Optimal Design and Evaluation Procedures for Drip Irrigation System

Abstract

The main objective of the present study was to develop decision support algorithm to design and select the most feasible sizes of pipes of irrigation network, it is written in Visual Basic 6.0, runs in a Windows environment, and uses a database with information on emitters and pipes available in the market, as well as on crops, soils and the systems under design. The design procedure is composed of mathematical design module and a linear optimization module. The mathematical design is based on hydraulics of flow in pipes, soil characters and crop water demand. The linear optimization module is presented to improve the technical design by optimizing size of network pipes using economic criteria. The module 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. User friendly windows are adopted for handling the databases and to manage the sub-models. The model allows creating and comparing a set of design alternatives relative to the pipe system and the emitters, consequently the model is applied, validated and verified by running it for three hypothetical textbook test cases and by comparing its results with data obtained from an existing farm located in Khartoum-North-Sudan. The performance of the drip system in the existing farm is evaluated by determining water distribution uniformity and variations of discharge in the network. The results indicate good distribution uniformity but high variation in discharge along the network. Hence the model was applied to optimize design and operating parameters of the farm irrigation system. In all of the tested cases application of the model III resulted in significant reduction in costs of the sizes of the pipes. Sensitivity analysis is made for the mathematical design module to determine hydraulic and operational limitations imposed on the system due to variations on pump total dynamic head, discharge at network nodes, time of irrigation, number of emitters and water requirement.