Showing papers by "Walter Collischonn published in 2007"
TL;DR: In this paper, a large-scale distributed hydrological model is described, which has been used in several large river basins in Brazil, including the Taquari-Antas River basin.
Abstract: Recent developments in hydrological modelling of river basins are focused on prediction in ungauged basins, which implies the need to improve relationships between model parameters and easily-obtainable information, such as satellite images, and to test the transferability of model parameters. A large-scale distributed hydrological model is described, which has been used in several large river basins in Brazil. The model parameters are related to classes of physical characteristics, such as soil type, land use, geology and vegetation. The model uses two basin space units: square grids for flow direction along the basin and GRU—group response units—which are hydrological classes of the basin physical characteristics for water balance. Expected ranges of parameter values are associated with each of these classes during the model calibration. Results are presented of the model fitting in the Taquari-Antas River basin in Brazil (26 000 km2 and 11 flow gauges). Based on this fitting, the model was the...
239 citations
TL;DR: In this paper, a large-scale hydrological model applied to part of the Paranaiba river basin between Itumbiara and Sao Simao power plants (75,000 km 2 ) using precipitation forecasts from the regional Eta model run by the Brazilian Center for Weather Prediction (CPTEC) was compared with those from the currently-used ARMA model and it was shown that forecast errors can be reduced considerably, during both wet and dry seasons.
70 citations
TL;DR: In this article, the authors presented a new methodology, which extends the upscaling method, to automatically extract length and slope of river reaches for large-scale grid-based hydrological models.
58 citations
Journal Article•
TL;DR: In this paper, a bacia do Paraguai Superior, situada no planalto da Bacia do Alto Paraguai, gera significativa parcela do aporte de vazao that garante ao Pantanal a sua alternância natural entre secas e cheias.
Abstract: A bacia do Paraguai Superior, situada no planalto da Bacia do Alto Paraguai, gera significativa parcela do aporte de vazao que garante ao Pantanal a sua alternância natural entre secas e cheias. A estimativa de sua pluviosidade, no entanto, sofre incertezas devido ao baixo numero de pluviometros na bacia. Neste contexto, estimativas espaciais de precipitacao podem se constituir numa ferramenta extremamente util. Estas estimativas, embora pouco precisas quando comparadas com valores puntuais medidos no solo, fornecem uma boa nocao da distribuicao espacial das chuvas.
Neste trabalho, sao analisados os campos de precipitacao e as precipitacoes medias obtidos do satelite TRMM, lancado com o intuito especifico de estimar precipitacao nos tropicos. Os campos foram comparados com os obtidos a partir de dados de pluviometros no solo sobre a bacia do Alto Paraguai ate a Fazenda Descalvados. Os resultados sao muito satisfatorios, mostrando que as estimativas deste satelite podem ser uma fonte alternativa de dados em caso de escassez de informacao.
37 citations
TL;DR: It is shown that for two catchments in Brazil, the simpler catchment models, which are unit hydrograph-based and require only rainfall, streamflow and air temperature data for calibration, perform about as well as more complex catchments that require additional information from satellite images and digitized maps of elevation, land-use and soils.
Abstract: The performance of a simple, spatially-lumped, rainfall-streamflow model is compared with that of a more complex, spatially-distributed model. In terms of two model-fit statistics it is shown that for two catchments in Brazil (about 30,000km^2 and 34,000km^2) with different flow regimes, the simpler catchment models, which are unit hydrograph-based and require only rainfall, streamflow and air temperature data for calibration, perform about as well as more complex catchment models that require additional information from satellite images and digitized maps of elevation, land-use and soils. Simple catchment models are applied in forecasting mode, using daily rainfall forecasts from a regional weather forecasting model. The value of the rainfall forecasts, relative to the case where rainfall is known, is assessed for both catchments. The results are discussed in the context of on-going work to compare different modelling approaches for many other Brazilian catchments, and to apply improved forecasting algorithms based on the simple modelling approach to the same, and other, catchments.
23 citations
Journal Article•
TL;DR: In this paper, a large-scale distributed hydrological model has been used to obtain streamflow forecasts for up to 12 days in advance using observed and predicted precipitation data, up to the time of forecast start.
Abstract: As part of a research project aimed to improve medium-range streamflow forecasts used in the operational planning of Brazilian hydro- electric power systems, a large-scale distributed hydrological model has been used to obtain streamflow forecasts for up to 12 days in advance using observed and predicted precipitation data Observed streamflow data up to the time of forecast start were used to update state variables calculated by the model This data assimilation was performed by applying an empirical procedure Several configurations of this empirical procedure have been tested and this paper presents results obtained in applying it to the Rio Grande basin, one of the test beds of the Hydrologic Ensemble Prediction Experiment (HEPEX), focusing on forecasts at Furnas sub-basin (51 900 km 2 ) Results show that flow forecasts were not improved by updating state variables related to river flow, while significant improvements were obtained by updating state variables related to groundwater storage
18 citations
TL;DR: In this article, the authors presented the result of integration between ETA atmospheric regional model and MGB-IPH distributed hydrologic model, to short-range streamflow forecast, in which a stochastic model was used to correct the forecasted streamflow by the forecasting of hydroclimatic model residues.
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
7 citations
TL;DR: In this article, a model was developed to represent the main abiotic and biotic processes of shallow aquatic ecosystems, which is comprised of three modules: (a) hydrodynamic; (b) nutrient transport and (c) biological which deals with phytoplankton productivity.
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-
4 citations
TL;DR: In this paper, a distributed hydrological model is used for real-time streamflow forecasting in the Paranaiba river basin, along the reach between Itumbiara and Sao Simao hydroelectric power plants.
Abstract: This paper presents a methodology for real-time streamflow forecasting based on a distributed hydrological model, using data of observed rainfall measured at raingauges and rainfall forecast by the ETA model running at the Weather Forecasting Center of the National Institute for Space Research. State variables of the hydrological model are updated according to a scheme which uses observed streamflow data that would be available in a operational application. The methodology was tested in the Paranaiba river basin, along the reach between Itumbiara and Sao Simao hydroelectric power plants. Results show that the addition of quantitative rainfall forecasts may lead to a significant reduction in operational streamflow forecasting errors in this basin. Key-words: distributed hydrological model, streamflow forecasting, rainfall forecasting.
2 citations
Journal Article•
TL;DR: In this article, a new criterion for water management in southern Brazilian sub-tropical wetlands through the use of biological indicators was presented, where the emergent aquatic macrophyte giant grass Zizaniopsis bonariensis, was used to define a suitability index.
Abstract: This study presents a new criterion for water management in southern Brazilian sub-tropical wetlands through the use of biological indicators. The emergent aquatic macrophyte giant grass Zizaniopsis bonariensis, was used to define a suitability index. Hydrological scenarios were combined with the suitability index, allowing the selection of good habitat water levels. The results showed the importance of biological indicators' inclusion in the criteria list for water management. Under some conditions predicted by traditional hydrological procedures this emergent macrophyte species would be stressed.
2 citations
01 Jan 2007
TL;DR: In this article, the influence of the events El Nino and La Nina in the precipitation of the region of the wetlands of the Taim was analyzed, and the authors determined quartiles 25% and 75% to define periods of extreme precipitation for the cities of Rio Grande and Santa Vitoria do Palmar between years of 1950 the 1998.
Abstract: O objetivo deste estudo foi analisar a influencia dos eventos El Nino e La Nina na precipitacao da regiao do banhado do Taim. Determinou-se os quartis 25% e 75% para definir periodos de precipitacao extrema para os municipios de Rio Grande e Santa Vitoria do Palmar entre os anos de 1950 a 1998, para verificar se os eventos El Nino e La nina consecutivamente determinam precipitacoes superiores e inferiores as normais climatologicas. Este estudo e importante, pois a agricultura e especialmente sensivel aos impactos da variabilidade climatica. Os resultados mostram que durante o evento El Nino as precipitacoes nao foram sempre superiores a normais climatologicas em todos os eventos, podendo ocorrer secas em periodos normais, durante o evento La Nina, em alguns eventos ocorreram periodos com precipitacao acima da normal climatologica e periodos com precipitacao em torno da normal climatologica. ABSTRACT The objective of this study was to analyze the influence of the events El Nino and La Nina in the precipitation of the region of the wetlands of the Taim. If it determined quartiles 25% and 75% to define periods of extreme precipitation for the cities of Rio Grande e Santa Vitoria do Palmar between years of 1950 the 1998, to verify if the events El Nino and La Nina respectively determines superior and inferior precipitations the normal climatologic. This agriculture study is important because is especially sensible the impacts of the climatic variability. The results show that during the event the El Nino rainfall were not always higher than normal climatologic in all events, drought may occur in normal periods, during La Nina event, in some events occurred with periods of precipitation above normal climatologic and periods with precipitation around the normal climatologic. Keywords: Precipitation, El Nino, La Nina, Taim.
Journal Article•
TL;DR: In this paper, the authors presented results obtained by using a methodology based on one-way coupling of the ETA regional atmospheric model run by the Brazilian Center for Weather Prediction with a large-scale hydrological model in three sub-basins of the Parana River basin.
Abstract: Forecasts of inflow into major reservoirs of the Brazilian hydroelectric power system are essential to the operation planning of this system Medium range forecasts of the order of a few days to two weeks were usually obtained by simple ARMA models, which do not include information of observed or forecast precipitation We present results obtained by using a methodology based on one-way coupling of the ETA regional atmospheric model run by the Brazilian Center for Weather Prediction with a large-scale hydrological model in three sub-basins of the Parana River basin Results were compared to the currently used ARMA model, showing that reductions in errors of inflow forecasts could be obtained Comparison of results in different sub-basins suggests that the quality of rainfall forecasts depends on climate