Marked each year on March 22, the United Nations hopes the 2012 event will focus attention on water's critical role in feeding the world.
The U.N. Food and Agriculture Organization (FAO) says the world will have to produce up to 70 percent more food to feed a global population expected to reach 9 billion people by 2050, from the current 7 billion. That will require better management of water, boosting farmers’ resilience to climate shifts, and cutting food and water waste.
Water consumption by agriculture is estimated to rise 19 percent by 2050, but the figure could be much higher if crop yields and production efficiency don't improve dramatically, warns the latest U.N. World Water Development Report.
Water scarcity already affects more than 40 percent of people on the planet, and two-thirds could be living under water-stressed conditions by 2025, according to the FAO.
"Agriculture has to be more efficient in water use - which means more crop per drop - otherwise the demand cannot be met and we will run into a big, big competition between water for agriculture, water for industrial purposes and water for municipalities," Alexander Müller, FAO's assistant director-general for natural resources and the environment, told journalists at the World Water Forum in Marseille, Paris, last week.
"If we don't find solutions for water and agriculture, we will not find solutions for the other sectors," he added.
In a guide to water and food security issues for World Water Day, the FAO points out that farm irrigation accounts for 70 percent of all water withdrawn from "blue water" sources such as rivers, lakes and aquifers. Only a fifth of the world's cultivated land is irrigated, but it contributes 40 percent of total food production.
Gao Zhanyi, president of the International Commission on Irrigation and Drainage, said this makes agriculture a vulnerable sector. "With the rapid development of urbanisation and industry, a lot of water previously used for irrigation in agriculture is now shifting to other sectors... So we have to use non-conventional water," he urged.
Non-conventional sources include water that is safe for reuse, treated waste water and desalinated water. Over 80 percent of waste water worldwide is not collected or treated, according to the U.N. water report.
ADAPTING TO CLIMATE CHANGE
Climate change is clouding the outlook further, because its main impacts are on water resources, the FAO says. A warming planet is widely predicted to result in more extreme weather patterns, bringing more frequent and intense droughts, flooding and heavy rainfall events. And the Mediterranean Basin and semi-arid areas of the Americas, southern Africa and Australia are expected to experience further reductions in water availability and quality.