Delays and declines in hydrological extremes in nivo‐glacial rivers of Mendoza, Argentina

Climate change is altering river regimes in mountainous regions, affecting water availability and the functioning of aquatic ecosystems. In the Andes Mountains, characterizing the natural flow regime is essential for establishing operational conditions that balance multiple water uses (irrigation, supply, hydropower) with the conservation of high‐elevation ecosystems in the context of increasing hydroclimatic variability. This study analyzes extreme hydrological conditions in nivo‐glacial rivers of the upper Mendoza River Basin (Argentina), using indicators of magnitude, frequency, duration, and timing of high (HP) and low (LP) pulses. Daily flow records from the Cuevas, Vacas, Tupungato, and Mendoza Rivers were used to define eight ecologically relevant extreme hydrological parameters over the period 1956–2023. The results reveal a reduction in the magnitude of extreme flows since 2010 (−30% to – 55%) and significant delays in their timing, with maximum and minimum flow shifting by 15–20 days later in recent decades. The duration of LP events increased by 120%–240% in the Cuevas, Tupungato, and Mendoza Rivers, while in the Tupungato River, HP events tended to occur less frequently but with longer durations. These changes are associated with a 0.1°C decade −1 rise in mean temperature and a ∼25% decrease in precipitation since 2009. Such trends have major implications for water resource management and the resilience of high‐Andean ecosystems under climate warming.