Theory question 111
West Africa and ECOWAS(a) On an outline map of West Africa, show (i) one area having less than four months of rainfall annually (ii) one area having rainfall all the year round (iii) the position of the high pressure belt in January
(b) Give three reasons for the length of the rainy season in (a)(i) above
(c) Explain three problems that rainfall may pose to agriculture in (a)(ii) above
Show the model answer
(a) Map: (i) Sahel – e.g. northern Niger, Mali, Mauritania/far north of Nigeria; (ii) coastal areas – e.g. SE Nigeria (Calabar), Liberia/Sierra Leone coast; (iii) sub-tropical high pressure over the Sahara (about 20-30°N)
(b) Far from the sea, so moist SW winds arrive late and leave early; the ITD reaches it only briefly in July-August; dominated by dry NE trade winds (harmattan) most of the year; high pressure and descending air over the Sahara
(c) Leaching of nutrients and acidic, infertile soils; soil erosion and flooding; waterlogging; difficulty drying and storing crops, rotting; pests and diseases thrive in humid conditions; weeds grow fast; hard to use machines on wet ground
Relate the short rainy season to the movement of the ITD.