The optimal design of distribution systems is a multi-objective process involving cost and performance. Reliability is one of the indicators used to quantify the performance of water distribution systems. In on-demand pressurized irrigation systems, different groups of hydrants operate simultaneously, generating variability in flow regimes, and can lead to uncertainties in water demand and in the pressure head available at the nodes. Based on these considerations, a new approach for computing the optimal irrigation network is presented considering: i) the stochastic variability of the discharges flowing into each section of the network; ii) the reliability of the pressure head at each hydrant, as performance indicator, iii) the variation of the on-farm uniformity distribution, and iv) the cost of the network.
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The model was applied to three Italian irrigation networks of different size (large, medium and small) and the results were compared with the same networks computed using the Clément and FAO models. The new approach showed an important cost reduction without any significant decrease in the system reliability.
