Theory question 111
Geography of Africa(a) Describe the methods of irrigation agriculture in either the Nile Valley or the Niger Valley
(b) Give reasons for the irrigation agriculture in any one of the river valleys
(c) Discuss the problems associated with irrigation agriculture in the river valley you have chosen above
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Nile valley:
(a) Basin (flood) irrigation – flood water held in embanked basins; perennial irrigation – dams/barrages (Aswan High Dam, Sennar) store water fed through canals all year; shaduf, sakia (water wheel), Archimedean screw; diesel pumps
(b) Desert climate with little rain; high evaporation; rich alluvial soils; large population needing food; cash crops (cotton) for export; reliable river water
(c) Salinisation and waterlogging; loss of silt behind dams so fertilisers are needed; water-borne diseases (bilharzia, malaria); high cost of dams and canals; silting of reservoirs; seepage and evaporation losses; disputes over Nile water
Choose one valley and keep (a)-(c) to it.