When will we run out of fresh water?

Geographer Anson Mackay on the freshwater resources, planetary boundaries and lake Urmia

videos | December 17, 2020

Will we run out of fresh water?

Weirdly enough, we will never run out of fresh water. I think that surprises a lot of people because you think of fresh water as being this very precious commodity, but from work that’s been done over the last couple of years we know that the amount of fresh water globally has actually increased compared to the amount that has been lost. So in terms of quantity, we will not run out of fresh water.

How can we manage water resources better?

We do have these concepts called ‘planetary boundaries’ which suggest a global use of freshwater but that doesn’t really make sense because the problem with fresh water is that it’s so unevenly distributed around the world that some places are rich in the resource and they’ll never run out, whereas in other places the resource is very limited and that is where the problems can arise.

Geographer Anson Mackay on the ecosystem services, the demands on freshwater around the Earth and the decline in biodiversity
Instead of having a planetary boundary what’s probably better way to think about it is to have a regional boundary or to think about fresh water in terms of environmental water flows. So we should be looking at fresh waters in the unit of, say, the catchment: that is the lake and all the rivers that flow into it. If we take out more water than flows through a river in a month, then that is going to pose problems for fresh water security. If you take out a lot of water that flows for many months from a river going in the lake, then that is clearly very problematic, and in that situation we will see an example of when fresh water becomes limiting and that’s when we have to take care.

What will happen if we take out too much water?

There are some very good examples of that around the world such as the Aral Sea in Uzbekistan and Kazakhstan, but also lake Urmia in Iran which is following a similar type of fate where 40 000 illegal wells are extracting water faster than it can flow into the lake.

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Professor of Geography, University College London
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