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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Drawdown and river bank stability

Green, Samuel John Unknown Date (has links) (PDF)
Drawdown is the lowering of the water level, and can refer to the groundwater, or the level of a river. In this thesis it will generally refer to a river going from a high flow condition to a lower flow condition. The rate of drawdown is expressed as either the change in flow per unit time, or the change in stage per unit time. The later is of most importance in terms of bank stability. (For complete abstract open document)
2

Effects of water-level management on the abundance and habitat use of waterfowl and marsh birds in the Saskatchewan River Delta, Manitoba, Canada

Baschuk, Mark 12 October 2010 (has links)
Waterbird habitat in the Saskatchewan River Delta (SRD) has been altered by numerous upstream and downstream anthropogenic developments. Wetland water-level management has been used in an attempt to mitigate these changes, but the effects on the local waterbird community are unknown. Using an experimental approach, I examined the effects of wetland water-level management on waterfowl and marsh birds in the SRD. In 2007, three wetland basins in the Summerberry Marsh Complex, Manitoba were partially drawn down and paired with three additional wetlands managed with high water levels. In 2008-09, I surveyed waterfowl within the study wetlands during different life stages using point counts and aerial surveys. Abundances of breeding marsh birds, including American Bitterns, Least Bitterns, Soras, Virginia Rails, Yellow Rails, American Coots, and Pied-billed Grebes were estimated using call-response surveys. Generalized linear and generalized linear mixed models were used to determine relationships between relative bird abundances and the physical characteristics, vegetation characteristics, and forage fish and invertebrate abundances within the wetlands. Dabbler species of waterfowl preferred the partial drawdown wetlands during nearly all life stages, except brooding. Diver species preferred the non-drawdown wetlands, but only during the spring-breeding and fall-staging periods. Invertebrate abundance affected wetland use by dabbler and diver species, particularly during the spring-breeding and brooding periods. Subsequently, wetlands with high forage fish abundances were avoided. In the fall, dabbler densities on the partial drawdown wetlands increased from an average of 0.4 birds per hectare to 1.5 birds per hectare. This influx was likely due to the accessibility and availability of submerged aquatic vegetation. The partial water-level drawdowns did not benefit any species of marsh birds examined. American Bitterns, American Coots, and Pied-billed Grebes chose the deeper, non-drawdown wetlands, due to high abundances of forage fish. Vegetation interspersion, particularly that offered by Schoenoplectus, was preferred by these species. Soras and Virginia Rails were not affected by water depth or vegetation characteristics, but were positively correlated to invertebrate abundances. Subsequently, the Sora avoided wetlands with high forage fish abundance. The conditions created by the partial water-level drawdowns did not meet the requirements of all species present in the SRD. Therefore, future wetland management should focus on providing a wide range of water depths within wetland complexes to accommodate the requirements of different avian species.
3

Effects of water-level management on the abundance and habitat use of waterfowl and marsh birds in the Saskatchewan River Delta, Manitoba, Canada

Baschuk, Mark 12 October 2010 (has links)
Waterbird habitat in the Saskatchewan River Delta (SRD) has been altered by numerous upstream and downstream anthropogenic developments. Wetland water-level management has been used in an attempt to mitigate these changes, but the effects on the local waterbird community are unknown. Using an experimental approach, I examined the effects of wetland water-level management on waterfowl and marsh birds in the SRD. In 2007, three wetland basins in the Summerberry Marsh Complex, Manitoba were partially drawn down and paired with three additional wetlands managed with high water levels. In 2008-09, I surveyed waterfowl within the study wetlands during different life stages using point counts and aerial surveys. Abundances of breeding marsh birds, including American Bitterns, Least Bitterns, Soras, Virginia Rails, Yellow Rails, American Coots, and Pied-billed Grebes were estimated using call-response surveys. Generalized linear and generalized linear mixed models were used to determine relationships between relative bird abundances and the physical characteristics, vegetation characteristics, and forage fish and invertebrate abundances within the wetlands. Dabbler species of waterfowl preferred the partial drawdown wetlands during nearly all life stages, except brooding. Diver species preferred the non-drawdown wetlands, but only during the spring-breeding and fall-staging periods. Invertebrate abundance affected wetland use by dabbler and diver species, particularly during the spring-breeding and brooding periods. Subsequently, wetlands with high forage fish abundances were avoided. In the fall, dabbler densities on the partial drawdown wetlands increased from an average of 0.4 birds per hectare to 1.5 birds per hectare. This influx was likely due to the accessibility and availability of submerged aquatic vegetation. The partial water-level drawdowns did not benefit any species of marsh birds examined. American Bitterns, American Coots, and Pied-billed Grebes chose the deeper, non-drawdown wetlands, due to high abundances of forage fish. Vegetation interspersion, particularly that offered by Schoenoplectus, was preferred by these species. Soras and Virginia Rails were not affected by water depth or vegetation characteristics, but were positively correlated to invertebrate abundances. Subsequently, the Sora avoided wetlands with high forage fish abundance. The conditions created by the partial water-level drawdowns did not meet the requirements of all species present in the SRD. Therefore, future wetland management should focus on providing a wide range of water depths within wetland complexes to accommodate the requirements of different avian species.
4

Planar and axisymmetric bottom withdrawal from a density-stratified reservoir

Ho, Juay C. January 1973 (has links)
Thesis (Ph. D.)--University of Wisconsin, 1973. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 185-190).
5

Jämförelse av beräknad och verklig grundvattensänkning vid vägportar

Franklin, Ida January 2005 (has links)
<p>Present master of science thesis has been carried out at the Swedish Road Administration consulting services (Vägverket Konsult) in Karlstad. The purpose of the study is to investigate how well the calculated drawdown of the groundwater table predicts the actual drawdown when the road and railway gates at the studied sites are built. For this purpose the groundwater levels at the three bridges were measured during 6 months. The bridges in question are two railway bridges situated in Ölme and Ulvåker and one road bridge crossing a pedestrian and cycling path in Lidköping.</p><p>In Ölme the calculated area of influence was smaller than the measured one. It differed up to 30 meters, i.e. 80 %.</p><p>In Lidköping the calculated area of influence agreed well with the measured one, but the groundwater level that the calculations were made from was more than one meter too low.</p><p>In Ulvåker the measured groundwater levels were influenced by other factors and no conclusions could be drawn.</p><p>When calculating how the groundwater level is affected from road and railway bridge constructions it is important to make sure to measure the groundwater level before the construction is made so that the unaffected level is known. Moreover the radius of the well should be set to a value less than 0.5 meters. It is also important that the conductivity is investigated thoroughly especially for confined aquifers. When measuring groundwater levels the examiner must make sure to plan the distances and depths of the piezometer wells, when to perform the measurements and how to protect the water in the wells from freezing.</p> / <p>Detta examensarbete är utfört på Vägverket Konsult i Karlstad. Syftet med arbetet är att med några exempel undersöka hur väl den beräknade permanenta grundvattensänkningen överensstämmer med den verkliga grundvattensänkning som görs vid byggen av vägportar. Arbetet utfördes genom att under 6 månader mäta grundvattennivåerna vid tre vägportar. De undersökta portarna är en väg – järnvägport i Ölme, en gång- och cykelväg – vägport i Lidköping och en väg – järnvägport i Ulvåker.</p><p>I Ölme framkom att den permanenta grundvattensänkningen har ett större influensområde än den beräknade. Differensen uppgick som mest till 30m vilket motsvarar en avvikelse på ca 80 %.</p><p>I Lidköping överensstämmer beräkningen av influensradierna väl med de uppmätta, medan grundvattennivån som beräkningarna gjordes från ligger drygt en meter för lågt.</p><p>I Ulvåker är den uppmätta avsänkningen påverkad av yttre faktorer och därför kan inga slutsatser dras.</p><p>Vid grundvattensänkningsberäkningar är det viktigt att den opåverkade grundvattennivån är känd, att brunnsradien sätts till ett tal mindre än 0,5 meter och att bestämningen av konduktiviteten är extra noga vid sluten akvifer. När grundvattennivåerna ska mätas bör avstånd och höjdnivå på grundvattenrören bestämmas noga, mätningarna utföras kontinuerligt under en längre tid och eventuell tillsats av frostskydd i grundvattenrören tänkas igenom.</p>
6

The use of inverse methods in the study of reservoir dynamics and water quality /

Anohin, Vadim V. January 2006 (has links)
Thesis (Ph.D.)--University of Western Australia, 2006.
7

Re-assembling Hetch Hetchy : water supply implications of removing O'Shaughnessy Dam /

Null, Sarah. January 2003 (has links) (PDF)
Reformatted version of the author's thesis (M.A.)--University of California, Davis, 2003. / Includes bibliographical references (leaves 40-44). Also available in PDF via the Internet.
8

IS WATER QUALITY IN BOONE LAKE A DAM PROBLEM? AN ASSESSMENT OF WATER QUALITY PRE- AND POST- DRAWDOWN

Grant, Annie, Luffman, Ingrid 04 April 2018 (has links)
Boone Lake was formed in 1952 by the impoundment of the South Fork Holston River in Sullivan and Washington counties, TN. The “V” shaped lake spans 6.88 square miles; it consists of two primary tributaries of approximately equal-length which meet just above the dam. South Fork Holston River makes up the northern arm and Watauga River feeds the southern arm. In October 2014, the discovery of a sinkhole led to detection of sediment-laden seepage under the earthen part of the dam. As a safety precaution, the reservoir was immediately lowered to an elevation of 1,352.5 feet, 10 feet below operational “winter” levels. It will remain there until the anticipated dam repair completion date of 2022. This study compares reservoir water quality data collected before seepage detection to data collected since drawdown to determine the impact of drawdown on water quality in the reservoir. Parameters analyzed were Dissolved Oxygen (DO), turbidity, conductivity (EC), Total Dissolved Solids (TDS), pH, temperature, and Escherichia Coli (E. coli). Data were compiled from two sources consisting of samples taken from 22 locations dispersed throughout each arm of the reservoir. Statistical analysis of pre/post-drawdown data was conducted using independent samples t-tests and Mann-Whitney tests as appropriate. Results of this study indicate water quality in Boone Lake has changed significantly since water levels were lowered. This change is likely due to flushing of the reservoir caused by ongoing dam repair. Conductivity, TDS, and E. coli levels have decreased significantly, suggesting improvements in water quality. Changes in temperature and pH were also found to be significant. Time series analysis of temperature and pH show significant trends overtime suggesting the lake will continue to warm and acidify. This combination of changes could negatively impact water quality, as metals trapped in lake sediments will likely become increasingly mobilized. Based on these findings, it is recommended that water quality data be collected regularly at consistent time intervals using a paired samples approach throughout the completion of the dam’s repair and continuing thereafter. Additionally, based on pH and temperature findings, it is recommended that water quality testing include testing for presence and concentrations of metals to stay vigilant to potential changes in the water column.
9

A comparative study of the population dynamics of four Amaranthaceae species

Schwartz, Lauren Michele 01 August 2015 (has links) (PDF)
Some of the most problematic agricultural weeds found in the Midwest United States are found in the Amaranthaceae family, such as Amaranthus palmeri and A. tuberculatus. These summer annual weeds are troublesome due to their competitive ability, high seed production, and resistance to herbicides from several modes of action which complicates management in field crops and has led to significant yield loss. Achyranthes japonica and Iresine rhizomatosa are two perennial species in the same family as A. palmeri and A. tuberculatus that occur in similar habitats as one another, but differ in invasiveness. Achyranthes japonica is a non-native, invasive species that is becoming a threat to forested areas and has been observed along agricultural field margins. Iresine rhizomatosa also occurs in forest habitats but is an endangered species in Illinois. This research seeks to determine the comparative life history and relative competitiveness of closely related weedy species when challenged with a dominant species. Specifically, select, closely related weedy species in the Amaranthaceae plant family that occur in southern Illinois were compared, i.e., Achyranthes japonica, Amaranthus palmeri, Amaranthus tuberculatus, and Iresine rhizomatosa. The first study examined the life history characteristics of A. japonica in regards to survivorship, growth and fecundity at two sites in southern Illinois (Chapter 2). Achyranthes japonica is a relatively new invasive species that has been poorly studied. This experiment showed that regardless of site, environmental factors had a significant effect on seedling emergence and seed viability, which decreased from 2012 to 2013 during a drought year and rebounded from 2013 to 2014 following flooding. On average, individuals at the driest site had higher performance and fecundity, regardless of year. The second experiment tested the relative competitive effect and response of the Amaranthaceae species to Glycine max, first in a greenhouse study that tested shading and nitrogen resource drawdown for each species, and second in a controlled field experiment that tested intraspecific competition (Chapter 3). In addition, A. japonica seedlings were planted as either unmanipulated seedlings (uncut A. japonica) or as a seedling cut back to the soil surface at the four-node stage (cut A. japonica) at which point seedlings have reached a perennial growth stage. The greenhouse experiment showed that the four species each drew down light significantly, but not nitrogen. Shading decreased the aboveground biomass of the species in comparison to unshaded controls. Supplemental nitrogen, however, increased the aboveground biomass of A. palmeri and A. japonica. The supporting controlled field experiment showed that the competitive response of the weed species to the presence of G. max showed a reduction in height compared to the weed species grown in monocultures. Glycine max and the weed species, except I. rhizomatosa, showed a similar competitive effect and response when aboveground biomass was measured. Achyranthes japonica attained the highest belowground biomass when grown as a monoculture and in the presence of G. max. A competitive effect ranking was determined to be A. palmeri > A. tuberculatus > cut A. japonica = uncut A. japonica = I. rhizomatosa with the competitive response ranking being the inverse. The third study implemented an integral projection model (IPM) to determine the population growth rate of each species and how they compared to one another (Chapter 4). This experiment showed that A. palmeri, A. tuberculatus and A. japonica each had a population growth rate greater than one indicating rapidly growing populations. By contrast, I. rhizomatosa had a population growth rate less than one indicating a declining population. The results suggest that A. japonica has not yet shown the ability to escape management strategies in agricultural fields implemented by farmers, but it is still an aggressive invasive species that farmers and land owners need to be able to identify. This species has many similar characteristics to the Amaranthus species, such as the ability to colonize in areas with limiting resources, continual flushes of germination throughout the growing season, the ability to outcompete other weed species, and high fecundity but, A. japonica also is a perennial species that can withstand removal of shoot material and has a high germination rate. Based on these results, only early detection and rapid response methods should be relied on to keep these species out of areas in and around agricultural fields. Iresine rhizomatosa’s performance in these studies was consistent with its rarity.
10

An Experimental Investigation of the Incipient Drawdown Conditions in Two-Layered Stratified Flow.

Gupta, Subhash 02 1900 (has links)
<p> An experimental study of stratified fluid flow phenomena for two equal depth, different density stratified liquids in a rectangular channel is presented. Two two fluid combinations were used, a sugar water and fresh water, and fresh water and varsol. The critical value of the determined densimetric Froude number at which the upper fluid began to participate in the flow was obtained and found to be 0.28 as against Huber's (1) predicted value of 2.76. It was concluded that the interfacial mixing and viscous effects are largely responsible for this difference. </p> <p> An attempt to extend Harleman's (7) work was made. The results obtained in present work were in good agreement with Harleman's (7) experimental work. </p> / Thesis / Master of Engineering (ME)

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