In Upper Volta and in the five other West African countries that form the Sahel - the semi-desert fringe south of the Sahara - the winter rains have failed yet again. For seven winters the rain has been too sparso to refill the water holes and rivers that make life possible in this arid region. Many experts believe the Sahara is in the process of marching South and that it will eventually engulf the whole of the Sahara and deprive the twenty million people who live there of their livelihood.

Upper Volte is listed by the United Nations as being among the 25 poorest nations on Earth. Its five and a half million people are predominantly farmers. Their main source of income is animal farming - beef and mutton. Last year one hundred and fifty thousand of Upper Volta's cattle died. This year, unless the rains miraculously return, far more will die. The effect is cumulative. Each succeeding drought multiplies the effect of the previous one. The water table is now so low that wells that have held water throughout living memory, are now dry.

To the North of Upper Volta, in Mali, the drought is even more harsh. Thousands of the country's nomadic tribesmen have been forced to drive their herds south into the already over-crowded grazing lands of Upper Volta. So, the effects of the drought are being magnified by over-grazing. The ground cover that holds the moisture in the soil is being eaten away.

Without massive international aid in the last two years millions of people would have starved in the Sahel. During 1973 international relief organisations shipped in half a million tons of grain. This year, faced with another winter rain failure, UN Secretary General Kurt Waldheim has asked for another half million tons of grain for famine relief in the Sahel. Upper Volta is particularly vulnerable with only one tenuous six-hundred-mile-long rail link to the sea at Abijan. The railway can carry no more than fifteen hundred tons a week.