Growing abstractions of freshwater (particularly for irrigation, public water supplies, industrial processes and cooling of electric power plants) and its resulting overuse are increasingly seen as a major risk to societies and prosperity across the world. This post looks at trends behind this issue with some data. It is also meant to respond to a question I received from one of my readers in February this year concerning longer-term developments and drivers of withdrawals of freshwater for human use.
Let me start with some general data.
||Annual freshwater abstraction globally, in km³
||World population, in million
||World GDP, in billion 2014 USD
Sources: Shiklomanov for the historic water figures and 2030 Water Resources Group for the forecast data, UN Population Division and World Bank/OECD
Since 1900, average annual freshwater withdrawals globally have grown significantly, from 600 km³ to more than 4,500 km³ in 2010. By 2030, withdrawals are expected to reach about 6,900 km³ per year. And yet, sustainable annual supply is only
about 4,200 km³
The main drivers behind this increase are the rise in the global population, on the one hand, and economic/technical progress on the other. The latter represents the net result of prosperity-driven higher per capita water withdrawals combined with improved water efficiency as enabled by technical progress.
||Average annual growth in freshwater abstraction, % p.a.
||Average annual increase in world population; % p.a
||Change in per capita abstraction, % p.a. (and litres per capita and day)
||0.8% (1,050 - 1,520)
||0.3% (1,520 - 1,790)
||1.2% (1,7920 - 2,280)
Sources: own calculation based on data from
Shiklomanov and 2030 WRG Charting our Water Future; UN Population outlook
Population growth, as the table shows, explains about half of the increase in freshwater withdrawals in the periods 1900-1950 and 2010-2030. In the intervening period 1950-2010, a period characterised by particularly high global population growth, demography was actually the dominant driver. In the total period 1900-2010, population growth can be considered to have contributed an additional 2,040 km³ to the initial volume of 600 km³ of freshwater withdrawn per year.
The increase in per-capita water consumption – for all uses, including water abstracted for irrigation, but not including water use in rain-fed agriculture – from 1,050 litres per capita per day to close to 1,800 litres 2010 added another 1860 km³ of total annual withdrawals.
There are several reasons behind the increase in per-capita withdrawals, let me mention two of them.
With a growing population, more land requiring irrigation (i.e. that is not rain-fed) is needed. Indeed, in the period between
1950 and1990, irrigated land increased by an average of 1.5% annually. Looking ahead to 2030, an increase of about 0.6% a year is expected.
A more significant driver is the rise in economic prosperity. The impact of economic prosperity is passed through in several ways: more water is needed to generate energy and more water is needed to provide for diets characterised by an increasing share of meat (calories and proteins from meat require ten times as much water as calories and proteins from plants do). As billions of people in developing and emerging economies continue to climb out of poverty, they consume more meat. Their meat consumption, compared to OECD countries, is still very modest - at 60-70 grams per capita/day - and so are the annual daily intake increases amounting to approximately 1-3 grams. But with the large number of people transitioning out of poverty and moving further up to some prosperity, itself a very positive development, this nonetheless has a significant impact on water balances.
On the positive side, however, we have seen and will continue to see significant improvements in water efficiency.
||Average annual growth in real world GDP, in %
||Efficiency of water use: Change in water withdrawals per USD of GDP (real at 2014 prices) in litres
||Improvement in water use efficiency: average annual rate of change in water withdrawals per USD of GDP, in %
||228 - 196 litres
||196 - 61 litres
||61 - 38 litres
(Additional) sources: OECD (pdf, 2Mb) and Citi (for GDP growth rates)
Water use fell from about 230 litres per USD of GDP (at constant 2014 USD) in 1900 to 60 litres in 2010, and a further decrease to less than 40 litres is expected to occur by 2030.
This brings me to the outlook: population growth will continue while high global GDP growth is also probable, despite the recent slowdown in China. Indeed, we are seeing the emergence of new growth engines, such as India or a number of African countries. Moreover, given its much higher share in world GDP today, even growth below 8% in China will keep global economic growth at high levels.
Global water withdrawals, in this scenario, will increase to 6,900 km³ per year, an amount that far exceeds sustainable supply of 4,200 km³ per year. This forecast, which represents the ‘status quo’ scenario drawn up by the 2030 Water Resources Group, also factors in accelerating improvements in water use efficiency – from 1.9% annually in the period 1950-2010 to 2.3% in the period 2010-2030.
As very little can be done to change population growth, and as economic growth is a positive factor, we must find ways to be much more ambitious concerning water efficiency.
If we want to be sustainable about our use of freshwater, the 2030 target will have to be limited to around 25 litres of freshwater withdrawals per USD of world GDP instead of 38 litres as indicated in the status quo scenario. This increases the required annual rate of improvement in water efficiency to close to 5%.
This is already per se quite ambitious, but there is also an additional challenge. Water savings only have an impact if achieved at the right place (where there is actual overuse, not, for instance, in rainy Switzerland), at the right time (not, for instance, during monsoon) and in the right form. I will come back to this in one of my next posts.
As ever, your comments on any points I have made in my post would be most welcome. And I would very much appreciate your ideas whether, or rather how these improvements might be possible.