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The main aim of the present study is to develop optimization process of water pipe networks design through studying the effect of pipe and pump costs on the optimization process in a network with a predetermined layout. Computer simulation and analytical solutions have been used for minimizing the Capital cost of multiple-outlet pipelines of drip water distribution system composed of many pipes with different diameters, while the variation in pressure head is restricted to assure the required outlet discharge uniformity. The present study focuses on developing a cost function design model for pump-pipelines system with emitters distributed along the pipelines. The model has been developed to support the design of micro irrigation systems and to advise farmers to improve drip system performance .The procedure uses the linear programming, in which pipe length with commercial pipe diameter is used as optimum variable and the factors affecting the pressure head along multiple-outlet pipelines are considered. The objective function, to obtain the optimal diameter of each pipe, is based on the capital cost of the piping system, pumps and the cost of energy required for operating the system. The model consists of an objective function that maximizes profit at the farm level, subject to appropriate geometric and hydraulic constraints. The main items considered affecting cost were: operating pressure within the network, the pipe diameter, and the pumping cost which include pumping station and energy. The hydraulic and operational limitations imposed on the system are: limiting maximum and minimum velocity, permissible pipe pressure, defined pressure at outlets, and defined discharge at selected points. Model solution employ WINQSB 6.0, and uses Excel database with information on emitters and pipes available in the market, as well as on crops, soils and the systems under design. The solution procedure is based on an iterative scheme and examined two case studies. Results obtained indicate model capability to cut down costs of pipes as compared to conventional design method.
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