Balancing water supply and demand in the coming decades will be a "painful" process, but one that cannot be ignored.
"The proportion of people living in countries chronically short of water ... is set to rise to 45 per cent (four billion) by 2050." In many areas, the problem will only get worse.
The challenge in meeting people's demand for water is partly down to the resource's finite nature.
Underground reserves of water — known as groundwater — have proven particularly important for farming in arid regions and also for providing drinking water to many of the world's largest cities. But, in many places, including India and China, the water is being withdrawn faster than it is naturally replenished.
Agriculture accounts for 70 per cent of global water use, and industry for 22 per cent — both are constantly growing in water demand.
Water scarcity is also affected by the terminology we use: for example irrigation is considered efficient even if 85 per cent of the water evaporates without reaching the crops.
Water as a commodity is difficult to manage because its values vary locally, and it is not evenly distributed: "China and India, with over a third of the world's population between them, have less than ten per cent of [the world's] water."
Meeting water demand in the future will be challenging, especially considering that people around the world think of free and unlimited access to water as their natural, democratic right.