The United Nations World Water Development Report 2025: Mountains and Glaciers - Water towers [EN/AR/RU/ZH/DE/HI/IT/KO/NE/PT/VI]

SHORT SUMMARY

The water resources we receive from mountains are literally melting away before our eyes.

Mountains and alpine glaciers – often referred to as the world’s ‘water towers’ – are becoming increasingly vulnerable to climate change and unsustainable human activities, threatening the water resources upon which billions of people and countless ecosystems depend.

The United Nations World Water Development Report 2025 – Mountains and glaciers: Water towers calls attention to the essential services and benefits mountain waters and alpine glaciers provide to societies, economies and the environment. With a focus on the technical and policy responses required to improve water management in mountains, the report covers critical issues such as water supply and sanitation, climate change mitigation and adaptation, food and energy security, industry, disaster risk reduction and ecosystem protection.

Addressing the global water crisis begins at the top.

Executive summary

In alignment with the designation of 2025 as the International Year of Glaciers’ Preservation and the 2022 resolution of the General Assembly of the United Nations on sustainable mountain development, this report draws worldwide attention to the importance of mountain waters, including alpine glaciers, in the sustainable development of mountain regions and the downstream societies that depend upon them, in the context of the rapidly changing mountain cryosphere.

Status of the world’s water resources

According to the most recent global estimates (from 2021), the agriculture sector dominates freshwater withdrawals (72%), followed by industry (15%) and domestic (or municipal) use (13%). Sector-specific freshwater withdrawals vary considerably as a function of a country’s level of economic development. Higher-income countries use more water for industry, whereas lower-income countries use 90% (or more) of their water for agricultural irrigation.

Over the period 2000–2021, global freshwater withdrawals increased by 14%, corresponding to an average growth rate of 0.7% per year. Most of this increase occurred in cities, countries and regions undergoing rapid economic development. Population growth does not appear to play a highly significant role in increasing demand for water. In fact, countries where per capita water use is the lowest, including several countries in Sub-Saharan Africa, are often those with the fastest growing populations.

Twenty-five countries – home to one-quarter of the world’s population – face ‘extremely high’ water stress every year. Approximately 4 billion people, or half the world’s population, experience severe water scarcity for at least part of the year.

Climate change is increasing seasonal variability in, and uncertainty about, water availability in most regions. Pollution, land and ecosystem degradation, and natural hazards can further compromise the availability of water resources.

Progress towards Sustainable Development Goal 6

Sustainable Development Goal (SDG) 6 seeks to ensure the availability and sustainable management of water and sanitation for all.

Progress towards all SDG 6 targets is off track – some severely.

For example, an estimated 2.2 billion people (27% of the global population) were without access to safely managed drinking water in 2022, with four out of five people living in rural areas lacking even basic drinking water services.

The situation concerning sanitation is worse, with 3.5 billion people worldwide lacking access to safely managed sanitation in 2022. Only half of the population had access to these services in Latin America and the Caribbean, and Central and Southern Asia. Coverage in Sub-Saharan Africa was a mere 24%.

Data gaps and deficiencies in monitoring continue to impede accurate assessment of the other SDG 6 targets, including on the management of water resources, water quality, water-related ecosystems and the enabling environment.

Mountain regions

As the ‘water towers’ of the world, mountains are an essential source of fresh water. They are vital for meeting basic human needs such as water supply and sanitation. These waters are also vital in ensuring food and energy security to billions of people living in and around mountain regions and in areas downstream.

The main economic activities in mountain regions are agriculture, pastoralism, forestry, tourism, mining, cross-border trade and energy production. Mountain regions provide high-value products such as medicinal plants, timber and other forest products, unique mountain livestock and speciality agriculture products. They are global hotspots of agrobiodiversity, with a large fraction of the world’s gene pools for agriculture and medicinal plants preserved in mountains.

Mountains feature a diverse range of ecological zones, each resulting from a specific combination of factors such as elevation, geomorphology, isolation and microclimatic conditions (e.g. insolation). Consequently, they often have higher endemic biodiversity than lowlands, including important genetic varieties of agricultural crops and animals. They also have an equally diverse range of human cultures.

Glaciers and the mountain cryosphere

The mountain cryosphere is one of the most-sensitive components of the Earth system to global climate change. Mountains generally supply more surface runoff per unit area than lowlands, due to higher precipitation and lower evaporation. Alpine glaciers also store and release water, albeit over much longer time-frames. In many high mountain regions, the formation of seasonal snow cover provides most of the freshwater storage.

Most of the world’s glaciers, including those in mountains, are melting at an increasing rate. However, snow-melt accounts for a greater volume of streamflow in most river basins with a cryosphere component, and is often substantially higher than glacier melt.

Global warming is accelerating glacier melt, decreasing snow cover, increasing permafrost thaw, and prompting more extreme rainfall events and natural hazards. Water flows from mountains will become more erratic, uncertain and variable. Changes in the timing and volume of peak and low flow periods, increased erosion and sediment loads will affect water resources downstream, in terms of quantity, timing and quality.

Dust, combustion-related soot deposits including black carbon, and microbial and algal growth on snow and glacier surfaces are becoming more common due to increased frequency and/or intensity of dust storms, air pollution and wildfires. They can accelerate melt rates by decreasing surface albedo until the next snowfall.

The consequences of climate change, including higher temperatures, glacial recession, permafrost thaw and changing precipitation patterns, can affect flood and landslide risks. The processes associated with these risks, such as debris flows and floods, avalanches, rock- and icefalls, landslide dam outburst floods and glacial lake outburst floods (GLOFs), can pose significant threats to communities, wildlife and infrastructure.

Food and agriculture

Agriculture and pastoralism are essential sources of livelihoods for people in rural mountain areas. One in two rural mountain dwellers in developing countries are vulnerable to food insecurity. Remoteness and inaccessibility, as well as land degradation (which leads to poor quality soils) and large variations in seasonal water supply, combine to create significant challenges for mountain agriculture.

Mountain communities preserve many of the rarest crop varieties and medicinal plants. They have developed valuable traditional knowledge and techniques in crop cultivation, livestock production and water harvesting that help to sustain entire ecosystems.

Indigenous Peoples in mountains have unique and valuable local knowledge, traditions and cultural practices that contribute to sustainable food systems, land management and biodiversity preservation. Terrace farming can be adapted to local slope conditions. Its numerous benefits include reducing surface water runoff, promoting water conservation, reducing soil erosion, stabilizing slopes, enhancing habitat and biodiversity production, and sustaining cultural heritage.

Responses to climate-driven impacts in mountains vary significantly in terms of goals and priorities, speed of implementation, governance and modes of decision-making, and the extent of financial and other resources to implement them. Adaptation responses commonly include changing farming practices, infrastructure development including for water storage, application of Indigenous knowledge, community-based capacity-building and ecosystembased adaptation (EbA).

Human settlements and disaster risk reduction

Roughly 1.1 billion people live in mountain regions, two-thirds of whom live in towns and cities. The remoteness of mountain communities, difficult terrain and heightened exposure to natural hazards often lead to higher costs for transport, infrastructure, goods and services. These also pose particular challenges for the financing, development and maintenance of water supply and sanitation systems, drainage networks and other essential water infrastructure.

Rapid and unplanned urbanization in mountain regions is also placing pressure on fragile mountain ecosystems, affecting water availability, quality and security. Decentralized water and sanitation systems can be particularly effective in mountain regions, reducing the risk of infrastructure damage in rugged terrain subject to frequent landslides.

Natural hazards such as landslides, earthquakes, floods, GLOFs and avalanches can damage the water supply and sanitation infrastructure, and disrupt access to water, sanitation and hygiene services. Such hazards increase the vulnerability of already vulnerable and often marginalized mountain communities, and destabilize some of their wealth-generating sectors, including agriculture, tourism and biodiversity.

Examples of adaptation actions in mountain regions include: feasibility studies for building emergency storage and bypasses and controlled releases from glacial lakes; river basin management and planning for basin optimization; monitoring temporal changes in glaciers; and establishing GLOF risk reduction and early warning systems in glaciated river basins.

Industry and energy

Water-dependent industries have developed in mountain areas where water and other resources are found in relative abundance. In addition to industrial and energy production, water is also required to process minerals, produce timber and develop tourism in mountain areas.

Hydropower generation is one of the main industries in mountain areas. The presence of a slope and the shape of mountain valleys make it possible to generate hydropower without building large dams and reservoirs. However, the construction and presence of dams and reservoirs, transmission lines and substations can have a significant negative impact on fragile mountain ecosystems.

Beyond water availability, a significant challenge for industry and energy is the elevation at which it is possible to operate. As such conditions can generate huge investment and running costs, industrial activities are typically limited to those with high returns on investment.

Industrial and energy development can affect water quality. Remote mountain areas can be difficult to regulate, resulting in uncontrolled water withdrawals and discharges, including pollutants.

Responses are available and are being developed to make industry and energy production in mountain areas more sustainable. The circular economy promotes water-use reduction, recycling of used water and reuse of water resources. Environmentally sound technologies encompass practices such as the use of less-polluting technologies, better resource management and efficient waste recycling. The greening of grey infrastructure or its replacement with green infrastructure can be particularly effective in mountain areas.

Environment

Mountain and highland ecosystems provide essential ecosystem services to people living in mountains, and to billions in connected lowland areas. Water regulation (including water storage and flood regulation) is one of the most important services.

Other key ecosystem services include reducing the risk of erosion and landslides, cooling local temperatures, carbon sequestration, providing food and fibres, and maintaining pools of genetic resources for locally adapted crops and livestock.

Forests cover an estimated 40% of mountain areas, performing a protective function against natural hazards by stabilizing steep slopes, regulating flows to groundwater, reducing surface runoff and soil erosion, and mitigating the potential for landslides and floods. Unsustainable tree cultivation can lead to increased soil erosion and reduced soil water infiltration.

Mountain soils develop under harsh climatic conditions. They differ significantly from lowland soils, as they are shallower and more vulnerable to erosion. Such soils are easily and often degraded by various human activities, especially removal of vegetation that exposes the bare soil. The recovery of degraded soils and thus ecosystems at high elevations is slow.

At the ecosystem level, most of the options for addressing the impacts of changes in the cryosphere and high mountains involve conserving or restoring ecosystem functionality to maintain or enhance ecosystem services at local to regional scales through nature-based solutions (NbS) or EbA. These approaches are now commonly seen as an adaptation component in the nationally determined contributions of many mountain countries around the world.