Thesis (Ph.D.) -- Mississippi State University. Department of Biological Sciences. / Title from title screen. Includes bibliographical references.

abstract: As much as 40% of the world's human population relies on rivers which originate on the Qinghai-Tibetan Plateau (QTP) (Xu et al. 2009, Immerzeel et al. 2010). However, the high alpine grasslands where these rivers emanate are at a crossroads. Fed by seasonal monsoon rains and glacial runoff, these rivers' frequent flooding contributes to massive losses of life and property downstream (Varis et al. 2012). Additionally, upstream grasslands, which regulate the flow of these rivers, are considered to be deteriorating (Harris 2010). This thesis examines the regional vulnerability of these rivers and highlights the impacts of several policy responses, finding that both climate change and grassland degradation pose significant challenges to Asia's water security. Additionally, I suggest that many of the responses elicited by policy makers to meet these challenges have failed. One of these policies has been the poisoning of a small, endemic, burrowing mammal and keystone species, the plateau pika (Ochotona curzoniae) (Smith and Foggin 1999). Contrary to their putative classification as a pest (Fan et al. 1999), I show that the plateau pika is instead an ecosystem engineer that actively increases the infiltration rate of water on the QTP with concomitant benefits to both local ecosystems and downstream hydrological processes. / Dissertation/Thesis / M.S. Biology 2012

abstract: Biological soil crusts (BSCs) dominate the soil surface of drylands in the western United States and possess properties thought to influence local hydrology. Little agreement exists, however, on the effects of BSCs on runoff, infiltration, and evaporative rates. This study aims to improve the predictive capability of an ecohydrology model in order to understand how BSCs affect the storage, retention, and infiltration of water into soils characteristic of the Colorado Plateau. A set of soil moisture measurements obtained at a climate manipulation experiment near Moab, Utah, are used for model development and testing. Over five years, different rainfall treatments over experimental plots resulted in the development of BSC cover with different properties that influence soil moisture differently. This study used numerical simulations to isolate the relative roles of different BSC properties on the hydrologic response at the plot-scale. On-site meteorological, soil texture and vegetation property datasets are utilized as inputs into a ecohydrology model, modified to include local processes: (1) temperature-dependent precipitation partitioning, snow accumulation and melt, (2) seasonally-variable potential evapotranspiration, (3) plant species-specific transpiration factors, and (4) a new module to account for the water balance of the BSC. Soil, BSC and vegetation parameters were determined from field measurements or through model calibration to the soil moisture observations using the Shuffled Complex Evolution algorithm. Model performance is assessed against five years of soil moisture measurements at each experimental site, representing a wide range of crust cover properties. Simulation experiments were then carried out using the calibrated ecohydrology model in which BSC parameters were varied according to the level of development of the BSC, as represented by the BSC roughness. These results indicate that BSCs act to both buffer against evaporative soil moisture losses by enhancing BSC moisture evaporation and significantly alter the rates of soil water infiltration by reducing moisture storage and increasing conductivity in the BSC. The simulation results for soil water infiltration, storage and retention across a wide range of meteorological events help explain the conflicting hydrologic outcomes present in the literature on BSCs. In addition, identifying how BSCs mediate infiltration and evaporation processes has implications for dryland ecosystem function in the western United States. / Dissertation/Thesis / Masters Thesis Geological Sciences 2015

abstract: Hydrological models in arid and semi-arid ecosystems can be subject to high uncertainties. Spatial variability in soil moisture and evapotranspiration, key components of the water cycle, can contribute to model uncertainty. In particular, an understudied source of spatial variation is the effect of plant-plant interactions on water fluxes. At patch scales (plant and associated soil), plant neighbors can either negatively or positively affect soil water availability via competition or hydraulic redistribution, respectively. The aboveground microclimate can also be altered via canopy shading effects by neighbors. Across longer timescales (years), plants may adjust their physiological (water-use) traits in response to the neighbor-altered microclimate, which subsequently affects transpiration rates. The influence of physiological adjustments and neighbor-altered microclimate on water fluxes was assessed around Larrea tridentata in the Sonoran Desert. Field measurements of Larrea’s stomatal behavior and vertical root distributions were used to examine the effects of neighbors on Larrea’s physiological controls on transpiration. A modeling based approach was implemented to explore the sensitivity of evapotranspiration and soil moisture to neighbor effects. Neighbors significantly altered both above- and belowground physiological controls on evapotranspiration. Compared to Larrea growing alone, neighbors increased Larrea’s annual transpiration by up to 75% and 30% at the patch and stand scales, respectively. Estimates of annual transpiration were highly sensitive to the presence/absence of competition for water, and on seasonal timescales, physiological adjustments significantly influenced transpiration estimates. Plant-plant interactions can be a significant source of spatial variation in ecohydrological models, and both physiological adjustments to neighbors and neighbor effects on microclimate affect small scale (patch to ecosystem) water fluxes. / Dissertation/Thesis / Doctoral Dissertation Biology 2015

abstract: The history of outdoor water use in the Phoenix, Arizona metropolitan area has given rise to a general landscape aesthetic and pattern of residential irrigation that seem in discord with the natural desert environment. While xeric landscaping that incorporates native desert ecology has potential for reducing urban irrigation demand, there are societal and environmental factors that make mesic landscaping, including shade trees and grass lawns, a common choice for residential yards. In either case, there is potential for water savings through irrigation schedules based on fluxes affecting soil moisture in the active plant rooting zone. In this thesis, a point-scale model of soil moisture dynamics was applied to two urban sites in the Phoenix area: one with xeric landscaping, and one with mesic. The model was calibrated to observed soil moisture data from irrigated and non-irrigated sensors, with local daily precipitation and potential evapotranspiration records as model forcing. Simulations were then conducted to investigate effects of irrigation scheduling, plant stress parameters, and precipitation variability on soil moisture dynamics, water balance partitioning, and plant water stress. Results indicated a substantial difference in soil water storage capacity at the two sites, which affected sensitivity to irrigation scenarios. Seasonal variation was critical in avoiding unproductive water losses at the xeric site, and allowed for small water savings at the mesic site by maintaining mild levels of plant stress. The model was also used to determine minimum annual irrigation required to achieve specified levels of plant stress at each site using long-term meteorological records. While the xeric site showed greater potential for water savings, a bimodal schedule consisting of low winter and summer irrigation was identified as a means to conserve water at both sites, with moderate levels of plant water stress. For lower stress levels, potential water savings were found by fixing irrigation depth and seasonally varying the irrigation interval, consistent with municipal recommendations in the Phoenix metropolitan area. These results provide a deeper understanding of the ecohydrologic differences between the two types of landscape treatments, and can assist water and landscape managers in identifying opportunities for water savings in desert urban areas. / Dissertation/Thesis / M.S. Civil and Environmental Engineering 2013

abstract: Land-atmosphere interactions of semiarid shrublands have garnered significant scientific interest. One of the main tools used for this research is the eddy covariance (EC) method, which measures fluxes of energy, water vapor, and carbon dioxide. EC fluxes can be difficult to interpret due to complexities within the EC footprint (i.e. the surface conditions that contribute to the flux measurements). Most EC studies use a small number of soil probes to estimate the land surface states underlying the measured fluxes, which likely undersamples the footprint-scale conditions, especially in semiarid shrublands which are characterized by high spatial and temporal variability. In this study, I installed a dense network of soil moisture and temperature probe profiles in the footprint region of an EC tower at two semiarid sites: a woody savanna in southern Arizona and a mixed shrubland in southern New Mexico. For data from May to September 2013, I link land surface states to EC fluxes through daily footprints estimated using an analytical model. Novel approaches are utilized to partition evapotranspiration, estimate EC footprint soil states, connect differences in fluxes to footprint composition, and assess key drivers behind soil state variability. I verify the hypothesis that a small number of soil probes poorly estimates the footprint conditions for soil moisture, due to its high spatial variability. Soil temperature, however, behaves more consistently in time and space. As such, distributed surface measurements within the EC footprint allow for stronger ties between evapotranspiration and moisture, but demonstrate no significant improvement in connecting sensible heat flux and temperature. I also find that in these systems vegetation cover appears to have stronger controls on soil moisture and temperature than does soil texture. Further, I explore the influence of footprint vegetation composition on the measured fluxes, which reveals that during the monsoon season evaporative fraction tends to increase with footprint bare soil coverage for the New Mexico site and that the ratio of daily transpiration to evapotranspiration increases with grass coverage at the Arizona site. The thesis results are useful for understanding the land-atmosphere interactions of these ecosystems and for guiding future EC studies in heterogeneous landscapes. / Dissertation/Thesis / M.S. Civil and Environmental Engineering 2013

O estado da drenagem urbana relaciona-se com o tipo e frequência de cheias, o aumento da poluição difusa e a degradação da qualidade da água. Como parte dos projetos FINEP/MAPLU \"Manejo de águas pluviais em meio urbano\" e FAPESP-IAV \"Assessment of impacts and vulnerability to climate change in Brazil and strategies for adaptation options\", o presente estudo teve por objetivo a análise experimental e a modelagem quali-quantitativa da poluição difusa da drenagem urbana com base ecohidrológica. O estudo foi realizado na área urbana da cidade de São Carlos, em 5 sub-bacias com áreas de drenagem entre 3,4 e 75,6 km², com grau de urbanização entre 0 e 100% e com potencial de escoamento (CN) de 58 a 95. Foram escolhidos 14 pontos para o levantamento de dados experimentais. Avaliando a continuidade dos rios, pode-se observar o impacto da urbanização na redução da qualidade no sentido da nascente à foz, com influência de esgoto. Os intervalos das variáveis de qualidade foram de: 235 a 35.000 kg/km²/ano para DQO; 0 a 7300 kg/km²/ano para DBO; 0 a 1378 kg/km²/ano para N-amoniacal; 0 a 133 kg/km²/ano para Fósforo Total e 7,8 x \'10 POT.4\' a 1,3 x \'10 POT.7\' NMP/km²/ano para coliformes fecais. Os maiores valores para as cargas específicas de DBO, DQO, N-amoniacal, Fósforo Total e Coliformes Fecais foram observados na saída das duas bacias com maior grau de urbanização. Dois indicadores ecohidrológicos foram aqui estudados: o indicador de continuidade X1 relaciona o número de afluentes laterais por unidade de comprimento do rio principal (nº/km), e X18, relacionado à vulnerabilidade, é obtido pelo produto entre velocidade e profundidade da água (m²/s). Em geral, X1 apresentou comportamento variado em cada sub-bacia, enquanto X18 mostrou elevação contínua no sentido de montante a jusante. A modelagem matemática foi realizada com o modelo SWMM no qual foram simulados cenários de macrodrenagem com base em mudanças no uso e ocupação do solo adaptados do Millenium Ecosystem Assessment. Para chuva de projeto com TR = 10 anos foram simulados cenários conforme o macrozoneamento, variando valores de CN, declividade e coeficiente de rugosidade n-Manning. Com horizontes futuros de uso e ocupação para os anos 2025, 2050, 2075 e 2100, os cenários de políticas reativas (\"GO\" e \"OS\") apresentaram vazão máxima específica e carga máxima de poluição específica superiores aos verificados nos cenários pró-ativos (\"AM\" e \"TG\"). Os resultados indicaram que a variabilidade quali-quantitativa da drenagem urbana é afetada não somente por aspectos antropogênicos, como lançamento de esgotos e falta de planejamento, como também por critérios ecohidrológicos mais complexos que sugerem aumentar expressivamente o monitoramento e simulações quali-quantitativas da poluição difusa urbana. / Urban drainage is influenced by the frequency of floods, the increase of diffuse pollution and the degradation of water quality. As a component of research projects FINEP/MAPLU \"Urban water management\" and FAPESP-IAV \"Assessment of impacts and vulnerability to climate change in Brazil and strategies for adaptation options\", this study aimed to do experimental analyses and quali-quantitative modeling of diffuse pollution of urban drainage based on ecohydrology. The study was developed at the urban area of São Carlos, in 5 sub-basins with drainage area between 3,4 and 75,6 km². The urbanization varies between 0 and 100% and the runoff potential (CN) between 58 to 95. Evaluating the continuity of the river, we can notice the impact of urbanization in decreasing water quality from upstream to downstream. Experimental analyses were made in 14 points and the quality variables oscillated between 235 - 35.000 kg/km²/yr to COD; 0 - 7300 kg/km²/yr to BOD; 0 - 1378 kg/km²/yr to N-NH3; 0 - 133 kg/km²/yr to total phosphorus and 7,8 x \'10 POT.4\' - 1,3 x \'10 POT.7\' MPN/km²/yr to fecal coliform. The highest values of specific charge for COD, N-NH3 and phosphorus were observed at sub-basins with high degree of urbanization. Two ecohydrological indicators were estimated. The continuity indicator X1, relates to the number of lateral affluents and to the length of the river. X18 is related to vulnerability, and obtained by the product between velocity and depth. The indicator X1 showed different behaviors in sub-basins, while X18 increased in direction upstream to downstream. Both indicators didnt show a tipical behavior. Mathematical modeling used SWMM model to simulate scenarios of macrodrainage based on land use changes adapted from Millenium Ecosystem Assessment. Rainfall of project with return period of 10 years was used to simulate scenarios in all sub-basins according to the macrozoning, ranging values for runoff potential (CN), slope and rugosity coefficient. The scenarios were simulated with horizons of use and occupation for the years 2025, 2050, 2075 e 2100. The reactive scenarios (\"GO\" and \"OS\") showed maximum specific flow and maximum specific load higher than the proactives scenarios (\"AM\" and \"TG\"). The results indicated that the variability quali-quantitative of an urban drainage is affected by antropogenic factors, like wastewater and lack of planning, and also by ecohydrologic criteria. This fact sugests the necessity of a significant increase in the monitoring and simulations quali-quantitaives of the diffuse pollution in urban drainage.

Na atualidade, o mundo enfrenta graves problemas de escassez de água decorrentes, principalmente, da degradação da sua qualidade. O conhecimento e a avaliação da qualidade da água são essenciais para o adequado gerenciamento dos recursos hídricos, portanto a água cumpre função de informação, servindo de indicador para o estágio de conservação ou de degradação de um corpo d\'água. O principal objetivo do presente estudo foi avaliar a qualidade da água de uma bacia urbana localizada na cidade de São Carlos, SP, em termos experimentais e de modelagem matemática, aplicando conceitos ecohidrológicos. Esta avaliação realizou-se por meio da análise de resultados experimentais obtidos em campo, através de quatro campanhas de amostragens de água realizadas em períodos secos (7 de novembro de 2008) e chuvoso ( dias 11, 17 e 18 de março de 2009), estabelecendo para cada campanha três pontos de coletas, uma localizada na bacia do córrego Gregório de 17,3 \'Km POT.2\', e as outras duas ao longo do córrego Monjolinho de 78 \'Km POT.2\'. Foram discutidos os resultados de parâmetros físico-químicos (pH, OD, turbidez, CE, DQO, DBO, fosfato, nitrogênio total, nitrato, nitrito e sólidos totais), biológicos (coliformes termotolerantes e totais) e metais (zinco, chumbo, cádmio, níquel, ferro, manganês, cobre e cromo) presentes na água, bem como foram analisados os efeitos das variações do nível da água e vazão nas características limnológicas dos corpos de água. Os resultados experimentais foram expressos tanto em termos de concentração (mg/L) como de carga específica (kg/ano.ha) a fim de se analisar a variação espacial da concentração e a carga em termos da área de drenagem acumulada e comprimento do rio. Abordou-se uma discussão ecohidrológica realizada com base em análise de quatro dimensões de variáveis: altura hidrométrica, vazão específica, índice de vulnerabilidade e cargas específicas de alguns parâmetros limnológicos. Finalmente, e a fim de avaliar aspectos quali-quantitativos da água para uma bacia urbana através da modelagem matemática, foi utilizado o modelo SWMM. Os resultados experimentais obtidos mostraram que existe extrema variabilidade quantitativa e qualitativa da água, devida principalmente a fatores antropogênicos de poluição, seja pela dinâmica variada de produção de resíduos que são lançados ao ar e à água, seja pela destruição de mecanismos naturais de regulação pela ocupação desordenada do espaço, além de se constatar que as variações do nível da água provocam uma série de transformações nas características limnológicas dos corpos de água causadas por interações entre o meio terrestre e o aquático. Constatou-se a aplicabilidade quali-quantitativa do modelo matemático utilizado, para uma bacia urbana, por meio da calibração dos hidrogramas simulados com hidrogramas observados, e a obtenção de resultados de concentrações de OD, fosfato, sólidos totais, DQO e DBO presentes na água do rio. / Today, the world faces serious problems of water scarcity due mainly to the degradation of its quality. Knowledge and assessment of water quality are essential for proper management of water resources, so the water acts as information function, serving as an indicator of the stage of conservation or degradation of a body of water. The main purpose of this study was to evaluate the water quality of an urban basin located in Sao Carlos city, Brazil, in terms of experimental and mathematical modeling, applying concepts of Ecohydrology. This assessment was carried out by the analysis of experimental results obtained in field works, through four sampling campaigns of water realized in a drought period (November 7,2008) and rainy periods (11, 17 and March 18,2009) establishing for each sampling campaign three points, one located in the basin of the stream Gregory of 17,3 \'KM POT.2\', and the other two along the stream Monjolinho of 78 \'KM POT.2\'. The results of physical and chemical parameters (pH, DO, turbidity, EC, COD, BOD, phosphate, total nitrogen, nitrate, nitrite and total solids), biological (fecal and total coliform) and metals (zinc, lead, cadmium, nickel, iron, manganese, copper and chromium) in the water, were discussed and analyzed the effect of water level variations and flow in limnological characteristics of water bodies. The experimental results were expressed in terms of concentration (mg/L) as the specific load (kg/year.ha) to analyze the spatial variation of the concentration and the load in terms of cumulative drainage area and river length. lt was approached an Ecohydrology discussion based on analysis of four variable dimensions: hydrometric height, flow specific vulnerability index and specific loads of some limnological parameters. Finally, in order to validate the quali-quantitative aspects of the water for an urban basin through a mathematical model, we used the mathematical model SWMM. The experimental results showed that there is an extreme variability in quantity and quality of the water, primarily due to anthropogenic pollution factors, either for the dynamic range of waste that are thrown into the air and water, or the destruction of the natural mechanisms of regulation by disordered occupation of the space, and besides evidencing that the variations of the changes in water level cause a series of transformations in limnological characteristics of the bodies watermark caused by interactions between the terrestrial and aquatic environments. lt was evidenced the quali-quantitative applicability of the mathematical model used, for an urban basin, through the calibration of the simulated hidrograms with observed hidrograms, and the obtained results of DO, phosphate, total solids, COD and BOD concentrations presents in the water of the river.

Os cursos d\'água são ecossistemas predominantemente heterotróficos com gradiente longitudinal e possuem uma capacidade natural de depurar a matéria orgânica. Entretanto, o lançamento indiscriminado de efluentes ultrapassa a capacidade de suporte do ambiente aquático. O principal objetivo do presente estudo foi analisar como a qualidade da água do rio, em termos experimentais e de modelagem matemática, expressa processos ecohidrológicos nas escalas espaço-temporais, para variações de variáveis físicas, químicas e hidrológicas. O presente estudo foi conduzido através da abordagem de bacias embutidas em seções transversais com áreas incrementais do rio principal e com 17 variáveis analisadas. A aplicação dessa metodologia foi feita para o rio Canha, com área de drenagem total de 126 \'KM POT.2\', situada num bioma subtropical, caracterizando-se por ser uma bacia rural e peri-urbana, localizada no Baixo Ribeira de Iguape - São Paulo. As amostragens foram feitas de setembro de 2006 a março de 2007, em oito seções transversais ao longo do eixo longitudinal do rio Canha. A fim de validar os dados obtidos em campo, um modelo matemático foi utilizado. Deste modo, o modelo 1D de fluxo permanente, o modelo QUAL2K, ajustou-se de maneira satisfatória para a maioria dos dados experimentais. Dados hidráulicos e hidrológicos obtidos em campo foram empregados como condição de contorno para calibração do modelo. Os resultados experimentais e simulados foram expressos tanto em termos de concentração (mg/L) como de cargas específicas (Kg/ano/ha). Esta comparação permite obtenção dos resultados através de um continuum a partir do aumento das escalas, enquanto fornece base para confrontá-los com hipóteses ecohidrológicas. A existência de duas estações distintas, seca e chuvosa, foi observada. Durante a estação chuvosa, observou-se maior diluição dos compostos no corpo d´água, porém em alguns casos, a influência da poluição difusa, devido à lixiviação do solo, foi verificada. As altas vazões tiveram impacto direto sobre as cargas específicas. Na estação seca, para a maioria das variáveis analisadas, evidenciou-se aumento na concentração, sugerindo que períodos de baixa vazão diminuem a capacidade de assimilação do rio. Por exemplo, as concentrações e cargas específicas de nitrogênio total foram altas para ambos os períodos, seco e chuvoso. Quando comparado com o sedimento do rio, ficou evidente que o nitrogênio é originário de fontes não pontuais. / Water courses are predominantly heterotrophic ecosystems with longitudinal gradient and present a capacity of self purification from organic matter. However, the uncontrolled release of effluents can exceed the carrying capacity of the aquatic ecosystem. The main objective of this study was to analyze how the river water quality, in terms of experimental surveys faced with mathematical modeling, envisages the processes evidences of fluvial ecohydrology at various spatiotemporal scales, for either seasonal or longitudinal changes of physic, chemical and hydrological variables. That study was performed through a nested catchment experiment, at cross-sections located at incremental drainage areas of the main river stem of the watershed and with 17 sampled variables. The application of this methodology was made at the Canha river, with a total drainage area of 126 \'KM POT.2\', under subtropical biome, with mixed, rural to peri-urban, land-uses, located at the downstream of the Ribeira de Iguape river basin, sited at State of Sao Paulo, Brazil. Four field campaigns were carried with sampling from September, 2006 to July, 2007, in eight cross-sections along the longitudinal axis of the Canha river. In order to cross-validate experimental samples at the river continuum scale with the drainage basin scale, a mathematical model was tested to simulate the water quality dynamics. In spite of 1-D, quasi-state modeling restrictions assumed, the QUAL2K model fits well to experimental data of most of variables surveyed during campaigns. Hydraulic basic samples and hydrological weather data were utilized as initial conditions to feed the mathematical model. Both experimental results and model simulations were expressed as mean river-concentrations (mass/volume) as drainage-area-specific loadings or yield (mass/time.area). The existence of two main seasons, dry and wet, was observed. During the rainy season, the ability to better dilute water loads was outlined; however, on some circumstances, the influence of diffuse pollution entered the stream due to soil leach is also depicted. High-water discharges had a direct impact on area-specific loads. In the dry season and for most of variables, high concentrations were evident, suggesting low-water discharges provoked a loss of the river\'s carrying capacity. For instance, nitrogen concentrations and nitrogen specific loads were quite high during both (dry, wet) periods. When compared to the river bottom sediments, it was evident that nitrogen could be originated from non-point sources outside the riparian areas. The results let the river continuum integrated processes across increasing scales, thereby providing the basis for confronting ecohydrological hypotheses.

Magister Scientiae - MSc / The research was driven by a need to increase the knowledge base concerning wetland ecological responses, as well as to identify and evaluate the factors driving the functioning of the Franschhoek Trust Wetland. An ecohydrological study was undertaken in which vegetation cover, depth to groundwater, water and soil chemistry were monitored at 14 sites along three transects for a 12 month period. The parameters used include temperature, pH, electrical conductivity (EC), sodium, potassium, magnesium, calcium, iron, chloride, bicarbonate, sulphate, total nitrogen, ammonia, nitrate, nitrite and phosphorus. T-tests and Principal Component Analysis (PCA) were used to analyze trends and to express the relationship between abiotic factors and vegetation. / South Africa