Mapeamento da fragilidade ambiental da microbacia do Alto Rio Grande - Nova Friburgo-RJ

A bacia hidrográfica do alto rio Grande (292,4 km²) se encontra na cabeceira do Rio Grande, afluente da bacia hidrográfica do Rio Dois Rios, que é contribuinte na margem direita da bacia hidrográfica do Rio Paraíba do Sul. Localiza-se na vertente a sotavento da serra do Mar, logo após o interflúvio, sendo importante para o abastecimento dos aqüíferos e manutenção dos recursos hídricos, pelo fato de a região se caracterizar como grande produtora agrícola. A análise de fragilidade ambiental é uma proposta metodológica de análise empírica da fragilidade de ambientes naturais e antropizados, como forma de subsídio para elaboração de planejamento ambiental. Este estudo objetivou avaliar a fragilidade ambiental da bacia do Alto do Rio Grande, no município de Nova Friburgo. Para isto foram avaliadas as condições naturais da região (declividade, solo, litologia e pluviosidade) assim como as características de uso e cobertura do solo, e gerados dois produtos: o mapa de fragilidade potencial, oriundo das características naturais da região, e o mapa de fragilidade emergente, que coadunou o mapa de fragilidade potencial com os tipos de uso e cobertura do solo. Foram detectadas a predominância de grau de fragilidade potencial em baixa (23%), alta (23,1%) e média (37,5%), com menores valores para a muito baixa (7,5%) e muito alta (8,7%). A predominância do grau de fragilidade emergente se manteve baixa (21,1%), alta (25%) e média (46,7%), e se viu diminuir os valores de muito alta (3,1%) e muito baixa (4%). Os resultados encontrados foram condizentes com a realidade encontrada em campo e a aplicação da metodologia de análise de fragilidade ambiental se demostrou poderosa ferramenta para o planejamento ambiental. Porém, foi constatada a necessidade de base cartográfica, mapas e dados temáticos mais detalhados para que a aplicação desta metodologia seja aprimoradaThe upper Rio Grande basin (292.4 km²) is located at the headwaters of Rio Grande, a tributary of the Dois Rios river basin, which is a contributor to the right bank of the Paraíba do Sul River basin. It is located on the leeward slope of the Serra do Mar, just after the interflow, being important for the aquifer supply and maintenance of water resources, since the region is characterized as a large agricultural producer. The analysis of environmental fragility is a methodological proposal of empirical analysis of the fragility of natural and anthropized environments, as a form of subsidizing the environmental planning process. This study aimed to evaluate the environmental fragility of the Alto do Rio Grande basin in the municipality of Nova Friburgo. The natural aspects of the region (slope, soil, lithology and rainfall) were evaluated as well as land cover and use characteristics, and two products were generated: the map of potential fragility, originating from the natural characteristics of the region, and the map of emerging fragility, which related the map of potential fragility with the land cover and use types. The prevalence of potential fragility was low (23%), high (23.1%) and medium (37.5%), with lower values for very low (7.5%) and very high (8.7%). The predominance of the emergent fragility degree remained low (21.1%), high (25%) and medium (46.7%), and the values of very high (3.1%) and very low (4 %) also low. The results were consistent with the reality found in the field and the application of the environmental fragility analysis methodology proved to be a powerful tool for environmental planning. However, it was verified the need for more detailed cartographic base, maps and thematic data in order to better apply this methodolog

Technical contributions to territorial planning and the use of ecosystemic services in a hydrographic basin with a water deficit in the Atlantic Rainforest of Brazil

The catchment basin of the Dois Rios River (R2R) (3159 km2) unites the climatic and environmental effects typical of areas located on the leeward side of mountain chains. It has a deficient water balance, with sparse and very specific wet areas. This study identifies delimitation areas, and characterizes and groups those basins and floodplains which show the greatest capacity for producing ecosystemic services related to maintaining the continuity of water resources in the R2R basin. Locations with higher pluviometric indices (1500 to 2800 mm/year) were selected and grouped into micro basins with the highest potential for capturing rainfall due to their being on the leeward side of the mountains in the region (with their slopes oriented to permit them to capture humidity and concave plane curvature). The 42 basins formed 4 groups, from which the 17 micro basins with the highest probability of providing ecosystemic services were chosen, belonging to Groups III and IV. Within these groups, the 498 floodplains with the highest potential for offering ecosystemic services (Group D) present the greatest capacity for water retention and sustainable effects (high average circularity index, higher altitudes and low occupation rates). The correct use of 0.0006% of the basin can guarantee the direct flow of the drainage for the entire basin. This strategy only requires renaturation measures, discipline with regard to the land uses and strict observance of the processes which generate ecosystemic services in the floodplains of these basins, resulting in relevant socio-environmental benefits for all socioeconomic segments within the R2R basin