Spatial and temporal analysis of water quality in the Cachoeira River basin, Bahia

Abstract

This work aimed to analyze the space-time variation of surface water quality in the Cachoeira River Basin, Bahia. Land use and land cover analysis, multivariate and non-parametric statistical tests were used to evaluate 17 physical-chemical and microbiological parameters of 9 monitoring stations, between 2008 and 2020. The basin showed predominance of areas of Pasture and Forest Formation, both reduced in 2020. The Savanna Formation, Mosaic of Uses and Urban Areas varied positively. All points violated the Maximum Permissible Value of Thermotolerant Coliforms, according to CONAMA Resolution 357/2005. Ribeirão Salomé had the lowest percentage of violations. The results of the Mann-Kendall trend analysis suggested that Suspended Solids was the parameter with the highest number of elevation trends in the basin. Principal Component Analysis showed that the parameters with the greatest temporal variability were: thermotolerant coliforms, solids (total, suspended and dissolved), biochemical oxygen demand and electrical conductivity. Throughout the basin, degradation of water quality was observed during the period studied, mainly related to the release of domestic sewage and the absence of riparian vegetation, evidencing the need for mitigation measures, aiming at the conservation and maintenance of this resource.