Umbrella

Umbrellas improve the quality of life in Africa. As this photograph of some Rwandese women shows, umbrellas are used to protect against both tropical sun and rain: the shelter they provide from the elements is essential.

The pictures tells another story, too. Whether umbrellas are used as parapluies or parasols, it is good to see that unsold and unwanted golf umbrellas find a useful home in the poorer countries of the world.

In fact, umbrellas are more often than not used as parasols. Their utility in tropical rain storms, frequently accompanied by high winds, is limited. The sheer intensity of the rain, thundering down in huge drops, makes it difficult to avoid being soaked even with the protection of an umbrella, courtesy of the splash factor as heavy raindrops explode on impact with the ground.

Water management is a challenge across most of the African continent. In most of East & Southern Africa, long dry spells are punctuated with monsoon rains, occasionally with catastrophic consequences. Most recently, heavy rain across East Africa has caused fatal landslides in both Kenya and Uganda, in locations where deforestation and cultivation on steep hillsides has weakened soil structures.

African farmers frequently bemoan poor rainfall, yet in fact most parts of East Africa have significantly higher annual rainfall levels than most of Europe. Poor water storage and utilisation, rather than absolute rainfall, is the real problem, though high ambient temperatures, altitude and low humidity also mean that water evaporation rates are much quicker. This fact was brought home to me during my spell with Tanwat (Tanganyika Wattle Company) in Njombe, SW Tanzania, where the establishment of a 600 hectare tea estate (Kibena Tea) relied on irrigation to achieve high volumes of green leaf. The water source for Kibena Tea was the Lihogosa wetland in the centre of the estate, dammed at one end to prevent rainwater from draining away too rapidly. The design was simple and, based on annual rainfall expectations, ought to have provided sufficient water for dry season irrigation, but the theory suffered from two errors in assumptions.

First, the designers had made the understandable but naive assumption that the Lihogosa annual rainfall would be the same as at the Tanwat Head Office. a few kilometres down the road. In fact, it turned out to be about 10% lower. Second, the wetland's water level fell by about 60 cm due to evaporation during the dry season, meaning that substantially less water than anticipated was available.

Tanwat's managers and advisors considered numerous solutions - some serious, some in jest - to deal with this intractable problem. Boreholes, improved irrigation technologies, raising the height of the dam.... and one, unforgettable, suggestion of covering the swamp with ping-pong balls to slow down evaporation. We didn't think of it at the time, but maybe a giant umbrella would have done the trick!