Optimizing the Outlet Distribution of Pipeline Irrigation for Rotation Irrigation with Hydraulic Loss in Consideration

Abstract

【Background】Low-pressure pipeline using pipes in lieu of open channels to convey water is a water-saving irrigation technology as it reduces leakage and evaporation. Low-pressure pipeline irrigation has been well documented and rolled-up in China, from dry farmlands in the north to paddy fields in the south, from well-irrigated areas to surface-water irrigated regions, from plain areas to hilly terrains. With the development in automation and the reduced cost of control systems, control of the outlets of the irrigation system has become more automatic. Modeling hydraulic dynamics at the outlets so as to optimize the outlet is hence required. 【Objective】We present a method in this paper to optimize outlet distribution of the low-pressure pipeline system for rotation irrigation with hydraulic head loss in the system being taken into account, aimed to meet the demand for water flow rate while in the meantime reduce the costs of electricity usage. 【Method】The optimization is to determine the hydraulic loss under different outlets so as to find their relationship with the inlet pressure in the pipeline network; it also considered hydraulic head loss in the system. The equivalent hydraulic loss coefficient of the pipeline inlet was calculated using a binary variable as independent variable, and calculation of the equivalent hydraulic loss coefficient of the pipeline inlet started from the end of the pipeline using the deduced - recurrence formula. The objective of the optimization is to minimize the energy used by the rotation irrigation, with water flow rate fixed. The genetic algorithm and the coding scheme were used to solve the optimization, in which the irrigation group numbers at each water outlet were taken as the optimization variables, with a constraint that each outlet can only run one irrigation group. 【Result】The energy required for the equal interval arrangement in the rotation irrigation was minimized, and the optimized results show that the optimized hydraulic loss coefficient could be reduced by 0.772 times compared to that obtained without optimization. 【Conclusion】The recursive formula for calculating the hydraulic loss at each outlet can take infinite or bounded parameters without producing singular values. The model can be combined with constant flow optimization; it is also suitable for non-equal spaced branch pipes with different diameters, with the head loss coefficient for each branch pipe calculated separately.

Keywords

• rotation irrigation
• hydraulic loss
• model
• genetic algorithm