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Water EES A07

LECTURE 11 The Future of Our Water Resources

International Water Management Institute in Sri Lanka Predictions
– Maps of areas that will most likely suffer from physical and economic water scarcity in 2025
(economic water scarcity means that shortage of water leads to negative consequences in the economic development)


? Water resources (WR) are still fundamentally the precipitation that falls upon the continents ? Only this amount of water is continually renewed and can thus be used sustainably ? Using our WR to produce good and services ( are becoming increasingly restricted ? Competition between humans and nature for WR is becoming more and more severe – means that humans would be fighting against their own life support

“Our Planet: How Much More Can Earth Take?” Jill J?ger (2007)
? 300years of unprecedented and uncontrolled growth behind us (for example massive land-use changes)

? One thing is clear: neither enough room nor enough resources available on Earth to allow further growth in the same way as the last 300 years
? What do we suspect that the future will bring?
– Climate change will continue – Further increase in population

? Climate change
– 2-5°C warmer than now – Precipitation will become more extreme – How the precipitation distribution on earth will change (on the continents will decrease or increase and what effects will have on WR)

? Population growth
– 1.2% annual population growth rate or 78 million people must be taken care of each year – 2050 will be around 9.5 billion people but the annual growth will only be 0.5 or 48 million people must take care – 2075 around 11 billion people – Two developments:
? More education and information that prosperity can be or can only be achieved by having fewer children ? More freedom for women to participate in deciding how many children they want

? The challenge for the future sustainable use of the water resources will be decided by food production
? Three questions arise :
– How much water is needed, in order to ensure the future food supply? – Which water will be used in the future to produce the additional food? Will it be irrigation water- blue water, or natural precipitation, i.e. green water? – Can improved use of the water resources defuse the conflict between agriculture and nature?

How Much Water We Will Need in the Future?
? Two tasks:
– We must end hunger by 2050 – The additional people must be provided with food (2050 - 9.5 billion people so 3 billion additional people)

? Green water flow by 2050 (km3/year)
– Present food supply – 7800 km3/year – Eradication of hunger – 2200 km3/year – Food supply for an additional 3 billion people – 3900 km3/year

– TOTAL = 13,900 km3/year or Earth’s life-support system must provide an additional 6100 km3/year

Where will the additional water come from?
? Use more blue water for irrigation (assumes
that there is enough blue water available) – Initially is taken from rivers – Now is increasingly extracted from the groundwater
(will come from fossil groundwater at ever-increasing depths)

? Can the irrigated areas be expanded?
– More than half of today’s irrigated areas are in Asia, mostly China and India – The increase in the next thirty years is estimated at only 0.6% per year (reasons salinization and falling groundwater levels) – the amount of water is estimated from 600- 800 km3/year (700 average) or 1/10 of 6100 km3/year – Saudi Arabia and Lybia already extract a large part of their irrigation water from fossil groundwater 8

– Due to increase in temperature (climate change), permafrost regions will thaw and the vegetation belt will move north.
? Problem will be low solar radiation and short vegetation periods will only allow low yields and thus low agriculturally-used green water ? In other regions e.g. the Mediterranean climate change will cause accelerated desertification


? What to do?
– Expansion of rain-fed agriculture (is there any
room to further expend the areas under rain-fed agriculture?)

– Diverting the water from neighboring ecosystems to the field (for example:
clearing a forest and using the water that would then be part of the surface flow, to irrigate new fields nearby)

? Brazil is planning to massively expend the production of ethanol from sugar cane in the next 25 years (thus less green water for natural system and food production)


Using water better: more crop per drop
? Use of blue and green water at today’s level or even at a lower level and to produce twice the amount of food (will be hard!) ? Different farm types have different yields (farms in African savanna)
– Small farms – Normal farms – Model farms (use rain, less fertilizers, localavailable technologies) – Commercial farms (European standards)
Yield increases


? Doubling of food production without requiring more green water or more efficient use of precipitation: – Increasing yields in rain-fed agriculture using genetically engineering plants – To breed for a higher harvest index, which is the fraction of the plant that is grain, in the biomass produced – Channeling more green water through the plants and decreasing evaporation from the ground (e.g. dense plant coverage)

– In total 1500 km3/year can be saved

through “more crop per drop”


Final Calculation
? 3900 km3/year of green water flow remains to
be provided (6100- 700-1500 = 3900 km3/year)



Ways to Achieve the Sustainable Use of Water Resources
? The Challenge to find an additional green water flow of 3900 km3/year without damaging the Earth’s life – support system

? We need: To realize the Earth is the whole entity and to learn how to go beyond national and cultural borders ? A few ways:
– Experts from various disciplines seek solutions together (e.g. integration gains in different regions through combined land and water management) – Area expansion (Will people do it anyway?), also more ocean area being used - aquaculture – Increased usage of water-surplus areas and trade with virtual water (Europe, US, Canada, Russia and Ukraine can produce surplus food)



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