Proposição de indicadores para a gestão de recursos hídricos da Bacia Hidrográfica do Córrego São Silvestre, Inhapim-MG

Abstract

The development of tools that assist in the integrated management of water resources, the environment and land use is important to meet the requirements of Law 9.433 / 1997 and the use of indicators applied to a geoenvironmental approach can contribute to planning in river basins. In this sense, the objective was to propose indicators as a way to subsidize the integrated management between water resources, environment and land use, using geoenvironments of the São Silvestre Stream Basin (BHCSS) as reference spatial units. Maps of delineation of the hydrographic basin, geology, geomorphology, pedology, altimetry, slope, rain erosivity, land use and occupation and Permanent Preservation Areas (APPs) were prepared, using the QGIS software version 3.4.13, using data Officials from the Geological Survey of Brazil (CPRM), Minas Gerais Water Management Institute (IGAM), United States Geological Survey (USGS) and the National Water Agency (ANA). Based on thematic maps, the basin was divided into geoenvironments, in which the indicators of degree of potential fragility, degree of hemerobia and degree of land use and occupation conflicts and APPs were evaluated. BHCSS has five geoenvironments, with characteristics similar to those of environmental indicators. The degree of potential fragility was considered low and medium in BHCSS, with a predominance of the middle class (more than 70% of geoenvironments). The degree of hemerobia showed a predominance of the middle (more than 75%) and minimal (between 5 and 19%) classes in all geoenvironments, indicating a medium technological dependence to support the ecological processes that occurred in the basin. Percentages of conflicts between land use and occupation and APPs above 54% were identified in all geoenvironments. It stands out, as the main potential of the basin, its low and medium potential fragility, which represents less chances of soil loss by erosion in a natural way, which reduces the risks of carrying and depositing sediments and changes in quality and quantity of water. On the other hand, the main weakness concerns conflicts in the use and occupation of land and APPs, considering that, in the different geoenvironments, the percentage of unprotected APPs varies from: i) from 78.21 to 89.20% of the APPs from springs ; ii) 62.75 to 83.07% in watercourse APPs; and iii) 57.07 to 86.53% in slope APPs. The results indicate the need to adopt soil and water conservation practices, adequate soil management and, mainly, actions for the restoration of APPs, aiming to guarantee the availability of water for the various uses demanded in BHCSS. Analyzing the result of the indicators, it was possible to define an order of prioritization for the realization of interventions between geoenvironments: Oxisoil40/Granite/Low hills and hills and Oxisoil40/Tonalite/ Low hills and hills, Oxisoil49/Metatonalite/Low hills and hills, Oxisoil49/Tonalite/Low hills and hills and Oxisoil49/Metatonalite/Mountainous. The compartmentalization of BHCSS in geoenvironments and the use of indicators proved to be efficient to highlight the weaknesses and potentialities of the basin and, therefore, to facilitate the indication of actions to be employed, from the environmental point of view, in order to guarantee availability water for multiple uses.