Water: managing global water resources
Blue planet thinking
19 April 2017
Bruce Keith sets out the challenges we face in managing global water resources and explores some innovative ways to promote efficiencies
The Earth is called the Blue Planet for good reason: 70% of its surface is covered by water. However, only 2.5% of this is freshwater and, of that, almost 69% is locked up in glaciers, 30% is groundwater and just 1.2% is surface water.
Not only is there very little 'available' freshwater, but losses are also significant. The Aral Sea, lying between Kazakhstan and Uzbekistan was once the world’s fourth largest inland body of water, but, due to the diversion of feeder rivers for irrigation schemes, it has all but disappeared. The eastern basin is now known as the Aralkum Desert.
Global water use is equivalent to the annual flow of the Amazon, the world’s largest river. Agriculture accounts for 69%, industry 23% and domestic use 8%. Water consumption is also highly variable – the estimated daily usage per person in the USA is 576 litres, in the UK 149 litres and in Mozambique 4 litres.
The appalling statistic that 1 billion people – nearly 15% of the world’s population – do not have access to clean water must not sit easy with any of us. The UN defines water stress where annual supplies are less than 1,700 cu. m per capita. There are serious shortages in Yemen, parts of Africa, California and Brazil. In Sao Paulo, the world’s 12th largest city, the figure is 200 cubic metres, which is defined as 'absolute scarcity'.
Estimates by UNESCO and other bodies on the resource implications of the goods and services we consume provide a useful comparator of litres of water used per kilogram of product. This is referred to as 'virtual water', a concept which identifies the amount of water used or embedded in the production of a commodity. Beef has a water footprint of 15,500 litres/kg, for instance, lamb 6,100 litres/kg, pork 4,800 litres/kg and chicken 3,900 litres/kg.
The principal pressures on freshwater resources are worth rehearsing.
- Global population growth: from 3bn in 1960, the world’s population now stands at 7.3bn and is expected to increase to 9.7bn by 2050. One third of these people alone will live in China and India.
- Urbanisation: a major feature of population concentration is the trend towards urbanisation, with 12% of the world’s population living in 28 megacities – that is, cities of 10m or more people.
- Improved living expectations: the Organisation for Economic Cooperation and Development predicts that global GDP will triple over the next 40 years, but this increasing urbanisation and wealth will lead to changing dietary preferences, with meat consumption rising significantly.
The UN Food and Agriculture Organization estimates that food production will need to increase by 60% by 2050 to meet this rising level of demand.
The crux is that water consumption is rising at 2.5% per annum, which is faster than the rate at which the world’s population is increasing.
Meeting the challenges
There are 3 basic options – use less water, use the same water more efficiently, and create more freshwater resources.
Using less water
Reduction in use might be achieved in the following ways.
- Population control: China’s discontinued 1-child policy avoided a population increase of 300m, which equates to a 20% decrease in water usage. No other society has contributed so much to global water security.
- Dietary changes: we could eat ourselves out of the problem, according to Tony Allan, Emeritus Professor of Geography at King’s College London, in his book Virtual Water (2011). Changing from a carnivorous to a vegetarian diet in industrial countries could reduce per-capita water consumption by 40%. We could also consider insect-based diets – a family of 4 who eat insect-derived food for 1 day per week could save 1m litres of water per annum over conventional agricultural production (see Figure 1).
- Stop wasting food: in the UK, we dispose of 7m tonnes of food each year, which is just throwing 'virtual water' away. Including the water footprint as part of the food labelling might make an impact on consumers.
- Use water for appropriate purposes: we use potable water not only to drink, but to wash the car and flush the toilet. Greywater – waste water from household activities such as washing and cooking – and alternative technologies need to become higher priorities.
Figure 1: Total water requirement for different food sources
Water use can also be reduced by innovation, in which the agricultural sector has an excellent record, with significant progress having been made in developing drought-resistant crops. For instance, Syngenta hybrid corn has been genetically modified to grow in water-stressed areas, and commercial planting is due to begin this year.
A new variety of the grain sorghum has also been developed in India with a deeper and more fibrous root system than maize and a waxy coating on its leaves. These features allow it to withstand periods of water stress and produce 7 tonnes/ha.
Global water use is the equivalent of the annual flow of the Amazon, the world’s largest river
Research at Harper Adams University in Shropshire is looking at the role of anti-transpirants in helping plants resist drought at crucial stages of their growth without reducing the yield. Genetically modified crops are also achieving results – there is evidence that some have a lower requirement for water.
There are also healthy improvements in livestock production. Aviagen, which breeds more than 50% of the world’s broilers, is developing its lifetime feed conversion ratio modelling to produce breeds of poultry that perform as well as or better than current breeds but using less water.
The most significant advances will continue to derive from attention to detail, and that is where precision agriculture – the fusion of information, skills and technology – will be critical. By bringing sensitivity to the timing and accuracy of input of water, fertilisers and sprays, farmers are able to apply their husbandry skills for the maximum benefit in managing their resources. Variable rate irrigation has been shown to save up to 50% of water in practical trials in the Canterbury Plains area of New Zealand.
More efficient resource use
The urban wastewater systems of the 21st century are significantly more reliable in removing contaminants. Israel sets the recycling benchmark high, reclaiming 100% of wastewater for non-potable uses, with a significant amount going into crop irrigation. In Spain and Italy, more than 4,000ha of various crops are irrigated using recycled water.
Recycling water on farms has some potential. Trickle water is used to control temperature in intensive broiler houses in Australia, and condensing water is captured after evaporative cooling and then recycled by the ventilation and cooling system.
Rainwater harvesting and other infrastructure provision should attract tax allowances to encourage sound, efficient water use, while advocacy of whole-farm planning should include water use as best practice, promoted through education and advisory services for farmers.
For an example of re-use, British Sugar is hard to better. At Wissington in Norfolk, in the world’s largest sugar beet factory, hot water that is a by-product of the combined heat and power system is fed through almost 400km of piping to greenhouses producing 140m tomatoes per year. The crop is irrigated by rainwater harvesting from 18ha of roofs.
Creating more water resources
The appliance of science and technology has seen considerable advances in accessing new sources of freshwater.
- Desalination: a significant reduction in the costs of desalination is due to improved membrane technology in the reverse osmosis process as well as a reduction of about a third in energy requirements since the 1970s. However, the major leap forward is the use of renewable energy, principally solar power.
In the Middle East, 70% of freshwater resources are derived from desalination. Globally, the consultancy Frost & Sullivan forecasts that the number of desalination plants will have doubled by 2019 from the current 13,000 to 26,000, as a result of water scarcity. The $1bn investment in the Carlsbad desalination plant near Los Angeles has been driven by 5 years of drought in California.
- Growing salt-tolerant crops: with 1bn ha of salinised soil worldwide, there is potential in growing crops that can withstand these salty conditions. Potatoes have been grown successfully in trials in the Netherlands, but the International Center for Biosaline Agriculture in Dubai is leading the field. Salt does, of course, accumulate in soils that are irrigated – 21% of irrigated land is subject to salt damage.
- Rainmakers: the US National Academy of Sciences says searching for ways to enhance precipitation is one of the most important challenges that can be tackled by science; the United Arab Emirates is developing innovative solutions to drought, concentrating on cloud-seeding techniques.
The World Economic Forum has stated: 'Water now presents the highest risk to the world over the next 10 years'
The future is bristling with new ideas – as, indeed, it must if we are to tackle some of the key challenges of feeding the global population by 2050. Predominant among these, with the presumption that it will exacerbate rather than quell the prognosis, is climate change, and its inextricable links to accelerating the water cycle.
Is the world taking heed?
In September 2015, the UN adopted its new Sustainable Development Goals (SDGs) as part of Transforming the World: The 2030 Agenda for Sustainable Development. There is a goal specifically dealing with 'water' and all but 3 of the remaining 16 SDGs have a direct or implied reference to water resources or water quality.
The World Economic Forum has stated that:
'Water shortage now presents the highest risk to the world over the next 10 years'.
The salient point is that prior to 2012, it did not even feature in the Forum’s top 20 risks.
Bruce Keith is President of the Chartered Institution of Water and Environmental Management and a past chair of the RICS Rural Faculty Board
- Related competencies include Management of the natural environment and landscape, Sustainability
- This feature is taken from the RICS Land journal (March/April 2017)