Showing papers in "Revista Brasileira de Recursos Hídricos in 2007"

Comparação de Métodos de Previsão de Vazões Naturais Afluentes a Aproveitamentos Hidroelétricos

Abstract: This study compares the results of different daily streamflow forecast models using information on observed and forecast rainfall, applied to hydropower plants of the Brazilian National Integrated System SIN. These streamflow forecasting models are defined to obtain future values up to 12 days ahead for the Iguaçu river basin, the river basin upstream from Itaipu and the Paranaíba river basin between Itumbiara and São Simão hydropower plants. These models are developed using various techniques, including concentrated and distributed rainfall-runoff models, a stochastic approach and different artificial intelligent technologies using fuzzy and data mining. Key-words: streamflow forecasts, rainfall forecasts, artificial intelligence, Iguaçu river, Paraná river, Paranaiba river, Itapu Hydropower Plant, São Simão Hydropower Plant, Salto Osório Hydropower Plant, Foz do Areia Hydropower Plant, SIN (National Integrated System)

Análise Multicritério como Instrumento de Gestão de Recursos Hídricos: O Caso das Bacias dos Rios Piracicaba, Capivari e Jundiaí

Abstract: This study suggests the use of environment sustainability indicators linked to multicriteria analysis. These indicators have been chosen from a framework called Pressure-State-Response. This framework is scientifically recognized and used in the formulation, organization and selection of environmental sustainability indicators. The study aims at evaluating the applicability of these instruments in the Piracicaba, Capivari and Jundiaí river basins which are located in the State of São Paulo. Twenty indicators were chosen from a diagnosis of the region studied and the aforementioned framework. Then the rivers basins that lie in the study area were ranked by order of preference and/or need depending on the previously chosen types of intervention. The indicators proposed and the multicriteria model RBRH — Revista Brasileira de Recursos Hídricos Volume 12 n.3 Jul/Set 2007, 117-127 127 (ELECTRE III) proved suitable for the case studied. The results obtained suggest that preference for a given intervention varies significantly among basins and may be important information to implement an action plan or investment program. Key-words: Sustainability indicators, multicriteria analysis, water resources management, river basin.

Metodologia Generalizada para Pré-Dimensionamento de Dispositivos de Controle Pluvial na Fonte

Abstract: This paper intends to develop a generalized, easyto-use method to design runoff source control devices, using generalized, explicit formulations. An explicit hydrological design solution is presented, applicable to most of the source control devices presenting storage capacity, including pervious pavements, infiltration devices (trenches, wells and ditches) and retention basins. The design rainfall is obtained using a Talbot formulation IDF curve. The rational method provides the input flow, and the nominal output volumes of the devices are given by maximum constant rates. The balance equations are built according to these simplifications, in order to explicitly establish design dimensions for runoff source control structures. Key-words: runoff source control, hydrological design, infiltration devices, storage devices.

Análise das Previsões de Precipitação Obtidas com a Utilização do Modelo Eta como Insumo para Modelos de Previsão Semanal de Vazão Natural

Abstract: In this paper we show the evaluation of the Eta model of ten-day precipitation forecasts in a 6-year study period of three basins in Brazil. For application in inflow forecast models, the precipitation forecasts were accumulated from one to ten days. The results indicate that the Eta precipitation forecasts have no clear systematic errors over these basins that can be treated with traditional statistical techniques. These forecasts generally underestimate the heaviest precipitation and perform better when rain accumulates over three or more days. Despite these forecast errors, the river discharge models have shown improvements when driven by these forecasts. Key-words: Precipitation forecasts, Eta Model, Discharge forecasts

Geoprocessamento como Ferramenta no Estudo de Correlação entre a Dinâmica da Cobertura Vegetal e a Evapotranspiração

Abstract: Changes in the plant cover of a watershed have significant impacts on the hydrologic processes and river water quality of the drained area. Attempting to evaluate this impact, this paper presents a case study referring to a 109 km drainage area, corresponding to the Serra Azul river in Minas Gerais. The study period is from 1984 to 2002. The variations in the hydrologic behavior were represented by the evapotranspiration: the water cycle component considered most affected by change in land surface cover. In this study evapotranspiration was estimated by the annual water balance and by the FAO — Penman — Monteith method. The study of plant cover dynamics was performed based on Landsat/TM mapping images, at 2-year intervals on average. In order to treat these images, geoprocessing methods were used to generate Thematic Maps of Vegetation and Land Use, by utilizing the SPRING software. Finally, it was attempted to establish correlations between the changes in the hydrologic behavior and the vegetation dynamics of the watershed, based on the Dense Forest parameter. With the available information, the correlations found were poor, within a reasonable confidence level. However, this study emphasizes the importance of environGeoprocessamento como Ferramenta no Estudo de Correlação entre a Dinâmica da Cobertura Vegetal e a Evapotranspiração 102 mental preservation activities that are developed in the

Avaliação da Interação Rio-Aqüífero a Partir de Dados Experimentais e de um Modelo Analítico

Abstract: Um estudo experimental e teorico da interacao que ocorre num sistema rio-aquifero foi realizado. A parte experimental consiste da liberacao de um pulso de agua de um reservatorio e medicao dos niveis d´agua do rio e do aluviao adjacente, de forma a determinar o gradiente hidraulico entre ambos. A parte teorica consiste em analisar a interacao rioaquifero no regime transiente por meio de um programa computacional, doravante denominado STLK1, desenvolvido por DeSimone e Barlow do United States Geological Survey (USGS). Tal programa faz uso da Transformada de Laplace e do conceito de Integral de Convolucao na resolucao analitica das equacoes que descrevem o sistema rio-aquifero. O modelo analitico e usado entao para estimar propriedades hidraulicas do aquifero, aquitarde e da margem do rio, avaliar as condicoes hidrologicas no aquifero, estimar o fluxo d´agua no sistema rio-aquifero e o volume armazenado no aquifero resultante da onda de cheia. Os resultados de carga hidraulica e fluxo sao comparados com resultados obtidos com o programa computacional MODFLOW. A analise realizada mostrou a aplicabilidade do programa STLK1, alem de levar a um melhor conhecimento da dinâmica da interacao rio-aquifero no Semi-Arido brasileiro.

Cálculo de Áreas Inundáveis Devido a Enchentes para o Plano Diretor de Drenagem Urbana de São Carlos (PDDUSC) na Bacia Escola do Córrego do Gregório

Abstract: Since 2002, the Municipality of São Carlos, SP, Brazil (PMSC) has developed a Master Plan, thereby establishing guidelines for flood prevention and control. However, the present scenario shows expensive, on-site antiflood works in São Carlos. Due to the absence of previous watershed planning, the area around the Municipal Market (MMSC) is continuously threatened by overspill flood events in the floodplain of Gregorio River. The purpose of this work is to provide information to support decision-making in the Master Plan using structural and nonstructural measures, such as flood zoning of risk-prone RBRH — Revista Brasileira de Recursos Hídricos Volume 12 n.2 Abr/Jun 2007, 05-17 17 areas. Critical flood events that produced inundation at MMSC were identified by interviewing people living in these urban risk-areas. Those critical events were simulated using integrated rainfall-runoff transformation and wave routing with the IPHS-1 concentrated model and the distributed model, HIDRORAS, whose results were compared. Input data were calibrated from monitored flood events. Uncertainties inherent to each model were identified. Results depict initial yardsticks for flood mapping to be included in the Master Plan agenda. Structural flood control measures consisting of a retention basin without excavation and non-structural measures such as increased infiltration area, were investigated. It was concluded that for urban watersheds like the Gregório basin, changes in the flow patterns due to urban streets are better represented by the distributed model, HIDRORAS. However, a number of uncertainties still remain for this model, such as the influence of saturated hydraulic conductivity of the soil. Key-words: Floods, urban drainage, flood-prone areas.

Previsão Hidroclimática de Vazão de Curto Prazo na Bacia do Rio São Francisco

Abstract: The streamflow forecast with large ranges depends on the precipitation forecast. The increase in the forecast ranges, in recent years, was because the development in the atmospheric and hydrologic models and their integrated application (hidroclimatic forecast). In this article is presented the result of integration between ETA atmospheric regional model and MGB-IPH distributed hydrologic model, to short-range streamflow forecast. In addition, a stochastic model was used to correct the forecasted streamflow by the forecasting of hydroclimatic model residues. The MGB-IPH distributed hydrologic model was adjusted to the São Francisco river basin (about 639,000 km2). The precipitation forecasts of ETA model, operated by Centro de Previsão de Tempo e Estudos Climáticos — CPTEC, was used as input to the hydrologic model. Streamflow forecasts were maded for the whole São Francisco basin, but the results were analyzed in details to the Três Marias and Sobradinho hydropowers. The precipitation forecasts of ETA model was made up to 10 days range and were produced streamflow forecasts up to two weeks to Três Marias and four weeks to Sobradinho. After the tenth day of forecast the precipitation was consider equal to zero. The results show that the hydroclimatic forecasts obtained to both hydropowers presents improvements in relation to the methods traditionally employed. Key-words: Streamflow forecast, precipitation forecast, São

Avaliação do Padrão da Composição Isotópica de Águas na Bacia do Rio Joanes: Implicações para a Interação entre Águas Superficiais e Subterrâneas

Abstract: The groundwater system in the metropolitan region of Salvador is a major source of fresh water used for urban and industrial uses. The stable isotope signature for meteoric water collected in Salvador, surface water from the Joanes river basin, and groundwater from aquifers in the metropolitan region of Salvador is used to evaluate some aspects of the interaction between surface and ground waters in this region. The results show: (i) the isotope signature for the surface water is about the same as for the meteoric waters, indicating that evaporation is not affecting the isotopic composition of surface water in the Basin; (ii) there is no enrichment in heavy isotopes from upstream to downstream Joanes, indicating interaction between surface water and groundwater in the basin; (iii) isotopic values of the groundwater near the Ipitanga river (Barreiras Formation) from free aquifers are similar to the meteoric waters, whereas the isotopic values for ground water from the São Sebastião aquifer, taken from depths with fossil waters, show a different isotope signature than the meteoric water; (iv) the linear regression from the isotopic value of the meteoric water is fitted by the line δD=12+8.7δO, similar to the values reported by IAEA (analyzed in 1965 a 1987), except the value of January 2004, very different from the mean value, probably associated with the quantity effect or with the influence of the inter-tropical convergence

Modelo de seguro para riscos hidrológicos

Abstract: O artigo trata da introducao de um modelo de seguro contra prejuizos causados pelas enchentes em uma microbacia hidrografica localizada em Sao Carlos, SP. A alta frequencia com que vem ocorrendo enchentes em muitas cidades brasileiras motivou o desenvolvimento deste estudo. Com o intuito de quantificar os acrescimos nas vazoes de cheias decorrentes dos avancos da urbanizacao, caracterizados, principalmente, pelo aumento de areas impermeaveis, foi escolhida uma area de teste na cidade de Sao Carlos, a regiao do micro-centro no corrego do Gregorio. Objetiva-se avaliar o "custo da incerteza" que a sociedade esta disposta a pagar, ou a sua reducao, usando mecanismos de transferencia de riscos como Seguros. Atraves de simulacao hidrologica e da avaliacao dos prejuizos nos eventos com inundacao, desenvolveu-se um modelo para a fixacao do premio a ser pago pelo segurados de modo a compatibilizar os valores de inundacao com o capital a ser acumulado pelo fundo de seguro contra enchentes

Estudo Comparativo de Três Formulações do TOPMODEL na Bacia do Rio Pequeno, São José dos Pinhais, PR

Abstract: TOPMODEL is a hydrological model with available formulation and computational code. Thus several applications and modifications have been performed since it was first published. However, there are few studies comparing the new modifications and the original formulation. As the comparative studies can show the real formulation improvements for certain objectives, the purpose of the present work is to compare and evaluate three TOPMODEL formulations using hydrograph simulations. The simulations were carried out in the Pequeno river watershed, São José dos Pinhais city, Paraná state, for two data series (calibration and validation). In RBRH — Revista Brasileira de Recursos Hídricos Volume 12 n.2 Abr/Jun 2007, 93-105 105 this work, the first TOPMODEL formulation (Beven et al., 1984), a modified one (Campling et al., 2002) and another modified one (Datin, 1998) were named MODEL 1, MODEL 2 and MODEL 3, respectively. The models were compared using their efficiency, uncertainty intervals and Shannon entropy values. Through the simulations the domain of model formulation error or input data error over parametrization error was observed. The models carried out similar hydrograph simulations. MODEL 2 was not recommended for hydrograph simulations in this watershed because it obtained the larger uncertainty intervals for all simulations and has one more parameter. Key-words: TOPMODEL, Rio Pequeno, uncertainty,

Simulação Hidrodinâmica 1D de Inundações em Sistema de Drenagem Urbana

Abstract: RESUMO O aumento da frequencia das inundacoes urbanas nas ultimas decadas, tem tornado cada vez mais importante a incorporacao de ferramentas que auxiliem no processo de tomada de decisao no gerenciamento da drenagem urbana. Neste trabalho e apresentada uma metodologia simplificada para simulacao de inundacoes, aplicada a uma pequena bacia hidrografica em Santa Maria-RS, utilizando dados observados. O modelo proposto permite a propagacao hidrodinâmica 1D do escoamento atraves da superficie das ruas e da rede de condutos. A interacao entre as redes e bi-direcional, realizada atraves de equacoes de vertedores. Os resultados das simulacoes foram satisfatorios, tanto na simulacao dos niveis de inundacao nas ruas como na representacao dos hidrogramas da bacia. A metodologia representa uma alternativa importante na simulacao e avaliacao de medidas de mitigacao das inundacoes urbanas, podendo economizar, com bons resultados, um grande esforco na programacao ou aplicacao de metodologias mais complexas.

Acumulação e balanço de sedimentos em superfícies asfálticas em área urbana de santa maria - rs

Abstract: Este trabalho apresenta resultados da caracterizacao dos sedimentos encontrados nas sarjetas de duas ruas asfaltadas em Santa Maria, RS. E tambem das amostras coletadas na estacao hidrossedimentometrica instalada na saida da microdrenagem, que tem como area de contribuicao uma das ruas onde ocorreu a coleta dos sedimentos secos. Os trabalhos de campo e de laboratorio ocorreram durante o periodo de abril a dezembro de 2005. As coletas de sedimento na sarjeta foram realizadas durante tres periodos distintos de amostragens com duracao media de 30 dias. As coletas de amostras liquidas ocorreram durante alguns eventos de precipitacao significativos a fim de determinar a concentracao de sedimentos em suspensao e a carga proveniente da drenagem. Os resultados das amostras de sedimento seco indicaram que o processo de acumulacao dos sedimentos nas superficies ocorre relativamente rapido apos um evento de precipitacao. O carreamento das particulas acumuladas nas superficies depende das caracteristicas da precipitacao e do escoamento, e os dados indicaram que os eventos de precipitacao removem apenas uma parte dos sedimentos presentes na superficie. As analises granulometricas das amostras de sedimento seco indicaram um diâmetro medio (d50) igual a aproximadamente 0,35 mm em ambas as ruas de amostragem. A concentracao de sedimentos proveniente da microdrenagem apresentou valores entre 8,0 a 6.000 mg/L. As analises granulometricas destas amostras constataram que o escoamento transporta particulas, que variam de muito finas a mais grosseiras, com o diâmetro medio variando de 0,01 mm a 12 mm, confirmando o transporte do material presente nas sarjetas e areas adjacentes pela microdrenagem.%%%%This paper presents the results from a street gutter sediment characterization study in two asphalted streets in Santa Maria - RS. It also presents the results from the samples collected at the station installed at the outlet of a drainage system. One of the dry sampled streets is the contribution area of the system. The field and laboratory tests were accomplished from April to December 2005. Dry sediment sampling was done in three different periods, each one of them with about 30 days. The solid-liquid samples were accomplished during some significative storm events in order to determine the suspended sediment concentration and load from the drainage system. The dry sediment samples results indicate that the sediment buildup process on impervious surfaces occurs relatively quickly after a raining event. The accumulated particles washoff depends on the rainfall and runoff characteristics and the data indicate the rainfall events remove only a small portion of the sediments found on the surfaces. The particle size analysis indicate that the two sampled streets present sediments with a measured median diameter of 0,35 mm The solidliquid samples concentration values ranged from 8,0 to 6.000 mg/L. These samples particle size analysis presented that the superficial flow carries particles, which range from the finer to more coarser, with a median…

Performance de Sensores de Precipitação do Tipo Tipping Bucket (Báscula) Um Alerta para a Ocorrência de Erros

Abstract: Tipping bucket rain gauges are widely used in meteorological and hydrometric automatic stations to measure precipitation. The performance evaluation carried out in the Barigui experimental river basin revealed substantial measurement errors. Recent research suggested a few possible sources of uncertainty, especially when there are Performance de Sensores de Precipitação do Tipo “Tipping Bucket” (Báscula) — Um Alerta para a Ocorrência de Erros 204 heavy rains. The results of laboratory tests, which confirmed underestimation of measurement under simulated heavy rain conditions, indicated that it is urgently necessary to widen the scope of this study in order to improve understanding of the performance of tipping bucket rain gauges in Brazil. Key-words: Tipping Bucket; precipitation; meteorological stations.

Calibração de Sondas do TDR em um Latossolo

Abstract: Among the various existing methods to estimate the soil water content, the Time-Domain Reflectometry (TDR) technique has raised great interest in recent years, due to many desirable characteristics, such as real time and automatic measurements, besides being a non-destructive method. Many authors, however, recommend the determination of a calibration curve for each type of soil. The main goal of this paper was to determine the TDR calibration curve for a “Latossolo Vermelho distroférrico” soil from the Donato experimental basin, at Pejuçara, Brazil. Two different methodologies were applied: a field technique and a laboratory method based on the use of undisturbed soil samples. The TDR field calibration showed big scatter, and did not allow the adjustment of a single curve. The use of soil samples that had not been disturbed in the laboratory proved to be a feasible alternative, allowing a greater control of the measured variables (soil dielectric constant and soil water content) and maintaining the original structural soil characteristics. No significant differences were observed among the different soil layers studied. The best fit to the soil water content (θ) and soil dielectric constant (ka) was obtained by the use of a third degree polynomial equation, presenting a determination coefficient (R) equal to 0.992. This adopted equation is significantly different from those previously developed by Topp et al. (1980) and Souza et al (2001). Key-words: TDR calibration, TDR

Validação da Chuva Estimada por Satélite CMORPH na Modelagem Hidrológica do Alto Iguaçú

Abstract: Atualmente, estão sendo desenvolvidos diversos produtos de estimativa de chuva por satélite. Entre eles, destacam-se os produtos que combinam sensores microondas de satélites polares, com sensores infravermelhos de satélites geoestacionários, sendo suas resoluções espaciais e temporais das mais variadas. O principal objetivo desse estudo é validar a estimativa de chuva por satélite CMORPH na bacia do rio Iguaçu até União da Vitória, através de um estudo de sensibilidade de modelagem hidrológica em relação ao tipo de dado de entrada (chuva estimada por satélites e medida por pluviômetros), escala da bacia hidrográfica (bacia do Iguaçu em Porto Amazonas, com área de 3.662 km2, e a bacia do Iguaçu em União da Vitória, com área de 24.211 km2), e densidade da rede de monitoramento (bacia do Iguaçu em Porto Amazonas, com uma única estação pluviométrica na sua exutória, e bacia do Iguaçu em União da Vitória, monitorada com uma rede de treze estações pluviométricas). Os principais resultados desse estudo são: (1) as incertezas da estimativa de chuva por satélite CMORPH são suficientes para que o produto seja usado como dado de entrada em sistemas de alertas de cheias para bacias maiores do que 1.000 km; (2) a resposta do modelo hidrológico depende significativamente do tipo de dado de entrada, da escala da bacia hidrográfica e da densidade da rede de monitoramento pluviométrico, e (3) o produto de satélite teve um viés de superestimar a chuva média, causando uma saturação mais rápida da bacia e aumentando os picos dos hidrogramas.

Variabilidade Espacial do Conteúdo de Água no Solo numa Pequena Bacia Rural : 3. Análise da Estabilidade Temporal do Padrão Espacial do Conteúdo de Água no Solo

Abstract: The temporal stability of spatial patterns of soil water contents was evaluated in a small rural catchment on the Sul-riograndense basaltic plateau, to identify sampling points that can reproduce the mean and extreme soil water content behaviours. The soil water content was monitored during one agricultural year. Samples were collected from a regular grid throughout the catchment, at 0 cm (soil surface) and 30 cm depth, and from two profiles, 280 m (Profile P1) and 320 m (Profile P3) long. The soil water content measurements were performed by gravimetric procedure at the surface and with TDR technique at deeper levels. Complete stability of soil water content spatial patterns at soil surface level was not observed, but it could be identified at 30 cm depth. Points with temporal stability in the catchment, especially at 30 cm depth and in profile P1 could be identified. The use of points of temporal stability allowed estimates of mean area of soil water contents with errors of less than 5% e 1% at the soil surface and 30 cm depth, respectively. Key-words: spatial variability; soil water content; small basins; temporal stability.

Efeito do nível de subdivisão em uma bacia hidrográfica na simulação da produção de sedimentos

Abstract: The SWAT (Soil and Water Assessment Tool) model was applied to simulate the sediment yield for the Ribeirão dos Marins watershed, in Piracicaba, Brazil. The application of the model requires georeferenced input data, which were processed through an interface between the model and a Geographic Information System (GIS). The watershed was divided into different levels, regarding the number and the size of the sub-basins. The simulated sediment yields for the different levels were compared to the observed data of a gauge located in the watershed, using the Nash and Sutcliffe Coefficient (COE) and the deviation between the simulated and the measured data (Dv). The main conclusion was that the different levels affect the final result of the simulation. Key-words: sediment yield; river basin.

Simulação de Eutrofização em Lagos Rasos II: Sistema do Taim (RS)

Abstract: Water resource management involves analyzing the different economic-social scenarios and environmental development. A shallow aquatic ecosystem such as wetlands or lakes can become eutrophic due affluent conditions, as well as physical, chemical and biological elements. Primary production responds to nutrient availability, suggesting that alterations at the top of the food-web can influence the highest trophic levels. Eutrophication is correlated with the variation in the composition of the phytoplankton population, which can be characterized as a strong biological indicator of the trophic level of those ecosystems. Aiming to evaluate the potential of eutrophication in shallow aquatic ecosystems a model was developed to represent the main abiotic and biotic processes of these systems. The considered model is comprised of three modules: (a) hydrodynamic; (b) nutrient transport and (c) biological which deals with phytoplankton productivity. This paper presents the sensitivity analysis of the biological parameters model, parameter calibration of the hydrodynamic model and eutrophication simulation of the Taim Hydrologic System (SHT-Sistema Hidrologico do Taim), whose aim is to identify regions with a high eutrophication potential. The sensitivity analysis of the biological parameters has shown that the chlorophyll a concentration is most sensitive to changes in the parameters involving water temperature effect and the losses due to respiration and grazing. The eutrophication simulations have shown that the shallow regions present the most favorable conditions for eutrophication, while in the deep region (pelagic region) and in the wetland region where solar radiation is decreased due to the aquatic macrophyte barrier found there, productivity is lower. Key-words: calibration, sensitivity analysis , phytoplank-