Showing papers in "Revista Brasileira de Recursos Hídricos in 2002"

Potencial de Reuso de Água no Brasil Agricultura, Industria, Municípios, Recarga de Aqüíferos

Abstract: No Capitulo 21“Gestao ambientalmente adequada de residuos liquidos e solidos”, Area Programatica B “Maximizando o reuso e a reciclagem ambientalmente adequadas”, estabeleceu, como objetivos basicos: "vitalizar e ampliar os sistemas nacionais de reuso e reciclagem de residuos", e "tornar disponivel informacoes, tecnologia e instrumentos de gestao apropriados para encorajar e tornar operacional, sistemas de reciclagem e uso de aguas residuarias".

Caracterização Física do Estuário do Rio Itajaí-açu, SC

Abstract: This paper describes some basic aspects about the hydrodynamics, hydrology and sedimentology of the Itajai-acu river estuary. It presents results of previous studies developed in the region about external driving agents (fluvial, marine and atmospheric), as well as about internal processes in the estuarine basin. In general, the estuary is of the salt-wedge circulation type, driven mainly by river discharge. Sea-level oscillation either due to astronomical or meteorological forces plays a minor role. Waves and wind appear to have no direct influence as driving agents of hydrodynamic and sedimentological processes in the estuary. The estuary exports most of the suspended sediment delivered by the river, although sediment can be also imported from the continental shelf through the landward bottom currents. Anthropogenic influence related to channel dredging has been changing the hydraulic and sedimentological behavior of the lower estuary systematically since the 50’s.

Gerenciamento da Drenagem Urbana

Abstract: RESUMO: O desenvolviment o urbano brasileiro tem produzindo um impacto significativo na infraestrutura de recursos hidricos. Um dos principais impactos tem ocorrido na drenagem urbana, na forma de aumento da frequencia e magnitude das inundacoes e deterioracao ambiental. Para o controle deste impacto e necessario desenvolver uma serie de acoes ordenadas de forma a buscar equilibrar o desenvolvimento com as condicoes ambientais das cidades. Este mecanismo e o Plano Diretor de Drenagem integrado com os outros planos de esgotamento sanitario, residuo solido e principalmente o de desenvolvimento urbano. Neste artigo sao apresentados os elementos basicos para a politica do Plano Diretor e a sua compatibilidade dentro da realidade brasileira, destacando-se: principios basicos de controle; estrutura do Plano, estrategias, interfaces com os outros planos e mecanismos de financiamento. Estes elementos foram apresentados para o Plano da cidade de Porto Alegre, concluida a sua primeira etapa e como propostas para os Planos da Regiao Metropolitana de Curitiba e Belo Horizonte.

Regionalização de Vazões Mínimas em Bacias Através de Interpolação em Sistemas de Informação Geográfica

Abstract: Streamflow regionalisation achieved using the traditional method of regional regression/homogeneous regions has limited accuracy when the available streamflow data is scarce. Since this is the case for most Brazilian watersheds, the uncertainties resulting from the regionalisation process may be significant. An alternative method, which uses a different approach (interpolation of known streamflow data in a GIS environment), is presented. In order to test the accuracy of both traditional and proposed methods, a case-study is presented, using actual streamflow data from a watershed in the state of Bahia. The proposed method outperformed the traditional method in both standard error and Nash & Sutcliffe (1970) criteria, indicating that the former could be more appropriate under conditions of limited streamflow data.

A Inserção da Água Subterrânea no Sistema Nacional de Gerenciamento

Abstract: During the last decades of the 20 Century, exhibiting an abundance of water appears to have been the formula to justify the great water waste and water quality degradation at unheard of levels. Therefore, the high cost of the water supply projects and the increasing scarcity of money have resulted in a better evaluation of available water resources. From this point of view, the main goal has been to seek an even more efficient water use and utilize more groundwater to reduce the costs of the water supply projects. Furthermore, groundwater is known to be the main freshwater reservoir of the Earth available through technical and financial means; it is affected only with great delay by rainfall variability and groundwater is the cheapest alternative to supply domestic, industrial and even agricultural water demands.

Estratégias Operacionais para Sistemas de Reservatórios via Algoritmos Genéticos (AGs)

Abstract: Reservoirs are generally essential components of water resources systems and their operational planning constitutes a target of investigation. In view of the characteristic degree of difficulty related to the operational strategy determination, increasing according to the system dimensions, several approaches have been proposed for their resolution. Currently, the increasing use of techniques inspired by robust mechanisms of nature has presented Genetic Algorithms (GAs) as alternative tools to solve such problems. However, there are several possible implementation procedures, besides the possibility of hybridization with conventional mathematical programming techniques, which help reduce the computing effort in the search of good solutions. The present study aims at reviewing the relevant literature related to the procedures used to solve reservoir operation problems by using Genetic Algorithms (GAs) and demonstrating the potentials of the method through a simple example of application to a hypothetical hydrothermal system with four hydroelectric plants. It is organized to formulate the problem, emphasize the different possibilities of implementing GA techniques, review existing studies and present some results obtained for the system analyzed system in order to foster further research.

Gerenciamento da Produção de Energia e Controle de Inundação: Foz do Areia no Rio Iguaçu

Abstract: Resumo: A operação de um reservatório para geração elétrica busca a maximização do nível e da vazão, o que pode gerar conflitos a montante e jusante do aproveitamento devido às inundações. Para gerenciar estes objetivos conflitantes é necessário um sistema da previsão de afluência de vazão ao reservatório integrado com a sua operação. Este sistema deve minimizar os impactos das inundações e maximizar a produção energética. Neste estudo é apresentada a metodologia de previsão de vazão de afluência em combinação com a operação de uma Usina Hidrelétrica que atenda os dois objetivos citados. A metodologia proposta utiliza um modelo ARIMA para a previsão de afluência da bacia afluente a montante da entrada do lago, onde os processos possuem maior memória e um modelo semi-conceitual (modelo chuva-vazão IPH II) para a parcela da bacia de contribuição direta ao lago do reservatório. Uma das importantes incertezas da previsão é a previsão da precipitação utilizada no modelo chuva-vazão citado. Neste caso, algumas alternativas foram estudadas (a) a chuva cessa a partir do instante em que se faz a previsão;( b) a previsão de chuva é conhecida; (c) usa-se uma previsão estocástica de chuva. Associada à previsão, foi desenvolvido um modelo de operação do reservatório que permitisse maximizar a produção de energia e garantir o cumprimento das restrições operacionais de segurança do reservatório e para a população de montante e jusante. Esta metodologia, apesar de utilizada em específico para o reservatório de Foz de Areia, representa um condicionante freqüente encontrado em diferentes reservatórios energéticos brasileiros. No caso de Foz de Areia, no rio Iguaçu, os resultados mostraram que a previsão realizada permite melhorar o atendimento das restrições e recuperação dos níveis do reservatório. Palavras-chave: /Previsão/tempo real/reservatório/

Stochastic Hydrology Revisited

Abstract: This paper reviews some of the stochastic methods used in applied hydrology over the past thirty years, the period during which the power and availability of computers grew rapidly, and methods of time-series modelling and simulation came into use which had previously been computationally prohibitive. Where stochastic methods are used to estimate the frequencies with which extreme hydrological events (floods, droughts) will occur in the future, these methods assume that hydrological processes are stationary, so that rainfall and runoff records from past years can be used to estimate how often extreme events will occur in the future. But where there are changes in land use or climate, hydrological processes also change, and the past may not be a good guide to the future. In South America, there have been extensive changes in land use during the last thirty years, and there is increasing evidence that climate is also changing. Standard hydrological procedures, such as estimating annual events with T-year return period, and regionalization of annual floods, then become inappropriate. The paper argues that under conditions of climate and land-use change, good assessment of the future frequency of extremes must await better knowledge of the physical processes that determine the behaviour of atmosphere and the oceans.

Perspectivas da Gestão da Água para o Século XXI: Desafios e Oportunidades

Abstract: A brief reference is made to the changing conditions of the relationship between man and water, which lead to a new water paradigm at the dawn of the 21 century. The main international initiatives related to water in the last three decades are put into perspective, from the 1977 Mar del Plata Water Conference to the 2000 World Water Vision and the 2002 Johannesburg World Summit on Sustainable Development. The notions of Sustainable Development of Water Resources and Integrated Water Resources Management are reviewed highlighting the increasing importance of the river basin as the basic unit for water resources management and planning. The role of the European Water Framework Directive is indicated as a strategic tool to structure a water policy, not only for the 25 States of the European Union and its extension, but also for other States, providing a framework of reference to reform their national water policies. Reference is made to the innovative character of the Water Framework Directive, the main steps of its implementation and the strategy for this implementation. Finally, the consequences of the new water paradigm for Portugal are discussed, three main issues being reviewed: climate change impacts on water resources; water resources management in PortugueseSpanish river basins; and the reform of the Portuguese institutional water management system.

Alocação e Realocação do Direito de Uso da Água: Uma Proposta de Modelo de Mercado Limitado no Espaço

Abstract: A crescente demanda por agua de boa qualidade em um contexto de limitacoes na oferta tem motivado a so- ciedade a pesquisar novos modelos legais e institucionais de gestao de recursos hidricos. A formulacao e aperfeico-amento de modelos que conduzam o processo de alocacao de aguas a um maior nivel de eficiencia tem recebido uma especial atencao por parte de pesquisadores e de formuladores de politicas de agua. um desses modelos, o mercado de aguas, tem sido objeto de muitos debates e polemicas. O mercado tem sido aplicado em varias partes do mundo, como no Chile, na Australia e no oeste dos Estados Unidos. O artigo apresenta conceitos teoricos sobre o processo de alocacao e realocacao de aguas e apresenta um modelo no qual o mercado de aguas esta inserido.

Response of a Natural Marsh to Chemical and Biological Inputs of Eutrophic Waters (Saladas, Corrientes, Argentina)

Abstract: Soto marsh is a non forested inland freshwater wetland with a humid subtropical weather and fed by rains and domestic wastes through the Soto lake. Main hydrological characteristics and the composition of vegetation and soil through which the water circulates are described. Chemical and biological conditions of water entering and leaving the marsh during dry and rainy periods were compared. Passage through the marsh reduces BOD5 by 64%, producing an average effluent of 2.2 mg.l. Average chlorophyll “a” concentration was reduces by 76% in relation to value recorded at inflow. During the rainy period, the concentration of chlorides, calcium, potassium and sodium was lower in the leaving of the marsh while in the dry period the concentration of anions and cations was very variable. Our results indicate that Soto marsh functions as a source of nutrients (phosphorus and ammonium) when the concentration of organic matter was high and the concentration of dissolved oxygen was low. In the Soto lake and at inflow of the Soto marsh, phytoplanton was dominated by cyanophyte, specially colonies of Microcystis aeruginosa while at the marsh outlet there were higher proportion of other algae. After passage through the marsh zooplankton abundance decreased specially rotifers populations characteristic of eutrophic environments. Comparing the same vegetation (Salvinia biloba), the number of invertebrates associated with the plants was higher in the lake than in the marsh. This decrease was more marked during the rainy period

Uma Visão Histórica dos Recursos Hídricos na Cidade de São Paulo

Abstract: This article presents a history of the water supply proposals in the city of São Paulo, from the end of the 19th century to the first three decades of the 20th century. The times at which water supply arose as a social problem and when controversies on the use of the Tietê river and of distant sources divided the opinions of famous experts were remembered.

Projeto e Implantação de um Sistema de Controle para Geração Automática de Perfis de Vazão

Abstract: This study describes the connection between the instrumentation and control of a pilot plant located in the Hydraulics Laboratory at UFMG. These pilot plants consist basically of a water tank receiving water from a pump driven by an induction motor connected to a frequency converter. Originally, the pilot plant operated in an openloop and, consequently, it was not possible to generate prespecified water flow profiles required to test reduced scale models of hydraulics structures. The purpose of this study was to implement a closed-loop control system in order to enable the pilot plant to produce the aforementioned water flow profiles. The closed-loop implemented consists basically of a differential pressure sensor and transmitter, a PID controller connected to the frequency converter and a PC. These devices were connected to the pilot plant and tuned in order to achieve water flow control. Some PID tuning methods were implemented in order to tune the controller. After this was done, it was possible to successfully produce standard water flow profiles using the pilot plant. Some results are presented and discussed in the study.

Curva NPSH(Q) de uma bomba centrífuga radial para rotações não padronizadas

Abstract: In many engineering applications, the operational conditions do not permit that a centrifugal pump works with the rotational speeds indicated in the catalogs (“standards”). In such a case, some professionals of the field have difficulties to obtain a reliable estimation of the H(Q) and NPSH(Q) performance curves for the chosen speed. It is shown that the use of homologous points provides good results only for the H(Q) curve estimation and that this methodology cannot be applied for the NPSH(Q) curve determination, only under certain conditions suggested.

Modelagem Numérica de Ondas de Submersão Utilizando o Modelo de Serre

Abstract: The purpose of this paper is to highlight the adaptability and validity domains of numerical models based on Boussinesq class equations (Serre ́s proposal) in the water waves generated by the study of local disturbance. Serre’s model proposed considers higher order derivate terms, previously neglected by Boussinesq that take into account the hypothesis that the horizontal component of velocity is uniform in depth, and the vertical component of velocity is linear from the bottom to the free surface. In this way, in the generation zone, Serre ́s model can stand high relative wave amplitudes (vicinity of the breaking phenomenon). Based on the numerical-experimental confrontation of results, it was possible to analyze the validity domains of this model and observe that, even using an implicit method (unconditionally stable) there are some restrictions that should be observed in using it.