Carlos Tucci

The MGB-IPH model for large-scale rainfall-runoff modelling

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 then applied to the Upper Uruguay River basin (52 000 km2), having similar physical conditions, without any further calibration, in order to test the transferability of the model. The results in the Uruguay basin were compared with recorded flow data and showed relatively small errors, although a tendency to underestimate mean flows was found.

Environmental Issues in the la Plata Basin

Abstract The la Plata River basin is one of the largest in the world, with an area of about 3 million km2. It includes parts of five countries (Argentina, Bolivia, Brazil, Paraguay and Uruguay) and the water resources of the la Plata basin are essential for their economic development. The main tributaries are the rivers Parana, Paraguay and Uruguay. Some of the main developments having environmental impacts that influence the basin have been the following: (1) developments of many hydropower reservoirs in the Upper Parana River, in Brazil, from 1960-90; (2) deforestation in the Parana, Uruguay and Paraguay basins from 1950-90; (3) introduction of intensive agricultural practice after 1970; (4) urban developments with change to flood regimes; and (5) navigation and conservation of the Upper Paraguay River. Since 1970, flow increases have been observed which may have been caused by changes in vegetation cover, or by climate variation. The changes have raised important issues for both water resource developm...

Large-Scale Hydrodynamic Modeling of a Complex River Network and Floodplains

This paper presents a one-dimensional hydrodynamic modeling of a large-scale river network and floodplains. The study site comprises the Upper Paraguay River and its main tributaries (a total of 4,800 km of river reaches) in South American central area, including a complex river network flowing along the Pantanal wetland. The main issues are related to preparing input data for the hydraulic model in a consistent and georeferenced database and to representing different flow regimes. Geographic information systems-based automatic procedures were developed in order to produce cross-sectional profiles that encompass the large floodplains and to link hydraulic data and spatial location. The marked seasonal flow regime and relative smooth hydrographs of Paraguay River were quite well reproduced by the hydraulic model. For the tributaries, it must be mentioned the model’s ability to simulate both cases when the hydrograph does not present a marked peak flow, due to water loss for the floodplain, and when the hyd...

Rainfall-based real-time flood forecasting

Abstract The use of conceptual rainfall-runoff models in real-time flood forecasting still presents problems, some of which relate to the updating of the mathematical model and to uncertainties associated with future rainfall. Both topics are approached in this study, in which a conceptual rainfall-runoff model (IPH-II) for real-time flood forecasting and a simplified stochastic model to determine the value of including quantitative rainfall forecasts were used. The methods were tested using data from a small watershed (the River Ray at Grendon Underwood, UK), for which 17 years of records were available. The results show that a simple method used to forecast rain falling during the next few hours, may help to improve real-time discharge estimates.

Flow regionalization in the upper Paraguay basin, Brazil

In Brazil the cost of collecting hydrological data is very high because drainage basins are large, access is poorly developed and the terrain often difficult. Both inland areas and the more developed coastal regions require knowledge of water resources in terms of basin yield and flood discharges. This paper describes procedures established for the regionalization of flood peaks, mean flows and low flows, based upon existing literature and the kind of hydrological data available in Brazil. The procedures were prepared for use to be used in the Pantanal, a large swamp area in the basin of the Paraguay River (360 000 km2).

The Taim wetland conflict: a compromise between environment conservation and irrigation.

Abstract The Taim federal environmental protection area was created in 1978 to promote conservation of this subtropical wetland, one of the last existing ecosystems of this kind in southern Brazil. However, the protected area does not include lake Mangueira, the Taims main water source, which is surrounded by intensive rice farming. Rice irrigation demands a large proportion of water during the dry season (40,000 m3/year out of 50,000 m3/year inflow to the lake). A severe drought (1989-1991) almost dried the Taim wetland, resulting in legal actions to enforce the conservation status. As a consequence, several studies were undertaken to elucidate the Taims hydrological behavior, and to determine adequate water resources management policies. Results show that the ecosystem cannot withstand the present rate of water extraction. The two problems are: (i) defining a suitable plan to manage water extraction, and (ii) ensuring that the farmers respect it. A plan has been proposed, which includes forecasting the available volume and the complementary use of water from the nearby lake Mirim. The final form of the regulations, and their enforcement procedures, are under discussion with federal law enforcement officers, federal and state environmental and water resources agencies, and farmers.

Simulation of the urbanization effect in flow

ABSTRACT A consequence of urban development in a basin is the increase of peak discharge and surface flow which may cause flooding. Main channel design has to take into account future city development. A mathematical conceptual rainfall-runoff model was developed in order to simulate an urban basin at Porto Alegre (Brazil). The model has four algorithms: depression, interception losses, soil storage, basin routing and channel routing. Based on the Urban Development Master Plan, some of the model parameters were modified and evaluated, and a preliminary assessment of the effect of urbanization on flow hydrographs was made.

Some scientific challenges in the development of South America's water resources

Abstract The natural environment of South America is enormously variable. It includes the tropical forests of the Amazon basin, the rich wetlands of the Pantanal, La Plata basin where human influences are predominant, the semiarid regions of Brazil, Argentina and Peru, as well as the high-altitude lakes of Bolivia. It is difficult to deal in depth with all aspects related to such a diversified environment. Consequently, a few selected topics concerned with water resources, economic development and scientific challenges are discussed. They are: (a) climatic variability and its effects on hydropower production and land use; (b) environmental management of the urban environment; and (c) sustainable water management in semiarid regions.

Flood control measures in União da Vitoria and Porto União: structural vs. non-structural measures

Abstract In recent years Uniao da Vitoria and Porto Uniao have suffered severe floods, after a long period of normal to low floods. The important economic losses and psychological impact generated a great deal of discussion and studies about their causes. The population blamed the backwater effect of the Foz do Areia dam for the impact of the floods. This fact caused a major conflict, that lasted more than ten years, between the population and the state power company, owner and operator of the dam. This paper presents the main flood causes, the dam impact and the structural and non-structural measures studied in order to cope with the problem.

Management of Navigation in the Jacui River

ABSTRACT Management of a river system is usually a difficult task due to conflicting water use purposes. The Jacui river (southern Brazil) has a drainage area of 70000 km2, with hydroelectric plants in its upper reach and three navigation dams in the middle and lower reaches. The former dams are used to meet peak power demand, producing great flow variations during weekdays and volume reduction during weekends. The navigation dams do not allow year round navigation due to sediment deposition, low-flow and upstream flow fluctuation. A hydrodynamic model was used to study flow routing, to test operation rules for the navigation dams and to forecast the levels in real time. In this paper, the calibration of the model and the operational criteria to be applied to each of the navigation dams during low-flow periods are presented. The model was calibrated with two recorded events showing maximum errors compatible with the river navigation requirements. Dam operation simulations showed that with the help of the ...