• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 208
  • 135
  • 36
  • 9
  • 6
  • 4
  • 4
  • 3
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 461
  • 461
  • 180
  • 174
  • 116
  • 115
  • 97
  • 91
  • 81
  • 55
  • 55
  • 43
  • 39
  • 38
  • 37
  • 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.
21

Development of aquatic communities in high-altitude mine pit lake systems of west-central Alberta

Sonnenberg, Rob January 2011 (has links)
Reclamation on the Cardinal River and Gregg River coal mines includes the construction of mine pit lakes connected to stream environments. Key physical, chemical and biological parameters of these “truck and shovel” lakes and their streams were investigated, and hypotheses regarding ecosystems and populations were tested. Findings include: Sphinx Lake and Pit Lake CD exhibit meromictic (partial-mixing) tendencies, but still function in a similar fashion to shallower, natural sub-alpine lakes. Elevated selenium concentrations as high as 16 ug/g (dry weight) were recorded in Rainbow trout (Oncorhynchus mykiss) eggs taken from gravid Sphinx Lake and Pit Lake CD fish. Potential detrimental effects associated with the bioaccumulation of selenium on fish reproduction were not observed. Stream water temperatures downstream of Sphinx Lake and Pit Lake CD were significantly warmer than in inlet streams and streams without pit lakes. Streambed concretions caused by calcite precipitation were documented and found to affect portions of the upper Gregg River basin. Remediation of this concretion is important for sustainability of trout populations. Aquatic communities including fish, invertebrates, zooplankton and aquatic plants are present in these pit lake systems. Athabasca Rainbow trout populations are self-propagating (spawning at the outlets) with higher densities downstream than there were prior to lake reclamation. The development of sub-alpine mine-pit lakes connected to the stream environment appears to be an appropriate and beneficial reclamation technique in this area. / xvi, 224 leaves : col. ill., map ; 28 cm
22

The challenge of implementing integrated water resources management (IWRM) in the Lower Okavango River Basin, Ngamiland district, Botswana.

Kgomotso, Phemo Karen January 2005 (has links)
Water resources management practice has undergone changes in management approaches and principles over time. It was previously characterised by what scholars refer to as the hydraulic mission where ‘extreme engineering’ was the order of the day (Allan, 2003). As Radif (1999) argues, water resources managers and policy makers were initially driven to manage and supply water to people for its direct use / these included drinking, growing food, and providing power for domestic and industrial use. This modus operandi continued until the end of the 1970s. Over two decades later, this focus is still prevalent in many countries in southern Africa including Botswana. As Swatuk and Rahm (2004) state, “augmenting supply is a continuing focus of government activity”. The National Water Master Plan (NWMP) is the current policy document guiding water resources management in Botswana and it focuses on supply-side interventions in response to increasing water demand. According to SMEC et al. (1991), the consulting company that conducted the NWMP study, “the investigation and studies... indicated the need for the continuing development of water supplies throughout Botswana over the next 30 years”. Based on these observations, government has developed significant human and technical capacity in exploiting both surface and groundwater resources (Swatuk and Rahm, 2004).
23

En studie av retentionen i floden Oder och dess avrinningsområden, Polen. / Investigation on the riverine retention in the Odra River, Poland

Dorozynska, Dorota January 2004 (has links)
<p>Nutrient enrichment is the main cause of the increasing eutrophication process in the Baltic Sea during last century. A prerequisite counteract this process the load of nutrients to the Sea must be investigated. The large contribution of nutrients to the Sea is caused by emission from the rivers within the drainage basin. For the total emission of nutrient into the Sea the retention process in the rivers has big influence. This process in the river system has been assumed as a not important part of the nutrient cycle. However some investigators have pointed out that the retention process occurs in the river and be an important part of the nutrient dynamics in the river. For the object of investigation the Odra River Basin was chosen, as an example of a large river basin in the Baltic Sea Drainage Basin. The Odra River is mainly localized in Poland and contributes substantially to the eutrophication of the Baltic Proper. The Odra River is one of the least dammed major rivers of the Baltic Proper and as such of especial interest in retention studies. The phosphorus was chosen as an example of nutrient in the eutrophication process. The purpose of the investigation is to determine the phosphorus retention within the river. Two different models were used to calculate the retention process in the river. The"Multiple Regression Model"turned out to be insignificant, therefore the results were computed by using a “similarity model”, based on similarities between load from monitored tributary basins and the rest of the sub-basin. The retention in the Odra River in the amounted to -4608 t yr-1, which is 43% of the total phosphorus emission to the Odra River. There is also stated that in the Notec and the Warta rivers the retention process occur in the amount of -1940 t yr-1 and -3007 t yr-1 respectively.</p>
24

En studie av retentionen i floden Oder och dess avrinningsområden, Polen. / Investigation on the riverine retention in the Odra River, Poland

Dorozynska, Dorota January 2004 (has links)
Nutrient enrichment is the main cause of the increasing eutrophication process in the Baltic Sea during last century. A prerequisite counteract this process the load of nutrients to the Sea must be investigated. The large contribution of nutrients to the Sea is caused by emission from the rivers within the drainage basin. For the total emission of nutrient into the Sea the retention process in the rivers has big influence. This process in the river system has been assumed as a not important part of the nutrient cycle. However some investigators have pointed out that the retention process occurs in the river and be an important part of the nutrient dynamics in the river. For the object of investigation the Odra River Basin was chosen, as an example of a large river basin in the Baltic Sea Drainage Basin. The Odra River is mainly localized in Poland and contributes substantially to the eutrophication of the Baltic Proper. The Odra River is one of the least dammed major rivers of the Baltic Proper and as such of especial interest in retention studies. The phosphorus was chosen as an example of nutrient in the eutrophication process. The purpose of the investigation is to determine the phosphorus retention within the river. Two different models were used to calculate the retention process in the river. The"Multiple Regression Model"turned out to be insignificant, therefore the results were computed by using a “similarity model”, based on similarities between load from monitored tributary basins and the rest of the sub-basin. The retention in the Odra River in the amounted to -4608 t yr-1, which is 43% of the total phosphorus emission to the Odra River. There is also stated that in the Notec and the Warta rivers the retention process occur in the amount of -1940 t yr-1 and -3007 t yr-1 respectively.
25

Mercury biomagnification in the upper South Saskatchewan River Basin

Brinkmann, Lars, University of Lethbridge. Faculty of Arts and Science January 2007 (has links)
In this thesis mercury concentrations in biota of the upper South Saskatchewan River Basin are assessed in three non-industrialized systems. Mercury levels in large sport fish (northern pike, walleye, lake trout) frequently exceeded the consumption limit of 0.5ppm. Goldeye and mooneye of the Oldman River and lake whitefish of Waterton Lakes were below 0.5ppm total mercury. Agricultural and urban effluents constituted no sources of significant mercury loadings to the Oldman River. A doubling of mercury biomagnification factors between longnose dace and their food suggests bioenergetic heterogeneity of these fish along the river gradient. Basin-specific mercury levels were detected for the upper and middle basins in Waterton Lakes, and are associated with food web characteristics, and fish bioenergetics. High mercury levels in a new reservoir were in part attributed to increased loadings from flooded soils, as is commonly observed, but also to bioenergetic constraints and growth inefficiency as a result of non-piscivory of this population. / xiii, 130 leaves : ill. ; 29 cm. --
26

The challenge of implementing integrated water resources management (IWRM) in the Lower Okavango River Basin, Ngamiland district, Botswana.

Kgomotso, Phemo Karen January 2005 (has links)
Water resources management practice has undergone changes in management approaches and principles over time. It was previously characterised by what scholars refer to as the hydraulic mission where ‘extreme engineering’ was the order of the day (Allan, 2003). As Radif (1999) argues, water resources managers and policy makers were initially driven to manage and supply water to people for its direct use / these included drinking, growing food, and providing power for domestic and industrial use. This modus operandi continued until the end of the 1970s. Over two decades later, this focus is still prevalent in many countries in southern Africa including Botswana. As Swatuk and Rahm (2004) state, “augmenting supply is a continuing focus of government activity”. The National Water Master Plan (NWMP) is the current policy document guiding water resources management in Botswana and it focuses on supply-side interventions in response to increasing water demand. According to SMEC et al. (1991), the consulting company that conducted the NWMP study, “the investigation and studies... indicated the need for the continuing development of water supplies throughout Botswana over the next 30 years”. Based on these observations, government has developed significant human and technical capacity in exploiting both surface and groundwater resources (Swatuk and Rahm, 2004).
27

Drought and upstream growth sow grain of uncertainty in the lower Colorado River basin

Barnett, Marissa McGavran 03 October 2014 (has links)
Cheap water, massive federal subsidies and political clout have sustained rice farming in the lower Colorado River basin for decades, but now the industry is in a precarious situation. Drought, population growth upstream and economic boom in Austin are pushing out the practice because of increasing demand for Texas’ scarce water resources. The tightening supply of water raised questions about the sustainability of producing such a water intensive crop in the state. Drought has cut off the cheap water to farmers for three years, and a mobilized coalition of upper river basin interests is calling for a permanent end to subsidized water. It’s increasingly clear that the politics of water in a drought-prone future is likely to side with cities, where voters are heavily concentrated. Rice farmers have scrambled to adapt. Larger rice farms have switched to groundwater. Some farmers have swapped rice for corn, milo or soybeans to keep their income. Crop insurance, which made up for at least 55 percent of the money lost in drought, softened the blow for rice farmers. But revenues in rice-related industries in Wharton, Matagorda and Colorado counties have dropped sharply and some businesses have already packed it in. These new realities cast uncertainties throughout the lower river basin, where locals fear this way of life is disappearing. / text
28

The twenty-first century Colorado River hot drought and implications for the future

Udall, Bradley, Overpeck, Jonathan 03 1900 (has links)
Between 2000 and 2014, annual Colorado River flows averaged 19% below the 1906-1999 average, the worst 15-year drought on record. At least one-sixth to one-half (average at one-third) of this loss is due to unprecedented temperatures (0.9 degrees C above the 1906-1999 average), confirming model-based analysis that continued warming will likely further reduce flows. Whereas it is virtually certain that warming will continue with additional emissions of greenhouse gases to the atmosphere, there has been no observed trend toward greater precipitation in the Colorado Basin, nor are climate models in agreement that there should be a trend. Moreover, there is a significant risk of decadal and multidecadal drought in the coming century, indicating that any increase in mean precipitation will likely be offset during periods of prolonged drought. Recently published estimates of Colorado River flow sensitivity to temperature combined with a large number of recent climate model-based temperature projections indicate that continued business-as-usual warming will drive temperature-induced declines in river flow, conservatively -20% by midcentury and -35% by end-century, with support for losses exceeding -30% at midcentury and -55% at end-century. Precipitation increases may moderate these declines somewhat, but to date no such increases are evident and there is no model agreement on future precipitation changes. These results, combined with the increasing likelihood of prolonged drought in the river basin, suggest that future climate change impacts on the Colorado River flows will be much more serious than currently assumed, especially if substantial reductions in greenhouse gas emissions do not occur. Plain Language Summary Between 2000 and 2014, annual Colorado River flows averaged 19% below the 1906-1999 average, the worst 15-year drought on record. Approximately one-third of the flow loss is due to high temperatures now common in the basin, a result of human caused climate change. Previous comparable droughts were caused by a lack of precipitation, not high temperatures. As temperatures increase in the 21st century due to continued human emissions of greenhouse gasses, additional temperature-induced flow losses will occur. These losses may exceed 20% at mid-century and 35% at end-century. Additional precipitation may reduce these temperature-induced losses somewhat, but to date no precipitation increases have been noted and climate models do not agree that such increases will occur. These results suggest that future climate change impacts on the Colorado River will be greater than currently assumed. Reductions in greenhouse gas emissions will lead to lower future temperatures and hence less flow loss.
29

Estudo e zoneamento geoambiental com auxilio de sig na bacia hidrográfica do Rio Santa Maria: sudoeste do Estado Do Rio Grande do Sul

Sccoti, Anderson Augusto Volpato January 2017 (has links)
A utilização massiva dos recursos naturais na atualidade, gera como uma de suas consequências, uma vasta depreciação dos componentes bióticos e abióticos que compõe o planeta Terra. A Bacia Hidrográfica do Rio Santa Maria possui uma diversidade fisiografica e constantemente vem sofrendo alterações ocasionadas pelas atividades antrópicas. Há uma demanda, por parte de educadores, técnicos e gestores da região, de informações ligadas a questão ambiental, de forma espacializada e georreferenciada. O presente trabalho possui como objetivo geral analisar e elaborar uma proposta de zoneamento geoambiental, utilizando métodos de mapeamentos automáticos na definição dos parâmetros naturais que servem como base para o estudo e zoneamento geoambiental. A metodologia está baseada na proposta metodológica para zonemanento Geoambiental desenvolvida por Trentin e Robaina 2005, porém como inovação nesse trabalho, optou-se por utilizar a avaliação do relevo através dos Geomorphons os quais serviram de base para a definição de compartimentos do relevo que cruzados com informações referentes a solo e litologias, originaram um mapa com informações fisiográficas. Através da interpolação do mapa fisiográfico com o mapa de uso e ocupação se obteve o mapa geoambiental. Nos resultados foram apresentadas informações sobre a morfometria da área em estudo, também foram definidas três unidades litológicas, três unidades simplificadas de solo, quatro compartimentos de relevo, quatorze unidades fisiográficas, seis classes de uso e ocupação do solo, ainda sete Sistemas e doze Unidades Geoambientais com isso foi possível definir e discutir sobre as potencialidades e suscetibilidades. A elaboração do zoneamento geoambiental, com base na definição de potencialidades e suscetibilidade, são delimitadas a partir de caracteristicas homogeneas da área de estudo, é uma importante ferramenta para avaliação e compreensão das alterações ambientais. Dessa forma, foi elaborado um diagnóstico, no qual foram apresentadas caracteristicas naturais e antrópicas da Bacia Hidrográfica do Rio Santa Maria. / The massive use of natural resources, generates as one of its consequences, a vast depreciation of the biotic and abiotic components that make up the planet Earth. The Santa Maria River Basin has a physiographic diversity and is constantly undergoing changes caused by anthropic activities. There is an existent demand, by educators, technicians and managers of the region, of information related to different topics in a spatialized and georeferenced. The present work has as general objective to analyze and elaborate a proposal of geoenvironmental zoning, using automatic mapping methods in the definition of the natural parameters that serve as the basis for geoenvironmental study and zoning. The methodology is based on the methodological proposal for Geoenvironmental zonemanento developed by Trentin and Robaina 2005, but as innovation in this work, it was decided to use the evaluation of the relief through the Geomorphons which served as the basis for the definition of relief compartments that crossed with Information on soil and lithologies, originated a map with physiographic information. Through the interpolation of the physiographic map with the map of use and occupation the geoenvironmental map was obtained. The results were presented with information on the morphometry of the study area, three lithologic units were defined, three simplified soil units, four relief compartments, fourteen physiographic units, six use classes and soil occupation, seven systems and twelve units Geoenvironmental with this it was possible to define and discuss about the potentialities and susceptibilities. The elaboration of geoenvironmental zoning, based on the definition of potentialities and susceptibility, are delimited from homogeneous characteristics of the study area, is an important tool for evaluation and understanding of environmental changes. In this way, a diagnosis was elaborated, in which natural and anthropic characteristics of the Santa Maria River Basin were presented.
30

Hydrological Impacts of Irrigation Schemes and Dams Operation in the Upper Niger Basin and Inner Niger Delta.

Maiga, Fatoumata 09 April 2019 (has links)
The Upper Niger Basins (UNB) and the Inner Niger Delta (IND) are integral parts of the Niger River Basin, which flows through 10 countries and constitutes the third longest river in Africa. Natural climate variability and human interventions are two major factors affecting the hydrological regime in the UNB and IND. This study focuses on the later factor, by assessing the hydrological impacts of key existing and planned manmade structures and irrigation schemes in the UNB: the Sélingué (existing dam in Mali), four variants of the Fomi/Moussako dam (planned in Guinea), and Office du Niger (irrigation scheme located in Mali). The Fomi /Moussako dam will be located in the headwaters of the UNB and therefore, is expected to alter the hydrological regime in large parts of the watershed. Expected impacts include a reduction of the flood peak which will adversely affect critical ecosystems in the IND, and higher flows directly downstream of the dams in the dry season to sustain irrigation. These higher flows will, however, be consumed by Office du Niger irrigation scheme, leading to possible severe water shortages downstream of the irrigation scheme and in the IND. This is likely to affect the Malian economy and the poorest parts of its population, as the IND is crucial for the socio-economic and ecological preservation and development of the population surrounding it. The hydrological impacts of the dams and the irrigation scheme were evaluated in this study by developing a model of the IND and UNB using SWAT (Soil and Water Assessment Tool). After the model was calibrated, the effects of the dams and the irrigation scheme on selected flow statistics (mean and standard deviation) were determined at fourteen hydrological stations. In general, the results have shown that (1) the Fomi/Moussako dam will noticeably reduce the downstream high flows, and reduce the average flow; (2) if the Fomi/Moussako dam was to be built, the alternatives with the least storage volume (Moussako 388.5') will have the least impacts on the downstream flows. To assist in related decision making for various users, a Decision Support System (DSS) was also developed. The goal of the DSS is to help users analyze the effects of dams and irrigation on the flow regime by performing a comparative analysis (presence and absence of dams and irrigation in the river). A number of potential adaptation measures were also proposed.

Page generated in 0.0628 seconds