Rapid urbanization is profoundly altering river ecosystems, leading to increasing degradation of water quality in urban rivers. This study, part of the ANR GloUrb project, analyzes the overall impact of urban expansion on the ecological quality of rivers since the 1980s. Based on an interdisciplinary approach mobilizing the eDPSIR (Enhanced Driving forces-Pressures-State-Impact-Response) conceptual framework, the study combines physico-chemical and biological data approached via the SEQ-Eau tool, socio-economic variables (demographics, land use, wastewater treatment) and digital discourse (web scraping).

The results highlight the impact of urban areas on rivers, with a significant difference in water quality deterioration between the upstream and downstream segments of urban areas, particularly in terms of biochemical oxygen demand (BOD), total phosphorus, ammonia nitrogen, nitrates, temperature and fecal coliforms. A high population/river flow ratio is correlated with marked ecological deterioration, particularly for organic and microbiological pollutants. In addition, analysis of numerical discourse confirms a concordance between public perception and actual levels of microbial contamination in several urban contexts. The recommendations arising from this analysis call for the reinforcement of wastewater treatment strategies and policies, the integration of simple environmental proxies for large-scale monitoring based on socio-economic indicators, and the use of digital tools for participatory ecological monitoring. The approach developed provides a framework for the systemic assessment of urban pressures on hydrosystems on a large scale.