Take a walk through the narrow streets of Sana'a, capital of Yemen and you'll come across the last remaining radish gardens. These small bursts of greenery amidst the desert dust are all that remain of a system that once fed and watered the city. At the height of Arabic science and ingenuity elaborate irrigation systems brought water into the mosques to wash the faithful. The used water was then diverted into large gardens of fabulous fertility.

Today Yemen is on the verge of a humanitarian crisis provoked largely by a chronic shortage of water. A fast expanding population coupled with a diversion of scarce water for the production of the narcotic drug, Khat has pushed the country's water supply to the limit. Reporter Leana Hosea has visited Yemen to find out if the wisdom of the Arabic engineers of the past can help bring water back to this parched nation.

Producer: Alasdair Cross.