This dissertation presents an experimental investigation of fluid flow, proppant settling and horizontal proppant transport in hydraulic fractures. The work is divided into two major sections: investigation of proppant settling in polymer-free surfactant-based viscoelastic (VES) fluids and development of a new method of proppant injection, referred to as Alternate-Slug fracturing. VES fluid systems have been used to eliminate polymer-based damage and to efficiently transport proppant into the fracture. Current models and correlations neglect the important influence of fracture walls and fluid elasticity on proppant settling. Experimental data is presented to show that elastic effects can increase or decrease the settling velocity of particles, even in the creeping flow regime. Experimental data shows that significant drag reduction occurs at low Weissenberg number, followed by a transition to drag enhancement at higher Weissenberg numbers. A new correlation is presented for the sphere settling velocity in unbounded viscoelastic fluids as a function of the fluid rheology and the proppant properties. The wall factors for sphere settling velocities in viscoelastic fluids confined between solid parallel plates (fracture walls) are calculated from experimental measurements made on these fluids over a range of Weissenberg numbers. Results indicate that elasticity reduces the retardation effect of the confining walls and this reduction is more pronounced at higher ratios of the particle diameter to spacing between the walls. Shear thinning behavior of fluids is also observed to reduce the retardation effect of the confining walls. A new empirical correlation for wall factors for spheres settling in a viscoelastic fluid confined between two parallel walls is presented. An experimental study on proppant placement using a new method of fracturing referred to as Alternate-Slug fracturing is presented. This method involves alternate injection of low viscosity and high viscosity fluids into the fracture, with proppant pumped in the low viscosity fluid. Experiments are conducted in Hele-Shaw cells to study the growth of viscous fingers over a wide range of viscosity ratios. Data is presented to show that the viscous finger velocities and mixing zone velocities increase with viscosity ratio up to viscosity ratios of about 350 and the trend is consistent with Koval’s theory. However, at higher viscosity ratios the mixing zone velocity values plateau signifying no further effect of viscosity contrast on the growth of fingers and mixing zone. The plateau in the velocities at high viscosity ratios is caused by an increase in the thickness of the displacing fluid and a reduction in the thin film of the displaced fluid on the walls of the Hele-Shaw cell. Fluid elasticity is observed to retard the growth of fingers and leads to growth of multiple thin fingers as compared to a single thick dominant finger in less elastic fluids. Observations show the shielding effect is reduced by fluid elasticity. Elastic effects are observed to reduce the thickness of thin film of displaced fluid on the walls of Hele-Shaw cell. The dominant wave number for the growth of instabilities is observed to be higher in more elastic fluids. At the onset of instability, the interface breaks down into a greater number of fingers in more elastic fluids. Experiments are performed in simulated fractures (slot cells) to show the proppant distribution using alternate-slug fracturing. Observations show alternate-slug fracturing ensures deeper placement of proppant through two primary mechanisms: (a) proppant transport in viscous fingers formed by the low viscosity fluid and (b) an increase in drag force in the polymer slug leading to better entrainment and displacement of any proppant banks that may have formed. The method offers advantages of lower polymer costs, lower pumping horsepower, smaller fracture widths, better control of fluid leak-off and less gel damage compared to conventional gel fracs. / text

Physical and chemical heterogeneities cause the porous media transport parameters to vary with scale, and between these two types of heterogeneities geological heterogeneity is considered to be the most important source of scale-dependence of transport parameters. Subsurface processes associated with chemical alterations result in changing reservoir properties with interlinked spatial and temporal scale, and there is uncertainty in the evolution of those properties and the chemical processes. This dissertation provides a framework and procedures to quantify the spatiotemporal scaling characteristics of reservoir attributes and transport processes in heterogeneous media accounting for chemical alterations in the reservoir. Conventional flow scaling groups were used to assess their applicability in scaling of recovery and Mixing Zone Length (MZL) in presence of chemical reactivity and permeability heterogeneity through numerical simulations of CO₂ injection. It was found out that these scaling groups are not adequate enough to capture the scaling of recovery and transport parameters in the combined presence of chemical reactivity and physical heterogeneity. In this illustrative example, MZL was investigated as a function of spatial scale, temporal scale, multi-scale heterogeneity, and chemical reactivity; key conclusions are that 1) the scaling characteristics of MZL distinctly differ for low permeability and high permeability media, 2) heterogeneous media with spatial arrangements of both high and low permeability regions exhibit scaling characteristics of both high and low permeability media, 3) reactions affect scaling characteristics of MZL in heterogeneous media, 4) a simple rescaling can combine various MZL curves by merging them into a single MZL curve irrespective of the correlation length of heterogeneity, and 5) estimates of MZL (and consequently predictions of oil recovery) will fluctuate corresponding to displacements in a permeable medium whose lateral length is smaller than the correlation length of geological formation. We illustrate and extend the procedure of estimating Representative Elementary Volume (REV) to include temporal scale by coupling it with spatial scale. The current practice is to perform spatial averaging of attributes and account for residual variability by calibration and history matching. This results in poor predictions of future reservoir performance. The proposed semi-analytical technique to scale-up in both space and time provides guidance for selection of spatial and temporal discretizations that takes into account the uncertainties due to sub-processes. Finally, a probabilistic particle tracking (PT) approach is proposed to scale-up flow and transport of diffusion-reaction (DR) processes while addressing multi-scale and multi-physics nature of DR mechanisms and also maintaining consistent reservoir heterogeneity at different levels of scales. This multi-scale modeling uses a hierarchical approach which is based on passing the macroscopic subsurface heterogeneity down to the finer scales and then returning more accurate reactive flow response. This PT method can quantify the impact of reservoir heterogeneity and its uncertainties on statistical properties such as reaction surface area and MZL, at various scales. / text

For this dissertation I studied phosphorus (P) sorption dynamics in the shallow groundwater of the southern Everglades. In particular, I examined how the ambient water type governs soluble reactive P (SRP) availability through adsorption/desorption reactions with the aquifer matrix. Chapter 2 investigated how P sorption dynamics of the mangrove root zone sediment are affected by high bicarbonate brackish groundwater compared to both fresh groundwater and saltwater. The results from chapter 2 show that the sediment exhibited exceptionally low sorption efficiency in the high bicarbonate brackish water, which would allow ambient water SRP concentration to be maintained at a higher level. Chapter 3 is a detailed analysis of how P sorption dynamics in two bedrock samples are affected by incremental increases in saltwater content in a freshwater-saltwater transition zone. The results of chapter 3 indicate that a sorption edge occurs at 3 mM Cl- concentration. In water exceeding this Cl- concentration, SRP would be expected to desorb from the bedrock due to a sharp decrease in sorption efficiency between the freshwater saltwater. These results suggest that SRP is active in the ion exchange front of saltwater intrusion, with a rapid increase in SRP availability expected at the leading edge of saltwater intrusion. A landward incursion of 3 mM Cl- concentration water would be expected to raise ambient SRP concentration along the affected aquifer zone, in turn increasing SRP availability in the ecosystem where the transitional waters discharge to the surface. Chapter 4 investigates the kinetics SRP release accompanying saltwater intrusion using a column of carbonate aquifer solids and alternating inflow between fresh groundwater and saltwater. The results show an immediate and high magnitude increase in SRP concentration when saltwater flows into the column. The combined results of this dissertation show that, in the southern Everglades and possibly other carbonate coastlines as well, water type strongly controls P sorption behavior of the sediment and bedrock, and may have a direct influence on the local ecology through increased P availability. A fundamental understanding of the abiotic exchange mechanisms between SRP and the aquifer solids can aid in the successful management and protection of this unique and important ecosystem.

The mixing zone developed at freshwater-seawater interface is one of the most important features in complex coastal hydrogeologic systems, which controls subsurface flow and reactive transport dynamics. Freshwater-seawater mixing-zone development is influenced by many physical and chemical processes, such as characteristics of geologic formation, hydrodynamic fluctuations of groundwater and seawater levels, fluid-rock interactions, and others. Wide mixing zones have been found in many coastal aquifers all over the world. However, the mechanisms responsible for wide mixing zones are not well understood. In this thesis, two hypotheses were proposed to explain wide mixing zones in coastal aquifers: (1) kinetic mass transfer coupled with transient conditions, which create the movement of the mixing zone, may widen mixing zones; and (2) aquifer stratification may widen the mixing zone. The hypotheses were tested by both multiscale numerical simulations and laboratory experiments. Numerical simulations were based on a variable-density groundwater model by varying mass transfer parameters, including immobile porosity, mobile porosity, and mass transfer coefficient, and the hydraulic conductivity contrast between aquifer layers. Laboratory experiments were conducted in a quasi-two-dimensional tank, where real beach sands were installed and foodstuff dyes were used to visualize the development of freshwater-seawater mixing zone. Major conclusions included (1) the mixing zone can be significantly widened when the mass transfer timescale and the period of transient boundary is comparable due to the nonequilibrium mass transfer effects; and (2) a thick mixing zone occurs in low-permeability layer when it overlays upon a fast flow layer. These results not only improve the understanding of the dynamics of mixing-zone development and its associated geochemical processes in coastal aquifers, but also identify hydrogeologic conditions for the model of sharp-interface approximation to be valid. In addition to better understanding the mechanisms and dynamics of mixing zone, this thesis also investigates cost-effective management of coastal groundwater resources. To protect and conserve limited water recourses in coastal regions, interest in aquifer storage and recovery (ASR) has been growing in recent years. ASR is a promising strategy for water resources management and has been widely used in many contaminated and saline aquifers. However, its performance may be significantly constrained by mass transfer effects due to the mobilization of solutes initially residing in immobile domains. Better understanding of kinetic mass transfer effects on ASR is needed in order to aid the decision-making process. A numerical model is developed to simulate ASR performance by combining the convergent and divergent dispersion models with a first-order mass transfer model. By analyzing the concentration history at the pumping well, we obtain simple and effective relationships for investigating ASR efficiency under various mass transfer parameters, including capacity ratio and mass transfer timescales, and operational parameters. Based on such relationships, one can conveniently determine whether a site with mass transfer limitations is appropriate or not for ASR and how many ASR cycles are required for achieving a positive recovery efficiency (RE).

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / Os reservatÃrios sÃo ambientes aquÃticos continentais que apresentam relaÃÃo estreita com a bacia de drenagem. Dentre as funÃÃes, ciclagem de fÃsforo e nitrogÃnio à essencial à manutenÃÃo e estruturaÃÃo das comunidades ecolÃgicas, principalmente do fitoplÃncton. A entrada de energia, matÃria por causas naturais e, mais intensivamente antrÃpicas e algumas caracterÃsticas dos reservatÃrios do semiÃrido brasileiro (radiaÃÃo solar, pluviosidade, temperatura e vento) podem possibilitar padrÃes diferenciados das variÃveis fÃsicas, quÃmicas e biolÃgicas e estabelecer condiÃÃes favorÃveis a dominÃncia de espÃcies da classe Cyanophyceae. Visando identificar correlaÃÃes destas variÃveis foram feitas coletas nictemerais das variÃveis fÃsicas, quÃmicas, climatolÃgicas e biolÃgicas durante os meses de fevereiro, maio, agosto e novembro no reservatÃrio Pereira de Miranda, localizado municÃpio de Pentecoste, semiÃrido brasileiro, em 2012. Foi observado que as alteraÃÃes de temperatura da Ãgua e velocidade do vento interferem nas variÃveis limnolÃgicas do reservatÃrio, principalmente na extensÃo da zona de mistura, sendo possÃvel distinguir duas fases: estratificada e desestratificada. AlÃm de alterar as caracterÃsticas limnolÃgicas as fases tambÃm provocam alteraÃÃes na estrutura das assembleias de fitoplÃncton, como a floraÃÃo de espÃcies do gÃnero Microsystis. ConcluÃmos que os padrÃes de estratificaÃÃo e desestratificaÃÃo sÃo os principais fatores de interferÃncia nas variÃveis limnolÃgicas e na estrutura do fitoplÃncton do reservatÃrio. / Reservoirs are freshwater ecosystems that have close relationship with the drainage basin. Among the functions, cycling of phosphorus and nitrogen is essential to the maintenance and structuring of ecological communities, mainly phytoplankton. Input of energy, raw natural causes and more intensive anthropogenic and some reservoir characteristics of the Brazilian semiarid region (solar radiation, rainfall, temperature and wind) can derive different patterns of physical, chemical and biological weapons and establish conditions conducive to dominance species of the class Cyanophyceae. To identify correlations of these variables were made collections nyctemeral of physical, chemical, biological and climatological during the months of February, May, August and November in the reservoir Pereira de Miranda, located city of Pentecost, the Brazilian semiarid region in 2012. It was observed that changes in water temperature and wind velocity interfere with limnological variables, especially in the extension of the mixing zone, it is possible to distinguish two phases: stratified and nonstratified. In addition to changing the limnological phases also cause changes in the structure of phytoplankton assemblages, such as flowering species of Microsystis. We conclude that the patterns of stratification and destratification are the main factors affecting the limnological and phytoplankton structure in the reservoir.

O impacto de um lançamento de efluente na qualidade da água do corpo hídrico depende de características do lançamento e do corpo hídrico, a exemplo de suas condições hidrodinâmicas. O conhecimento das relações entre os fatores envolvidos permite avaliar os riscos envolvidos, alterar a forma de lançamento de efluentes de modo a reduzir seu impacto e reduzir os custos com as formas de controle da poluição, entre outras ações. Nesse contexto, o objetivo deste trabalho é compreender as relações entre os fatores dominantes das condições hidrodinâmicas e a dispersão de poluentes na região nordeste da Laguna dos Patos, buscando identificar formas de utilizar a modelagem hidrodinâmica para melhorar a gestão do corpo hídrico e de lançamento de efluentes. A área de estudo consiste na região nordeste da Laguna dos Patos, no Rio Grande do Sul, onde o vento e a vazão afluente são os fatores determinantes de circulação de água. O modelo utilizado (IPH-A) apresentou boa representação da variação de nível, exceto pelo posto mais próximo da região estuarina, e da circulação de água. O coeficiente de dispersão foi definido a partir da comparação visual da simulação da dispersão dos sedimentos em suspensão afluentes ao Lago Guaíba e a pluma do Guaíba observada em imagens de satélite. Cenários de vento e vazão foram determinados a partir da análise da série histórica de dados de vento na estação de Rio Grande e da vazão afluente ao Lago Guaíba.Os resultados dos ventos sudoeste e nordeste foram semelhantes ao verificado na literatura com uso de modelo bidimensional para o corpo lagunar. Na região nordeste, uma célula de circulação entre o Banco das Desertas e o Banco dos Abreus é observada no sentido horário (anti-horário) para os cenários com vento sudoeste (nordeste). O vento sudeste provoca o aumento do nível na margem oeste e redução na margem leste É observada uma maior renovação de água na região ao norte do Banco das Desertas e menor troca de água com a Lagoa do Casamento do que nos cenários anteriores. Nos cenários de vento nulo, as velocidades da água na região nordeste da laguna são bastante baixas. A vazão necessária para manutenção do nível na laguna dependeu do vento predominante. Os diferentes cenários de vento produziram diferentes plumas de dispersão do lançamento de efluente simulado, seguindo os padrões da circulação de água no local. As maiores concentrações foram observadas no local de lançamento do efluente para o cenário de vento nulo e a maior área de influência foi observada para os cenários de vento nordeste (maior velocidade de vento simulada). Para os cinco dias de simulação, foi observada pouca influência da vazão afluente no nível e na circulação de água do corpo lagunar e, consequentemente, na dispersão de poluentes. Os resultados evidenciam a necessidade de as concentrações de lançamento permitidas serem estabelecidas com base em estudo da dispersão física do efluente no corpo hídrico receptor, conforme determinado pela legislação nacional para corpos d’água onde não se aplica a vazão de referência. A consideração de uma zona de mistura onde as concentrações dos parâmetros podem estar em desacorpo com o enquadramento do corpo hídrico é debatida nas discussões. As simulações permitiram ainda identificar locais prioritários para monitoramento dos efeitos do efluente lançado na qualidade da água, cenários críticos para conflitos de uso da água considerando outros usos na região e verificar possíveis consequências do encurtamento ou alongamento do emissário. / The aim of this study is to understand the relationship between hydrodynamic and the pollutants dispersion in the northeast region of the Patos Lagoon, looking for identify ways of using hydrodynamic modeling to improve water resources and effluent discharge management. The study area is the northeastern region of Patos Lagoon, a chocked lagoon in the brazilian state of Rio Grande do Sul, where winds and freshwater runoff drive water circulation. The model IPH-A performed well, except for the estuarine region. The dispersion coefficient was defined from the visual comparison between the dispersion of suspended sediments on Guaíba Lake simulated and observed in satellite images. The wind and freshwater runoff scenarios were determined by analyzing the historical wind data series at the Rio Grande station and the freshwater discharge of the main tributaries of Guaíba Lake. The results for the scenarios of the southwest and northeast winds were similar to those observed in the literature using a two-dimensional hydrodynamic model. In the northeast region, a circulation cell between the Banco das Desertas and Banco dos Abreus is observed clockwise (counter-clockwise) for the southwest (northeast) wind scenarios. The southeast wind increases water level in the west margin and reduces in the east margin. It is observed a more intense water exchange in the region to the north of the Banco das Desertas and less water exchange with the Casamento Lagoon than in the previous scenarios In null wind speed scenarios, the water velocities in the northeast region of the lagoon are quite low. The water inflow necessary to maintain the water level in the lagoon depends on the wind condition. Different wind scenarios produced different effluent plumes, following the local water circulation patterns. The highest concentrations were observed at the effluent discharge site for the scenario with null wind speed and the largest area of influence was observed for the northeast wind scenario (highest simulated wind speed). Due to the only 5-days period of simulation, little influence was observed of the freshwater runoff on the water level and on the lagoon circulation, and, consequently, on the dispersion of pollutants. This evidences the need for the maximum permitted concentrations of pollutants to be established based on a study of the physical dispersion of the effluent in the receiving water body, as determined by national legislation for water bodies where the reference flow does not apply. The simulations also allowed to identify priority sites for monitoring the effects of effluent discharge on water quality, critical scenarios for water use conflicts considering other uses, and to verify possible consequences of changes in emissary length.

O impacto de um lançamento de efluente na qualidade da água do corpo hídrico depende de características do lançamento e do corpo hídrico, a exemplo de suas condições hidrodinâmicas. O conhecimento das relações entre os fatores envolvidos permite avaliar os riscos envolvidos, alterar a forma de lançamento de efluentes de modo a reduzir seu impacto e reduzir os custos com as formas de controle da poluição, entre outras ações. Nesse contexto, o objetivo deste trabalho é compreender as relações entre os fatores dominantes das condições hidrodinâmicas e a dispersão de poluentes na região nordeste da Laguna dos Patos, buscando identificar formas de utilizar a modelagem hidrodinâmica para melhorar a gestão do corpo hídrico e de lançamento de efluentes. A área de estudo consiste na região nordeste da Laguna dos Patos, no Rio Grande do Sul, onde o vento e a vazão afluente são os fatores determinantes de circulação de água. O modelo utilizado (IPH-A) apresentou boa representação da variação de nível, exceto pelo posto mais próximo da região estuarina, e da circulação de água. O coeficiente de dispersão foi definido a partir da comparação visual da simulação da dispersão dos sedimentos em suspensão afluentes ao Lago Guaíba e a pluma do Guaíba observada em imagens de satélite. Cenários de vento e vazão foram determinados a partir da análise da série histórica de dados de vento na estação de Rio Grande e da vazão afluente ao Lago Guaíba.Os resultados dos ventos sudoeste e nordeste foram semelhantes ao verificado na literatura com uso de modelo bidimensional para o corpo lagunar. Na região nordeste, uma célula de circulação entre o Banco das Desertas e o Banco dos Abreus é observada no sentido horário (anti-horário) para os cenários com vento sudoeste (nordeste). O vento sudeste provoca o aumento do nível na margem oeste e redução na margem leste É observada uma maior renovação de água na região ao norte do Banco das Desertas e menor troca de água com a Lagoa do Casamento do que nos cenários anteriores. Nos cenários de vento nulo, as velocidades da água na região nordeste da laguna são bastante baixas. A vazão necessária para manutenção do nível na laguna dependeu do vento predominante. Os diferentes cenários de vento produziram diferentes plumas de dispersão do lançamento de efluente simulado, seguindo os padrões da circulação de água no local. As maiores concentrações foram observadas no local de lançamento do efluente para o cenário de vento nulo e a maior área de influência foi observada para os cenários de vento nordeste (maior velocidade de vento simulada). Para os cinco dias de simulação, foi observada pouca influência da vazão afluente no nível e na circulação de água do corpo lagunar e, consequentemente, na dispersão de poluentes. Os resultados evidenciam a necessidade de as concentrações de lançamento permitidas serem estabelecidas com base em estudo da dispersão física do efluente no corpo hídrico receptor, conforme determinado pela legislação nacional para corpos d’água onde não se aplica a vazão de referência. A consideração de uma zona de mistura onde as concentrações dos parâmetros podem estar em desacorpo com o enquadramento do corpo hídrico é debatida nas discussões. As simulações permitiram ainda identificar locais prioritários para monitoramento dos efeitos do efluente lançado na qualidade da água, cenários críticos para conflitos de uso da água considerando outros usos na região e verificar possíveis consequências do encurtamento ou alongamento do emissário. / The aim of this study is to understand the relationship between hydrodynamic and the pollutants dispersion in the northeast region of the Patos Lagoon, looking for identify ways of using hydrodynamic modeling to improve water resources and effluent discharge management. The study area is the northeastern region of Patos Lagoon, a chocked lagoon in the brazilian state of Rio Grande do Sul, where winds and freshwater runoff drive water circulation. The model IPH-A performed well, except for the estuarine region. The dispersion coefficient was defined from the visual comparison between the dispersion of suspended sediments on Guaíba Lake simulated and observed in satellite images. The wind and freshwater runoff scenarios were determined by analyzing the historical wind data series at the Rio Grande station and the freshwater discharge of the main tributaries of Guaíba Lake. The results for the scenarios of the southwest and northeast winds were similar to those observed in the literature using a two-dimensional hydrodynamic model. In the northeast region, a circulation cell between the Banco das Desertas and Banco dos Abreus is observed clockwise (counter-clockwise) for the southwest (northeast) wind scenarios. The southeast wind increases water level in the west margin and reduces in the east margin. It is observed a more intense water exchange in the region to the north of the Banco das Desertas and less water exchange with the Casamento Lagoon than in the previous scenarios In null wind speed scenarios, the water velocities in the northeast region of the lagoon are quite low. The water inflow necessary to maintain the water level in the lagoon depends on the wind condition. Different wind scenarios produced different effluent plumes, following the local water circulation patterns. The highest concentrations were observed at the effluent discharge site for the scenario with null wind speed and the largest area of influence was observed for the northeast wind scenario (highest simulated wind speed). Due to the only 5-days period of simulation, little influence was observed of the freshwater runoff on the water level and on the lagoon circulation, and, consequently, on the dispersion of pollutants. This evidences the need for the maximum permitted concentrations of pollutants to be established based on a study of the physical dispersion of the effluent in the receiving water body, as determined by national legislation for water bodies where the reference flow does not apply. The simulations also allowed to identify priority sites for monitoring the effects of effluent discharge on water quality, critical scenarios for water use conflicts considering other uses, and to verify possible consequences of changes in emissary length.

O impacto de um lançamento de efluente na qualidade da água do corpo hídrico depende de características do lançamento e do corpo hídrico, a exemplo de suas condições hidrodinâmicas. O conhecimento das relações entre os fatores envolvidos permite avaliar os riscos envolvidos, alterar a forma de lançamento de efluentes de modo a reduzir seu impacto e reduzir os custos com as formas de controle da poluição, entre outras ações. Nesse contexto, o objetivo deste trabalho é compreender as relações entre os fatores dominantes das condições hidrodinâmicas e a dispersão de poluentes na região nordeste da Laguna dos Patos, buscando identificar formas de utilizar a modelagem hidrodinâmica para melhorar a gestão do corpo hídrico e de lançamento de efluentes. A área de estudo consiste na região nordeste da Laguna dos Patos, no Rio Grande do Sul, onde o vento e a vazão afluente são os fatores determinantes de circulação de água. O modelo utilizado (IPH-A) apresentou boa representação da variação de nível, exceto pelo posto mais próximo da região estuarina, e da circulação de água. O coeficiente de dispersão foi definido a partir da comparação visual da simulação da dispersão dos sedimentos em suspensão afluentes ao Lago Guaíba e a pluma do Guaíba observada em imagens de satélite. Cenários de vento e vazão foram determinados a partir da análise da série histórica de dados de vento na estação de Rio Grande e da vazão afluente ao Lago Guaíba.Os resultados dos ventos sudoeste e nordeste foram semelhantes ao verificado na literatura com uso de modelo bidimensional para o corpo lagunar. Na região nordeste, uma célula de circulação entre o Banco das Desertas e o Banco dos Abreus é observada no sentido horário (anti-horário) para os cenários com vento sudoeste (nordeste). O vento sudeste provoca o aumento do nível na margem oeste e redução na margem leste É observada uma maior renovação de água na região ao norte do Banco das Desertas e menor troca de água com a Lagoa do Casamento do que nos cenários anteriores. Nos cenários de vento nulo, as velocidades da água na região nordeste da laguna são bastante baixas. A vazão necessária para manutenção do nível na laguna dependeu do vento predominante. Os diferentes cenários de vento produziram diferentes plumas de dispersão do lançamento de efluente simulado, seguindo os padrões da circulação de água no local. As maiores concentrações foram observadas no local de lançamento do efluente para o cenário de vento nulo e a maior área de influência foi observada para os cenários de vento nordeste (maior velocidade de vento simulada). Para os cinco dias de simulação, foi observada pouca influência da vazão afluente no nível e na circulação de água do corpo lagunar e, consequentemente, na dispersão de poluentes. Os resultados evidenciam a necessidade de as concentrações de lançamento permitidas serem estabelecidas com base em estudo da dispersão física do efluente no corpo hídrico receptor, conforme determinado pela legislação nacional para corpos d’água onde não se aplica a vazão de referência. A consideração de uma zona de mistura onde as concentrações dos parâmetros podem estar em desacorpo com o enquadramento do corpo hídrico é debatida nas discussões. As simulações permitiram ainda identificar locais prioritários para monitoramento dos efeitos do efluente lançado na qualidade da água, cenários críticos para conflitos de uso da água considerando outros usos na região e verificar possíveis consequências do encurtamento ou alongamento do emissário. / The aim of this study is to understand the relationship between hydrodynamic and the pollutants dispersion in the northeast region of the Patos Lagoon, looking for identify ways of using hydrodynamic modeling to improve water resources and effluent discharge management. The study area is the northeastern region of Patos Lagoon, a chocked lagoon in the brazilian state of Rio Grande do Sul, where winds and freshwater runoff drive water circulation. The model IPH-A performed well, except for the estuarine region. The dispersion coefficient was defined from the visual comparison between the dispersion of suspended sediments on Guaíba Lake simulated and observed in satellite images. The wind and freshwater runoff scenarios were determined by analyzing the historical wind data series at the Rio Grande station and the freshwater discharge of the main tributaries of Guaíba Lake. The results for the scenarios of the southwest and northeast winds were similar to those observed in the literature using a two-dimensional hydrodynamic model. In the northeast region, a circulation cell between the Banco das Desertas and Banco dos Abreus is observed clockwise (counter-clockwise) for the southwest (northeast) wind scenarios. The southeast wind increases water level in the west margin and reduces in the east margin. It is observed a more intense water exchange in the region to the north of the Banco das Desertas and less water exchange with the Casamento Lagoon than in the previous scenarios In null wind speed scenarios, the water velocities in the northeast region of the lagoon are quite low. The water inflow necessary to maintain the water level in the lagoon depends on the wind condition. Different wind scenarios produced different effluent plumes, following the local water circulation patterns. The highest concentrations were observed at the effluent discharge site for the scenario with null wind speed and the largest area of influence was observed for the northeast wind scenario (highest simulated wind speed). Due to the only 5-days period of simulation, little influence was observed of the freshwater runoff on the water level and on the lagoon circulation, and, consequently, on the dispersion of pollutants. This evidences the need for the maximum permitted concentrations of pollutants to be established based on a study of the physical dispersion of the effluent in the receiving water body, as determined by national legislation for water bodies where the reference flow does not apply. The simulations also allowed to identify priority sites for monitoring the effects of effluent discharge on water quality, critical scenarios for water use conflicts considering other uses, and to verify possible consequences of changes in emissary length.