Saturday, July 17, 1999 Published at 22:07 GMT 23:07 UK
Food at risk as water drips away
Irrigation in Slovenia: When the water dries up, the crops will wither
By Environment Correspondent Alex Kirby
A US conservation group says the world's impending water shortage could reduce global food supplies by more than 10%.
The group, the Worldwatch Institute, based in Washington DC, says the shortage could lead not only to hunger but also to civil unrest and war.
Sandra Postel is the author of a book published by the institute on the water crisis, entitled: "Pillar of Sand: Can the Irrigation Miracle Last?"
Heavy reliance on irrigation
She says: "Without increasing water productivity in irrigation, major food-producing regions will not have enough water to sustain crop production."
Postel says in the book that one threat to the productivity of irrigation is excessive pumping of groundwater from subterranean aquifers.
Earlier research by Worldwatch illustrated the scale of the problem:
Two further problems are the growing diversion of irrigation water for use in cities, and the build-up of salinity in the soil.
The book says there is an annual "water deficit" of about 160 billion cubic metres - enough to produce nearly 10% of the world's grain.
Countries which are short of water are buying more and more on the world grain market.
Jordan imports 91% of its supplies from abroad, Israel 87%, Saudi Arabia 50% and Egypt 40%.
One region that relies heavily on irrigation is north-east Africa. There, Worldwatch says, competition for the waters of the Nile will get fiercer.
The total population of Ethiopia, Sudan and Egypt stands at 157m today.
By 2050 it is projected to reach 388m.
A mix of strategies
Postel says the world needs a "blue revolution" to double water productivity in the next 30 years.
She says drip irrigation systems, which deliver water straight to the plant's roots, can cut water use by from 30-70%.
They also raise crop yields significantly, and are in use in the US, Europe and Asia.
Farmers in Texas have improved their water efficiency to more than 90% by using efficient sprinklers.
And Malaysian rice farmers have cut water wastage by almost half by planning irrigation better, shoring up canals, and sowing seeds directly in the field rather than transplanting seedlings.