Sustainable futures
Towards achieving global freshwater sustainability
As the UK has just experienced one of its driest springs on record, Professor Simon Gosling reflects on his research into sustainable solutions for managing the planet’s freshwater
Too much, too fast: Rethinking water use in a warming climate
In 2025, the UK experienced one of its driest springs on record, and in May 2025, the Environment Agency declared a state of drought for the north-west of England. This announcement has sparked growing concerns about water shortages if dry conditions continue later in the year.
Around the same time, the UK Government announced plans to build two major reservoirs—the first since the 1990s. This is a step in the right direction as major infrastructure projects like dams and reservoirs are some of the ways we can respond to increasing variability and extremes in water availability in the future.
Understanding the global water crisis is essential to finding long-term solutions
In this article, I take a step back to explore the global picture: why improving water resource management is urgent, and how it can be achieved.
Ask yourself: how many people are exposed to water scarcity across the globe? Ten million? One hundred million? In reality, the numbers are far higher. While estimates vary, due to the many ways water scarcity can be defined, our research suggests that between 1.6 and 2.4 billion people are affected. It is generally accepted that more than 2 billion people currently live under water-scarce conditions. This is expected to rise considerably as the planet continues to warm, as some regions get drier, and as growing populations place more pressure on the limited amounts of freshwater we have available.
Sadly, this should not come as a surprise. Society has had a marked effect on freshwater resources globally. I recently contributed to an international study that shows how freshwater levels on land have departed from their ‘pristine’ states, much more frequently in recent decades than in pre-industrial times, when there was far less human activity. This shift has occurred across almost half of the world’s land surface as shown in the image below. These shifts have serious implications, not just for ecosystems and biodiversity, but for essential human uses like agriculture, industry, and domestic use.
One of the most visible examples of this impact is the dramatic shrinking of the Aral Sea since the 1960s, a large-scale change that can be seen from space.
We have now crossed a critical threshold in global freshwater availability. This is what scientists call a "planetary boundary", that is, a safe operating space for humanity based on Earth's natural systems. In the past, we used water within these limits. But over the last few decades, in many regions, we have begun using more water than is sustainably available. In practical terms, we are exceeding what nature can replenish.
All these growing pressures on the global water cycle call for an urgent expansion of existing approaches to sustainable water management, both at pace and at scale. This is key to securing water sustainability for current and future generations.
Percentages of land area that have seen deviations from pre-industrial times in streamflow and soil moisture. The graphs highlight examples of the deviations for specific regions. Source: Porkka et al. (2024).
Scaling up solutions to sustainable water supply
There are many examples around the world of technologies that can help form part of the solution. One of these is desalination, which involves taking seawater from coastal areas and converting it into freshwater by removing the salt. Desalination can also be done inland, where the source is brackish water, such as rivers that are saltier than typical freshwater ones. The use of desalination has also grown steadily since the 1970s. Today, there are more than 1,500 operational plants worldwide, with nearly 50% of global desalinated water produced in the Middle East and North Africa.
Another example is inter-basin water transfer, which involves moving freshwater from one river basin to another—across local, national or even regional boundaries—using canals. This helps meet the water needs of drier areas. In the United States, for instance, 150 river basins already receive water through inter-basin transfers. One of the largest examples is China’s South-North Water Transfer Project. The first phase alone took 10 years to complete, water is transported across a 2,900-kilometre network from the Yangtze, Huai, Yellow and Hai river basins in southern China to the north, where water shortages are common due to a drier climate and a large population. The project now supplies water to 170 million people for domestic use.
The feasibility of inter-basin transfers has also been explored in England. One study showed how, in the future, transferring water from the north-east of England during the winter months could help meet water shortfalls in London, without negatively affecting supply in the source regions.
The water cycle and water management processes that can be simulated by the current generation of Global Water Models participating in ISIMIP. We are using these models to explore how water management adaptations could help to provide sustainable water supply in the future globally.
Source: Müller Schmied and Gosling et al. (2025).
Our approach
I am excited to be leading a team of international scientists investigating the potential for major interventions that could help secure more sustainable global water supplies in the future.
Under the framework of the Intersectoral Model Intercomparison Project (ISIMIP), the Global Water Sector of ISIMIP is exploring how changes in the way we manage water might improve the sustainability of planetary freshwater resources.
We are developing scenarios that show how water management could evolve in response to pressures from climate change and population growth. These scenarios include shifts in global land use, changes in irrigation demand, the construction of new dams, and the implementation of inter-basin water transfers. We have also created scenarios for future desalination, which explore where seawater might be used as a viable source of freshwater in new regions.
The scenarios reflect plausible adaptations in different parts of the world, depending on how water availability is projected to change with the climate. Some areas may experience little change and therefore require minimal new infrastructure, while others that are expected to become drier are more likely to need major adaptation. In building the scenarios, we take into account practical factors that influence whether and when such adaptations might be implemented. These include the strength of national economies, the distance of basins from the sea (especially important for inter-basin transfers), and demand for water across agriculture, industry, and domestic use.
We are running these scenarios through Global Water Models, computer models that simulate the water cycle and human water management across the world’s land surface. These models help us understand the extent to which different adaptation strategies could support sustainable water availability in the future. They also help us identify potential hotspots, where limited water access might worsen existing inequalities.
Balancing water management solutions requires careful consideration of environmental and social trade-offs.
As you might expect, none of these potential solutions come without environmental or social drawbacks. Trade-offs will likely be necessary to balance the benefits that engineering technologies provide against their environmental impacts.
For example, managing the waste brine left over from desalination remains a challenge, due to the ecological harm that high salt levels and chemicals can cause when released into the environment. Large-scale dam projects can disrupt the natural functioning of rivers, fragmenting them and significantly affecting river biodiversity. Water losses due to evaporation from canals used in inter-basin water transfers can be considerable, for instance, over 8% of the water diverted in China’s South-North Water Transfer Project is lost to evaporation. Moreover, many large projects require resettlement of populations. The construction of China’s Three Gorges Dam, for example, involved relocating over 1.3 million people to make way for the 175-meter-deep reservoir created by the dam.
It is crucial that the environmental and social impacts of these methods are considered right from the start, and that associated risks are carefully managed and minimised. The global water cycle is a key part of the Earth system, so altering one part inevitably affects others. While projects like these are built with the best intentions and for very important reasons, it is essential that efforts to secure water security do not come at the expense of the natural environment. Taking a balanced, holistic approach that respects the interconnectedness of Earth’s systems will be fundamental to effective global water management in the future.
This article was written by Professor Simon Gosling, and it forms part of the Institute for Policy and Engagement's campaign highlighting research that showcases how the University of Nottingham is advancing the Sustainable Development Goals (SDGs) at different levels.
Simon Gosling
Simon Gosling is a climate change impact scientist whose research focuses on environmental sustainability, including how climate change affects the water cycle and human health. He uses climate and hydrological models to study changes in average conditions and extremes like floods and droughts. His work also examines the links between climate change and temperature-related health. His work bridges science with policy and impact-focused research. Some of his recent publications can be found here.