Análise ambiental da bacia hidrográfica do Ribeirão Lindóia (PR): integração entre geoprocessamento e qualidade da água na identificação de pressões antrópicas e sazonais

Abstract

The development of society is associated with the availability of water resources, which has had a significant impact on water bodies. Environmental analysis of river basins is a crucial environmental management tool, enabling the application of various methodologies to understand the interactions between the abiotic and biotic components of the system. In this context, an environmental analysis was developed in the Lindóia stream watershed (BHRL), located in the municipalities of Londrina and Ibiporã (PR), with the objective of evaluating its environmental dynamics and identifying how physiographic characteristics, the evolution of land use and occupation, and seasonal variations and different anthropogenic pressures are reflected in water quality. The study was structured in three main stages. The first corresponded to geoprocessing analyses, involving the morphometric characterization of the basin and the spatiotemporal analysis of land use and occupation from 1985 to 2023. The second stage consisted of field visits, with nine water collection campaigns carried out during rainy and dry periods at 10 sampling points distributed across rural and urban areas, covering four water bodies in the BHRL (Lindóia stream, Quati stream, Água das Pedras stream, and Cabrinha stream), assessing water quality through physical chemical and microbiological parameters, in addition to toxicity tests with Allium cepa (A. cepa) seeds. In the third stage, the water quality data were submitted to multivariate statistical analysis using Canonical Discriminant Analysis (CDA), preceded by assumption tests (normality and homoscedasticity) and Spearman's correlation analysis (ρ). CDA was used to evaluate seasonal (rainy and dry periods) and spatial differences between sampling points, allowing the identification of the most relevant parameters for group discrimination. The morphometric characterization of the BHRL revealed an oblong-shaped basin with predominantly gentle undulating relief and a drainage network of 1st to 3rd order, conditions that favor anthropic occupation but increase vulnerability to erosion processes and changes in runoff when associated with soil sealing. The spatiotemporal analysis of land use and occupation revealed strong urban expansion, which now occupies more than half of the basin, especially at the headwaters and in the middle section, with irregular occupations in environmentally fragile areas. Water quality showed statistically significant seasonal differences and a spatial gradient of degradation from the headwaters to the mouth, with the downstream points being the most degraded, with the most significant values during rainfall, but with evidence of recurrent pollution during the dry season. Even with a class III classification, total phosphorus and Escherichia coli (E. coli) values above the limits established by CONAMA Resolution No. 357/2005 were recorded, in addition to genotoxic and mutagenic effects in bioassays with A. cepa, suggesting chronic exposure to point and diffuse sources of pollution. Taken together, these results point to a situation of compromised water quality in the BHRL and highlight the need for integration between territorial planning, sanitation, and water resource management to mitigate impacts and restore the basin.