“Water, water everywhere, nor any drop to drink” wrote the English poet Samuel Taylor Coleridge in 1798 in “The Rime of the Ancient Mariner”. Such sentiments still reverberate over 200 years later as water has become the centre of world attention as never before. Even in the 1950s, water was reasonably available, with few demands, although some countries were never without severe floods and droughts, particularly in tropical, arid and semi- arid regions. As populations gradually increased and water demands grew, governments responded by building more storage dams and diverting rivers to maintain widespread water availability. However, since the late 1990s, the world has faced a very different future of impending water scarcity (Box 1.1). The global population has expanded rapidly and is expected to reach 9.7 billion by 2050. Innovative technologies have produced step changes in economic growth, prosperity and living standards, mainly across Europe and North America, but to such an extent that water resources are reaching their limits, and technologies can no longer keep pace with demand.

Since the late 1980s, world leaders have been sounding an alarm about an impending water crisis. The World Economic Forum, which provides an overview of shocks and trends from a business perspective every year (from 2012 to 2020), has identified water crises as one of the top five risks with a severe global impact. In 2021, a survey among national leaders from 88 countries across all regions responsible for achieving sustainable water use for over six billion people identified climate change and associated pressures on water supplies and worsening floods and droughts as the highest water- related risks facing their countries (Water Policy Group 2021). Climate change, driven by industrialization, is becoming more visible through frequent and severe floods and droughts. Shocks from international financial turmoil, pandemics (Covid- 19), conflict (in Ukraine and the Middle East) and significant catastrophes like earthquakes have added to the impact on water availability, especially in areas where access to clean drinking water is already limited.