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Over the past 25 years, Junín de los Andes, a city in Northern Patagonia, has undergone significant urban expansion, nearly doubling in size. Concurrently, the Chimehuín River, a vital freshwater resource for the region, has experienced various environmental changes. This study analyzes the water quality of the Chimehuín River by examining physical-chemical parameters and macroinvertebrate populations following The GLOBE Program Hydrosphere Protocols. Historical data from 2000 to 2025 were compared with new sampling data to identify trends and potential causes of water quality variations. This research seeks to answer the following questions: What changes have occurred in the Chimehuín River's water quality over the last 25 years? Which of the analyzed parameters have varied the most in water quality? Results show that while physical-chemical parameters largely remain within normal ranges, fluctuations in dominant macroinvertebrate taxa and EPT% (Ephemeroptera, Plecoptera, and Trichoptera) suggest localized anthropogenic and climatic impacts. Notably, a decrease in maximum river flow was seen, likely influenced by prolonged drought periods, urbanization, and sediment deposits from volcanic activity. The 2015 Calbuco volcanic eruption contributed to a temporary decline in water quality, particularly affecting macroinvertebrate communities in the following years. However, recent data from 2025 suggest a recovery trend in both macroinvertebrate populations and water quality indices. This study underscores the importance of long-term monitoring to assess the interplay between natural disturbances and human activities. Findings highlight the need for sustainable land-use planning and continued water quality assessments to mitigate potential future impacts. Further research should focus on integrating additional biological indicators and expanding sampling efforts to enhance understanding of long-term environmental changes in the Chimehuín River. Keywords: Water quality, Chimehuín River, Macroinvertebrates, Volcanic impact, Anthropic impact.