(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 (...

(a) Outline map of West Africa (features to show)

• (i) Area with less than four months of rain: shade the far north (Sahel/Sahara margin), e.g. northern Mali/Niger/northern Nigeria, where the short rainy season lasts under four months.
• (ii) Area with rainfall all year round: shade the southern coastal belt near the Equator, e.g. the Guinea coast/Niger Delta and the mountains of Cameroon, which have rain in every month.
• (iii) Position of the high-pressure belt in January: draw the continental high pressure (with the ITD/ITCZ pushed south, near the coast) lying over the Sahara in the north, from which the dry north-east trades (Harmattan) blow.

(b) Three reasons for the length of the rainy season in the dry north (a)(i)

• The area lies far inland/far north, away from the sea, so it is reached by the moist maritime south-west monsoon for only a short part of the year.
• The rain-bearing ITD (Inter-Tropical Discontinuity) reaches it only briefly around July-August before retreating southward, giving a short single rainy season.
• For most of the year the dry, dust-laden north-east trade winds (Harmattan) dominate, keeping the area dry and shortening the rains.

(c) Three problems rainfall poses to agriculture in the wet coastal south (a)(ii)

• Heavy, continuous rain causes serious soil erosion and leaching, washing away nutrients and lowering soil fertility.
• Excessive moisture encourages pests, weeds and crop diseases (fungal rots) and hinders the drying and storage of harvested crops.
• Waterlogging and flooding damage crops, and the lack of a dry season makes it hard to grow crops that need a dry spell to ripen and makes farm operations difficult.