Energy is required for pumping water in the irrigation pipe distribution networks. The need for this energy and its cost are continuously increasing due to the on-going expansion of the Arab countries in general and the Gulf countries in particular in using modern irrigation systems in their agricultural irrigation projects. Most pumped pipe-networks designed on hydraulic basis only without paying attention to the cost of power, thus huge loss in energy and capital needed for projects operation occur Sometimes. The design is based on economical basis without taking hydraulic aspects into consideration which results in low performance efficiency of the system or damage to the pipe network and consequently high maintenance costs.
The paper presents computerized mathematical model for optimal design of main pipe distribution networks of sprinkler irrigation system using linear programming. The pressure head at the inlet of the pipe distribution network is assumed unknown, thus the objective is to minimize the sum of the initial cost of the pipe network and the cost of energy for pumping.
The constraints included the minimum and maximum pressure head at all points along the pipes of the network in addition to the flow rates requirements within the network and at the inlet of each farm .
The study revealed that using the proposed model in the design assuming unknown inlet pressure head to system has resulted in 9.32% saving in the total cost of the network compared to the existing design which is based on known inlet pressure head for a selected irrigation sector inside a large planned irrigation project near Mosul city, northern Iraq.
Key words: Optimal Economical Design, Irrigation Pipe Network.