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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

Dendrohydrological reconstruction and hydroclimatic variability in southwestern British Columbia, Canada

Mood, Bryan Joel 19 November 2019 (has links)
The hydrology of southwestern British Columbia is influenced by the region’s mountainous topography and climate oscillations generated from the Pacific Ocean. While much of the region is characterized as a temperate rainforest, recent summers are defined by record-breaking droughts that focus attention on the threat to regional water supply security likely to accompany future climate changes. The limited length and distribution of hydrological records in southwestern British Columbia provide poor context for resource managers tasked with developing policy and water management strategies. The purpose of the dissertation was to describe long-term variability in several key hydroclimatic variables and hydroecological interactions that may be used in updated water resource policy and management strategies. Specifically, the research focused on developing long-term proxy records of April 1 snow water equivalent (SWE), summer streamflow, spring lake levels, and salmon abundance from tree ring records. A secondary goal of the dissertation was to identify the role and influence of several key climate oscillations on regional long-term hydroclimatic and ecological variability. Freshet contributions from melting snow are critical for sustained summer streamflow in southwestern British Columbia. Even so, few manual snow survey stations exist within the region are of sufficient length to understand the full range of natural SWE variability. Long-term April 1 SWE records were constructed by establishing statistical relationships with the radial growth of high-elevation trees and April 1 SWE records. Explaining 51% and 73% of the total variance in the instrumental SWE records in coastal and continental settings, the reconstructions provide high-resolution descriptions of April 1 SWE over the past three centuries and help position the remainder of the dissertation. Negative phases of the Pacific Decadal Oscillation (PDO) and El Niño-Southern Oscillation (ENSO) were shown to strongly influence April 1 SWE totals. Both reconstructions illustrate repeated step-changes in April 1 SWE during the last 300 years and show that coastal areas may be more sensitive to annual variability than snowpack that accumulates in more continental locations. Water shortages in the Metro Vancouver area in recent summers are linked to low total winter snowpack and early spring melt. Dendrohydrological analysis of dry-season streamflow was conducted to determine if the instrumental range has been underestimated over the past several centuries. A regionalized record of July-August streamflow for the Capilano and Seymour watersheds, which supply the Metro Vancouver area, was modelled from present to 1711using tree-rings. Explaining 54% of total variance over the instrumental period, the models show that below-average streamflow events are becoming more frequent. When compared to those characterizing the past 300 years, streamflow totals from 1977 to present have consistently fallen well-below the average long-term discharge. Further analyses indicated that negative ENSO and PDO conditions strongly influenced July-August runoff trends since 1711, as have climate regimes related to the Pacific North American pattern (PNA). The increased frequency in recent years of reduced summer runoff in southwestern British Columbia has led many communities to rely on natural and dammed reservoirs to supplement their water needs. Where communities rely on natural lakes, this dependence may have socioeconomic consequences if lake levels fall below those necessary to supply built infrastructure. Unfortunately, there are few lake level records in southwestern British Columbia and none of sufficient duration to understand the full range of variability in natural lake systems. Harrison Lake is the only natural lake with a lake level record exceeding 50 years. Using the average April water level dataset, a dendrohydrological model was constructed that explained 49.5% of total variance. The model was used to reconstruct a proxy record of April water levels spanning the interval from 1711 to 1980. Averaging 9.37 m in depth, lake levels in Harrison Lake ranged from 8.9 to 10.0 m over the past 300 years. These variations were shown to be statistically associated with negative and positive phases of ENSO and positive phases of PDO. April water levels in Harrison Lake have been, on average, 0.13 m lower since the mid-1930s compared to the previous 200 years. This reduction in storage capacity amounts to a loss of almost 300-million litres of stored water since the start of instrumental records. Salmon play a vital economic, cultural, and social role in many southwestern British Columbia communities. There is concern that salmon populations in the region are under threat, as changing climates alter and impact their spawning habitat. While various lines of research have sought to determine the response of salmon to these changing conditions, population records that extend only to 1951 hinder a complete understanding of the impacts. Two dendroecological models were constructed to provide a longer-term perspective of regional salmon-climate relationships. Explaining 48.2% and 48.9% of variance in observed Chinook and Coho salmon abundance since 1951, the models were used to construct proxy escapement records extending to the 1700s. Spectral analysis revealed that the reconstructions account for generational life histories and that low-frequency climate variability was associated with fluctuations in abundance. Both the Chinook and the Coho reconstructions show phase dependent relationships to climate oscillations generated from the Pacific Ocean. The Coho record is strongly linked to negative winter and spring ENSO, while the Chinook record was shown to be associated with negative PDO conditions. The identified relationships to teleconnections generated in the Pacific Ocean to our record indicates that both species are sensitive to oceanic interactions prior to entering natal habitats. Taken together, the reconstructions illustrate that the observational record encompasses a period of lower-than-average abundance and that neither accounts for the full range of variability in annual abundance when considered over the past three centuries. The proxy tree-ring records presented in this dissertation provide new information about climate-water resource relationships in southwestern British Columbia. Significant phase-dependent associations, especially to negative phases of the PDO and ENSO, were shown to exert long-term influences on the state of several critical hydroclimatic variables over the last 300 years. Additionally, the research illustrates that over the instrumental period, both streamflow and lake volumes in the region have consistently remained below those characterizing the previous two to three centuries. These findings are of direct use to resource managers tasked with developing new policy and strategies under present and future climate change, in that they offer singular insights into the full range of natural hydroclimatic variability in southwestern British Columbia. / Graduate
2

Hydroekologický monitoring a revitalizace malého vodního toku / Hydroecological monitoring and revitalisation of small water course

Řídký, Vojtěch January 2018 (has links)
This diploma thesis describes the hydroecological monitoring of the small water course Stanůvka in the South Moravian Region. Hydroecological monitoring was carried out according to the recognized methodology of the Ministry of the Environment of the Czech Republic. In the thesis is suggested a revitalization of this water course. At the end of the thesis a comparison of the current state of the water course and the condition proposed by the revitalization is made and the contribution of this revitalization is evaluated.
3

Hydroekologický monitoring a revitalizace malého vodního toku / Hydroecological monitoring and revitalisation of small water course

Komendová, Denisa January 2019 (has links)
This thesis deals with the hydroecological monitoring and river restoration of the Syrovinka watercourse in Hodonín district. In the framework of the hydroecological monitoring a river hydromorphological assessment was conducted as a part of assessing the ecological status of watercourse, to meet the requirement of the Water Framework Directive. Hydroecological monitoring was conducted using methodology HEM 2014, which is accepted as a national standard by the Ministry of Environment of the Czech Republic. Problematic reaches of watercourse were determined and for the selected reach a river restoration measures have been designed. Subsequently, an efficiency of river restoration was evaluated. The main benefits of designed river restoration are the restoration of ecological function and the support of natural water retention in floodplain.
4

Hydroekologický monitoring Sopřečského potoka a možnosti zlepšení jeho stavu / Hydromorphological monitoring of Sopřečský stream and and possibilities of its improvement

Sirůčková, Renáta January 2020 (has links)
This thesis deals with the hydroecological monitoring of the Sopřečský potok and possibilities of its improvement. The Sopřečský potok is located in the Pardubice Region in the Elbe River Basin. In the first phase of the work, hydroecological monitoring was carried out and then the hydromorphological state of the watercourse was evaluated. All procedures comply with the requirements of the Water Framework Directive. On the basis of its evaluation and taking into account the delimitation of ÚSES elements, the sections on which the measures to improve the state of the watecourse were implemented were selected. The effect of the modifications on the hydromorphological state was again evaluated. In conclusion, there is a comparison and summary of the proposed modifications to the existing state of watercourse.
5

Komplex opatření v povodí Javornického potoka pro zlepšení kvality vody v malé vodní nádrži Rosnička / Set of arrangements in Javornický stream floodplain for Rosnička pond water quality improvement

Špaček, Ondřej January 2022 (has links)
This thesis deals with the projection of water management and erosion control measures in the Javornický stream floodplain to improve water quality in the Rosnička pond near the town of Svitavy. In the teoretical part, the author summarized current practices in the areas of small river restorations and protection against soil erosion in the Czech Republic. In the practical part, the analasis of the area was first made, including the analysis of natural conditions, hydroecological monitoring of watercourses according to the HEM 2014 method and quantification of soil loss conditions according to the USLE method. Then, revitalization measures on the Javornický stream were designed to improve the self-purification of water and the restoration of ground water in the floodplain, as well as two variants of erosion control measures on agricultural areas to reduce the input of sediments into the hydrographic network. Finally, conceptual and technical recommendations for the implementation of these measures were formulated, as a basis for planning and decision-making of the political leadership of the town of Svitavy.

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