Análise das relações superfície-atmosfera na bacia hidrográfica do Rio das Velhas em uma perspectiva multiescalar: proposta de síntese

Abstract

The hydrographic basin of the Rio das Velhas is one of the main sub-basins of the São Francisco River, having in its territory the capital of the state of Minas Gerais and its metropolitan region (RMBH). Since it drains the most industrialized and densely populated region of the state, the parts of the basin close to the RMBH go through an increasing process of degradation, which also manifests in the medium and low basin where the agricultural activities predominate, contributing to the mischaracterization of the riverbanks and increasing the number of pesticides in its waters. The climate is one of the natural elements of biggest importance for the spacial organization of the basins since it affects the processes of surface modelling as well as the quantity and distribution of water. Because of that the scientific knowledge regarding the behavior of the climate attributes is timely and essential to the planning of economic development and the projects of smart use of natural resources. An essential piece of the spatial intervention planning is the mapping of the environmental characteristics from which one can stablish diagnostics and predictions for anthropic actions that optimize the balance between environment quality and life quality. In this context this work aims to achieve an analysis of the relationship between the surface climate controls and their atmospheric response in the hydrographic basin of Rio das Velhas. The main product of this research is the creation of a climate map of the units of the basin, with the intention of contributing to the actions of water planning and management and recovery of the water courses performed by the Comitê de Bacia Hidrográfica do Rio das Velhas (CBH-Velhas). The results show that the spatial variation of the meteorological attributes on Rio das Velhas is strongly conditioned by the geographical relief in different scalar levels while on time, the climate of the hydrographic basin of Rio das Velhas changes monthly under the influence of the latitudinal position of the basin and annually under the influence of phenomens and complex mechanisms of the macroclimate. In a zonal scale the basin is inserted in the Tropical Brasil Central Climate, characterized by the precipitation seasonality, hot rainy summers and mild dry winters. The surface of the basin is split into rough highlands of the Quadrilátero Ferrífero on the South, Serra do Espinhaço on the west border, lowland and undulating in the depression of the Rio São Francisco in the central region and east of the basin and these cut the zonal climate into two regional units: the Altitude Tropical Climate and the Typical Tropical Climate. These two units differentiate themselves by the high total rainfall and reduced air temperature in the former in opposition to a reduced total rainfall and high temperature in the later. However, these units show distinct characteristics of altitude, rugosity, and latitudinal position inside, which influences the intensity of the thermal and rainfall characteristics, generating the configuration of sub-regional and local units. The climate processes involved in the discretization of the climate units were illustrated in schematic profiles as well as the scalar relations identified in the area.