The UN's food agency marked World Water Day on Tuesday by calling for new and innovative approaches to ensuring city dwellers in developing countries have access to safe and adequate water supplies.

"Ensuring access to nutritious, affordable food for the poorer of these city-dwellers is emerging as a real challenge," Alexander Mueller, a Food and Agricultural Organisation (FAO) spokesman said in a statement.

"Within the next 20 years, 60 percent of the world's population will live in cities, with most urban expansion taking place in the developing world," the assistant head of Natural Resources said.

The Rome-based FAO warned that increased water supplies will be needed by growing city populations for drinking, washing and cooking, as well as for expanding marketplaces, agro-industry and food processing operations.

"This array of pressures on urban water supplies requires non-conventional alternatives to creating more resilient cities," Mueller said.

Rainwater harvesting in cities holds great potential for urban agriculture, the FAO said, but is an idea relatively untapped so far.

Many low-income city-dwellers have long relied on backyard gardens or chicken coops as a way to supplement their incomes and feed their families.

Urban residents, who purchase rather than grow their own food, are especially vulnerable to increases in food prices, which in turn has seen a return to traditional practises of cultivating food in urban settings, the agency said.

"Right now, farmers and cities are competing for water. Cities are using water then putting it back out, polluting the environment," Javier Mateo-Sagasta, a specialist with FAO's Water Unit, said in the statement.

"It would make so much more sense if more of the water used in the cities was then cleaned and re-used in agriculture," he said.

FAO said it is working with its member countries to explore options for water re-use, pointing out that in Tunisia, where treatment infrastructure is well established, 30-40 percent of purified wastewater is used in agriculture.

Farmers in the Tula Valley, downstream from Mexico City, irrigate 90,000 hectares of land using yearly 1 500 million cubic meters of untreated municipal wastewater.

earlier related report
UN calls for action on water, slums crisis in cities
Cape Town (AFP) March 22, 2011 - The world needs to act immediately to tackle an urban crisis of growing city slums that lack water and sanitation, a top UN official warned Tuesday on World Water Day.

"We have a crisis, we must recognise that," Joan Clos, UN Habitat executive director, told an event marking the day.

"We need to act now. This is a common action at the same time against the slums and against lack of water and sanitation. It's the same problem, it's the same solution: urban planning."

Targets set by the UN poverty-reduction Millennium Development Goals had seen improvements but unplanned urbanisation and unprecedented migration to cities have expanded slums without basic services.

"In general, more or less, everything is improving. But in the urban environment in some parts of the world and in Africa in particular we are facing a crisis. Things are not improving, they are worsening," said Clos.

According to the United Nations, 27 percent of the world's city dwellers in the developing world lives without piped water at home, while proper sanitation faces even greater challenges.

A UN report on Monday said 400 million of Africa's one billion people live in cities, a number projected to rise to over 1.2 billion by 2050.

Sixty percent live in slums, with those without safe drinking water at over 55 million and some 175 million without reasonable sanitation in 2008.