The Mogambo project is situated in the Lower Juba basin. The climate is semi-arid and annual average rainfall is only about SO0 mm per year. Almost all crop water requirements are met from the Juba river. Chapter 3 summarizes crop water requirements for the Mogambo project and other developments planned for the next 10 years and gives incremental water usages expected in the immediate, short and medium terms. An analysis of river flows expected in each month at various locations is reported in Chapter 4. These water availability are compared with incremental future water uses, which take account of all medium-term development on the Juba, to give the net availabilities at Mogambo. Drainage rates from cropped areas are discussed in Chapter 5, using daily water balances and allowing for rainfall, infiltration and evaporation.