Showing papers in "Revista Brasileira de Recursos Hídricos in 2004"

Quantificação dos Benefícios Ambientais e Compensações Financeiras do "Programa do Produtor de Água" (ANA): II. Aplicação

Abstract: In spite of the relative success of soil & water conservation programs in Brazil in the last 20 years, they have not explicitly considered their off-site benefits, or utilized compensation instruments. Considering these shortcomings, as well as the new trends in agri-environmental programs, the Brazilian National Water Agency-ANA developed a conservation and reclamation project aimed at strategic water supply sources, where the financial incentives for the participants are proportional to the off-site benefits provided, relative to the sedimentation abatement. Since the latter is not a trivial process, it was emulated by a simplified version of the Universal Soil Loss Equation-USLE, at the farm level. Thus, the financial incentives for the participant farmers were estimated as a function of the erosion and sedimentation abatement provided, as well as the cost of the adoption of the practice. The simplicity and robustness of the proposed method, as well as the ease of the certification process in the field, allow its decentralized implementation by watershed committees or cooperatives. The theoretical and methodological aspects of this project, entitled “Water Provider Program”, are presented in this paper. An example of the application of the method to a rural watershed in Brazil is presented in a companion paper, in this same issue (Chaves et al., 2004). APENDICE A A simplificacao proposta para a USLE, dada pela equacao [3] requer, no caso de introducao da pratica de terraceamento em nivel, uma demonstracao de que a reducao da erosao A, na equacao [2], e uma funcao linear da reducao do fator de comprimento de rampa, L. Na USLE, o fator L e definido como sendo (Wischmeier & Smith, 1978): L = ( l / 22,1)M [A1] Onde: l (m) = comprimento de rampa da gleba, e M = coeficiente proporcional a declividade da rampa (M varia entre 0,1 a 0,5). Como o terraceamento em nivel reduz o comprimento de rampa ( l ) mas nao a declividade da vertente, o valor de M na equacao [A1] nao e afetado. Assim, supondo que uma vertente agricola de area igual a 100 ha, com comprimento igual a l0=200m seja reduzida, com a introducao do terraceamento, a 4 vertentes iguais de l1=50 m (ou seja, l1= l0/4). Teremos assim a seguinte reducao relativa na perda de solo, A (t/ha ano): A1/A0 = L1/L0 = [( l1/22,1)M/( l0/22,1)M] [A2] = [(50/22,1)M (200/22,1)M] = 1⁄4 ou 25%, como queriamos demonstrar. Assim, no caso de terraceamento em nivel, um fator adicional (L) devera ser introduzido no fator consolidado Z, na estimativa de Z0 e Z1 para as equacoes [3] e [4]: Z = C*P*L [A3] Onde C e P foram definidos anteriormente.

Análise Multicritério para a Avaliação de Sistemas de Drenagem Urbana Proposição de Indicadores e de Sistemática de Estudo

Abstract: The urbanization process that has occurred in the last few years has been causing changes in the hydrologic cycle. These changes are making the classic systems work to the limit leading to some crises. To reduce these effects, some alternative techniques (BMPs) are being developed based mainly on stormwater retention and infiltration. For this case, there several different possible conceptions of drainage systems currently available, and it is important to have tools to compare the technical, social and environmental efficiency of these alternatives. The main purpose of this paper was to propose indicators that can be used to evaluate different types of urban drainage systems. These indicators were used and verified by utilizing two different methods of multicriteria analysis, Electre III and Compromise Programming, in three case studies of chosen areas whose drainage projects included differently conceived systems with classic, intermediaries and alternative techniques (BMPs). Several important conclusions were reached, such as the preference for alternative techniques over classic ones, when comparing environmental and social aspects with the hydraulic and hydrologic ones.

Uma Formulação Alternativa do Método Interativo de Gradiente Hidráulico no Procedimento de Calibração dos Parâmetros Hidrodinâmicos do Sistema Aqüífero

Abstract: The iterative hydraulic gradient method is an indirect inverse method for estimation of hydraulic parameters as aquifer transmissivity or hydraulic conductivity for groundwater flow model. In this method, the inverse problem is defined as an optimization problem with the objective function to minimize differences between interpolated (observed) and simulated (calculated) hydraulic gradients, which results in a simultaneous minimization of differences between observed and simulated hydraulic heads. The key feature of this method is its clear hydrology concept that is consistent with Darcy’s law and its spatially independence of optimality conditions. Because of the spatial independence, a multidimensional optimization problem can be solved by many one-dimensional optimizations procedures simultaneously, which reduces substantially the computation time and allow an unlimited number of the estimated parameters while traditional inverse technique encounters difficulty in bypassing the convergence problem in the often ill-posed linear system. In this study an alternative approach of the hydraulic gradient procedure is presented and tested successfully on a heterogeneous hypothetical aquifer system confirming that minimizing gradient residuals in the entire model domain leads to minimizing head residuals too. The simulated example demonstrates that the iterative method of hydraulic gradient is efficient and practical to be used for estimation of hydraulic parameters in complex real-world modeling projects. Key-works: hydraulic conductivity; aquifer system.

Erosão Potencial Laminar Hídrica na Bacia do Alto Taquari

Abstract: Identification of areas (counties and sub-basins) of the Upper Taquari Basin (UTB) presenting the highest hydric sheet erosion potential is fundamental to guide future interventions aiming at minimizing erosion in the region and consequently its severe reflexes on the Pantanal wetland. The potential of soil loss in the UTB was evaluated using the Universal Soil Loss Equation (USLE), geoprocessing techniques and computer routines. Mean annual rain erosivity on the UTB was 7,914.3 Mj mm ha -1 year, varying between 7,000 and 9,000 Mj mm ha year. Soil erodibility did not vary among counties and sub-basins, and the mean value was 0.0356 t h Mj mm. The topographic factor LS of the USLE presented the highest variation and therefere mostly influenced the distribuition of soil loss on the UTB. The average potential soil loss total amount was 555,6 t ha year. The municipality os Alto Araguaia-MT, due the rougher relief (LS = 3,22), presented the higher potential soil loss of the UTB (990 t ha year). Other counties with high risk of erosion are: Costa Rica-MS, Rio VerdeMS, Alto Taquari-MT and Alcinópolis-MS. Erosion potential did not vary among sub-basins. Areas of litholic soils on the UTB, located on steep relief, presented mean potential of soil loss of 1,839.8 t ha year. Key-words: potential erosion; Upper Taquari Basin; Pantanal wetland.

Análise de Alterações na Receita Líquida Otimizada de um Perímetro Irrigado no Semi-Árido sob Condições de Variações Hídricas e Econômicas

Abstract: A system of two interconnected reservoirs, Coremas and Mãe D’Água, is located in the southwest of Paraiba state and fed by three rivers: Piancó, Emas and Aguiar. Together they are the largest reservoir of the Paraiba state and the third largest in the northeast of Brazil. Its water is used for human supply, hydroelectric power generation, irrigation and fishing activities and to meet downstream water demands from the Rio Grande do Norte state. Recently, an open channel, which is connected to the Mãe D’Água reservoir and has a 4 m/s water carrying capacity and a length of 37 Km, was built to supply water to a nearly 5000 ha irrigation site in the neighborhood of the city of Sousa-PB. The aim of this work is to study the behavior of the system and ways to maximize the economical benefits by choosing irrigation areas for 13 selected types of fruits and their corresponding irrigation systems while covering all water demands for the reservoirs. The mathematical model uses a successive linear programming method, in order to take into account problem nonlinearities. The system is modeled using 85 decision variables and 1479 constraints that represent the physical and operational behavior of the system, including reservoir sustainability. The analyses were performed using sets of 6 years of hydro-climate data series, as well as their monthly mean values, which represent dry, normal, wet and average scenarios. Sensitivity analyses were also performed taking into account the variability of water costs, crop sale prices and the maximum amount of water that may reach the irrigated perimeter through the open channel. Key-words: Irrigated perimeter; irrigation areas.

Energia Firme de Sistemas Hidrelétricos e Usos Múltiplos dos Recursos Hídricos

Abstract: This paper presents an optimization model for the calculation of the firm energy of hydropower plants. The model represents the hydro operation in detail (water balance of plants in cascade, storage-dependent production factor, tailwater elevation curve, evaporation as a function of the wet area, etc.) as well as transmission constraints. Results with the model for the existing hydro plants of Brazil show that the calculated firm energy is smaller than the sum of the assured energy certificates of these plants. This means that there will be a new energy rationing in case the worst historic hydrology happens again in the future. A revision of the methodology is proposed, ensuring that the resulting firm energy considers both the hypothesis of the worst drought observed in the past and the decreasing availability of water for energy production, due to other uses.

Impactos de Ações Antrópicas em Bacias de Manancial Rurais de Montanha Sobre Parâmetros de Qualidade de Água

Abstract: The objective of the research was to analyze the impacts of human actions, including deforestation, on water resources in small watersheds. A case study developed in the Santa Maria de Jetibá district, located in the mountains of the state of Espírito Santo, Brazil, aimed at assessing the local impacts of human actions on previously forested areas. This case study was performed analyzing and crossing basin information using GIS and water resources monitoring, comparing the pedological, geomorphological, climatic and water quality and quantity characteristics of forested basins that had suffered anthropic action. This allowed observations and conclusions about the consequences of removing native vegetation on the water resources in four watersheds. Water quality assessments showed the worst conditions in farming areas due to soil erosion, fertilization, irrigation and slash-and-burn. It was concluded that the magnitude of the impacts of farming activities on drained water quality depended on soil occupation and levels of use, forms of land management in the watershed, the existence of rural households and small-scale hog farming activities. Streamflows, types of soil and vegetation cover have proved to be important factors influencing water quality. It has been shown that parameters such as Dissolved Oxygen, pH and Temperature depend less than other parameters on anthropic activities in the rural watersheds studied. These parameters were most influenced by soil types and local climatic and topographic conditions. The effective protection of forests was observed using the Water Quality Index since the best results came from basins presenting greater vegetation cover and in a more advanced stage of regeneration. The more anthropised basins presented the lowest indices and more parameters in worse conditions. This confirms the protection provided by forests in mountain regions and the serious impacts of deforestation and human occupation on water resources in small watersheds. Key-words: watersheds; human activities; water quality.

Modelagem hidrológica de uma microbacia florestada da Serra do Mar, SP

Abstract: Utilizou-se o modelo hidrologico TOPMODEL, baseado em aspectos fisicos e topograficos, em uma das tres microbacias do Laboratorio de Hidrologia Florestal Eng. Agr. Walter Emmerich, do Instituto Florestal/SP. O modelo usa um indice topografico que indica as areas de contribuicao para o defluvio da microbacia e permite simular a vazao e analisar o comportamento hidrologico da microbacia. A primeira parte do trabalho buscou determinar os valores iniciais dos parâmetros de calibracao, testar a validade das premissas do modelo, e, principalmente, compreender melhor o funcionamento hidrologico da bacia D. Os resultados indicam uma eficiencia maior para as simulacoes de eventos isolados do que para as de periodos longos. A simulacao do comportamento hidrologico em funcao do corte raso mostrou uma diminuicao do tempo de pico e um aumento significativo do volume de vazao simulado: de 17 % a 44 %, em comparacao a bacia D coberta com floresta. Mostram, tambem, que de 7 % a 93 % do defluvio e gerado a partir das areas variaveis de afluencia (A.V.A.)

Calibração de Modelos de Redes de Distribuição de Água Utilizando Modelo de Simulação Hidráulica Dirigido pela Pressão (MSHDP) e Método Híbrido AG-Simplex

Abstract: Brazil’s water distribution systems usually present a high percentage of so-called physical losses, of which a significant portion is caused by leakage. Therefore, it is of fundamental importance, not only from a financial standpoint – in terms of the pumped and chemically treated water – but also particularly from that of the preservation of this natural resource, to effectively control leakage and the systems’ behavior under several operational conditions. In order to gain a better understanding of the real behavior of a water distribution network, several calibration techniques, including models to evaluate leakage, have been proposed. Those models normally consider the correlation between pressure and leakage, as well as the interdependence of pressure and demand in response to the varying levels of pressure in a water distribution system. The present study seeks to extend these models through the development of a computational routine based on leakage and on pressuredependent demand, in conjunction with the hydraulic simulator EPANET 2 (Rossman, 2000), using the data from a hypothetical network to calibrate the absolute roughness and parameters of the leakage model. To this end, inverse models are used based on the technology of Genetic Algorithms (GAs) and the hybrid procedure (GAs and Simplex Method Nelder and Mead, 1965). Comparisons between both two optimization models have been performed, demonstrating hybridization advantages in terms of computational processing time and improved solutions.

Uma Análise na Dragagem do Complexo Estuarino-Lagunar Mundaú/Manguaba em Alagoas através de um Modelo Numérico Hidrodinâmico Bidimensional ? Resultados Preliminares

Abstract: The objective of this research is to prepare a schematic proposal for an action plan and integrated management of a lagoon ecosystem. The case of the Mundaú/Manguaba estuarine-lagoon complex (CELMM) system located southeast of the city of Maceió, state of Alagoas, is used as an example. It is necessary to develop a strategic intervention program in the region covered by CELMM, with definitions of structural and non-structural measures and necessary institutional arrangements in order to be sure that the actions will be implemented. In this study, a proposal to dredge CELMM is presented by simulating a two-dimensional hydrodynamic numeric model. The purpose of this engineering work is to allow greater exchange of water between the continent and the ocean, partially solving the hydrodynamic problem, and enabling a certain amount of cleaning in the estuary. Among the main preliminary results of this implementation is the increased prism of tides and mass flow.

Utilização do Método Inverso para a Caracterização Hidrodinâmica de um Neossolo Flúvico

Abstract: The parameters of the soil-water retention curve and the hydraulic conductivity curve of the superficial layer (5-17 cm) of a Fluvent soil, with a loamy sand texture, were determined by using the inverse method. The hydraulic functions used were combined, thus forming the so-called VGBC(B) (van Genuchten-Burdine/ Brooks&Corey) and VGBC(M) (van Genuchten-Mualem /Brooks&Corey) models. On a surface plot, located in the Experimental Station of the Group of Soil Physics of DEN-UFPE, the water content data and the matric potential of the water in the soil were obtained automatically and stored in a datalogger every 30 minutes for 72 hours, at the depths of 5, 11 and 17 cm. The implementation of the inverse method was accomplished by combining the hydraulic model, which solves the equation of Richards, with the subroutine DBCONF that minimizes an objective function by using the quasi-Newton method. The parameters α and n of h(θ) and Ks, and c of K(θ) were obtained by minimizing the sum of the squares of the deviations between the measured and the calculated water content at the depth of 11 cm. The inverse method was shown to be effective in determining the parameters of h(θ) and K(θ). Both models showed the same ability to describe the experimental data.

Perfil das Fazendas de Camarão em Águas Interiores, na Região do Baixo Jaguaribe

Abstract: The growing demand for shrimp in the global market, the overpricing of coastal areas, the high density of shrimp farms in the estuaries, compromising the preservation mangrove areas, and the capacity of the species Litopenaeus vannamei to adapt to low salinity Perfil das Fazendas de Camarão em Águas Interiores, na Região do Baixo Jaguaribe 108 waters (about 0.5 ‰) have fostered the development of inland shrimp production in Brazil, especially in the State of Ceará. This paper aims to analyze the profile of inland shrimp production in the Baixo Jaguaribe region, State of Ceará. In order to accomplish this objective, questionnaires were applied to shrimp producers and the geographic coordinates of each farm along the Jaguaribe River were recorded between the Castanhão and the Itaiçaba reservoirs. In the fieldwork conducted between February and July of 2003, 36 shrimp farms were identified, encompassing 420,34 ha in the municipalities of Quixeré, Russas, Jaguaruana and Itaiçaba. Considering the 32 farms analyzed, they are responsible for the generation of 201 direct jobs in this region, an average of 0.6 jobs/ha. The average productivity of these farms is estimated at 3,547 kg/ha. For shrimp farming to be sustainable in the long run, it is necessary to foster research related to the evaluation of the river capacity to cover the high water demand and dilute the effluents of this activity, wastewater recirculation and reuse systems, acclimation techniques, shrimp feeding and pest control in low salinity waters.

Calibração de um Modelo de Rede de Distribuição de Água para um Setor de Abastecimento Real Contemplando Vazamentos

Abstract: Physical changes occurring over time require that hydraulic models to forecast the behavior of water distribution networks have their parameters reevaluated through calibration. There are several difficulties inherent to the calibration process of real networks, amongst which one can highlight those resulting from poor existing records such as uncertainty about the existence and position of networks valves. Many calibration methods have been proposed in literature, usually based on several analytical equations and optimization techniques. The need to estimate network parameters in terms of roughness and local parameters of pressure and leakage relations for systems subject to relevant leakage can be recognized. An iterative Calibração de um Modelo de rede de Distribuição de Água para um Setor de Abastecimento Real Contemplando Vazamentos 54 two-step calibration method is proposed here, in which the GAs (genetic algorithms) are used as a tool to resolve corresponding inverse problems, whose results prove robust to identify roughness, sections with valves and leakage model parameters.

Soluções de Compromisso na Tomada de Decisão sobre a Operação Diária de Sistemas Urbanos de Abastecimento de Água

Abstract: The application of specific operational research modeling tools to the operation planning of urban water supply systems has allowed to have better design criteria and operational management. However, the solutions described in a broad literature review have encompassed the use of simulation and optimization models addressing only a single objective which represents the main decision maker expectations without any effort to include any other objective. This work takes two conflicting operational objectives into account aiming at a comparison between them. The methodology is applied to the water supply main network of the metropolitan region of São Paulo, which is called “Alça Leste”. The minimization of the temporal variability of the water flow into the treatment station (ETA) and the operation cost minimization were selected among the possible set of operational objectives. A linear programming algorithm is adopted by using the commercial package GAMS with the solver CONOPT. The non-linear structure of the problem is surpassed by successive iterations.

Avaliação dos parâmetros do modelo de vazamentos para setores de rede da cidade de São Carlos - SP

Abstract: Greater environmental consciousness indicates the need to make more effective use of the natural resources water and energy. Thus, several studies have been developed to reduce leakage losses in water supply distribution systems. However, the success that may be achieved depends on the degree of realism of the parameters employed to express leakage as a function of pressure. It could also be said that effective operational control of urban water supply systems requires evaluations supported by mathematical models to forecast behavior, providing answers to these systems in terms of leakage, when they are relevant, in order to deal with the different operational conditions to which they may be submitted. The purpose of this paper is report our experience in determining the values for the pressure-leakage model Avaliação dos Parâmetros do Modelo de Vazamentos Para Setores de Rede da Cidade de São Carlos-SP 96 parameters, based on nocturnal tests conducted in sectors of the water supply network in the city of São Carlos, S.P. Key-words: Leakage; water supply.

Uso da Técnica de Avaliação do Terreno para a Elaboração de Carta de Susceptibilidade à Erosão na Bacia do Prosa ? Campo Grande, MS

Abstract: This work involves erosion conditioning processes evaluation in a specific drainage basin in urban environment and susceptibility analysis in different basin parts identified in terms of its physical environment homogeneous properties. The main criterion for physical environment zoning was morphologic, using terrain evaluation technique. The studied area involves Córrego do Prosa Basin, in Campo Grande (MS), witch was selected due to its accelerated urban occupation and its serious problems with erosion processes. In order to characterize erosion conditioning we survey geologic and geomorphologic information and human activities. For surveying, classification and analysis of attributes we used Zuquette (1987 and Uso da Técnica de Avaliação do Terreno para a Elaboração de carta de Susceptibilidade à Erosão na Bacia do Prosa – Campo Grande, MS 38 1993a) methodological proposition while to provide the natural units zoning were used terrain evaluation technique, with Lollo (1996) systematic. Results were represented in 1:15.000 scale maps. The considered attributes were rocks, soils, slope inclination, landforms (until land element level) and human occupation. These attributes were classified to susceptibility chart generation (final chart). Terrain evaluation technique shows high efficacy in physical environment zoning to describe its different levels of erosion processes development potential. Key-words: Geomorphology; terrain evaluation.

Regionalização de Parâmetros Hidrológicos Utilizando Análise Difusa

Abstract: This paper addresses the application of the fuzzy sets theory in regionalization of hydrologic parameters in small and medium basins. Fuzzy analysis is appropriate for multi criteria modeling of impacts under uncertainty for water resources management and modeling. In hydrology the uncertainties are mostly related to physiographic characteristics of the basins and also to imprecision and scarcity of hydrologic data. The following techniques of fuzzy logic were used: analysis of clustering of numerical data by the \"c-means\" algorithm and fuzzy goal regression. The investigation focused on regionalization of mean daily discharge (mean, coefficient of variation and probability weighted moments); and of maximum annual flow (mean and coefficient of variation). The conclusions are based on performance indices of the results and comparison of the results of this dissertation with other regionalization methods. Through the case study it was possible to verify that the application of fuzzy tools as a water resources modeling technique, in this case, regionalization of hydrologic parameters, is justified by better results than those obtained with standard statistical methods.