Waters of the Toledo - Brazil river: from the preserved source to the degraded mouth.

This study assessed the water quality of the Toledo River through monthly monitoring over one year at five sites, spanning from its headwaters to its mouth. Principal Component Analysis (PCA) and Analyses of Variance (ANOVA) indicated a progressive increase in physicochemical parameters along the river course and occasional elevated concentrations of copper and iron. This deterioration in water quality is correlated with a transition in land use, evolving from a preserved headwater to the influx of agropastoral nutrients in rural areas and industrial and domestic wastewater in urban zones. Consequently, a critically degraded condition was observed at the river mouth. Given this scenario, there is an urgent need to implement mitigation and sustainable management strategies to restore this vital water resource.