Scientists from around the world have assessed the planet’s 78 mountain glacier–based water systems and, for the first time, ranked them in order of their importance to adjacent lowland communities, as well as their vulnerability to future environmental and socioeconomic changes. These systems, known as mountain water towers, store and transport water via glaciers, snow packs, lakes and streams, thereby supplying invaluable water resources to 1.9 billion people globally—roughly a quarter of the world’s population.

The research, published in the prestigious scientific journal Nature, provides evidence that global water towers are at risk, in many cases critically, due to the threats of climate change, growing populations, mismanagement of water resources, and other geopolitical factors. Further, the authors conclude that it is essential to develop international, mountain-specific conservation and climate change adaptation policies and strategies to safeguard both ecosystems and people downstream.

Globally, the most relied-upon mountain system is the Indus water tower in Asia, according to their research. The Indus water tower—made up of vast areas of the Himalayan mountain range and covering portions of Afghanistan, China, India and Pakistan—is also one of the most vulnerable. High-ranking water tower systems on other continents are the southern Andes, the Rocky Mountains and the European Alps.

To determine the importance of these 78 water towers, researchers analyzed the various factors that determine how reliant downstream communities are upon the supplies of water from these systems. They also assessed each water tower to determine the vulnerability of the water resources, as well as the people and ecosystems that depend on them, based on predictions of future climate and socioeconomic changes.

Of the 78 global water towers identified, the following are the five most relied-upon systems by continent:

  • Asia: Indus, Tarim, Amu Darya, Syr Darya, Ganges-Brahmaputra
  • Europe: Rhône, Po, Rhine, Black Sea North Coast, Caspian Sea Coast
  • North America: Fraser, Columbia and Northwest United States, Pacific and Arctic Coast, Saskatchewan-Nelson, North America-Colorado
  • South America: South Chile, South Argentina, Negro, La Puna region, North Chile

The study, which was authored by 32 scientists from around the world, was led by Prof. Walter Immerzeel (Utrecht University) and Dr. Arthur Lutz (Utrecht University and FutureWater), longtime researchers of water and climate change in high mountain Asia.


The Paris Agreement requests each country to outline and communicate their post-2020 climate actions, known as their NDCs. These embody efforts by each country to reduce national emissions and adapt to the impacts of climate change. As ratifying parties, Armenia, Georgia and Uzbekistan must therefore outline how they intend to implement their NDCs and provide information on what the focus of this spending will be. To support this effort, the Asian Development Bank (ADB) is implementing a knowledge and support technical assistance cluster which will help enhance capacities of developing member countries (DMCs) in meeting their climate objectives by assisting in refining and translating nationally determined contributions (NDCs) into climate investment plans.

In this work package, ADB aims to support Georgia, Armenia, and Uzbekistan with the implementation of their NDCs through developing urban climate assessments (UCAs) and mainstreaming low carbon and climate resilience measures into urban planning processes. FutureWater contributed to this effort by supporting knowledge creation in relation to climate change and adaptation which will help each country to make more informed climate investment decisions.This was accomplished by conducting analysis of downscaled climate model ensembles for different climate change scenarios and synthesising data related to urban climate risk.

Climate change trend assessments were conducted using the NASA-NEX downscaled climate model ensemble combined with ERA-5 climate reanalysis products. To determine climate risk at the urban level, a number of openly available datasets were analysed and compiled using a spatial aggregation approach for 16 cities in the area. Results were presented as user-friendly climate risk profiles at the national and urban scales, allowing for insights into climate trends and risks over the coming century. These will be presented to non-expert decision makers to help support Armenia, Georgia and Uzbekistan develop targeted and informed NDCs.

The North–South Corridor serves as the main transport artery for the region, which spans quite diverse and spectacular terrains from the historic capital of Georgia, Mtskheta, up north to Stepantsminda in the Great Caucasus mountain range. The road experiences heavy traffic and is unsafe due to a design that is inadequate for the challenging geographical and climatic conditions, particularly in winter. The area is prone to avalanche, landslide, and snow load risks, which cause frequent and extended closures of the road. The two-lane highway provides a low standard alignment and is characterized by substandard open tunnels and avalanche galleries, in which modern trucks cannot pass simultaneously. An upgrade of the existing road alignment with improved geometry and avalanche galleries was considered but deemed inappropriate as it would not address the core climate-related risks.

Recognizing these challenges, the government has therefore requested ADB’s and EBRD’s assistance to improve the North–South Corridor. The climate-resilient project road will allow more traffic to travel on it safely and will remain fully operational all year. A detailed Climate Risk and Vulnerability Assessment (CRVA) report has been developed for the project road. The projected increase in extreme precipitation events is considered as the most important climate risk for the project road. This not only leads to higher extreme discharges, but can also lead to more frequent landslides, mudflows, and avalanches. The climate model analysis yields following conclusions for the project area:

  • Temperature increases by about 2 °C (RCP4.5) to 2.7 °C (RCP8.5) are to be expected
  • Minimum and maximum temperature are likely to change inconsistently, with maximum air temperatures increasing more than minimum air temperatures. This implies a larger diurnal temperature range for the future
  • Extremes related to temperatures (e.g. warm spells, extremely warm days) are likely to increase in frequency and intensity
  • Precipitation totals are likely to stay reasonable constant
  • Precipitation extremes are likely to increase in frequency and intensity. Maximum 1-day precipitation volumes with return periods of 25, 50 and 100 years are expected to increase by about 10% to 20%.

Stress tests were carried out by the project road design consultant team using +10% and +20% increased precipitation input for return periods used in the engineering design. These tests revealed that bridges have sufficient capacity in the current design to cope with higher discharge levels in the future, although it would be prudent to check the bridge substructure designs for higher flow velocities and the possibility of increased debris content in the flow. The tests indicated that a small proportion of the transversal and longitudinal drainage systems might have insufficient capacity to cope with the increased precipitation extremes. These should be identified, and their dimensions increased appropriately.

Wereldwijd zijn er 78 watersystemen waarvan gletsjers en sneeuw de voornaamste zoetwaterbron zijn. Deze systemen worden dan ook de watertorens van de wereld genoemd. Hiervan zijn 1,9 miljard mensen afhankelijk – ongeveer een kwart van de wereldbevolking. Een groot internationaal onderzoeksteam, geleid door de Universiteit Utrecht in samenwerking met National Geographic, heeft in kaart gebracht welke watertorens het belangrijkst zijn voor de mensen die benedenstrooms leven, en ook hoe kwetsbaar ze zijn voor veranderingen in klimaat en socio-economische factoren. Ze publiceerden hun resultaten op 9 december in het prestigieuze Nature.

De groep onderzoekers laat in hun publicatie zien dat door klimaatverandering, de toenemende wereldbevolking, slecht gebruik van waterbronnen en andere geopolitieke factoren de watertorens in gevaar zijn. Het is daarom essentieel om per bergketen internationaal beleid en strategieën te ontwikkelen, willen we deze primaire zoetwaterbronnen behouden en zowel ecosystemen als mensen stroomafwaarts beschermen.

De kwetsbaarste watertoren
Nergens ter wereld zijn zoveel mensen afhankelijk van één watertoren als van de Induswatertoren in Azië, schrijven de onderzoekers. Deze ijs- en watermassa beslaat een groot deel van het Himalayagebergte en ligt verspreid over delen van Afghanistan, China, India en Pakistan. Het is tevens de kwetsbaarste watertoren. Ook van de zuidelijke Andes, de Rocky Mountains en het Alpengebergte zijn erg veel mensen afhankelijk.

Afhankelijkheid en kwetsbaarheid
Om te berekenen hoe belangrijk elk van deze 78 watertorens zijn hebben de onderzoekers verschillende factoren bekeken die iets zeggen over hoe afhankelijk benedenstroomse gemeenschappen zijn van de watertoevoer van deze systemen. Ook bepaalden ze van elke watertoren de kwetsbaarheid van de watertoevoer, maar ook de kwetsbaarheid van de mensen en ecosystemen die hiervan afhankelijk zijn, gebaseerd op voorspellingen van het toekomstig klimaat en socio-economische veranderingen.

De top vijf kwetsbaarste watertorens per continent zijn:

  • Azië: Indus, Tarim, Amu Darya, Syr Darya, Ganges-Brahmaputra
  • Europa: Rhône, Po, Rijn, Noordkust van de Zwarte Zee, Kaspische Zeekust
  • Noord-Amerika: Fraser, Columbia and NW US, Pacific and Arctic Coast, Colorado, Saskatchewan – Nelson
  • Zuid-Amerika: Zuid-Chili, Zuid-Argentinië, Negro, La Puna regio, Noord-Chili

Het volledige overzicht vind je hier.

Uniek onderzoek
Het onderzoek werd uitgevoerd door 32 wetenschappers van over de hele wereld en werd geleid door prof.dr. Walter Immerzeel en dr. Arthur Lutz van de Universiteit Utrecht en onderzoeksbureau FutureWater. Beiden doen al jaren onderzoek naar veranderingen in klimaat en waterhuishouding in de Aziatische hooggebergtes.

“We hebben niet alleen gekeken naar hoeveel water er zit opgeslagen in de watertorens, maar ook hebben we onderzocht hoeveel water er benedenstrooms nodig is en hoe kwetsbaar deze systemen zijn voor veranderingen in de komende decennia”, vertelt Immerzeel. “Dat maakt ons onderzoek uniek.” Lutz vult aan: “Door alle watertorens ter wereld te onderzoeken konden we aantonen welke het belangrijkst en kwetsbaarst zijn. Deze watertorens zouden bovenaan de prioriteitenlijst moeten staan op de regionale en internationale politieke agenda’s.”

Perpetual Planet Partnership
Dit onderzoek werd mede mogelijk gemaakt door National Geographic en Rolex als onderdeel van hun Perpetual Planet Partnership. Hun doel is om inzichtelijk te maken met welke uitdagingen onze planeet te maken heeft op het gebied van het onderhouden van het leven op aarde. Ze ondersteunen onderzoek naar deze systemen, en stellen leiders over de hele wereld in staat om oplossingen te ontwikkelen om onze planeet te beschermen.

Alle data en rankings zijn beschikbaar via een interactieve visuele tool op de website

There is great potential for hydropower in Georgia, and this natural resource is likely to be increasingly utilised for power generation in the future. With the escalating demand for energy, government authorities are keen to harness renewable energy from the country’s main rivers. Often these projects aim at remote communities for which connecting to the national power grid is expensive. Hence, local hydropower production is an attractive and sometimes viable option. Critical is to conduct accurate feasibility assessments for hydropower generation at the different potential sites of interest considering climate change impacts. This work is a glacio-hydrological assessment of the expected river discharge at the planned hydropower sites in the Mestiachala river, Georgia.

Based on the requirements of the project, the Spatial Processes in Hydrology (SPHY) cryospheric-hydrological model was selected for the assignment. SPHY is a hydrological model that simulates the runoff at any location within the basin at a daily timescale. SHPY is ideal to assess glacier and snow influence in the river discharge and evaluate the impact of climate change. SPHY was used to predict the river discharge for the extended period of record and provide enhanced flow duration curves for hydropower assessment. In addition, total runoff components were quantified such as snow and glacier runoff.

This glacio-hydrological assessment delivered river discharge estimates for intake locations of two planned runoff river hydropower plants near Mestia, Georgia. The assessment included the calibration of a hydrological model, daily river discharge simulation for an extended period of record (1980-2015), climate change scenarios, and the derived flow duration curves to evaluate the flow operation of hydropower turbines. In addition, total runoff components were quantified such as snow and glacier runoff.

The daily river discharge was simulated at the two intake locations for two future periods (for the end of the concession period and for the end of century period) considering two climate change scenarios (RCP4.5 and RCP8.5). Hydrological model simulations were developed using future precipitation and temperature predictions and future glacier extent predictions. The climate change scenarios provide an evaluation of flow operation uncertainty. The daily flow calculations for the two sites can be used in the hydropower calculations, and to assess the overall profitability of the planned investment, taking into account energy prices, demand, etc.

The SREB is part of the Belt and Road Initiative, being a development strategy that focuses on connectivity and cooperation between Eurasian countries. Essentially, the SREB includes countries situated on the original Silk Road through Central Asia, West Asia, the Middle East, and Europe. The initiative calls for the integration of the region into a cohesive economic area through building infrastructure, increasing cultural exchanges, and broadening trade. A major part of the SREB traverses Asia’s high-altitude areas, also referred to as the Third Pole or the Asian Water Tower. In the light of the planned development for the SREB traversing the Third Pole and its immediate surroundings, the “Pan-Third Pole Environment study for a Green Silk Road (Pan-TPE)” program will be implemented.

The project will assess the state and fate of water resources in the region under following research themes:

1. Observed and projected Pan-TPE climate change
2. Impacts on the present and future Water Tower of Asia
3. The Green Silk Road and changes in water demand
4. Adaptation for green development

The Silk Road Economic Belt (SREB) is part of the Belt and Road Initiative, being a development strategy that focuses on connectivity and cooperation between Eurasian countries. Essentially, the SREB includes countries situated on the original Silk Road through Central Asia, West Asia, the Middle East, and Europe. The initiative calls for the integration of the region into a cohesive economic area through building infrastructure, increasing cultural exchanges, and broadening trade. A major part of the SREB traverses Asia’s high-altitude areas, also referred to as the Third Pole or the Asian Water Tower. Most hydrological research has focused on the southern parts of the mountain ranges (i.e. the river basins encompassing the Hindu Kush, Karakoram and Himalayan mountain ranges, whereas the northern and western domains of the Third Pole (i.e. the domains traversed by the planned SREB) form a research gap. The Chinese Academy of Sciences launched a multi-year research programme called Pan-Third Pole Environment (Pan-TPE), focusing on climate change on the Tibetan Plateau, its impacts, and the development of pathways to sustainable development.

FutureWater works together with Utrecht University and the Institute of Tibetan Plateau Research to quantify climate change impacts for hydrology on the Third Pole.

Given the strong role of large-scale hydrology in the proposed research activities, the spatial domain of the activities encompasses the river basins of the Third Pole which are traversed by the SREB. The included SREB transects are the branch connecting Beijing to Central Asia via Xi’an and Urumqi, and the China-Pakistan Economic Corridor connecting Southwest China to northern Pakistan. This means that the river basins of the Amu Darya, Syr Darya, Indus, and Yellow river are included, as well as the Tarim and Gobi interior basins. The research activities encompass the entire river basins, but particularly focus on the SREB transect.

The project involves a close collaboration with Chinese counterparts. To this end, a training program was conducted at Institute of Tibetan Plateau Research, Beijing (ITP) from 14th October to 18th October, 2019. This training was attended by nineteen researchers (3 female and 16 male) from ITP. The overall objective of this training was to train glacio-hydrological modeling with FutureWater’s Spatial Processes in Hydrology (SPHY) model, and transfer the knowledge regarding the Pan-TPE Water Tower hydrological model. The participants used the SPHY hydrological model to understand the changes in the glacio-hydrological regime of their own region of interest. The first days of the training were mainly dedicated to understanding of the basics of hydrological modelling using SPHY. The participants were encouraged to develop the SPHY model of their own interest area. The later part of training was dedicated to share and discuss the Water Tower model set up by FutureWater.

Overall, the training fulfilled all the needs of the project, and was positively evaluated by the participants. This training program has encouraged the researcher from ITP to use SPHY in their future research, and lead to further enhancement of the collaboration between Chinese and Dutch researchers. More information about the SPHY model as well as model documentation, tutorials and software downloads can be found on the SPHY website.

Below, you can find some pictures, taken during the training at the Institute of Tibetan Plateau Research.






Vorige maand werd bekend dat gletsjers in de Himalaya in de afgelopen twintig jaar sneller zijn gesmolten dan in de jaren daarvoor. De gewasproductie en het levensonderhoud van 129 miljoen boeren is afhankelijk van het smeltwater uit deze gletsjers. Dat concludeert een internationale groep van onderzoekers, waaronder FutureWater teamleden, in een nieuwe studie die vandaag verschijnt in Nature Sustainability.

Met ruim 900 miljoen inwoners behoren de stroomgebieden van de Indus, de Ganges en de Brahmaputra in Zuid-Azië tot de meest dichtbevolkte gebieden ter wereld. De watervoorziening in deze gebieden is voor een groot deel afhankelijk van smeltende gletsjers en sneeuw uit de Himalaya. Dit smeltwater wordt gebruikt voor de irrigatie van gewassen en voorziet de landbouw van voldoende water in periodes van droogte en weinig regenval.

Irrigatie met smeltwater

Tot voor kort was onduidelijk wat het belang van dit smeltwater precies is voor de landbouwproductie en hoeveel van de 900 miljoen inwoners hiervan afhankelijk zijn. Deze studie laat zien dat 129 miljoen boeren hun land (gedeeltelijk) irrigeren met water afkomstig uit sneeuw en gletsjers in de bergen. Hiermee alleen al kan een totale jaarlijkse hoeveelheid voedsel voor 38 miljoen mensen worden verbouwd.

Met name boeren in het stroomgebied van de Indus zijn voor groot deel afhankelijk van smeltwater, omdat hier weinig neerslag valt. In het droge seizoen is 60% van al hun watergebruik afkomstig uit de bergen. Boeren in stroomgebieden van de Ganges zijn relatief minder afhankelijk van het inkomende smeltwater, maar het is ook hier essentieel voor landbouwproductie in het droge seizoen. Bijvoorbeeld voor de productie van suikerriet.

Getransporteerd over honderden kilometers

De onderzoekers hebben geanalyseerd wanneer de gletsjers smelten, hoe het smeltwater zich vermengt met regen en grondwater en vervolgens getransporteerd wordt naar de irrigatiesystemen. “In de Indus en Ganges zijn grote irrigatiesystemen met kanalen die het water uit de rivier over soms honderden kilometers transporteren,” vertelt Hester Biemans, onderzoeker bij Wageningen University & Research en eerste auteur van de studie. “Dit onderzoek laat voor het eerst zien hoeveel smeltwater in irrigatiesystemen terecht komt, wat er met de opbrengst gebeurt als er geen smeltwater meer is, en in welke periode smeltwater cruciaal is voor welke oogst. Met name de productie van rijst en katoen blijken hier sterk afhankelijk van te zijn.”

Politieke keuze

Eerder onderzoek wees al uit dat een derde van het ijs in de Himalaya voor het einde van deze eeuw is gesmolten. Met het verder smelten van het gletsjerijs en onvoorspelbaarder worden van het moessonseizoen, moeten boeren tijdig gaan anticiperen, benadrukken de onderzoekers. “Boeren kunnen bijvoorbeeld eerder zaaien, of gewassen gaan telen die minder water nodig hebben,” legt Biemans uit. “Katoen is een gewas dat veel water nodig heeft. Dit kan wellicht beter op andere plekken verbouwd worden waar meer water beschikbaar is. Maar een dergelijke keuze is grotendeels politiek. Met dit onderzoek voorzien we de politiek van de informatie die nodig is om goede beslissingen te kunnen nemen.”

“Om dit te kunnen onderzoeken hebben we de kennis over landbouw en irrigatie van Wageningen University & Research gecombineerd met onze kennis over processen rond gletsjers, sneeuw en water in de Himalaya.” zegt Walter Immerzeel van de Universiteit Utrecht. Arthur Lutz, onderzoeker bij de Universiteit Utrecht en FutureWater voegt daaraan toe: “In het stroomgebied van de Indus blijkt de rol van smeltwater verreweg het belangrijkste te zijn. In dat gebied gaan we nu samen vervolgonderzoek doen hoe de rol van smeltwater zich in de toekomst zal gaan ontwikkelen als het klimaat veranderd en de watervraag toeneemt.”

Deze studie is onderdeel van het grotere project Hi-Aware naar klimaatadaptatie in de stroomgebieden van de Indus, Ganges en Brahmaputra. In een vervolgonderzoek wordt gekeken hoe het belang van smeltwater zich gaat ontwikkelen als het klimaat verandert en de watervraag toeneemt, en hoe boeren zich hierop aan kunnen passen.

On 18 March FutureWater organized the first SPHY-model User Day for core developers and users of the SPHY-model. Ten core developers and users from FutureWater, Utrecht University, Wageningen University & Research and CEBAS Spain gathered at the Wageningen International Congress Centre to discuss the upcoming new release of SPHY and the way forward for effective collaboration and co-development of the model.

FutureWater started the development of the Spatial Processes in Hydrology (SPHY) model back in 2005 with the first version of FutureView. Over the years FutureWater developed the modelling suite further and since 2012 the modelling suite is known as SPHY. It is a fully distributed physics based modular hydrological model proven to be suitable for a wide range of applications all over the world, with particular suitability for data-scarce areas. It is used in research as well as consultancy assignments in the fields of climate change impacts, hydropower and river basin and watershed management. Over the last years multiple other organizations outside FutureWater started to develop new components for SPHY.

Dr Philip Kraaijenbrink presenting best practices of Git and version control.

Dr. Joris Eeckhout (CEBAS, Spain) presented the new features and structure of the upcoming SPHY release (SPHY v3.0), which features new modules to simulate soil erosion processes. Other participants of the SPHY model user day presented their SPHY development and application plans for the upcoming year. Planned developments include improved routing for better simulation of extreme events, improved snow and glacier melt routines, and a hydropower production module. A significant part of the day was dedicated to a discussion on the way forward for efficient co-development of SPHY by the different involved organizations.

FutureWater is now working on an improved version management environment to facilitate efficient co-development of SPHY. The participants agreed to make the SPHY-model User Day an annually recurring event to enhance the exchange of knowledge and best practices in the use and development of SPHY.

The current United Nations Climate Change Conference COP24 held in Katowice, Poland once more demonstrates the world’s climate change concerns. In the Indus, Ganges, and Brahmaputra river basins, a global climate change hotspot and home for about 900 million people, these concerns are pressing, since the river systems provide water resources for the important agricultural, domestic, and industrial sectors that serve these people. Meltwater from glaciers and snow feed the headwaters of these rivers and are strongly influenced by rising temperatures. In addition, the monsoon and its dynamics that determine the regional hydrology are expected to change. Climate change is however not the only concern. Strong socio-economic developments and a rapid and continuous population growth will result in tremendous increases in water demand and related to that to an increasing pressure on water resources. It is very likely that a water gap will develop in the future. To address this, a joint study of FutureWater, Utrecht University, Wageningen Environmental Research, and ICIMOD was conducted to assess the combined impacts of climate change and socio-economic developments on the future “blue” water gap in the Indus, Ganges, and Brahmaputra river basins until the end of the 21st century. To this end, the team coupled a hydrological model simulating the future changes in the upstream high mountain water reserves stored in snow and ice (SPHY) and a hydrology and crop production model simulating future changes in the downstream water balance incorporating water use for agricultural, domestic and industrial purposes (LPJmL). The latest climate change projections and socio-economic scenarios were used as inputs for their models. The results are presented in an (open-access) paper that has been published recently in Hydrology and Earth System Sciences.

The projections show that the future socio-economic developments will lead to an increasing water gap (unmet demand) in the Indus and Ganges river basins towards the end of the 21st century. Scenarios: RCP45 = moderate climate change, RCP85 = strong climate change, RCP45-SSP1 = moderate climate change + sustainable socio-economic development, RCP85-SSP3 = strong climate change + unsustainable socio-economic development.
Abbreviations: Sust. = Sustainable, Dom. = Domestic, Ind. = Industrial

The findings of this study indicate that the surface water availability will increase, which can mainly be attributed to increases in monsoon precipitation. Besides the increases in surface water availability, water consumption by irrigation will most likely decline due to shorter growing seasons that emerge from temperature increases, and a shift from blue water irrigation to green water/rainfed irrigation due to increases in precipitation. However, this increase in water availability cannot outweigh the strong increases in water demand that are associated with the strong socio-economic development, and will thus likely lead to a substantial increase in the water gap with 7% and 14% in the Indus and Ganges river basins, respectively, during the 21st century. This implies the importance of robust adaptation strategies to cope with future water shortages in the region.