Daniel Allasia

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.

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...

South America Land Use and Land Cover Assessment and Preliminary Analysis of Their Impacts on Regional Atmospheric Modeling Studies

Data provided by two important sources of information on land use and land cover (LULC), MODIS-2009 and GLOBCOVER-2009, were analyzed for South America in order to assess differences related to their application in numerical modeling studies. Even though on a South American basis, the two databases showed a Pearson correlation coefficient above 85%, on a regional analysis, the correlation stayed within the range of 0%-100%, depending on the territorial unit analyzed. Significant differences were observed in most of the land cover classes, with only forested areas presenting a good level of agreement. In terms of territorial units, only areas in the Amazon region, where forest cover is predominant, showed significant correlation levels. Crops and urban classes presented the greatest differences between the two analyzed files. Results of meteorological simulations indicated that such observed discrepancies are able to cause strong impacts on modeling scenarios and important bias on simulated variables, being a crucial feature for weather and climate forecast and diagnostic.

Biosorption of cationic dyes by Pará chestnut husk (Bertholletia excelsa)

Pará chestnut husk (Bertholletia excelsa) (PCH), an agro-industrial waste largely generated in Brazil, was employed as a low-cost and efficient biosorbent to remove the cationic dyes Crystal Violet (CV) and Methylene Blue (MB) from aqueous media. PCH presented an amorphous structure containing carboxylic acids, esters, ketones and aldehydes on the surface. Non-porous and irregular particles were also observed. For both dyes, the biosorption capacity was favored under acid conditions. Equilibrium was attained within 40 min at 25 °C with a PCH dosage of 0.5 g L-1. The biosorption kinetic curves were satisfactory explained by the pseudo-first-order model. The Freundlich model was best for representing the equilibrium curves. The maximum biosorption capacities were 83.6 and 83.8 mg g-1 for CV and MB, respectively. PCH was efficient for treating a simulated textile effluent containing several dyes and chemicals, achieving a color removal of 90%. In this way, PCH can be considered as an option for treating colored effluents containing textile dyes.

Potential of Araucaria angustifolia bark as adsorbent to remove gentian violet dye from aqueous effluents

Araucaria angustifolia bark (AA-bark), a waste generated in wood processing, was evaluated as a potential adsorbent to remove Gentian Violet (GV) dye from aqueous solutions. The AA-bark presented an amorphous structure with irregular surface and was composed mainly of lignin and holocellulose. These characteristics indicated that the adsorbent contains available sites to accommodate the dye molecules. The GV adsorption on AA-bark was favored at pH 8.0 with adsorbent dosage of 0.80 g L-1. Pseudo-nth order model was adequate to represent the adsorption kinetics of GV on AA-bark. A fast adsorption rate was verified, with the equilibrium being attained within 30 min. Equilibrium data were well represented by the Langmuir model. The maximum adsorption capacity was 305.3 mg g-1. Adsorption was spontaneous, favorable and endothermic. AA-bark was able to treat a simulated dye house effluent, reaching color removal values of 80%. An excellent performance was found in fixed bed experiments, where the length of the mass transfer zone was only 5.38 cm and the breakthrough time was 138.5 h. AA-bark can be regenerated two times using HNO3 0.5 mol L-1. AA-bark can be used as a low-cost material to treat colored effluents in batch and fixed bed adsorption systems.

Geoprocessamento Aplicado à Determinação do Índice de Susceptibilidade das Captações por Poços Tubulares do Sistema Aquífero Serra Geral em Frederico Westphalen – Rio Grande do Sul

The issue related to the contamination of the superficial and underground water resources, associated to the lack of environmental monitoring, instigates researchers and professionals to seek new information and methods to promote a proper management. Thus, searching for a better understanding of the susceptibility to contamination of groundwater resources in the city of Frederico Westphalen -RS, Rio Grande do Sul, Brazil, and its potential sources of contamination. This work combines the methodologies of Susceptibility Index (IS) with the Pollutant Origin Surcharge Hydraulically (POSH) system through geoprocessing tools. For this, it has built up a database of hydrogeological information based on System Groundwater Information (SIAGAS) from the Geological Service of Brazil, to the depth parameters of water level and the material of the aquifer. Also, there has been raised information of relief and land use from the images provided by the United States Geological Survey (USGS). From this information, we determined the IS and applied the POSH method for the determination of potential sources of pollution load generation from the local aquifer. The results showed an IS ranging from low to very low in 14% of the city, moderately low in 55%, moderate high at 30% and higher by 1%, with the largest classes found east of the city mainly in the areas of agricultural crops subsistence. The use of POSH method indicated that the potential sources of contaminant load generation are located in areas of moderate to high susceptibility to contamination. These being areas more susceptible to contamination from diffuse sources, depending on annual crops of surface and groundwater sources. Therefore, it was concluded that the geoprocessing techniques applied in the relationship between the IS and POSH, optimize the identification of potential sites and sources of groundwater pollution, being useful in monitoring and environmental planning.