Ecological Status Assessment of the Upper Una River: Physico-Chemical and Microbiological Perspectives

Abstract

The aim of this study was to assess the ecological status of the upper course of the Una River at eight sampling locations, four of which are situated within the protected area of Una National Park and four downstream, beyond the tourist and urban zones of the City of Bihać. The sampling sites were selected according to the “post-pollution input” principle, aiming to identify which of the selected locations contribute most to the river’s pollution. Physico-chemical parameters (pH, dissolved oxygen, permanganate index, BOD₅, TOC, ammonia, nitrates, total nitrogen, orthophosphates, and total phosphorus) were analyzed following Bosnia and Herzegovina’s water legislation, alongside microbiological assessment.

The results indicated that most physico-chemical parameters correspond to a high ecological status, with slight local fluctuations in BOD₅ and TOC values classifying the river as having a good ecological status, and ammonia indicating a moderate status. Microbiological analysis revealed spatial heterogeneity in the concentrations of total coliforms, Escherichia coli, and Enterococcus faecalis, which were detected in urban and tourist-influenced zones. Statistical analysis (ANOVA) showed no significant differences (p ˃ 0.05) between locations inside and outside the protected area, whereas PCA analysis distinguished sites based on their chemical and microbiological composition and their contribution to pollution. The findings confirmed that local anthropogenic impacts mainly result from fecal contamination. Comparison with data from other rivers in Bosnia and Herzegovina and Europe suggests that the Una River still maintains favorable ecological conditions, although continuous monitoring remains crucial for preserving water quality.