Glaciers, water sentinels: monitoring, research, and global drought impacts

Glaciers are massive reservoirs of solid water that have formed over millennia, acting as archives of Earth's climatic past. As irreplaceable water reservoirs, they play a crucial role in regulating hydrological balances and sustaining millions of people worldwide. Their accelerated melting due to global warming is an unmistakable sign of a silent water crisis, a transformation that directly impacts ecosystems, economies, and local communities. On the occasion of World Water Day, dedicated this year to glacier preservation, it is essential to reflect on how science can contribute to understanding, monitoring, and developing adaptation strategies to address these changes.

The vital role of glaciers: water reservoirs in crisis

The importance of glaciers as water reservoirs is evident in many mountain systems, where their melting is a fundamental contributor to river flow, ensuring water availability during drought periods. Across various regions of the world, the ongoing reduction of glacial masses is already having tangible consequences on water security. In the Andes, for instance, the cryosphere provides up to 86% of the water supply for La Paz, Bolivia, during the driest months, playing a key role in sustaining water availability for millions of people¹. In Europe, Alpine glaciers contribute significantly to river flow, particularly during summers characterized by reduced precipitation. In 2022, for example, glacier melt accounted for approximately 17% of the Po River's total discharge in August, partially offsetting the effects of an exceptionally hot and dry summer and supporting minimum ecological flows crucial for ecosystems and agriculture².

This process, however, comes at a high cost: the water flowing in rivers today originates from a non-renewable reservoir that is gradually depleting. The progressive loss of glacier mass threatens to profoundly disrupt global hydrological balances. Recent studies indicate that glacier melting rates are accelerating, with mass loss in most cases exceeding that recorded over past centuries³. If current climatic trends persist, glaciers will no longer be able to act as "water banks," depriving entire regions of a fundamental resource for water regulation and increasing the risk of water crises in the coming decades.

The link between glacier melts and drought: the role of snow droughts

The acceleration of glacier melting is exacerbated by snow droughts, periods characterized by abnormally low seasonal snow accumulation. This can result from below-average snowfall or higher temperatures that hinder snow accumulation, ultimately intensifying and advancing the seasonal melt process. Snow cover is a fundamental component of the mountain cryosphere: beyond nourishing glaciers, it acts as an insulating and reflective layer, regulating the thermal balance of the soil and permafrost.

Climate change is significantly altering the key variables that determine the formation and persistence of snow cover. At all elevations, rising air temperatures and increased solar radiation accelerate snowmelt, reducing snow cover duration and directly impacting mountain water resources. This transformation not only disrupts the mountain hydrological cycle but also amplifies the vulnerability of regions dependent on seasonal snowmelt.

The World Drought Atlas highlights how, on a global scale, the reduction of seasonal snow and glacier resources is already having tangible effects. Designed as a global map to decode the connections between climate, policy, and society, the Atlas serves as a crucial tool for anticipating and managing drought risk. Its findings underscore significant implications for the stability of mountain ecosystems and the water security of local communities.

Drones and models for glacier monitoring: three case studies

To better understand and predict the evolution of glaciers and their ability to provide water, increasingly advanced tools are being employed. CIMA Research Foundation, for example, has developed monitoring and modeling techniques that allow for the collection of valuable data on the state and evolution of glacial reserves. "The use of drones has revolutionized our ability to observe glaciers, enabling data collection over large areas and providing an unprecedented level of detail on ablation and accumulation processes, thereby contributing to a more effective management of mountain water resources," explains Umberto Morra di Cella, researcher at CIMA Research Foundation and UAV pilot.

Glaciers, water sentinels: monitoring, research, and global drought impacts

Europe: Rutor Glacier (Italy)

The Rutor Glacier, one of the largest in the Italian Alps, has been the focus of extensive mapping efforts led by CIMA Research Foundation in collaboration with ARPA Valle d'Aosta. The use of drones has facilitated the acquisition of high-resolution digital terrain models, enabling detailed monitoring of surface evolution and melt dynamics while highlighting the growing vulnerability of this Alpine water reservoir. The collected data have been instrumental in refining hydrological models at a regional scale, improving water availability forecasts in mountain basins and supporting the management of water resources for various uses.

South America: Charquini Sur Glacier (Bolivia)

In the Bolivian Andes, the Charquini Sur Glacier (Cordillera Real) serves as a natural laboratory for studying the impacts of climate change on tropical ice reserves. Highly sensitive to climate variability, it is a primary water source for La Paz and El Alto, cities with a combined population exceeding 2.3 million inhabitants. In this area, CIMA Research Foundation has conducted advanced monitoring campaigns utilizing UAV technology.

"Thanks to drone observations, we have been able to precisely quantify glacier surface changes and seasonal snow cover reduction. These data are fundamental for understanding how the tropical cryosphere is responding to climate change and for predicting future water availability in the region," states Simone Gabellani, head of the Hydrology and Hydraulics department at CIMA Research Foundation. The collected aerial data are also being integrated into local hydrological models to inform water management strategies.

Asia: monitoring the Himalayas

Often referred to as Asia's "Water Tower", the Himalayas hold vast reserves of snow and ice, essential for supplying water to millions of people. However, the World Drought Atlas reports a growing water deficit in this region: between 2023 and 2024, snow droughts reduced seasonal snow cover by 8-16 days, with some areas experiencing up to a full month of lost snowpack⁵. These changes have direct implications for agriculture, hydropower generation, and regional hydrological stability.

Monitoring these shifts is challenging due to the vastness of the terrain and the scarcity of in-situ measurements. "Local community expertise is crucial in refining adaptation strategies and understanding climate change impacts on the mountain cryosphere," explains Tessa Maurer, researcher at Fondazione CIMA and co-lead author of the World Drought Atlas.

Beyond glacier melt, rising temperatures and declining snowfall are accelerating permafrost degradation, altering mountain ecosystems and impacting the migratory patterns of Tibetan pastoralist communities. These transformations highlight that the cryosphere's decline is not an isolated phenomenon but part of a systemic shift reshaping the entire hydrological balance of the region⁶.

These three stories, despite belonging to different geographical contexts, share a common thread: the race against time to monitor and quantify glacier water reserves. The integration of advanced technologies represents a fundamental step in providing essential data to develop adaptation strategies in an increasingly pressing climate change scenario.

The S3M model for snow and ice prediction

Within this framework, the S3M model emerges as a key tool for studying the evolution of glaciers and snow cover over time. "Thanks to advanced monitoring and data collected in Valle d'Aosta, we have been able to quantify a 20-30% reduction in glacier mass balance over the past decades, with an increasingly pronounced variation in seasonal water availability," explains Francesco Avanzi, researcher at CIMA Research Foundation. "These data allow us to calibrate the S3M model, providing reliable scenarios for water management in mountain regions." Coupled with predictive models, S3M enables the estimation of snow and ice evolution in response to future climate scenarios, supporting the sustainable management of water resources in mountainous areas.

Future scenarios and adaptation strategies: how science can shape water management?

According to the IPCC Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC), if greenhouse gas emissions continue at their current rate, Alpine glaciers could lose up to 90% of their mass by 2100. These projections confirm the urgency of action, requiring an integrated approach that combines scientific research, monitoring, and adaptation strategies.

In the Himalayas, communities are implementing innovative solutions such as ice stupas, artificial ice structures that store water in winter and gradually release it in warmer months. In Italy, the IT-WATER project integrates climate and hydrological data with high-performance computing (HPC) to develop tools for managing water crises.

The World Drought Atlas highlights these dynamics on a global scale, demonstrating how drought demands integrated and inclusive responses. It provides a fundamental scientific foundation for understanding how drought impacts different segments of the population in varied ways, and for proposing solutions to mitigate these effects. To explore these issues further, you are invited to join our webinar "Navigating Drought: The World Drought Atlas. Analyses, Impacts, and Global Case Studies " on March 28, where experts from CIMA Research Foundation and the European Commission's Joint Research Centre will discuss the impacts of drought and strategies to address it.

Science offers tools to understand, monitor, and anticipate the future of water resources. However, without conscious and informed water management, the risk of water crises becomes increasingly concrete. Each year that passes narrows the window for action-and with it, the chance to preserve these essential ecosystems. The question is no longer whether we should act, but how much time we have left to do so.