A questão da água e impactos socioambientais: caracterização morfométrica e diagnóstico ambiental na Bacia Hidrográfica do Rio São Bartolomeu no Nordeste Goiano

Abstract

In the face of contemporary environmental problems, water is one of the most impacted resources. The management of water resources is fundamental for improving the availability and the quality of this resource. To do so, it is necessary to use facilitating tools in the elaboration of diagnoses, guides to the projects of management of Drainage Basins (DB). This study aims to the morphometric characterization and analysis data for the diagnosis of environmental impacts in the anthropic area of the São Bartolomeu River Basin in the Northwest of Goiás State. For the development of the study, is used the Geographic Information Systems (GIS) for morphometric analysis of the micro-basin, together with the bibliographical review, fields observations and macroscopic analysis of environmental impacts in the springs. There are also monthly measurements of river flow and the development of thematic maps, for preliminary analysis of more recurring environmental problems. Public geospatial databases, such as INPE, SIEG, USGS, and educational institutions such as UFG, are used to assist in the preparation of the maps. As results were identified areas with erosionability factor considered High, in 80% of the soils of the DB, and Very High in another 18.6%. In relation to the relief, the slope is well distributed, presenting 51.43% of the area with Very Weak Fragility classes (up to 6% inclination), and Weak (with 6 to 12%). The sections that have a mean slope (12 to 30% slope) occupy 29.9% of the area. The remaining 18.67% have Very Strong Fragility (above 30% slope). Crossing the slope data with the soil classes, the Map of the Degree of Susceptibility to Laminar Erosion was obtained, which indicated the equivalent of 36% of the area in classes I and II, as Extremely Susceptible and Very Susceptible respectively, demonstrating that practices for soil conservation should be used in at least 1/3 of the BH. Another 17.81% is with Moderate Susceptibility, and the highest class, 46%, is the less Susceptible to laminar erosion, provided that good management practices are observed and soil cover maintained. It was also verified by the land use map that 53.27% of the area has a low degree of protection by the vegetation cover, represented mostly by Cerrado Rupestre (rupestrian savannah) in the highest levels, and degraded pastures in the lower and less sloping plots. About 4.6% of the DB soil is totally exposed, with severe erosive processes, such as ravines and gullies, already present in specific areas. About 10% of the basin is covered by natural grasslands and planted pastures in good condition of conservation, which must be well managed in order to not lose this degree of protection. The remaining 37.39% are occupied by Cerrado Stricto Sensu (Savannah), Capoeiras (secondary forests), Riparian Forests, Seasonal Forests, and Veredas (marshes), which have a good degree of protection and should preferably be kept in this state. It is evident that more than 50% of DB is under full protection by the National Park of Chapada dos Veadeiros, and under sustainable use by six more Private Natural Heritage Reserves (RPPN). It is emphasized that these Conservation Units are fundamental to the maintenance of the natural resources of the Cerrado in the region, and, consequently, to the conservation of the water resources of the São Bartolomeu River and its tributaries. It is also verified that the use of GIS is efficient for several spatial analyzes, as well as for monitoring DBs on a temporal scale. The work presented here may serve as a basis for exploring important issues for the conservation of springs and the management of natural resources in the BHRSB, assisting in territorial management in the area studied and serve as a reference for analysis of other river basins.