O bulbo molhado formado na irrigação por gotejamento pode ser modelado a partir informações das propriedades físico-hídricas do solo. Mas apesar do grande progresso na modelagem, a aplicação de modelos na irrigação e drenagem ainda não foi implementada em nenhum nível de maneira substancial. Assim, o objetivo do presente trabalho foi desenvolver um modelo numérico utilizando a técnica dos volumes finitos para estimar a forma e as dimensões do volume de solo molhado sob irrigação por gotejamento, e verificar a validade do modelo através da comparação com dados recolhidos em condições experimentais. O ensaio foi conduzido na área experimental do Departamento de Engenharia de Biossistemas da Escola Superior de Agricultura Luiz de Queiroz-ESALQ/USP. As sondas de TDR foram confeccionadas segundo procedimentos descritos por Souza et al. (2006). O perfil do bulbo molhado formado no solo abaixo de um emissor do tipo gotejador foi determinado para 3 tipos de material: areia, solo arenoso e solo argiloso e para 3 vazões nominais do emissor: 2, 4 e 6 L/h. Cada uma das combinações entre tipo de solo e vazão foi repetida três vezes em caixas (1000 L) diferentes, totalizando 27 medições. Um modelo numérico foi desenvolvido para simular a distribuição da água no perfil do solo abaixo de uma fonte pontual. A solução da equação diferencial para o movimento da água em solo não saturado foi realizada pela discretização do espaço-tempo utilizando a técnica dos volumes finitos. Um algoritmo em linguagem Visual Basic foi escrito para implementar o conjunto de equações e simular a evolução do bulbo molhado no tempo. Foi simulada a formação do bulbo molhado nas mesmas condições do experimento, e gráficos de isolinhas de umidade foram traçados no software Surfer. O modelo numérico proposto foi capaz de simular a formação do bulbo molhado em diferentes condições de tipo de solo e vazão do emissor. / The soil water patterns in drip irrigation can be modeled from physical and hydraulic properties of soil. But despite the great progress in modeling, the models have not been implemented at any level in irrigation and drainage. The objective of this study was to develop a numerical model using finite volume technique to estimate the shape and dimensions of the wetted soil volume under drip irrigation and verify the validity of the model by comparing data collected under experimental conditions. The trial was conducted at the experimental site of the Department of Biosystems Engineering, Escola Superior de Agricultura Luiz de Queiroz- ESALQ/USP. The TDR probes were manufactured according Souza et al. (2006). The soil water patterns under a drip emitter type was determined for three types of material: sand, sandy soil and clay soil and three nominal flows of the emitters: 2, 4 and 6 L/h. Each of the combinations of soil type and flow rate was repeated three times in boxes (1000 L), totaling 27 measurements. A numerical model was developed to simulate the distribution of water in the soil profile below a point source. The solution of the differential equation for the movement of water in unsaturated soil was carried out by the discretization of space-time using the technique of finite volume. An algorithm in Visual Basic language was written to implement the set of equations and simulate the evolution of wetted soil volume in time. Contour plots of soil water content were drawn in Surfer software. The proposed numerical model was able to simulate wetted soil volume under different conditions of soil type and flow of the emitter.

Les eaux souterraines constituent une réserve d’eau potable non négligeable, leur alimentation se fait en majeure partie par les précipitations, appelée recharge des nappes. Du fait de leur grande importance, la compréhension du fonctionnement de ces ressources en eau est plus que jamais indispensable. Celle-ci passe par l’élaboration de modèles mathématiques. Ces outils nous offrent une meilleure appréhension et une bonne prévision des phénomènes physiques. Les systèmes hydrogéologiques sont généralement très complexes et caractérisés par des dynamiques hydriques très variables dans le temps et dans l’espace. Cette complexité a attiré l’attention de nombreux hydrogéologues et un grand nombre de modèles très sophistiqués a été développé afin de décrire ces systèmes avec précision. Cependant, la prise en compte de la recharge de ces réservoirs reste toujours un défi dans la modélisation hydrogéologique. En effet, le plus souvent, les modèles hydrogéologiques simulent l’écoulement dans la nappe tout en considérant la recharge comme une constante sur le domaine et indépendante du système. De plus, elle est souvent calculée de façon simplifiée. Or, la recharge traduisant la quantité des précipitations atteignant les nappes est une composante hydrologique complexe et variable car elle interagit avec les nappes et dépend des conditions climatiques, du couvert végétal et du transfert de l’eau dans le sol. Ce présent travail vise à intégrer cette recharge variable et complexe aux modèles hydrogéologiques. À cet effet, un modèle couplé a été développé. Une première partie de ce modèle permet de calculer la recharge des nappes en modélisant les interactions précipitations-sol et l’hydrodynamique dans le sol. Cette modélisation a été effectuée en utilisant des modèles conceptuels simples basés sur des lois empiriques (Gardénia, Nash) et des modèles physiques résolvant l’équation de Richards. La recharge ainsi calculée est intégrée à la deuxième partie du modèle simulant l’hydrodynamique dans les nappes décrite par l’équation de diffusivité. Des méthodes numériques précises et robustes ont été utilisées pour résoudre les équations du modèle mathématique : les éléments finis non conformes ont été utilisés pour résoudre l’équation de diffusivité et l’équation de Richards est résolue sous sa forme mixte par une méthode itérative en temps. En somme, ce modèle couplé permet de décrire les variations de niveaux de nappe à partir des données météorologiques connaissant les paramètres caractéristiques de cet aquifère. [...] / Groundwater is the main available water resource for many countries; they are mainly replenished by water from precipitation, called groundwater recharge. Due to its great importance, management of groundwater resources is more essential than ever, and is achieved through mathematical models which offer us a better understanding of physical phenomena as well as their prediction. Hydrogeological systems are generally complex thus characterized by a highly variable dynamic over time and space. These complexities have attracted the attention of many hydrogeologists and many sophisticated models that can handle these issues and describe these systems accurately were developed. Unfortunately, modeling groundwater recharge is still a challenge in groundwater resource management. Generally, groundwater models are used to simulate aquifers flow without a good estimation of recharge and its spatial-temporal distribution. As groundwater recharge rates show spatial-temporal variability due to climatic conditions, land use, and hydrogeological heterogeneity, these methods have limitations in dealing with these characteristics. To overcome these limitations, a coupled model which simulates flow in the unsaturated zone and recharge as well as groundwater flow was developed. The flow in the unsaturated zone is solved either with resolution of Richards equation or with empirical models while the diffusivity equation governs flow in the saturated zone. Robust numerical methods were used to solve these equations: we apply non-conforming finite element to solve the diffusivity equation and we used an accurate and efficient method for solving the Richards equation. [...]

Made available in DSpace on 2015-03-04T18:50:36Z (GMT). No. of bitstreams: 1 Vitor.pdf: 5712854 bytes, checksum: b3b56770c9a5e06888ee08b2683bc9e8 (MD5) Previous issue date: 2011-07-01 / Conselho Nacional de Desenvolvimento Cientifico e Tecnologico / O movimento da água em solos não saturados (zona vadosa) pode ser descrito pela equação de Richards, obtida pela combinação da equação de conservação de massa e da lei de Darcy-Buckingham. Usualmente essa equação é representada sob três formas básicas: h - baseada na carga de pressão, θ - baseada na umidade volumétrica e mista - baseada na combinação das duas variáveis. Essas equações são matematicamente equivalentes; porém, em geral, suas aproximações numéricas podem levar a resultados bastante diferentes. Neste trabalho foram validados e comparados modelos numéricos, implementados em um código computacional na linguagem C, para a aproximação da equação de Richards, nas suas três formas, em uma dimensão. Para isso, empregou-se o método de diferenças finitas centrado no espaço e atrasado no tempo. Visando melhorar a conservação de massa dos modelos utilizados e o tempo de execução do programa, principalmente em problemas que apresentam mudanças bruscas nas condições de contorno e/ou camadas estratificadas, foram também implementadas três estratégias para a escolha do passo de tempo, assim como técnicas para aproximar as não-linearidades nos pontos intermediários da malha computacional e naqueles situados nas interfaces das camadas. A validação dos modelos acima se deu através da comparação das soluções aproximadas com a solução semi-analítica de Philip e a totalmente analítica de Srivastava e Yeh para colunas de solos homogêneas e estratificadas. A partir de dados disponíveis na literatura avaliou-se também a precisão e a eficiência das metodologias estudadas nas: i) aproximações da condutividade e da capacidade hidráulica e ii) na aplicação das estratégias de passo de tempo, quanto à precisão dos resultados simulados, à conservação de massa e ao tempo de execução do programa. De acordo com o desempenho das metodologias analisadas foram apontadas as melhores opções para a solução de cada problema, indicando-se assim alternativas na implementação de modelos numéricos para o escoamento da água na zona vadosa.

L'objectif de cette thèse est de décrire et de hiérarchiser les processus à l'origine du ruissellement sur les parcelles artificiellement drainées, en prenant en compte non seulement les fluctuations de la nappe superficielle, mais aussi la dégradation éventuelle de la structure du sol en surface. A cet effet, trois axes complémentaires de recherche ont été développés. <br />Le premier axe est consacré à l'étude de l'évolution de la structure de l'horizon travaillé du sol au cours d'une pluie en présence de nappe superficielle, grâce à des simulations de pluie en laboratoire. Les profils de masse volumique mesurés par radiographie aux rayons X indiquent que l'effondrement et le changement de masse volumique lié à la croûte de battance sont plus marqués en conditions initiales très humides. Le modèle proposé d'évolution de la masse volumique avec la profondeur et au cours de la pluie, reproduit correctement cet effet.<br />Le deuxième axe a pour objectif de déterminer les propriétés hydrodynamiques de la croûte de battance à partir de données issues de nouvelles simulations de pluie associées à un modèle s'appuyant sur la distribution de la masse volumique du sol avec la profondeur. Les paramètres de ce modèle, estimés par méthode inverse, sont comparables aux mesures de masse volumique effectuées par rayons X, et permettent de correctement reproduire le comportement hydraulique du système, confirmant la forte baisse de la conductivité hydraulique en surface due à la croûte de battance.<br />Enfin, le troisième axe s'appuie sur le suivi expérimental d'une parcelle agricole drainée du bassin versant de Mélarchez (Seine et Marne) associé à une modélisation (logiciel HYDRUS 2D). Les observations durant l'hiver 2003-2004 confirment que le ruissellement est globalement limité en raison de la présence du drainage. L'affleurement de la nappe reste le facteur prédominant à l'origine du ruissellement, même si la croûte de battance, créée notamment par ce premier type de ruissellement, est susceptible d'augmenter les quantités ruisselées. La modélisation permet d'étudier le comportement du système sous d'autres conditions pluviométriques. En particulier, les périodes de retour des pluies conduisant à l'affleurement de la nappe et les conditions d'écoulement lors de ces affleurements sont analysées.

Introduction Lake Mzingazi is the only suitable source of domestic water supply for the Richards Bay community. Rapid industrialisation in the city of uMhlathuze, accompanied by an influx of people, has resulted in informal settlement occurring around the lake. The uncontrolled activities of this development threaten to pollute the water source. Previous studies in1979 conducted by Council of Scientific & Industrial Research indicated that Lake Mzingazi water was still within acceptable limits in terms of the Department of Water Affairs & Forestry guidelines. The lake water quality was that of a Class I water resource, which is excellent for domestic use. Pollution of the lake can result from diffuse sources of pollution due to settlement of communities around it. Water purification costs could escalate thus forcing an increase in water tariffs. If pollution resulted in the lake being unable to be utilized, the Richards Bay community will be seriously affected, as it would necessitate the importing of water from distant regions. Either way, the expense of acquiring water would increase. All living organisms rely on adequate water for their survival. Worse still are human beings for their water should not only be adequate but should be of good quality to prevent health risks and even death. It is in view of these possibilities that the study was undertaken. Aim The aim of the study is to assess the extent of physical, chemical and biological pollution in Lake Mzingazi due to non-point sources and to recommend necessary protection measures that need to be implemented to prevent any negative health impact on surrounding communities. At present there are no restrictions and no protection of the lake from pollution except that no recreation is allowed into the lake at present. Methods Several objectives were set in order to focus on specific issues. One of the objectives was to inform the communities around the lake about the study. Sampling of the lake water was conducted monthly from June to November 2006 (using a boat). Pictures of areas around the lake were also taken for further analysis. At each sampling run, 36 samples were taken and delivered to a laboratory accredited by the South African National Accreditation Standards for analyses. Six sampling runs were completed. Secondary data for the period of 1998 to 2005 were obtained from uMhlathuze Municipality in order to establish pollution trends and for comparison purposes with the Department of Water Affairs and Forestry guidelines. Results The findings of the study revealed that the quality of the lake water is still within acceptable limits when compared with the Department of Water Affairs & Forestry guidelines; however, informal settlement threatens the future of the lake by encroaching into the lake banks. Discussion There is definitely a risk of pollution to Lake Mzingazi as long as there are no pollution prevention plans in place. Recommendations All data should be stored in a centralized information system to avoid losing valuable information. The Water Services Authority must develop and maintain a water quality-monitoring programme that will capture all changes occurring in the lake. / Thesis (MMed.)-University of KwaZulu-Natal, Durban, 2009.

This research critically examines the process of public participation in the politically contested arena of environmental impact assessment (EIA) in two case studies: the Ekati diamond mine in Canada’s Northwest Territories and the Richards Bay Minerals project in KwaZulu-Natal, South Africa. Each case offers the chance to examine and compare the potentialities of expanded public participation in EIA and the promise of deliberative environmental decision-making. The concept of deliberative public participation has become the new normative standard for citizen engagement in numerous planning and policy-making processes, including EIA. It calls for increased participation by previously disadvantaged communities in the decisions that affect them through multi-stakeholder dialogue. Addressing the need for a realistic assessment of deliberative democratic practice, this study explores the limits of deliberative process by looking at specific examples of EIA, bringing into focus political processes, power relations and the structural conditions affecting citizen engagement.

No description available.

<p>This thesis presents a method for solving partial differential equations (PDEs) using articial neural networks. The method uses a constrained backpropagation (CPROP) approach for preserving prior knowledge during incremental training for solving nonlinear elliptic and parabolic PDEs adaptively, in non-stationary environments. Compared to previous methods that use penalty functions or Lagrange multipliers,</p><p>CPROP reduces the dimensionality of the optimization problem by using direct elimination, while satisfying the equality constraints associated with the boundary and initial conditions exactly, at every iteration of the algorithm. The effectiveness of this method is demonstrated through several examples, including nonlinear elliptic</p><p>and parabolic PDEs with changing parameters and non-homogeneous terms. The computational complexity analysis shows that CPROP compares favorably to existing methods of solution, and that it leads to considerable computational savings when subject to non-stationary environments.</p><p>The CPROP based approach is extended to a constrained integration (CINT) method for solving initial boundary value partial differential equations (PDEs). The CINT method combines classical Galerkin methods with CPROP in order to constrain the ANN to approximately satisfy the boundary condition at each stage of integration. The advantage of the CINT method is that it is readily applicable to PDEs in irregular domains and requires no special modification for domains with complex geometries. Furthermore, the CINT method provides a semi-analytical solution that is infinitely differentiable. The CINT method is demonstrated on two hyperbolic and one parabolic initial boundary value problems (IBVPs). These IBVPs are widely used and have known analytical solutions. When compared with Matlab's nite element (FE) method, the CINT method is shown to achieve significant improvements both in terms of computational time and accuracy. The CINT method is applied to a distributed optimal control (DOC) problem of computing optimal state and control trajectories for a multiscale dynamical system comprised of many interacting dynamical systems, or agents. A generalized reduced gradient (GRG) approach is presented in which the agent dynamics are described by a small system of stochastic dierential equations (SDEs). A set of optimality conditions is derived using calculus of variations, and used to compute the optimal macroscopic state and microscopic control laws. An indirect GRG approach is used to solve the optimality conditions numerically for large systems of agents. By assuming a parametric control law obtained from the superposition of linear basis functions, the agent control laws can be determined via set-point regulation, such</p><p>that the macroscopic behavior of the agents is optimized over time, based on multiple, interactive navigation objectives.</p><p>Lastly, the CINT method is used to identify optimal root profiles in water limited ecosystems. Knowledge of root depths and distributions is vital in order to accurately model and predict hydrological ecosystem dynamics. Therefore, there is interest in accurately predicting distributions for various vegetation types, soils, and climates. Numerical experiments were were performed that identify root profiles that maximize transpiration over a 10 year period across a transect of the Kalahari. Storm types were varied to show the dependence of the optimal profile on storm frequency and intensity. It is shown that more deeply distributed roots are optimal for regions where</p><p>storms are more intense and less frequent, and shallower roots are advantageous in regions where storms are less intense and more frequent.</p> / Dissertation

Thesis (doctoral)--Magadh University, 1981. / Text in English, appendices in Sanskrit. Includes bibliographical references (p. 332-356).

Thesis (M.A.)--Brigham Young University. David M. Kennedy Center for International Studies. / Contains bibliographical references.