The high Andean basins of Peru and Ecuador supply freshwater to approximately 60% and 70% of their respective national populations. However, these systems are increasingly threatened by glacier retreat, land-use transformation, and climate variability, which jeopardize long-term water security. This study presents an integrative narrative review of 58 peer-reviewed scientific publications published between 2011 and 2025, focusing on hydrological modeling, cryospheric dynamics, hydrometeorological monitoring, climate change impacts, and ecohydrological processes in tropical Andean mountain systems. Following a systematic selection process, the reviewed evidence was organized into five thematic areas: advances in hydrological modeling under data-scarce conditions, validation of satellite precipitation products, glacio-hydrological and cryospheric dynamics, hydroclimatic scenario simulation, and ecohydrological approaches. The results reveal a sustained methodological transition from semi-distributed conceptual models (SWAT, HEC-HMS, and GR2M) toward physically based distributed models (MGB, PREVAH, and JULES), integrated with satellite products (GPM-IMERG, SM2RAIN, and ERA5-Land) and machine learning algorithms, significantly reducing the limitations associated with data scarcity. Climate projections under CMIP6 scenarios indicate increases of up to 60% in extreme precipitation intensity and up to 39% in annual runoff in some basins, while glacier mass loss could reduce dry-season water storage by as much as 25% over the coming decades. At the same time, land-use changes, including the conversion of páramo ecosystems to pasturelands and deforestation, have been shown to alter baseflow and infiltration processes independently of climatic forcing. The synthesis further reveals that water resilience in the Andes cannot be fully understood through physical hydrology alone. The conservation of water-regulating ecosystems such as páramos, bofedales, and montane forests plays a critical role in maintaining hydrological regulation and sustaining water availability under changing environmental conditions. The review highlights the importance of integrating hydrological processes, cryospheric dynamics, and ecosystem functions to improve water resilience assessments and support sustainable water resources management in the tropical Andes.

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