(a) The methods of irrigation agriculture in the Nile valley are:
(i) Basin or flooding mathod - involves the seasonal flooding of the nearby lands in the Nile Valley during which the flood water is trapped and cannot flow back into the Nile Valley
(ii) Perennial Method - involves the damming of rivers to create artificial reservoirs which can supply water to irrigation canals at any time of the year
(iii) The Shaduf Method - The oldest method during which farmers collect water from river channel, either with a bucket or a water bag, and pour it on their farms.
(b) Reasons for irrigation agriculture in Nile valley are:
(i) To supply water to the soil as little or no rainfall is experienced around these areas
(ii) To fight drought as Egypt experiences desert climate
(iii) To produce crops all year round.
(c) Problems associated with irrigation agriculture in the Nile Valley are:
(i) There is the problem of fluctuation in the level of water used for irrigation purposes
(ii) Presence of excess of mineral salt like sodium which are injurious to plant growth
(iii) Over-flooding could be disastrous
(iv) Construction of many dams disturbs normal flow of water.