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The integration of research groups on network analysis using geographic information systems (GIS)


The Piracicaba river basin is a subtropical watershed located in the southeastern region of Brazil. With an area of 12400 km2, its main rivers are: Piracicaba, Atibaia and Jaguari. The climate is subtropical (type C in the Koeppen classification). The annual average temperature is 20ºC. The annual average rainfall is 1400 mm, or a grand total of 1.76 x 1010 m3 of water for the basin. The final annual average discharge is equal to 165 m3.s-1 or 0.52 x1010 m3.year-1. The basin is a typical example of the new landscape resulting from development in tropical and sub-tropical regions. Establishment of intensive industrial and agricultural process were followed by a significant population growth. The population in the basin is estimated in approximately 3 million people, with a growth rate of almost 6% per year. This fact is imposing increases in both the water consumption and the urban sewage load. Almost 80% of thepopulation is served by sewage systems, but only 5% of the generated load is treated before dumping in the rivers. As a consequence, the estimated load due to urban sewage increased from 50 tons of BOD/day in 1960 to 200 tons of BOD/day in 1990. The Piracicaba River basin, is one of the most intensively cropped area in Brazil. Sugar cane is the main crop; its cropped area increased dramatically, from 62,000 ha in 1975 to almost 270,000 ha in 1988. There are small watersheds in the basin almost 100% covered with sugar cane. During the last decade the rivers in the basin were subjected to acute pollution problems due to urban sewage and sugar cane industry residues. The later may be of two main types: nonpoint sources linked to the transport of sugar cane material with the runoff, and a point-source due to the direct dumping of the industry waste water and residues in the river. For 1977, the impact of the point source alone was estimated to be equivalent to the organic pollution generated by a city of 3 millions habitants. This accelerated populational and industrialgrowth had led to a significant increase in the water demand. If nothing is be changed, by the year 2000 there will not be enough water supply to cities and industries. Therefore, the futurescenario for the basin is critical. Progressively less water availability, coupled with progressively poor water quality is foreseen. In this scenario, we propose a two years project to study the basic working mechanism of the basin as a natural entity. We will assume the rivers as natural integrator of the process which occur in their drainage system. The rivers will be divided in a series of linked sectors, and mass balances of water and materials for each one of this sectors will be det. (AU)

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