The principal tasks included in the terms of reference for the supplementary study are summarised below: ol; liUndertake a topographical survey of the whole project area and beyond its boundary, by up to 500 m where necessary. /li; liCarry out a semi-detailed soil survey of the project area including comprehensive in situ and laboratory analyses of soil and water samples./li; li Review the hydrology of the Juba river with particular regard to' the low flow periods and project flooding and the influence of Bardheere dam on the project. /li; liCarry out a preliminary design of the irrigation and drainage system including layout drawings, canal and drain longitudinal and cross-sections, flood protection details, pump station design, typical structure drawings and preliminary details of project infrastructure./li; /ol

This annex examines the economic and agricultural background in Somalia, and discusses the marketing mechanisms and financial and economic crop prices. Economic models for the project are constructed and analyzed, and the recommended model is discussed in detail

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.

This volume gives results of a semi-detailed soil survey carried out over a total gross area of 9,559 ha of the Mogambo irrigation project area. The report aims to extend the results of earlier studies on soils in the area . This is achieved by a more detailed observation network of survey sites in the area in particular within the Juba alluvial sails (five sites/km2). It also provides more quantitative data on the soil chemical and physical properties as an additional aid in soil classification for planning the development of irrigation in the area. Soil units identified are described in terms of modal characteristics and the variation found within the unit with profile descriptions for a11 pits and selected auger holes included in Appendices II and III. The nature of the mapped boundaries is fully described. The land was classified making use of the United States Bureau of Reclamation (USBR) methods, modified to suit the conditions found in the area. Suitability for rice and for field crops other than rice were considered separately and special use Class 4 was used to indicate areas more suitable for sprinkler development. Limitations affecting land suitability are denoted by the use of suitable land class suffix letters.

The goal of the project is to strengthen the capability of the water Development Agency of the Government of Somalia to design and implement a national water resource development program. The Project will assist in the collection of adequate national hydrogeologic, economic and social data and will provide technical assistance and commodities for a production drilling program. Data collected under the will enable the National Water Cormnittee (NWC) to establish priorities for a rational approach to national water resource development

In this report, written after a visit to Somalia to evaluate irrigation potential, the hydrometric data base is questioned as regards both its validity and its representativity. Steps to improve the basic data are proposed which include technical assistance to check and re-establish station ratings over a period of one year. The design plan of the juba high dam is discussed and attention drawn to the necessity of seeking the best professional advice to determine this parameter which has a direct bearing upon the safety and the cost of the dam. Present and proposed irrigation in the Shebelle and Juba valleys are examined.

The terms of reference for this Additional Study called for two alternatives (A and B) to be investigated. The development for alternative A has been based on the proposals of the Supplementary Study and allows for future expansion to the full area. The development for alternative B has been chosen as the beat area to be implemented independently of any future expansion. Alternative A identifies 2 052 ha net of surface irrigation and 163 ha net of overhead irrigation, and alternative B Identifies 1,809 ha net of surface irrigation end 122 ha net of overhead irrigation.