Showing papers in "Revista Brasileira de Recursos Hídricos in 2005"

Classificação Hidrológica de Solos Brasileiros para a Estimativa da Chuva Excedente com o Método do Serviço de Conservação do Solo dos Estados Unidos Parte 2: Aplicação

Abstract: The rainfall-runoff model of the United States Department of Agriculture (USDA) Soil Conservation Service (SCS) is often used in engineering projects, either to calculate excess rainfall or for a design hydrograph. However, it is known that the main parameter of the method is the runoff curve number (CN). It is also known that the hydrologic soil classification is very important to estimate CN and it has not been developed for tropical soils such as those in Brazil. Sartori et al. (2005) point out a few difficulties for its application and present a suggestion for hydrologic soil classification in Brazil based on the work of Lombardi Neto et al. (1989). As all proposals deserve to be evaluated, this study is developed to analyze the responses of the rainfall-runoff model of SCS applied to the original hydrologic soil classification and with the classification suggested by Sartori et al. (2005) to observed precipitation events in order to estimate excess rainfall and peak flow which was obtained with the triangular unit hydrograph of the SCS and with the mean unit hydrograph representing Ribeirão dos Marins watershed, in the municipality of Piracicaba, São Paulo, Brazil, with an area close to 21.87 RBRH – Revista Brasileira de Recursos Hídricos Volume 10 n.4 Out/Dez 2005, 19-29 29 km. The simulated results using two hydrologic soil classifications were compared to the events observed in the watershed. From the comparisons made it was observed that a better result was obtained with the hydrologic classification suggested by Sartori et al. (2005) and with the representative unit hydrograph of the watershed. These results indicate that the hydrologic soil classification suggested by Sartori et al. (2005) is more appropriate for the soil conditions in the watershed studied and that the unit hydrograph of the SCS tends to overestimate peak flow

Desempenho de Fórmulas de Tempo de Concentração em Bacias Urbanas e Rurais

Abstract: Time of concentration is one of the most widelyused measures of basin response for calculating design rainfalls and floods. Paradoxically, it is also a hydrological parameter that designers find difficulty in accepting as a criterion, because there is little information about applicability of the various empirical formulas that are available. Although Kibler (1982) and McCuen et al. (1984) are important references which clarify various aspects regarding origin, use and applicability of empirical formulas for concentration time, doubt and uncertainty remain concerning the absolute and comparative performance of these formulas, particularly for those in the Portuguese literature, despite groundbreaking work of Porto (1995). This situation motivated the work reported in the present paper, whose aim was to evaluate errors of 23 formulas for time of concentration, including those most commonly found in the Brazilian technical literature. It aimed to seek out whatever information was available concerning formula origin and theoretical limitations, and to assess performances of the different formulas when tested using data from urban and rural basins. Results showed that it was possible to use time-of-concentration formulas on basins whose areas were much larger than those used to calibrate them, especially under rural conditions. In the case of urban basins, the best-performing formulas for urban use showed wider error bands than the corresponding formulas for use in rural areas. The work did not seek to put all the formulas in order of rank, but to supply indicators for a basis of careful case-by-case selection. Key-words : time of concentration, hydrograph, floods, Kirpich, urban basins, rural basins.

Avaliação do Transporte de Sedimentos no Rio Barigüi

Abstract: The transport of solid materials as a consequence of soil erosion due to environmental degradation can cause serious problems in a river stream inducing soil deposition and provoking dynamic changes for the bulk flow. Better understanding the main mechanisms of transport and the evaluation of sediments load, greater is the chance of an efficient diagnosis to solving or minimizing the consequences associated to soil deposition. This paper brings the preliminary results refering to suspended solids monitoring for the Barigüi river in the metropolitan area of Curitiba. The results presented in this paper were compared with the obtained by FILL et al. (2002). The total and suspended solids concentration kept the same order of magnitude in both study, reflecting a stable soil and use occupation dynamic in the watershed. The sedimentdischarge curve did not show a good errors estimate; this is an indication that better dependent variables must be attempted as turbidity, Secchi disk measurements and rainfall data. Key-words: sediment transport; Barigüi River; sedimentdischarge curve.

Análise da Exatidão de Diferentes Métodos de Interpolação para Geração de Modelos Digitais de Elevação e Obtenção de Características Morfométricas em Bacias Hidrográficas

Abstract: The use of digital elevation models is part of practically all studies of environmental components using Geographic Information Systems. However, due to the complexity of the relief and the large number of features, most of the interpolation methods used to derive Digital Elevation Models (DEM) produce results that, depending on the nature of the studies proposed, can compromise the quality and accuracy of the information. Therefore, the present study aimed to analyze comparatively the quality and level of accuracy of the DEMs generated by the following interpolation methods: IDW, SPLINE and TOPOGRID. According to visual and statistical analyses, TOPGRID and Spline Tensionado presented the best results. Key-words: Interpolation, IDW, Spline, TOPOGRID, DEM

Comparação de Métodos de Estimativa de Recarga de Aqüíferos em Uma Planície Aluvionar na Bacia Hidrográfica do Alto Tietê (São Paulo)

Abstract: Three different methods were used to estimate the groundwater recharge in an alluvial plain of the Upper Tietê Basin (São Paulo, Brazil): water-table fluctuation (WTF), water balance (WB) and Darcyan approach (DA). Six multilevel monitoring wells were installed at the University of São Paulo campus in the city of São Paulo, a lowto-medium density urban area subject to a humid tropical climate. Hydraulic heads were monitored weekly, every third day or after rainfall events, for WTF and DA recharge estimations (September 2003 to January 2004), and for WB methods, mean temperature and total rainfall were measured monthly (January 2003 to January 2004). Different methods and/or different time period result in different recharge estimations. For the WB method at least one year of precipitation and temperature data are necessary. The WTF method can be estimated using short-term elevations (periods of one to three days) or long-term fluctuations (periods of months or years), resulting in two distinct recharge estimates. For the short and long-term approaches respectively 282 mm and 187 mm were estimated for the period of September 2003 to January 2004. DA can also be used for short and long time intervals. For the same 5 months, the recharge was 66 mm, calculated using the monthly mean hydraulic gradient. Applying the WB method, no recharge was detected during this period. For the year of 2003 the calculated recharge was only 48 mm. Key-words: water-table fluctuation; water balance; Darcyan approach.

Avaliação da Recarga Subterrânea Através da Variação do Nível Potenciométrico no Aqüífero Dunas/Paleodunas, Fortaleza, Ceará

Abstract: There are no methods to evaluate recharge that can be generally applied to different areas because we must consider the characteristics of each area. Moreover, meaningful practical implications lead to uncertainty as to the results obtained in each procedure, if they cover a larger area than the one observed. The method used in this study was the direct measurement of the potentiometric level variation by monitoring the static level in six observation wells. The recharge calculated at the monitoring point was regionalized using criterion L to calculate total recharge, considering the zoning of the potentiometric surface. The area studied is located on the northeastern side of the municipality of Fortaleza, state of Ceará, Brazil. The climatic conditions are a dry period from July to December and humid from January to June. The average annual precipitation is about 1500mm with monthly average temperatures ranging from 26.1 to 27.5C. Quaternary sediments form the aquifer system: dunes, paleo-dunes and alluvium, considered a unique system for the purpose of RBRH – Revista Brasileira de Recursos Hídricos Volume 10 n.2 Abr/Jun 2005, 49-57 57 regionalizing the recharge estimations. The results led to the volumes of 6590000 m, 4040000 m and 1200000 m for the years 1996, 1997 and 1998 respectively, in a 16.77Km area. Key-words: groundwater recharge; potenciometric level.

Estabelecimento da Operativa de um Mecanismo de Transposição de Peixes do Tipo Elevador com Caminhão-Tanque

Abstract: In fish transfer mechanisms it is necessary to provide a variable stream flow that is used to attract the shoals of fishes to enter the system. This procedure requires reducing the volume of water available for power generation at the Hydropower Plant. In this study the possibility is assessed of establishing an operational rule for a fish elevator, in which the number of fish transferred is maximized and water use is minimized. Thus the operation of the fish transfer mechanism using a fish elevator with tanker truck installed at the Santa Clara Hydropower Plant was followed between November 19, 2003 and March 19 2004. Based on the results, two alternatives were proposed: prioritization of transfer cycles during the day, with nighttime operations only when it rains, and operating the mechanism during higher flow periods. Compared to the current type of operation, the alternative proposed might mean an increase of up to 35% in the number of individuals of migratory species transferred, and also a saving, at current values, of up to R$547,000.00, considering current interest rates of 8% and a 30-year life of the enterprise

Um método paramétrico de avaliação do potencial de salinização de reservatórios aplicado a regiões semi-áridas

Abstract: SOUZA FILHO, F. A. ; CAMPOS, J. N. B. Um metodo parametrico de avaliacao do potencial de salinizacao de reservatorios aplicado a regioes semi-aridas. RBRH, Porto Alegre, v. 10, n. 2, p. 05-14, abr./jun. 2005.

Vazão Mínima do Vale Médio do Rio Jaguari Mirim

Abstract: The present study evaluates the seven-day annual minimum flow, in the middle Jaguari Mirim river, using a 50-year historical data series interpreted by the Type I and III Extreme Value Distributions (Gumbel and Weibull Distributions). The reference flow and specific flow were also computed. The results show that Q7,10 and the reference flow were the same with the value from 1.74 to 1.75 m /s. The minimum specific flow computed was 0.0028 m/s.km. Key-Words: Q7,10 , QREF, Jaguari Mirim River.

Regionalização da Depleção Regional com Dados Primários de Vazão

Abstract: This paper proposes a method to obtain proportionality factors for low flows between points on a river network, based on discharge measurements at those points during recession phases in the basin. Discharge measurements, considered as primary data because they are not obtained from a stage-discharge curve, were correlated with classical physiographic characteristics in a regionalization process that combines these characteristics with low flow characteristics. The method, here called the regional-depletion method, was developed for use in basins with few flow-gauging stations, where it is necessary to synthesize low-flow characteristics at various points, using such flow records as are available. The method is especially attractive where licenses for water use are to be granted in basins where flow data are scarce. The method was developed and applied for this purpose in the basin of the River Santa Maria, in the Brazilian State of Rio Grande do Sul. Some intensive field visits for discharge measurement in sections of interest were sufficient to provide consistent estimates of the factors of proportionality Key-words: water use licenses; regionalization; low flow; Rio Grande do Sul

Avaliação de um Método de Assimilação de Erros nas Previsões de Vazões de Curto Prazo Afluentes ao Reservatório da UHE Camargos

Abstract: Hydrological forecasting is an important tool in the planning and operational control of water resources systems The purpose of data assimilation or updating procedures, as applied to short-term streamflow forecasting is to improve accuracy and provide more reliable results In this paper, streamflow forecasting is accomplished by means of a conceptual rainfall-runoff model, named Rio Grande, which has been applied to simulate the inflows of the Rio Grande river basin to the reservoir of the Camargos hydropower plant, in the Brazilian state of Minas Gerais This model consists of three main modules: the Production Module, which is responsible for the runoff formation over the sub-basin area, the Concentration Module, which is responsible for the flow concentration at the outlet of the sub-basin, and the Propagation Module, which is responsible for flow propagation through the river channel A stochastic model for the simulation of errors in each sub-basin is proposed, in order to update the short-term forecasts of inflows to the Camargos reservoir Data assimilation is based on the correction of simulated discharges by adding to them the forecasts of the stochastic model errors The stochastic models considered here are of the p-th order autoregressive AR(p)-type and/or of the p-th and q-th order autoregressive and moving average ARMA(p,q)-type The analysis of the results shows that the application of that procedure to the upstream control stations closest to the reservoir may considerably improve short-term inflow forecasting Key-words: Hydrological forecasting; reservoir

Exploração Sustentada do Aqüífero Dunas / Barreiras na Cidade de Natal, RN

Abstract: The water supply of the city of Natal, RN, Brazil is obtained mainly from the Dunas / Barreiras aquifer in the urban area. Due to the rapid development of the city and the limited amount of natural recharge to the aquifer, studies must be developed for a reliable evaluation of the water balance and aquifer vulnerability. This study deals with the evaluation of water balance, including natural recharge, water exploitation, water losses to rivers and sea, and wastewater reuse. A sustainable use model is applied in order to specify the optimal exploitation as a function of aquifer characteristics and recharge. The problem of nitrate contamination is also considered. The results show the need to maintain the present level of recharge and water reuse in order to ensuree groundwater use sustainability. Another alternative is to import water from neighboring areas.

Transporte de Sedimentos de Fondo en el Rio Salado (Santa Fe, Argentina)

Abstract: Se calculo el transporte de sedimentos de fondo (gsf) en un tramo de 7,3 km del curso inferior del rio Salado (Santa Fe, Argentina) a partir de mediciones de campo (metodo indirecto) y aplicando distintas formulas con el objetivo de establecer cual de ellas presenta un mejor ajuste. Se realizaron dos relevamientos hidrograficos espaciados en 30 dias. Se midieron las dimensiones de 27 dunas, cuyas longitudes variaron entre 64 m y 8 m, y sus alturas entre 1 m y 0,42 m, y se calcularon sus velocidades de desplazamiento. Con esa informacion se determino la carga de sedimentos de fondo por el metodo indirecto. Las variables hidrodinamicas empleadas en las formulas de transporte resultaron de la aplicacion del modelo HEC-RAS, calibrado y validado en base a mediciones hidrometricas. Los resultados sedimentologicos obtenidos muestran que aproximadamente el 95% del material del lecho corresponde a arenas medias y finas, y el resto a material fino. Se concluye que la formula de Engelund-Fredsoe y la de Meyer-Peter y Muller son las que mejor ajuste presentan con respecto a los valores medidos en campo, con errores que varian entre el 8% y el 30% y entre el 4% y el 27%, respectivamente. Tomando como primera aproximacion el valor de transporte total (gs) calculado por la formula de Engelund-Hansen para el rio estudiado, el transporte de fondo representa entre un 3% y un 9% del total

Otimização e Simulação Comparativa de Cenários de Outorga

Abstract: The implementation of a sustainable water resources grant system requires a basin-wide water balance study taking into account water availability and demands. This paper presents a water balance formula whose main characteristics are simplicity and consideration of seasonal and interannual variability of water resources available in the basin. Different grant criteria are simulated and presented in this paper using the proposed model. The aspects evaluated are: priorities among different users; allocation criteria of water between the sections; criteria to define the number of management stretches; effect of interannual variability of water availability; effect of the seasonal water availability and environmental effects of the grant. Key-words: water balance, grant criteria, water availability, demand

Impacto de las Sequías en la Recarga Natural al Acuifero Libre

Abstract: The present study analyses the unconfined aquifer behaviour in the context of seasonal and interannual climatic variability, and particularly precipitation variability, during the dry periods in Santa Fe Province, with the aim of finding quasi-periodicities and trends, both in precipitation and the freatic level. Droughts were defined by the decilic analysis of historical precipitation records, while spatial and temporal variability was analysed by a Spectral Analysis of the Dry Compound Years in order to establish the harmonic dials which characterise the climatic conditions of each region. As well as this, different statistics methods were applied to assess the response of the unconfined aquifer during droughts. It was observed that the frequency of occurrence of annual droughts has decreased over the whole Province of Santa Fe since 1970, showing an average of a drought every three years until 1969, and one every five years from that date onwards. Considering the relative amounts of precipitation, it was concluded that the more intense dry periods take place during autumn, winter and spring rather than summer, or at an annual level. An overall decrease in the recharge by precipitation was observed in the whole studied area during the drought periods, which manifested itself in sustained falls in the freatic levels. For two seasons, the recharge was estimated between 2.2 and 5.9% of precipitation in those periods. The decrease at the freatic level in the dry compound years varied from 0.58 to 3.79 m with a volume variation between 580 and 3790 m3/ha. The spatial and temporal behaviour of the dry periods showed that the amplitude and phase values of the three most significant harmonics in the series correspond to the dry compound years. Both the summer rainfall and the winter droughts stress the amplitude of the second harmonics, which contain information of the amount of precipitation and represent the annual precipitation cycle, whereas the summer droughts diminish it. The low temporal variability of the freatic level can be inferred in the aquifer, in contrast to the high precipitation variability. The harmonic dials in the region graphically showed that the second spectral component is the most significant, while the first shows its relation to the EL NIÑO region. It could be noticed that, at the freatic level, there is a regional characterisation similar to that of rainfall, with a homogeneous north region regarding the first harmonic, as well as in the centre-south region. The results indicate that, on average, both the north region and the centre-south region of Santa Fe Province have a homogeneous behaviour as regards intensity and time of occurrence, while the extreme southern region shows a behaviour with peculiar characteristics during the dry events. Key-words: atmosphere-aquifer relations, droughts, recharge

Utilização de Redes Neo-Fuzzy Neuron para Predição de Vazões

Abstract: The prediction and modeling of a river’s outflow series is important not only for energy production, but also for the safety of population living near its banks. Progress in system identification has contributed significantly to the consistency and reliability of outflow modeling. Over the last decade there has been much research in the use of models based on artificial neuron networks (RNA). A major contribution to this area has been the integration of fuzzy logic with RNAs, leading to neuron-fuzzy models. Among these, Neo-Fuzzy-Neuron networks have been successful in mapping non-linear systems. In this paper, NFN networks are applied to predict daily outflows, through an assessment of the viability of using a single NFN structure for modeling tributary outflows at all stations within a subcatchment. To apply the methodology, case studies were used with the daily flow data from 15 stations belonging to sub-catchment 46 ( Sao Francisco river ). One of these stations, the most comprehensive and complete, was chosen as a reference for modeling the data of the others. The NFN networks gave excellent outflow prediction results for the stations studied. In addition, the inclusion of movingaverage (MA) inputs considerably improved the results obtained using only models with auto-regressive terms, particularly with regard to validation. The viability of obtaining a single NFNARMA (p,q,np) structure for modeling the entire sub-catchment 46 has been established

Modelagem Hidrológica da Bacia do Riacho Gameleira (Pernambuco) Utilizando TOPSIMPL, uma Versão Simplificada do Modelo TOPMODEL

Abstract: The hydrological model TOPSIMPL presents similar characteristics to TOPMODEL, but uses only 4 parameters. Hydrological modeling with TOPSIMPL uses the Digital Elevation Model and takes into account the effective upstream contributing area of each cell and the soil slope to calculate a topographical index that represents the potential for saturating each cell. River basin flow is calculated based on rainfall, state of water saturation and water deficit for each cell. TOPSIMPL was applied to the Gameleira river basin, a tributary of Tapacurá river in Pernambuco (Brazil). A Digital Elevation Model was calculated, a data acquisition system was installed, rainfall and flow rate were recorded minute-by-minute for 34 months. Calibration and validation of TOPSIMPL were performed for a few rainfall periods in the Gameleira basin and the results showed a good representation of output flow.

Campos de Precipitação Parte I: Fundamentos Teóricos e Estudos Preliminares

Abstract: This article discusses the precipitation field composition using two data sources: rain gauges and radar. The main characteristics of the equipment are listed and some precipitation field compositions are presented. The relative point rain gage and radar values were confronted and compared with data in the literature. Preliminary tests with these methods were done to evaluate and select some of them for further studies presented in part II