Mountain regions are highly vulnerable to the impact of climate change, with rising temperatures and shifting precipitation patterns, influencing the hydrological behavior of critical headwaters. River flow in these regions is sustained from rainfall and snow/ice melt, which follow various pathways, including overland flow, interflow, and groundwater, with distinct geochemical signatures. Changes in river geochemistry can thus serve as an indicator of flow pathways and residence times changes under the changing climate. This study investigates seasonal and long-term changes in river geochemistry and controlling factors over the periods of available data (1970-2022 and 2001-2022) in the Sheep River, which is an Eastern Slope River of the Canadian Rockies with a monthly average discharge of 7.5 m3/s. The river’s Ca-Mg-HCO₃ water type is consistent with the dominance of carbonate rocks in its headwaters. The C-Q relationships reflect varying degrees of groundwater dilution by a low solute end member. Over 1970–2022, a significant reduction in the C-Q slope (indicating increased dilution) was observed for Na, Cl, and K, while Ca, Mg, and SO₄ exhibited more chemostatic behavior. Trend analysis (1970–2022) revealed significant increases in major ions (i.e., Ca, Mg, SO4, Na, Cl, and K), especially during winter, spring freshet, and late summer, correlating with changes in climatic variables such as lagged precipitation and snowpack loss. The observed trends for major ions may suggest increased groundwater contributions under changing climatic conditions. The findings provide valuable insights for sustainable water resource management and developing climate adaptation strategies in alpine regions.
