Identificação das fontes de sedimentos na avaliação da sustentabilidade ambiental de uma bacia hidrográfica

Abstract

Considering the watershed as a fundamental unit of environmental management entails recognizing the intimate relationship between soil and the hydrological cycle, with erosion being its most pronounced effect. Identifying sediment sources within a watershed allows for the development of mitigation strategies for these effects. The Fingerprinting method, based on the use of geochemical tracers, proves to be a valuable tool in sediment source identification. Within the sustainability equation of a region, the Watershed Sustainability Index (WSI) emerges as a viable alternative for assessing watershed sustainability. This work comprises two chapters: the first discusses the utilization of the Fingerprinting methodology to identify sediment production sources through geochemical variables in a watershed located in southern Rio Grande do Sul. The second chapter explores the application of the Watershed Sustainability Index, adapted to consider sediment quality, in assessing environmental sustainability within the same watershed. The selected watershed was that of the Epaminondas stream, which accounts for 70% of the drainage area and supply of the Santa Bárbara basin, responsible for 60% of the urban supply in the municipality of Pelotas. With an area of 33 km², the studied basin's primary activities include agriculture, livestock farming, mining, and leisure sites. In chapter 1, results indicate that the Fingerprinting technique proved suitable for identifying sediment production sources in the analyzed basin. The selected variables were sufficient to assess sediment source contributions, and the sampling grid positively impacted the results by distributing points according to study areas. In Chapter 2, the WSI of the Epaminondas Stream Watershed was 0.57, considered intermediate. Hydrological (H) and Environmental (E) indicators contributed the most to this classification. Incorporating sediment quality as a new component of the Hydrological indicator did not decisively affect the WSI of the basin. However, this parameter showed potential to be more representative in measuring the environmental quality of studied basins, particularly those with greater anthropogenic impact.