estat objecte de la seva atenció. Estudis recents alerten de la fragilitat de les regions Mediterrànies enfront del canvi global, i per tant, urgeixen els estudis focalitzats en aquests ecosistemes.
El principal objectiu d'aquesta tesi ha estat l'estudi de la variabilitat de la dinàmica dels nutrients, en particular del nitrogen, durant les crescudes en relació a la seva dinàmica en condicions de cabal basal en una riera intermitent, Fuirosos, en una conca Mediterrània. La hidrologia i la dinàmica dels soluts a la riera de Fuirosos s'ha comparat amb les de la Grimola, un dels seus efluents més importants. Hi ha diferències litològiques notables entre les dues conques. A més la riera de Fuirosos té zona al.luvial i està flanquejada per un bosc de ribera ben desenvolupat, mentre que la riera de Grimola no té zona al.luvial ni tampoc una zona riberenca ben diferenciada. Per tant, els efectes de (i) la mida de la conca, (ii) la litologia, i (iii) la presència d'una zona al.luvial i riberenca sobre la hidrobiogeoquímica d'un riu, van poder ésser contrastats comparant les rieres de Fuirosos i Grimola. L'estudi es va realitzar al Parc Natural del Montnegre-Corredor al Vallès Oriental entre els anys 1998 i 2004.
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Whittle, Don. "Stream mesocosms in ecological risk assessment : experimental, analytical and ecological considerations." Thesis, University of Sheffield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339940.
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Tin, Tin Htwe. "Bed Deformation and Navigable Channel Characteristics in Braided Stream." Kyoto University, 2018. http://hdl.handle.net/2433/235073.
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Harris, Rebecca Margaret Louise. "The effect of experimental drought disturbance on macroinvertebrate assemblages in stream mesocosms." Thesis, University of Birmingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435312.
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Dinger, Matthew J. "Experimental study of the three-stream scalar mixing in a turbulent coaxial jet." Connect to this title online, 2009. http://etd.lib.clemson.edu/documents/1249066149/.
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Martinskas, Vytautas. "The Modernistic Experiments in Gertrude Stein’s and John Dos Passos’s Creative Works." Bachelor's thesis, Lithuanian Academic Libraries Network (LABT), 2012. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2012~D_20120831_103048-28157.
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The object of the Bachelor Thesis is the modernistic experiments in Gertrude Stein’s and Jon Dos Passos’ creative works. The aim of the present research is to analyze the modernistic experiments in Gertrude Stein’s and John Dos Passos’s creative works. In order to achieve the aim the following objectives have been set: 1) to present and analyze theoretical material concerning modernism; 2) to analyze modernistic experiments in Gertrude Stein’s and John Dos Passos’s creative works; 3) to compare G. Stein’s and J. Dos Passos’s artistic linguistic experiments and creative means.
The methodology applied in the present Thesis included: 1) the historical-comparative method was applied in order to review and compare the definitions of literary modernism in different countries; 2) Ihab Hassan’s concept of modernism, which helped describing the phenomenon of modernism and specifying its basic peculiarities, and 3) the theory of comparativistics that allowed determining the correlation of literary modernism and non-linguistic discourses.
In the Bachelor Thesis modernistic experiments were treated as the linguistic experiments with language, words and their meaning, grammatical and syntactical forms, way of narration and text composition. For practical analysis G. Stein’s “Tender Buttons” (1914) and J. Dos Passos’s “The 42nd Parallel” (1930) were chosen. In the course of the research the scientific literature concerning the theoretical background of modernism appearance, the variety... [to full text]Bakalauro darbo objektas – modernistiniai eksperimentai Gertrude’s Stein ir Johno Dos Passoso kūryboje. Darbo tikslas – analizuoti modernistinius eksperimentus Gertrude’s Stein ir Johno Dos Passoso kūryboje. Tikslui pasiekti buvo nustatyti šie uždaviniai: 1) Apžvelgti ir analizuoti mokslinę literatūrą apie modernizmą kaip istorinį kultūros raidos etapą; 2) Nagrinėti modernistinius eksperimentus Gertrude’s Stein ir Johno Dos Passoso kūriniuose; 3) Palyginti Gertrude’s Stein ir Johno Dos Passoso naudojamus kalbinius eksperimentus bei kūrybos būdus. Bakalauro darbo metodologiją sudaro: 1) Istorinis lyginamasis metodas, kuris naudojamas įvairių šalių literatūrinio modernizmo apibrėžčių apžvelgimui ir palyginimui; 2) Ihabo Hassano modernizmo koncepcija, kuri taikoma modernizmo fenomeno aprašymui bei jo pagrindinių ypatumų nustatymui; 3) Komparatyvistikos teorija, leidusi apibrėžti literatūrinio modernizmo ir neliteratūrinių diskursų sąsajas. Šiame darbe modernistiniai eksperimentai traktuojami kaip lingvistiniai eksperimentai su kalba, žodžiais ir jų reikšmėmis, su gramatinėmis bei sintaksinėmis formomis, su pasakojimo būdais ir teksto kompozicija. Praktinei analizei atlikti buvo pasirinktas Gertrude’s Stein kūrinys „Švelnios sagos“ (1914) ir Johnno Dos Passoso romanas „Keturiasdešimt antroji paralelė“ (1930). Tyrimo metu buvo analizuota teorinė literatūra apie modernizmo atsiradimą, jo ideologines nuostatas bei chronologines ribas. Identifikuota šių reiškinių įvairovė... [toliau žr. visą tekstą]
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Poff, Boris, Daniel G. Neary, and Gregory P. Asner. "How Useful is LiDar in Establishing a Stream Gauging Network in a Tropical Experimental Forest." Arizona-Nevada Academy of Science, 2008. http://hdl.handle.net/10150/296688.
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Bankey, Laura Anne. "Responses of Cytochrome P450IA in Freshwater Fish Exposed to Pulp Mill Effluents in Experimental Stream Channels." W&M ScholarWorks, 1993. https://scholarworks.wm.edu/etd/1539617660.
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Karbassi, Massoumeh. "Analytical and experimental studies of the stability limits of nonpremixed flames in a co-flowing stream." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq24541.pdf.
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Chadwick, Kenneth Michael. "An experimental investigation of the breakup of a viscoelastic non-newtonian fluid in a supersonic stream." Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/42082.
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Weiss, Julien. "Experimental determination of the free stream disturbance field in the short duration supersonic wind tunnel of Stuttgart University." [S.l. : s.n.], 2002. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10316296.
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Kelsey, Scott Alan. "Impact of Land Use on Headwater Stream Organic and Inorganic Carbon Export in a Temperate Midwestern Experimental Watershed." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1460651004.
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Schneider, Judith. "The response of biota in experimental stream channels to a 24-hour exposure to the herbicide, Velpar L." Thesis, University of Ottawa (Canada), 1994. http://hdl.handle.net/10393/9630.
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Ten experimental stream channels, fed from a Laurentian steam were used to examine the short-term impact of a pulse of Velpar L on stream periphyton and invertebrates. Velpar L was added to five alternating channels for 24 hours with the other five channels serving as controls. The mean concentration of hexazinone in the treatment channels varied over time from 145 $\mu$g L$\sp{-1}$ to 432 $\mu$g L$\sp{-1}$. Periphyton chlorophyll a-specific productivity was significantly reduced during the Velpar L treatment. Within 24 hours after the termination of the Velpar L treatment, productivity returned to control levels. Mean periphyton biomass, measured as the quantity of chlorophyll a per unit area, was not affected by the Velpar L treatment. In addition, the concentration of hexazinone that reduced periphyton chlorphyll a-specific productivity by 50% after a four hour exposure was determined. This value was only 3.6 $\mu$g L$\sp{-1}$ of hexazinone. Thus, low concentrations of Velpar L affect stream periphyton but the impact appears to be temporary. Velpar L did not cause an increase in the drift of insects or other macroinvertebrates. Mean density of benthic macroinvertebrates increased slightly with time in the Velpar L-treated channels and nearly doubled in the control channels. The mean length of individual macroinvertebrates decreased slightly over time in the control channels but not in the treated channels. However, the changes in mean density, biomass and length were not statistically significant. The variance of the invertebrate lengths increased over time in both the control and Velpar L-treated channels, which suggests that the size distribution of the invertebrate community varied with time. (Abstract shortened by UMI.)
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Morris, Noel Alexander. "An experimental and computational study of moderately under-expanded rocket exhaust plumes in a co-flowing hypersonic free stream." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282347.
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Papanikolaou, Nancy. "An experimental investigation of the flow structure and stability limits of jet diffusion flames in a co-flowing oxidizing stream." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0013/NQ31062.pdf.
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Vander, Vorste Ross. "The hyporeic zone as a primary source of invertebrate community resilience in intermittent alluvial rivers : evidence from field and mesocosm experiments." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10259/document.
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Un paradigme émergent prédit que les perturbations influencent les processus qui déterminent l'organisation des communautés. L'assèchement des rivières (disparition complète d'eau de surface pour une durée déterminée) est une perturbation naturelle affectant les cours d'eau dans de nombreuses régions du monde. De plus en plus de cours d'eau pérenne s'assèchent en réponse aux changements globaux. Toutefois, l'effet de ces assèchements sur les communautés aquatiques et les processus impliqués dans leur résilience restent mal quantifié et mal compris. A travers quatre études allant de suivis de terrain à des expérimentations in-situ et des mésocosmes en laboratoire, une résilience exceptionnelle des communautés d'invertébrés a été mesurée dans huit rivières alluviales. La zone hyporhéique semble être la principale source de recolonisation expliquant la forte résilience de ces communautés. En laboratoire, l'augmentation de la température et de la compétition intra-spécifique entraine une migration de Gammarus pulex dans la zone hyporhéique. L'augmentation de la profondeur de la zone hyporhéique lors d'assèchements pourrait réduire la résilience et avoir des effets sur les fonctions de l'écosystème (décomposition de litière). Ces résultats montrent que les assèchements n'ont pas toujours des effets sévères sur les communautés d'invertébrés des rivières alluviales qui semblent même très résilientes. La zone hyporhéique joue un rôle primordial dans la résilience des communautés des cours d'eau. Un accent devrait être mis sur la protection de la zone hyporhéique dans les rivières alluviales afin de préserver cette capacité de résilience face aux changements globauxUnderstanding community response to disturbance is essential to identifying processes that determine their assembly and to predicting the future effects of climate change on biodiversity and ecosystem functions. Drying (complete loss of surface water) is a natural disturbance affecting 50% of rivers worldwide and is occurring more in perennial rivers due to climate change. However, its effects on aquatic invertebrate communities and the underlying processes contributing to their resilience (i.e. return to pre-drying or undisturbed levels) have not been well quantified. Using 4 congruous field and mesocosm experiments to quantify community resilience and identify its primary sources in environmentally harsh alluvial rivers. First, I found communities in 8 alluvial rivers were highly resilient to moderate and severe drying. Second, I showed that the hyporheic zone (saturated interstitial sediments) can be the primary source of colonists, promoting high community resilience. Third, I found high water temperature and intraspecific competition caused Gammarus pulex, a common benthic detritivore, to migrate into the hyporheic zone. Fourth, I found increasing depth to the water table diminished the hyporheic zone’s role as a source of colonists by reducing survival of G. pulex. My results support an emerging concept that harsh ecosystems are highly resilient and indicate that the effects of drying on biodiversity and ecosystem functions could vary across river systems. In alluvial rivers, the hyporheic zone can contribute strongly to community resilience and management should focus on protecting and restoring vertical connectivity to maximize resilience to climate change
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Diehl, Melinda S. "Using Stream Chemistry to Evaluate Experimental Acidification and Natural Recovery in the Paired Catchments at the Bear Brook Watershed in Maine (1989-2003)." Fogler Library, University of Maine, 2006. http://www.library.umaine.edu/theses/pdf/DiehlMS2006.pdf.
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Holm, Christian Franz. "Spatial habitat use of young-of-the-year Atlantic salmon (Salmo salar) in response to changing stream discharge and population density : testing the instream flow model concept in a controlled experiment." Thesis, University of Stirling, 2001. http://hdl.handle.net/1893/26677.
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Many rivers are affected by man-induced regulations of stream-flow. The effects of these on the instream biota have been studied widely and it is generally accepted that assessment tools for the management of regulated rivers are of vital importance. In particular predictive instream habitat models like the Physical Habitat Simulation Model (PHABSIM) have become popular for this purpose with users world-wide. These models predict discharge-related changes in instream habitat availability for target species by modelling the hydraulic geometry of the river reach on the one and the microhabitat preferences of the species on the other side. Despite their popularity, validation studies for this approach have met many difficulties which are mostly related to the biological part of the model, the habitat preference curves. A review of these studies undertaken here reveals that very little information has been published on two main assumptions of the models: 1. The habitat preference of a species is independent of stream discharge 2. The habitat preference of a species is independent of the species population density Most validation studies are undertaken in field situations. As such they frequently have had problems relating to sampling the microhabitat use consistently, a lack of experimental control and variations in other secondary variables. It was thus decided to conduct controlled experiments in a large indoor flume. Young-of-year Atlantic salmon (Salmo salar) caught in a nearby stream were stocked into pool-riffle sequences, landscaped within a natural substrate, in observation areas of 3.6 metres length and 1 metre width. Microhabitat use of fish was recorded at three different discharges within a 15-fold discharge variation. It was found that the mean column velocity preference of the juvenile salmon, calculated by the standard method, varied largely, mainly due to a shift of preference for low water velocities. "Weighted usable area" (WUA) calculations, the final output of instream habitat models, varied up to two-fold due to these differences in preference. Habitat preference also varied with population density. Fish preferred the riffle habitat at low population density and the pool habitat during high population density. Fish used higher mean column velocities during low population density. There are hence fundamental problems related to the approach of using density functions as preference indices as is commonly done for building habitat preference curves, because of a bias for habitat availability. A new approach using Geographic Information Systems (GIS) is taken by comparing the microhabitat conditions fish experience at their chosen positions with the conditions fish would have experienced had they maintained the positions used at the other discharges. It was found that fish adjusted their positions towards significantly different microhabitats between low flow positions and the positions at the other two flows. This research demonstrates how microhabitat use and preference of wild-caught juvenile salmon varied with discharge and population density in a large near-natural flume. The error introduced by these variations to instream habitat model predictions was large. It confirms that habitat preference curves built as density functions on empirical fish observation data are bound to misrepresent the overall habitat requirements of a species life stage which in the case of juvenile salmon appeared wide and flexible over the range of discharge.
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Vázquez, Garcia Eusebi. "Influence of hydrology on dissolvedorganic matter quantity and properties in a temporal Mediterranean stream = Influència de la hidrologia sobre la quantitat i disponibilitat de la matèria orgànica dissolta en una riera temporal mediterrània." Doctoral thesis, Universitat de Barcelona, 2013. http://hdl.handle.net/10803/128863.
Full textAbstract:
The studies presented in this thesis focus on the biogeochemistry of dissolved organic matter (DOM) in an intermittent stream in a Mediterranean climate zone, with great emphasis on extreme hydrologic events: floods and the seasonal drought period. The changes in concentration and molecular weight, and the properties, especially those related to its origin, and bioavailability to the microbial community. The samplings were carried out during a wide span of years in order to characterize the concentration – discharge responses (C-Q) initially, and more intensively during the different periods of the hydrologic year (wet, drought and transitional periods) in order to capture the widest possible picture of the dissolved organic matter dynamics and processing. The last chapter is a review of different fluorescence spectroscopy and UV-vis absorbance methods applied in DOM characterization.
The main conclusions from these works are:
1. The most probable C-Q response types represent only a 40% of all cases from the data set. Therefore, the majority of DOC and NO3-Q responses fall within some low probability C-Q response types.
2. The dry-wet transition does not present a typical C-Q response. Instead, it promotes the diversity of DOC-Q responses. The 33% of events comprised during this period contribute to the 41% of the total DOC-Q response diversity. On the other hand, it does not enhance NO3-Q responses.
3. The most important driver for the succession of NO3-Q responses is the periodicity of the magnitude of storms (ΔQ) is, while the effect of the seasonal temperature change (i.e., Tday), appears more perceptible after the removal of the signal of the weaker and more frequent rain episodes.
4. The occurrence of a severe summer dry period favored the mobilization and transport of labile DOC, as shown by the 56% of retention across the stream – riparian interface, during the following hydrological transition period. Furthermore, the DOC retention during this period was preferential from high to low molecular weight fractions. In the case of no apparent hydrological transition all DOC molecular weight fractions were equally conservative.
5. During both drought and rewetting periods DOC and DON bioavailability are not tied to a MW fraction. During the rewetting period, although there is no clear pattern of bioavailability according to any DOC MW fraction, 50% of cases at which DOCMW release is observed (BDOCMW<0) correspond to the LMW fraction.
6. In general, DOCMW dynamics fit within the framework that storm events enhance the input of larger molecular weight DOC fraction (higher than 1 kDa), but DONMW does not. Furthermore, the hydrologic characteristics of the rewetting period evidence an asynchronous mobilization of DOC and DON.
7. DOC bioavailability is heavily influenced by DON content rather than molecular weight. Furthermore, bioavailability seems to be regulated by the DOC:DON ratio presenting a threshold value of 13. The most remarkable case is that of DOCLMW that shifts from refractory to bioavailable when its DOC:DON ratio is lower than 13.
8. Drought causes a gradual hydrological fragmentation of the fluvial network enlarging the variability of DOM properties, and amplifying the biogeochemical variability of a fluvial system.
9. Sampling sites with lotic water bodies in summer show DOM properties similar to those observed in autumn under base flow hydrological conditions and reflect the prevalence of terrestrial inputs. In contrast, in isolated and lentic water bodies, DOM analyses reveal a supplementary contribution of autochthonous organic matter, originated by in situ microbial processes.
10. BDOC estimated during summer indicates an upper threshold of 40% that is also observed during the rewetting period. This allows asserting that the highest bioavailable DOC concentration can be reached during two ecosystem perturbations of opposite sign.Els articles presentats en aquesta tesi es centren en els aspectos biogeoquímics de la materia orgànica dissolta (DOM) en una riera temporal en una zona de clima mediterrani. Concretament, s’estudien els efectes dels events hidrològics extrems, les crescudes i les sequeres estacionals pròpies de la regió mediterrània, en la concentració i les propietats de la matèria orgànica dissolta. Els paràmetres utilitzats en la caracterizació de la DOM permeten principalment establir l’origen d’aquesta i establir la seva biodisponibilitat per a les comunitats microbianes del riu. En l’aspecte quantitatiu també es realitza un estudi més detallat mitjançant el fraccionament en diferents rangs de pes molecular. La recollida de dades inclou una sèrie temporal llarga que permet estudiar les despostes concentració – cabal (C-Q) tant del carboni orgànic dissolt com del nitrat, i d’uns mostreigs de camp intensius que permeten obtenir una imatge precisa dels diferents períodes de l’any hidrològic (període humit, de sequera i de transició hidrològica). Els resultats d’aquests treballs permeten copsar la variabilitat de les respostes C-Q, que en el cas del DOC veuen augmentada la seva variabilitat durant el període de transició hidrològica. En el cas del nitrat s’observa que les respostes es troben relacionades amb la magnitud y l’interval de temps entre episodis de precipitació. Pel que fa a la biodisponibilitat de les diferents fraccions moleculars, mentre que els estudis inicials apunten a una immobilització selectiva de les fraccions més grans a la interfase ripariana, estudis següents postren que la concentració de nitrogen orgànic dissolt és cabdal a l’hora de determinar si una fracció és biodisponible o no. A nivell hidrològic es conclou que tant durant la transició hidrològica com durant el període de transició hi ha una amplificació dels processos biogeoquímics que permeten estudiar el sistema fluvial amb més profunditat. No obstant, durant la fragmentació hidrològica es produeix una augment en la variabilitat biogeoquímica mentre que durant la transició hi ha una tendencia a l’homogeneïtzació.
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Peipoch, Güell Marc. "The role of Primary Uptake Compartments on stream Nitrogen cycling = El paper dels Compartiments Primaris en el ciclatge del Nitrogen als ecosistemes fluvials." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/146351.
Full textAbstract:
The main goal of this thesis is to investigate how (15)N natural abundances can help understanding the role of different primary uptake compartments (i.e., biofilm, filamentous algae, bryophytes, macrophytes; PUCs) on stream nutrient retention. The experimental design of this thesis involved the examination of patterns of variability in the (15)N signatures of Dissolved Inorganic Nitrogen (DIN) and PUCs at three different spatial scales: the watershed/global scale, the reach scale, and the habitat scale; as well as the (15)N transfer between them. At each level of organization, a common goal of examining how intrinsic (i.e., among PUCs) and extrinsic (i.e., environmental) factors influence (15)N signatures of DIN and PUCs was addressed, but quite different tools and experimental approaches were used depending on each scale.
At the global scale, results showed that land use in the catchment is a key driver of the variability in (15)N signatures of both DIN and PUCs. In particular, (15)N signatures of DIN and PUC are higher in streams draining catchments with agriculture and urban activities than in those draining forested catchments; whereas within each stream, major among-compartments differences in (15)N signatures are between photoautotrophic and detrital-based compartments.
At the reach scale, results for the different functional groups of macrophytes in streams indicate that direct assimilation of stream water DIN is occurring by submersed and amphibious species; while species of macrophytes located at the stream-riparian edge most likely rely on DIN sources other than those provided by stream water DIN. Moreover, in streams influenced by inputs from wastewater treatment plants (WWTP), DIN uptake by submersed and amphibious macrophytes seems to be mainly in the form of N03• On the other hand, results for the (15)N transfer between photoautotrophic PUCs and stream water DIN showed that variation in DIN uptake of photoautotrophic PUCs is principally driven by nutrient concentration and light incidence, rather than by the particular characteristics of each PUc. On the contrary, variation in autotrophic N turnover is more remarkable among photoautotrophic PUCs than among study reaches, suggesting an intrinsic control by the particular characteristics of each PUC on N turnover, and being relatively independent of environmental influences.
Finally, results from tracer (15)N additions at the habitat and microhabitat scales revealed
that spatial heterogeneity of microbial N uptake at the microhabitat scale is characterized by a mosaic of patches dominated by microhabitats of low N, with hot spots of highly active N uptake accounting for the 20% of the reach coverage. Particularly, spatial variation of epilithon N uptake at microhabitat scale is principally driven by flow velocity, while spatial variation of N uptake by detrital compartments is controlled bya combination of biophysical factors, indicating the relevance of organic matter characteristics on their role of stream water N uptake. Overall, these results indicate that the extent to which spatial variation in microbial N uptake at fine scales is integrated at the whole-reach scale is potentially affected by factors operating at the ecosystem level, such as the degree of canopy cover, which determines the relative abundance of each PUc.
Results from this present thesis highlights that changes in the major land uses within the catchment, changes in the degree of riparian vegetation and/or in the DIN loads of stream ecosystems caused by WWTP inputs, or losses of spatial heterogeneity in the stream channel can have a significant incidence on the way that PUCs contribute to N cycling at the reach scale, which ultimately dictates the N dynamics of stream ecosystems.
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Bastias, Álamo Elliot. "The role of leaf litter quality and streambed hydro-morphology on in-stream leaf litter dynamics = El rol de la qualitat de la fullaraca i de la hidro-morfologia del tram fluvial en les dinàmiques de la fullaraca als rierols." Doctoral thesis, Universitat de Barcelona, 2018. http://hdl.handle.net/10803/586045.
Full textAbstract:
Understanding the dynamics of leaf litter inputs in streams involves assessment of retention, spatial distribution and processing of leaf litter inputs. However, leaf litter dynamics in streams has been mostly studied by determining the controlling factors of leaf litter processing, ignoring if leaf litter inputs are retained within the streams, and how these inputs are spatially distributed within the streambed. Furthermore, leaf litter processing in streams is not an isolated process because it can be linked with the dynamics of solutes of these streams. In fact, leachates from leaf litter provide to the streams with dissolved organic matter (DOM), as well as, dissolved nutrients (i.e., nitrogen [N] and phosphorous [P]). Also, the mineralization of leaf litter inputs implies the releasing of dissolved forms of C and nutrients to the stream water column. In addition, microbial communities inhabiting leaf litter uptake dissolved forms from water column during leaf litter decomposition. Despite the obvious linkage between leaf litter processing and in-stream solute dynamics, few studies provided information about the main drivers controlling this connection.
In order to understand how leaf litter dynamics operates in stream ecosystems, the present thesis aims to examine (a) how the hydro-morphological characteristics of the recipient stream can influence the retention, spatial distribution, physical fragmentation and decomposition of leaf litter inputs. Moreover, we also examine (b) the interaction between leaf litter processing and in-stream dynamics of dissolved organic carbon and dissolved inorganic nitrogen and how it varies depending on the leaf litter species considered. To
approach this aim, we specifically examine how the leaf litter quality of different riparian tree species can influence: (b1) the chemical-composition and bioavailability of leaf litter leachates to streams (b2) the uptake of DIN and DOC from water column by microbial decomposers during decomposition process and how it is related to the activity of microbial decomposers and, (b3) how microbially-driven leaf litter decomposition vary among streams which covered a wide gradient of inorganic nutrient concentrations.
The present thesis reveals that heterogeneity of water velocity within a reach is a factor controlling different aspects of leaf litter dynamics in streams because not only influences the fraction of leaf litter retained but also how these inputs are spatially distributed and further processed within the streams. Therefore, we indicate that the relevance of leaf litter inputs as organic matter source to in-stream communities can be subjected to the hydro- morphological characteristics of the receiving stream reaches, since they determine the spatial heterogeneity of water velocity within the reach. In addition, we suggest that leaf litter quality influence on the chemical and structural properties of the leaf litter-leachates and also how these leaches are used by in-stream microbial assemblages. The quality of leaf litter can also dictate the microbial demands of dissolved C and N from the water column. Finally, we suggested that the influence of in-stream nutrient concentrations on leaf litter decomposition can be subjected to the leaf litter quality. Considering all our results together we suggest that riparian composition, which dictates the quality of leaf litter inputs, may control the linkage between leaf litter processing and in-stream C and N solute dynamics. However, the heterogeneity of water velocity may be the most relevant factor determining the importance of leaf litter to streams because it can control the probability that leaves contribute to the stream metabolism or to be exported downstream.Para comprender cómo funciona la dinámica de la hojarasca en arroyos, la presente tesis pretende examinar (a) cómo las características hidro-morfológicas del lecho del arroyo pueden influir en la retención, distribución espacial, fragmentación física y descomposición de la hojarasca. Además, también examinamos (b) la interacción entre el procesamiento de hojarasca y la dinámica del carbono orgánico disuelto y nitrógeno inorgánico disuelto del arroyo y cómo varía dependiendo de las especies de hojarasca consideradas. La presente tesis revela que la heterogeneidad de la velocidad del agua dentro de un tramo es un factor que controla diferentes aspectos de la dinámica de hojarasca en arroyos, ya que no solo influye en la fracción de hojarasca retenida, sino también en cómo estas entradas se distribuyen espacialmente y se procesan en los arroyos. Por lo tanto, indicamos que la relevancia de las entradas de hojarasca como fuente de materia orgánica para las comunidades del arroyo puede estar sujeta a las características hidro-morfológicas de dicho ecosistema, ya que determinan la heterogeneidad espacial de la velocidad del agua dentro del mismo. Además, sugerimos que la calidad de la hojarasca influye en las propiedades químicas y estructurales de los lixiviados de hojarasca y también cómo estos lixiviados son utilizados por los microorganismos del arroyo. La calidad de la hojarasca también puede dictar las demandas microbianas de C y N disuelto de la columna de agua. Finalmente, sugerimos que la influencia de las concentraciones de nutrientes del arroyo en la descomposición de la hojarasca puede estar sujeta a la calidad de la hojarasca. Teniendo en cuenta todos nuestros resultados, sugerimos que la composición del bosque de ribera, que determina la calidad de las entradas de hojarasca, puede controlar el vínculo entre el procesamiento de la hojarasca y la dinámica de solutos C y N del arroyo. Sin embargo, la heterogeneidad de la velocidad del agua puede ser el factor más relevante para determinar la importancia de la hojarasca en las corrientes, ya que puede controlar la probabilidad de que las hojas queden retenidas en el arroyo o se exporten aguas abajo, perdiéndose como fuente de materia y energía.
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Guarch, Ribot Alba. "Dissolved organic matter fluctuations in an intermittent headwater stream: from storm oscillations to decadal hydrological changes = Fluctuacions de la matèria orgànica dissolta en un riu de capçalera intermitent : de crescudes a canvis hidrològics decennals." Doctoral thesis, Universitat de Barcelona, 2017. http://hdl.handle.net/10803/406137.
Full textAbstract:
Dissolved organic matter (DOM) is an important source of carbon for aquatic microorganisms and it regulates many biogeochemical processes. Therefore, changes in river DOM concentration and properties could notably affect the functioning of fluvial and coastal ecosystems and alter the global carbon cycle. The DOM in headwater streams is strongly influenced by hydrology, as a consequence of the modification of catchment flow paths with high discharges. During storm events, the catchment hillsides are washed and terrigenous DOM is transported to rivers. In the Mediterranean region, the precipitation regime and evapotranspiration strongly modulate fluvial hydrology, which shows low discharges in summer and even flow disappearance. These dry–wet cycles of conditions affect many ecological and biogeochemical processes.
In this thesis, I analyse a long time series of discharge and DOM data from Fuirosos, an intermittent headwater stream in NE Spain. My aim is to examine the relationship between DOM and hydrology at different temporal scales. First, I characterise the hydrological regime of this Mediterranean stream. A decrease in discharge was revealed, although trends in temperature and precipitation were not significant. In contrast, I did not find a clear temporal trend in dry period duration. However, rewetting has been significantly delayed, moving from September to October. The frequency of storm events decreased over the interval 1998–2015, showing a significant positive relationship with solar activity with a 2-year lag.
Dissolved organic carbon (DOC) concentration saw a slight decrease during the study period, which was opposed to that observed in boreal systems. This pattern might respond to a reduction of terrigenous DOC input from forest hillsides as a consequence of the decrease in flushing episodes. The DOC temporal dynamics during the rewetting was regulated by dry period duration. Discharge oscillations explained up to 50% of total DOC variability during the wet period. Notably, this weight of discharge increased significantly over the years.
DOM quality was also explored, and described in terms of absorbance and fluorescence properties. Most of the DOM properties were strongly related to discharge, revealing the input of allochthonous, degraded, aromatic, humic and large-molecular DOM under high flow conditions. However, these relationships were altered during drying and rewetting periods. The DOM responses at the individual storm event scale were highly heterogeneous. Multiple linear regression and commonality analyses showed that, in addition to the magnitude of storm episodes, antecedent hydrological conditions, namely pre-event basal flow and the magnitude of the previous storm event, played a significant role in regulating the trends and shapes of DOM–discharge hysteresis.
Finally, I identified the differences and similarities in the DOM–discharge relationships between the intermittent Mediterranean stream analysed herein and a perennial Alpine stream with higher mean discharge (Oberer Seebach). The DOM in Fuirosos was significantly more concentrated, more terrigenous, more degraded, more aromatic and more humified. The sign of the global DOM–discharge response was the same in both streams. However, discharge was a more robust predictor of DOM variability in Oberer Seebach. In fact, low flow and rewetting periods in Fuirosos introduced considerable dispersion into the relationship. During snowmelt
in Oberer Seebach the sensitivity to discharge also decreased or disappeared. The flushing/dilution patterns were essentially associated with the magnitude of storm events in Fuirosos. In contrast, the DOM quality change was more coupled to basal flow conditions in Oberer Seebach, while the storms were behind the DOC oscillations.
This study attests to the importance of generating and analysing long-term and high-frequency biogeochemical series, which allow relationships between DOM and hydrology to be explored in intermittent headwater streams that are subjected to extreme hydrological regimes.La matèria orgànica dissolta (MOD) és una important font de carboni per als microorganismes aquàtics i regula molts processos biogeoquímics. La MOD en els rius de capçalera està modelada principalment per la hidrologia. A la regió mediterrània, el règim de precipitació i evapotranspiració impacta fortament la hidrologia fluvial, que mostra cabals baixos a l’estiu i pot arribar fins i tot a la seva desaparició. En aquesta tesi hem analitzat un sèrie temporal a llarg termini de cabal i MOD a Fuirosos, un riu de capçalera intermitent al NE de la Península Ibèrica. El nostre objectiu era examinar la relació entre la MOD i la hidrologia en diferents escales temporals. Primer, vam caracteritzar el règim hidrològic d’aquest riu mediterrani. Al llarg de l’estudi es va revelar una disminució del cabal, no vam trobar una tendència temporal clara en la durada de la sequera i la freqüència de les crescudes va disminuir en l’interval 1998–2015. La concentració de carboni orgànic dissolt (COD) ha patit una lleugera disminució durant el període d’estudi, cosa que contrasta amb el que s’ha observat en sistemes boreals. La dinàmica temporal del COD durant el període de transició va ser regulada per la durada del període sec. La qualitat de la MOD també va ser explorada, i descrita en termes de propietats d’absorbència i fluorescència. La majoria de les propietats de la MOD van ser clarament relacionades amb el cabal. No obstant, aquestes relacions van ser alterades durant els períodes de fragmentació i de transició. A més de la magnitud dels episodis de crescuda, les condicions hidrològiques prèvies juguen un paper significatiu perquè regulen les tendències i formes de les histèresis MOD–cabal. Per acabar, vaig identificar les diferències i semblances en les relacions MOD–cabal entre el riu mediterrani intermitent analitzat i un riu perenne alpí amb un cabal mitjà superior (Oberer Seebach). Aquest estudi testifica la importància de generar i analitzar sèries biogeoquímiques de llarga durada i alta freqüència, que permeten explorar les relacions entre la MOD i la hidrologia en rius de capçalera intermitents que estan subjectes a règims hidrològics extrems.
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Hellyer, William N. "Assessment of Benthic Macroinvertebrate Community Impairment from High-Aluminum Acid Mine Drainage in Middleton Run, Ohio, USA and the Impact of Ingested Aluminum on Crayfish Growth." Ohio University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1399465953.
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Braudrick, Christian A. "Entrainment, transport, and deposition of large woody debris in streams : results from a series of flume experiments." Thesis, 1997. http://hdl.handle.net/1957/33808.
Full textAbstract:
Although there has been extensive research on the geomorphic and ecologic role of
large woody debris (LWD) in streams, the dynamics of LWD in streams are poorly
known due to various measurement difficulties during floods. In this thesis I present the
results of two flume experiments on the dynamics of wood in streams. The first
experiment examined the effects of piece interaction on wood transport, while the second
evaluated a theoretical model predicting the threshold of movement, and factors
controlling the deposition of individual logs. Flume experiments allow us to model the
wood movement under a variety of piece geometries, piece concentrations, and hydraulic
conditions.
The first experiment showed that logs moved in three distinct transport regimes;
congested, semi-congested, and uncongested transport. During congested transport the
logs move as a single mass and occupy > 33 % of the channel area. Uncongested transport
occurs when the logs are moving as individuals and occupy < 10 % of the channel area.
Semi-congested transport is intermediate between these two transport regimes and occurs when wood moves in clumps of 2-3 logs. Transport regime was dependent upon the ration of the volumetric input rate of pieces to the flow, and to a lesser degree, the ratios of the piece length to channel width and piece diameter to channel depth. The transport regime was reflected in the deposit. Congested transport deposits have a higher portion of their pieces oriented parallel to flow than uncongested and semi-congested transport. We expect that congested transport will occur in low-order channels where input rates are high and channel geometry is small relative to piece size. Uncongested transport will dominate large channels where input rates are lower relative to flow and channel geometry is large relative to piece size.
Our theoretical model and these experiments indicate that the entrainment of individual logs was dependent upon the angle of the piece, and the presence/absence of rootwads. Although previously noted as a first-order control on piece movement, piece length had little effect on the entrainment threshold, but did affect the distance transported. The distance transported decreased with increases in the ratios of the piece length to average channel width (L[subscript log]/w[subscript av]), the piece length to the radius of curvature (L[subscript log]/R[subscript c]), and the piece diameter relative to average depth (D[subscript log]/D[subscript av]). These three ratios comprise the debris roughness. Increased debris roughness caused a general decrease in distance transported. Pieces with high debris roughness can travel further than predicted if they have high momentum, and over 50 % of their channel area deeper than the depth at which the piece floats. These results indicate that flume experiments and theoretical models, tools that have been extensively used to study sediment dynamics, are a useful in examining wood dynamics.Graduation date: 1998
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Nowinski, John David. "Intra-meander groundwater-surface water interactions in a losing experimental stream." Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-08-1873.
Full textAbstract:
Groundwater-surface water interactions between streams and shallow alluvial aquifers can significantly affect their thermal and chemical regimes and thus are critical for effective management of water resources and riparian ecosystems. Of particular significance is the hyporheic zone, an area delineated by subsurface flow paths that begin and end in surface water bodies. Although detailed work has examined hyporheic flow in the vertical dimension, some studies have suggested that the drop in a stream’s elevation as it flows downstream can laterally extend the hyporheic zone. This study examines intra-meander hyporheic flow using extensive field measurements in a full-scale experimental stream-aquifer system. Synoptic head measurements from 2008 and 2009 and a lithium tracer test were conducted to determine the extent and nature of hyporheic flow within the meander. Permeability was measured and sediment cores were analyzed from 2008 to 2009 to assess aquifer properties. Finally, transient head and temperature measurements were collected during flooding events to assess the sensitivity of intra-meander hyporheic flow and temperature to stream discharge. Results verify that hyporheic flow through meanders occurs, but show that it is sensitive to whether a stream is gaining or losing water to the subsurface overall. In addition, permeability and core grain size results indicate moderate heterogeneity in permeability can occur in aquifers composed of relatively uniform sediment. Results also demonstrate that permeability in alluvial aquifers can evolve through time. Such evolution may be driven by groundwater flow, which transports fine particles from areas where porosity and permeability are relatively high and deposits them where they are relatively low, thus creating a positive feedback loop. Finally, measurements during flooding indicate that steady-state hyporheic flow and the thermal regime within the aquifer are largely insensitive to stream discharge. Together, these results expand upon previous field studies of intra-meander hyporheic flow and verify previous modeling work, although they demonstrate a level of complexity within these systems that should be considered in future work.text
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Ho, Jinn-Tsair, and 何進財. "An Experimental Study of Fuel Droplet Ignition in Convective Hot Stream." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/51828098004168340298.
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Kao-ChingTang and 唐高晴. "Experimental Study of Submarine Braided Channels in response to Channel Width and Stream Power." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/7vfrft.
Full textAbstract:
碩士國立成功大學
水利及海洋工程學系
106
Submarine braided channels produced by turbidity currents have multiple bars and channels, similarly to the morphology of subaerial braided rivers. How-ever, we still have limited understanding for the mechanism of submarine braided channels. In this study, we used physical experiment to study the effects of limited channel width and stream power on the submarine braided channels. For the ex-periments, plastic sand was used to simulate deep-sea sediment, and saturated brine was used as the dense underflow. Our results show that total braiding inten-sity (BIT) and active braiding intensity (BIA) in all runs approach to a stable value and reflect the degree of braiding. Furthermore, the ratio of braiding intensity (BIR) produced in this study are higher than that of Lai et al., [2017]. Finally, we find that the braiding intensities in our study have low correlation with dimen-sionless power. The possible reason may due to the absence of considering the effects of sediment discharge and initial channel width.
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Kuok-PongLeong and 梁國邦. "Experimental Studies on Self-Ignition of a Hydrogen Transverse Jet in a Supersonic Free-Stream." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/59077094667765187495.
Full textAbstract:
碩士國立成功大學
航空太空工程學系碩博士班
100
Fundamental to the success of hypersonic air-breathing propulsion system are the efficient injection, mixing, and combustion process that occur inside the combustion chamber. This research is focused on the self-ignitability of a transverse fuel, hydrogen gas, injected into a simulated supersonic combustor environment. Our experimental approach uses a reflected shock tunnel located in National Cheng Kung University, Taiwan, to provide the high total enthalpy flow associated with the scramjet combustor entry condition of M = 2.0, T0 = 2000 K, p0 = 12 MPa, T = 1200 K and p = 1.5 MPa. A upstream (also called backward) detonation-driven shock tube is also built and used successfully to supply hydrogen fuel at up to T0 = 505 K and p0 = 16.5 MPa for the experiment. In the first set of tests, the ignition of the transverse hydrogen injection from a 2mm wall orifice in a flat plate. In the investigations, a high speed camera is used indicates the location of the shock structures and an intensify CCD (ICCD) detector with hydroxyl (OH) radical wave length filter ( 307 nm) is used to map the regions of ignition in the near-field by the intensity of OH-chemiluminescence. Results show that the significant spontaneous ignition can be clearly observed in the recirculation region caused by the interaction between the traverse hydrogen fuel jet and also in the large scale eddies structure in downstream. Two heat flux sensors and PCB pressure transducer are flush-mounded on the model and also help to give a sign of combustion.
35
Chen, Yen-Tu, and 陳彥圖. "An Experiment on the Relation between Sediment Delivery and Deposition with a Storm Event in Torrential Stream." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/06973544104191355920.
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碩士國立中興大學
水土保持學系
91
Abstract Lots of landslides were occurred and yielded sediments in mountain areas of Taiwan. The movement of these sediments will produce scouring or settling along the stream bed, depending on the hydraulic conditions. The unequilibrium of channel bed due to scouring or settling will influence the design for the torrent control works. Therefore, this study is going to investigate the sediment delivery and deposition in Gan-hsi watershed and conduct a simulated experiment in laboratory. A relation between sediment delivery and deposition will be trying to derive for the application. According to field investigation, the maximum scouring of each pile during flooding is greater than the deposition depth after flooding, and the deposition quantities have a tendency to increase to downstream. There are weak relations between total rainfall and channel variations, however the channel variations significant relates to rainfall intensity basing on hydrologic data. According to different peak discharges of simulated experiment result, there are scouring often occurred in the upstream, and there are deposition phenomenon displayed in the downstream. And each cross section of canal has stronger scouring capability between 0.75 with 1.00 for Q/Qp, it reach surely to 2.0(cm/min) for scouring velocity. In the same hydrograph circumstances the sediment concentration during flood raising period is higher than during flood recession period, because movable bed tends gradually to become mild during flood and brings on shear stress to become small. In the other head, there are power function’s relations increasing between qs/q and slope of movable bed, because steeper slope of movable bed increases larger horizontal quantity of gravity for sediment and stronger tractive force.
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Weiss, Julien [Verfasser]. "Experimental determination of the free stream disturbance field in the short duration supersonic wind tunnel of Stuttgart University / vorgelegt von Julien Weiss." 2002. http://d-nb.info/965959546/34.
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Pritzl, Mark Robert. "The performance and application of drum-type seepage meters and a simple experiment to determine if denitrification is occurring in stream bottom sediments within the North Carolina coastal plain." 2004. http://www.lib.ncsu.edu/theses/available/etd-10312004-092423/unrestricted/etd.pdf.
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