Extreme Precipitation in the Lerma Santiago River System: A Comprehensive Spatio–Temporal Analysis from 1950 to 2018

Climate change is intensifying extreme weather events and placing increasing pressure on global water resources, particularly in regions with high climatic variability such as Mexico. However, long-term changes in precipitation patterns and their implications for water resource vulnerability remain insufficiently characterized. This study analyzes historical precipitation trends from 1950 to 2018 and evaluates their implications for water resource vulnerability in the Lerma Santiago River System, one of Mexico’s most critical hydrological systems. A longitudinal analysis of nearly seven decades of precipitation data was conducted. Data quality and homogeneity were ensured using the RHtestV4s tool, and climate extremes and trends were assessed with the RClimDex package following ETCCDI guidelines. The findings indicate a significant decline in annual precipitation, with reductions of approximately 15% in downstream areas. Consecutive dry days increased by nearly 20%, while consecutive wet days decreased by about 10%. Although rainfall intensity has increased, events are concentrated over fewer days, amplifying water-scarcity risks. These climatic pressures are further compounded by dam construction, which restricts water availability. The results highlight the high vulnerability of the Lerma Santiago River System to combined climatic and anthropogenic stresses, underscoring the urgent need for integrated, multi-scale water and climate management strategies to enhance regional resilience.