Nelly Bassily | August 25, 2008
If you walk through the streets of Accra, don’t be surprised to see heads of lettuce sprouting beneath power lines or cassava growing in culverts. The urban landscape is becoming increasingly green, and Ghanaians are increasingly eating fruits and vegetables grown in cities.
This is what’s known as urban agriculture, and it’s being welcomed across Africa, where nearly all countries face food shortages. But urban agriculture has its own scarcity problems – particularly a shortage of clean water.
Many of the crops grown by urban farmers are irrigated with wastewater from household or industrial use, or a mix of the two. Not all of this wastewater is safe. As a result, some fruits and vegetables grown in cities are actually unsuitable for human consumption.
Karim Salifou moved from the countryside to Ghana’s capital to look for work. When he couldn’t find a job, he started growing lettuce to sell in the market. Mr. Salifou has only one source of water for his crops, a polluted pond. He has seen the water quality in the pond deteriorate. People used to fish in the pond, but now it’s filled with chemicals that have killed the fish and made the water unsafe to drink.
A new study on the use of wastewater in agriculture in developing countries was released by the International Water Management Institute, or IWMI, last week. The report revealed that wastewater is most often used in the production of vegetables and cereals. This leads to health risks for consumers, especially in the case of vegetables which are consumed raw.
Liqa Raschid-Sally is a researcher with IWMI. She says that in 70 per cent of the 53 cities studied, industrial wastewater was not treated, but was returned directly to lakes and streams. Ms. Raschid-Sally says the serious risks associated with industrial wastewater are not well known to the general public.
At the same time, urban crops irrigated with wastewater account for a significant portion of the food supply in African cities. And urban agriculture provides livelihoods for many of the poorest urban dwellers.
Since clean water is in short supply, the IWMI study concludes that stopping the use of wastewater in urban agriculture would worsen food shortages. But there are ways to reduce the risks associated with consuming urban crops.
For example, in Ouagadougou, Burkina Faso, some farmers have constructed storage basins to collect wastewater from a brewery. They only use the water when they judge that the water is of acceptable quality, based on its appearance, smell, and taste.
In Ghana, many farmers stock wastewater in ponds, allowing solid materials to settle to the bottom. This method reduces the level of bacteria in the water.
Around the globe, some 200 million farmers irrigate their crops with wastewater.