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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

Simulation and evaluation of water yield response to vegetation management on a forested watershed in Arizona

Hekman, Louis Harry,1945- January 1977 (has links)
A methodology is presented for evaluating timber clearing as a means for beneficially increasing water yields from forested watersheds. Stochastic models of temperature and precipitation are developed and used to generate long term synthetic records of rain, snow, snowmelt, and potential evaporation. A deterministic hydrologic watershed model transforms the synthetic climatic data into long term streamflow records reflecting the hydrologic effects of clearing selected percentages of watershed area, either on a permanent or rotational basis. The simulated streamflow regimes are then analyzed in relation to the impacted reservoir and water supply system. Evaluation categories discussed include timber and forage production, agricultural water supply, flooding, hydroelectric power production, and reservoir-based recreation. A 38.8 square mile watershed on the East Fork White River in east-central Arizona is used to illustrate the procedures developed in this study. Vegetation management alternatives modeled are permanent conversion of 0, 20, 33, 50, 67, and 100 percent of the watershed area, as well as periodic harvesting, with subsequent timber regrowth, of 20, 33, and 50 percent of the watershed area. A hypothetical reservoir system serves as the basis for evaluating a 250 year simulated streamflow record induced by each management option. All conversion activities result in increased streamflow, better ability to meet water demands, greater recreational activity, and more power production. However, potential for flood damage and wasted reservoir releases also increase. Depending on specific management objectives, the ultimate choice lies within the 20 to 50 percent range of permanent conversion activities.
2

Metal cycling in terrestrial and aquatic ecosystems

Perusse, Martin January 1990 (has links)
The present study examines the cycling of elements in the biosphere. The first chapter proposes a theoretical framework for this cycling based on both metal/ligand theory and mass balance studies. Empirical modelling serves as an alternative and complement to mass balance studies in predicting the export of elements from watersheds. Watershed output (export per unit area per unit of time) is predicted using atmospheric deposition rates, an element bonding strength index, the watershed area and a forest classification (deciduous vs coniferous). Finally the last chapter examines, in a speculative fashion, the partitioning of elements between the atmosphere and hydrosphere as a function of element behaviour and discusses the ecological consequences of human activity on this partitioning.
3

Metal cycling in terrestrial and aquatic ecosystems

Perusse, Martin January 1990 (has links)
No description available.
4

Geometric simplification of a distributed rainfall-runoff model over a range of basin scales.

Goodrich, David Charles. January 1990 (has links)
Distributed rainfall-runoff models are gaining widespread acceptance; yet, a fundamental issue that must be addressed by all users of these models is definition of an acceptable level of watershed discretization (geometric model complexity). The level of geometric model complexity is a function of basin and climatic scales as well as the availability of input and verification data. Equilibrium discharge storage is employed to develop a quantitative methodology to define a level of geometric model complexity commensurate with a specified level of model performance. Equilibrium storage ratios are used to define the transition from overland to channel-dominated flow response. The methodology is tested on four subcatchments in the USDA-ARS Walnut Gulch Experimental Watershed in southeastern Arizona. The catchments cover a range of basins scales of over three orders of magnitude. This enabled a unique assessment of watershed response behavior as a function of basin scale. High quality, distributed, rainfall-runoff data were used to verify the model (KINEROSR). Excellent calibration and verification results provided confidence in subsequent model interpretations regarding watershed response behavior. An average elementary channel support area of roughly 15% of the total basin area is shown to provide a watershed discretization level that maintains model performance for basins ranging in size from 1.5 to 631 hectares. Detailed examination of infiltration, including the role and impacts of incorporating small-scale infiltration variability in a distribution sense, into KINEROSR, over a range of soils and climatic scales was also addressed. The impacts of infiltration and channel losses on runoff response increase with increasing watershed scale as the relative influence of storms is diminished in a semi-arid environment such as Walnut Gulch. In this semi-arid environment, characterized by ephemeral streams, watershed runoff response does not become more linear with increasing watershed scale but appears to become more nonlinear.
5

Thunderstorm runoff in southeastern Arizona.

Osborn, H. B.(Herbert B.),1929- January 1971 (has links)
Almost all runoff-producing rainfall on small watersheds (100 square miles and less) in southeastern Arizona results from air-mass thunderstorms. On large watersheds (1,000 square miles and greater) frontal systems which may include thunderstorm activity or snowmelt produce the major flood peaks as well as much of the annual runoff. Air-mass thunderstorms are of short duration and limited areal extent, and generally occur in the late afternoons and early evenings in July, August, and September. Runoff-producing rainfall may occur from frontal-convective systems at any time although they are most common in southeastern Arizona in September. Rainfall and runoff records have been collected from the 58- square-mile Walnut Gulch rangeland watershed near Tombstone in southeastern Arizona by the Agricultural Research Service since 1954. These data represent the best information available on thunderstorm rainfall-runoff relationships in the Southwest. At present there are 95 recording rain gages and 22 permanent runoff-measuring stations on the Walnut Gulch watershed. Runoff-producing thunderstorm rainfall is extremely variable both in time and space, and is therefore difficult to measure accurately and define precisely. Isohyetal mapping for rainfall from individual thunderstorms both for total rainfall and shorter durations within the storm provides good qualitative information, and also provides some quantitative limits on storm movement, intensities and volumes, and areal extent. Runoff records from Walnut Gulch and other Arizona watersheds indicate that peak discharge and runoff volume from individual thunderstorms decrease with increasing watershed size because of the limited areal extent of runoff-producing thunderstorms and because cf the increasing channel abstractions with increasing watershed size. Channel abstractions greatly alter runoff hydrographs as flood surges move through the ephemeral channel system. Five major runoff-producing thunderstorms on Walnut Gulch between 1957 and 1967 were used to develop a model for the maximum expected rainfall in southeastern Arizona. The model was based on maximum 30-minute point rainfalls within the average 60-minute runoff-producing thunderstorm. Over 2.5 inches of rainfall has been recorded in 30 minutes on Walnut Gulch during 3 thunderstorms in 15 years of record (1955-1969). A thorough search of U.S. Weather Bureau and other records indicated that no storms of this combined intensity and magnitude have been recorded in Arizona. Therefore, for design purposes, the expected mean 30-minute rainfall for southeastern Arizona was estimated as 3 inches. Regression analysis was used to estimate peak discharges for major runoff events on Walnut Gulch and to develop a rainfall-runoff model for Walnut Gulch. Peak discharges were correlated with the maximum 30-minute rainfall, which was considered the core of runoff-producing rainfall for major runoff events. Antecedent channel conditions and distance between watershed outlet and runoff-producing rainfall had little effect on the correlation. The coefficients of determination for the regression equation correlating thunderstorm rainfall and peak runoff were 0.92 and o.84 for watershed 5 (8 square miles) and watershed 1 (58 square miles), respectively. With the model for maximum expected rainfall and the rainfall-runoff model for estimating peak discharge from maximum 30-minute rainfall, maximum discharge for the 58-square-mile Walnut Gulch watershed was 23,000 c.f.s. Assuming a normal distribution of errors, within 95 percent confidence limits, the limits were 19,000 and 27,000 c.f.s., and assuming the Chebyshev inequality, the limits were 15,000 and 31,000 c.f.s. Recurrence intervals for 20-, 50-, and 100-year storms and the maximum peak discharges were developed for small watersheds (100 square miles and less) from Walnut Gulch data. The curves were compared to a family of curves for Arizona watersheds up to several hundred thousand square miles. The family of curves based on Walnut Gulch data were much steeper, strongly suggesting that there are 2 families of curves, one steeper family for the small watersheds (100 square miles and less) which is based on runoff peaks from air-mass thunderstorms, and another flatter family of curves for the large watersheds (1,000 square miles and greater) which is based on runoff peaks from frontal-convective systems and snowmelt. The 2 families of curves probably intersect between 100 and 1,000 square miles.
6

Information transfer for hydrologic prediction in engaged river basins

Patil, Sopan Dileep 08 November 2011 (has links)
In many parts of the world, developed as well as developing, rivers are not gauged for continuous monitoring. Streamflow prediction at such "ungauged" river catchments requires information transfer from gauged catchments that are perceived to be hydrologically similar to them. Achieving good predictability at ungauged catchments requires an in-depth understanding of the physical and climatic controls on hydrologic similarity among catchments. This dissertation attempts to gain a better understanding of these controls through three independent research studies that use data from catchments across the continental United States. In the first study, I explore whether streamflow similarity among nearby catchments is preserved across flow conditions. Catchments located across four river basins in the northeast United States are analyzed to quantify the spatio-temporal variability in streamflows across flow percentiles. Results show that similarity in catchment stream response is dynamic and highly dependent on flow conditions. Specifically, the coefficient of variation is high at low flow percentiles and gradually reduces for higher flow percentiles. This study concludes that high variability at low flows is controlled by the dominance of high evaporative demand, whereas low variability at high flows is controlled by the dominance of precipitation input relative to evapotranspiration. In the second study, I examine whether streamflow similarity among catchments exists across a wide range of climatic and geographic regions. Data from 756 catchments across the United States is used and daily streamflow at each catchment is simulated using distance-based streamflow interpolation from neighboring catchments. With this approach, high predictability at a catchment indicates that catchments in its vicinity have similar streamflows. Results show that high predictability catchments are mainly confined to the Appalachian Mountains, the Rocky Mountains, and Cascade Mountains in the Pacific Northwest. Low predictability catchments are located mostly in the drier regions of US to the west of Mississippi river. Results suggest that streamflow similarity among nearby catchments is more likely in humid runoff-dominated regions than in dry evapotranspiration-dominated regions. In the third study, my goal is to identify what constitutes the essential information that must be transferred from gauged to ungauged catchments in order to achieve good model predictability. A simple daily time-step rainfall-runoff model is developed and implemented over 756 catchments located across the United States. Results show that the rainfall-runoff model simulates well at catchments in humid low-energy environments, most of which are located in the eastern part of the US, the Rocky Mountains, and to the west of Cascade Mountains. Within these regions, transfer of the parameter characterizing hydrograph recession provides reliable streamflow predictions at ungauged catchments, with a loss in prediction efficiency of less than 10% in most catchments. The results presented in this dissertation show that climate exerts a strong control on hydrologic similarity among catchments. The results further suggest that an understanding of the interaction between climate and topography is essential for quantifying the spatial variability in catchment hydrologic behavior at a regional scale.
7

A study of runoff losses from different slopes and lengths in a small watershed

Azar, Emanuel January 1940 (has links)
In recent years, both the state and federal governments of the United States have at last recognized erosion as a serious problem affecting the people of this land socially and economically, just as it affected the people of those kingdoms now buried in the sands of the deserts. Because of the seriousness of the problem, studies are being instituted on larger scopes than ever before and there is a greater realization of the pressing need for more adequate information about erosion, its causes, effects, prevention, and other related factors. That intense rainstorms result in higher rates of runoff is an acknowledged fact. These rates of runoff play an important part in studies made by soil conservationists, and upon their studies will depend the same success or failure of conservation practices. Soil conservationists have already espied the need for planning projects or designs that will take care of maximum runoffs which are to be expected at definite frequencies. The United States Geological Survey has collected records and made investigations of great value to engineers of navigation and flood control projects, as well as power developments and other such works which interest students of hydrology and soil conservation. Moreover, experiment stations in practically every state are cooperating with soil conservationists and soil specialists in attacking erosion problems facing the nation. The goal of all these investigations is towards finding means by which to help Nature in keeping the land so clothes that erosion may be kept within the natural limits. Hence, work is being conducted on many various problems. One particular problem upon which more information is needed is that runoff, its causes and effects in the Limestone Valley and Uplands Region in the State of Virginia. With the idea of making some contribution, therefore, that may help effect a solution by making available data for the above region, this problem was chosen as a subject for a Master’s thesis. / Master of Science
8

Caracterização temporal e espacial da temperatura do ar e da evapotranspiração de referência na Bolívia /

Choque Conde, Esteban January 2017 (has links)
Orientador: João Francisco Escobedo / Banca: Valéria Cristina Rodrigues Sarnighausen / Banca: Rodrigo Máximo Sanchez Román / Banca: Paulo Andre de Oliveira / Banca: Carlos Roberto Pereira Padovani / Abstract: The objective of this research was to study air temperature and reference evapotranspiration (ETo) in the different agroecological zones of Bolivia (Plains, Valleys and Andean) using statistical and geostatistical models, with air temperature database of 235 meteorological stations in Bolivia and 41 of neighboring countries was used. The study is presented in two chapters: The first describes the characterization of the values of the medium (Tmed) maximum (Tmax) and minimum (Tmin) air temperature, through three spatial distributions: Departments, hydrographic basins and agroecological zones. Being the latter the best alternative of analysis. Linear regression analysis allowed to obtain the estimation equations for Tmed, Tmax and Tmin in function of altitude, with high determination coefficients (R2). The deviations resulting from comparisons between the seasonal and monthly equations estimated values in relation to the annual average suggest, in most altitudes, seasonal or monthly equations use, mainly for Tmed and Tmin. Were presented the spatial variations Tmed, Tmax and Tmin through isothermal maps. The maps show the strong influence of altitude on temperature values, placing higher isotherms in the Plains zone (lowlands) and lower in the Andean zone (highlands). The second chapter describes the characterization of ETo in the three agroecological zones of Bolivia, using temperature as the input variable: McGuinness - Bordne, Hargreaves - Samani and Thornthwaite. All three ... (Complete abstract click electronic access below) / Resumen: La presente investigación tuvo por objetivo estudiar la temperatura del aire y la evapotranspiración de referencia (ETo) en las diferentes zonas agroecológicas de Bolivia (Llanos, Valles y Andina) a través de modelos estadísticos y geoestadísticos, con base de datos de temperaturas del aire de 235 estaciones meteorológicas de Bolivia y 41 de países vecinos. El estudio es presentado en dos capítulos: El primero describe la caracterización de valores de la temperatura media (Tmed) máxima (Tmax) y mínima (Tmin) del aire, mediante tres distribuciones espaciales: Departamentos, cuencas hidrográficas y zonas agroecológicas. Siendo esta última la mejor alternativa de análisis. Un análisis de regresión lineal logró obtener las ecuaciones anuales que estiman la Tmed, Tmax e Tmin en función de la altitud, con elevados coeficientes de determinación (R2). Las desviaciones resultantes de comparaciones entre las ecuaciones estacionales y mensuales en relación a la media anual sugieren, en la mayoría de las altitudes, el uso de ecuaciones estacionales o mensuales, particularmente para Tmed e Tmin. Fueron presentadas las variaciones espaciales de Tmed, Tmax e Tmin por medio de mapas isotérmicas, los mapas evidencian la fuerte influencia de la altitud sobre valores de Tmed, Tmax e Tmin, marcando isotermas de valores más altos en la zona de los Llanos (zonas bajas) y, de valores más bajos en la zona Andina (zonas altas). El segundo capítulo describe la caracterización de ETo en tres zonas agro... (Resumen completo clicar acceso eletrônico abajo) / Resumo: O presente pesquisa teve por objetivo estudar a temperatura do ar e a evapotranspiração de referência (ETo) nas diferentes zonas agroecológicas da Bolívia (Lhanos, Vales e Andina) por meio de modelos estatísticos e geoestatísticos, com base de dados de temperatura do ar de 235 estações meteorológicas da Bolívia e 41 de países vizinhos. O estudo é apresentado em dois capítulos: O primeiro descreve a caracterização dos valores de temperatura média (Tmed) máxima (Tmax) e mínima (Tmin) do ar, mediante três distribuições espaciais: Departamentos, bacias hidrográficas e zonas agroecológicas, sendo esta última a melhor alternativa de análise. Uma análise de regressão linear permitiu a obtenção das equações de estimativa Tmed, Tmax e Tmin em função da altitude, com elevados coeficientes de determinação (R2). Os desvios resultantes das comparações entre os valores estimados das equações sazonais e mensais em relação à média anual sugerem, na maioria das altitudes, o uso das equações sazonais ou mensais, particularmente para Tmed e Tmin. Foram apresentados as variações espaciais da Tmed, Tmax e Tmin por meio de mapas isotérmicas. Os mapas comprovam a forte influência da altitude sobre valores de Tmed, Tmax e Tmin, colocando isotermas de valores mais altos na zona dos Lhanos (zonas baixas) e, de valores mais baixos na zona Andina (zonas altas). O segundo capítulo, descreve a caracterização da ETo nas três zonas agroecológicas da Bolívia, utilizando a temperatura como variável de entrada... (Resumo completo, clicar acesso eletrônico abaixo) / Doutor
9

The effect of urbanization on watershed runoff.

Foerster, Eugene Paul,1932- January 1972 (has links)
A study was undertaken to determine the effect of urbanization on the rainfall-runoff relationship of a semiarid region. A concentrated network of rain gages was installed on the urban Tucson Arroyo-Arroyo Chico Watershed located in the city of Tucson, Arizona. Rainfall data from this watershed were compared with that of the non-urban Atterbury Experimental Watershed located to the southeast of the city of Tucson in order to determine if there were significant differences in the runoff from these two watersheds. In addition, test plots were constructed by the researcher for the study of the effects of intensity of precipitation, season, antecedent moisture, and percent of impervious cover on the rainfall-runoff relationship. Data from the test plots were compared with that of the Tucson Arroyo-Arroyo Chico Watershed. A prediction model was developed for the Tucson Arroyo-Arroyo Chico Watershed. The feasibility of retaining urban runoff for more beneficial uses was investigated. It was determined that the runoff from the urban Tucson Arroyo- Arroyo Chico Watershed was 4.75 times greater per square unit of area than that from the non-urban Atterbury Experimental Watershed. Significant factors in the rainfall-runoff relationships of the test plot data were found to be intensity of precipitation and amount of impervious cover. Season was found not to be significant. Antecedent moisture was a significant factor in the analysis of variance of the data. However, it was not significant in the regression analysis. In the comparison of the test plot data and the data from the Tucson Arroyo-Arroyo Chico Watershed, it was found that intensity of precipitation was the predominant factor in the rainfall-runoff relationship. In plotting the effects of intensity of precipitation versus runoff, the resulting graph indicated an increasing effect of impervious cover and intensity of precipitation on runoff from the test plots. A regression model was developed from the data of the Tucson Arroyo-Arroyo Chico Watershed. The factors of average precipitation and intensity of precipitation accounted for 82 percent of the variation in the analysis. Of these two factors, intensity of precipitation accounted for 68 percent of the variation. Duration of precipitation and the antecedent moisture index did not significantly increase the correlation coefficient of the regression analysis when they were included. The projected runoff from the city of Tucson would amount to less than 10 percent of the present yearly use. The treatment necessary for the domestic use of urban runoff would be greater than the present cost of producing municipal water from well-sites. Recharging this water into the groundwater supply appears to be the most feasible method of utilizing urban runoff at this time.
10

Caracterização fitossociológica da vegetação ripária e qualidade da água do córrego do cintra (Botucatu SP) em função da ação antrópica /

Belluta, Ivalde, 1963- January 2012 (has links)
Orientador: Sérgio Campos / Coorientador: Assunta Maria Marques da Silva / Coorientador: Vera Lex Angel / Banca: Luciano Nardini Gomes / Banca: Osmar Delmanto Junior / Banca: Jandira Liria B. Talamoni / Banca: Raimundo Leite Cruz / Resumo: Bacia hidrográfica é a unidade geográfica que se ajusta aos objetivos de planejamento agrícola e ambiental, cuja área é sensível e imprescindível para sua integridade física e qualidade da água, devendo ser protegida pela vegetação. A sub-bacia do Córrego do Cintra (1.136,8ha) está localizada à noroeste de Botucatu SP, tem suas nascentes no Campus da UNESP de Rubião Junior e segue fluxo ao norte até o Rio Tietê. Este trabalho teve como objetivo geral caracterizar a estrutura e o estádio sucessional da mata ripária, avaliar a qualidade da água e detectar fontes de poluição pontual e difusa naquela sub-bacia. O método fitossociológico utilizado foi o de ponto-quadrante, aplicado em três áreas de mata ripária; os índices Dr, Dor, IVC, Diversidade e Similaridade foram obtidos através de cálculo em planilha eletrônica e do programa Past; o estádio sucessional foi determinado pela proporção de espécies de cada grupo ecológico. Os parâmetros físico-químicos e espécies químicas da água foram amostrados em oito pontos no período de 2007 a 2009 e para avaliar o comportamento de cada variável nos locais de amostragem, foram realizadas análises de variâncias seguidas do teste de Tukey e também a análise de componentes principais. Estes parâmetros, as análises microbiológicas e as dos metais mais tóxicos foram determinados pelo Standard Methods for the Examination of Water and Wastewater e comparados aos valores máximos permitidos (VMP) do Conama, Classe II, e quanto para os defensivos agrícolas utilizou-se o método cromatográfico. Nas três áreas de amostragem foram encontradas 2.241 indivíduos arbóreos de 145 espécies... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Watershed is the geographic unit that meets the goals of agricultural and environmental planning, the area of which is sensitive and essential for its physical integrity and water quality and thus must be protected by the vegetation. The subwatershed of Cintra Stream (1,136.8ha) is located northwest to Botucatu, São Paulo State, and has its springs in the Campus of UNESP at Rubião Junior, flowing towards north until Tietê River. The general aims of this study were to characterize the structure and the successional stage of the riparian forest, to assess the water quality and to detect punctual and diffuse pollution sources in that subwatershed. The adopted phytosociological method was the point-quadrant, applied to three areas of riparian forest; the indexes RD, RDo, CVI, Diversity and Similarity were obtained by calculation in spreadsheet and the software Past; the successional stage was determined based on the proportion of species of each ecological group. The physico-chemical parameters and the chemical species of water were sampled at eight sites from 2007 to 2009, and to assess the behavior of each variable at the sampling sites, analyses of variance were done followed by Tukey's test and analysis of the main components. These parameters, microbiological analyses and analyses of the most toxic metals were determined according to the Standard Methods for the Examination of Water and Wastewater and compared to Conama's maximal allowed value (MAV), Class II; for pesticides, the chromatographic method was used. In three sampling areas, 2,241 arboreal individuals and 145 species were found; they belonged to 55 botanical families, and the most representative family was Fabaceae with... (Complete abstract click electronic access below) / Doutor

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