Integrated Water Quality Assessment of the Drenica River Using Macroinvertebrates and PROMETHEE Decision Method

Biotic indices based on benthic macroinvertebrates are widely recognised as reliable tools for assessing the ecological status of freshwater systems, as they respond sensitively to anthropogenic pressures. This study evaluated the ecological condition of the Drenica River in Kosovo, during 2023–2024 by combining macroinvertebrate-based indicators with physicochemical parameters. Eight monitoring sites (L1–L8) were surveyed, yielding 3,913 individuals from 20 families. The benthic community was dominated by pollution-tolerant and semi-tolerant taxa, while sensitive Ephemeroptera, Plecoptera, and Trichoptera (EPT) groups were scarce. The diversity indices showed higher biodiversity at L2 and L5, while L3 and L6 exhibited lower values, reflecting pollution impacts that were confirmed by PROMETHEE multi-criteria analysis. Biotic indices (BMWP, ASPT, FBI, EPT, SWRC) indicated a general decline in water quality along the river, while L2 maintaining a moderately good status, whereas L6–L8 reflected poor ecological conditions linked to anthropogenic activities. Multivariate analyses further confirmed these patterns: dissolved oxygen correlated positively with macroinvertebrate diversity, whereas high levels of COD, TDS, NO₂⁻, and PO₄³⁻ suppressed sensitive taxa but favoured tolerant groups. NMDS and cluster analyses identified two major pollution zones, while PROMETHEE ranking placed downstream sites among the most vulnerable. The integration of macroinvertebrate indices, physicochemical parameters, and decision-support modelling, this study provides a comprehensive picture of ecological degradation in the Drenica River. The findings emphasise the urgent need for targeted management measures such as stricter wastewater control, reduced agricultural runoff, and continuous biomonitoring to restore and safeguard the river’s ecological integrity.