Limited on-demand water delivery as a managerial strategy to enhance operational flexibility in pressurized irrigation networks

Implementing fully on-demand irrigation in existing rotational networks often requires extensive and costly infrastructure rehabilitation, limiting its practical applicability in many irrigation systems. Therefore, identifying operational strategies capable of improving delivery flexibility without major structural modification remains a critical challenge. In this study, limited on-demand operation was evaluated as an intermediate operational strategy for two pressurized drip irrigation networks in Iran operating under rotational water distribution systems: the gravity-fed Ziviyeh network and the pump-supplied Lali network. Hydraulic performance under different operational scenarios was simulated using the COPAM modeling framework, while network flexibility was evaluated using the Delivery Flexibility Index (DFI). The results showed that neither network could reliably support fully on-demand operation under existing conditions because the minimum required hydrant pressure was satisfied in only 10% and 13% of operational combinations in the Ziviyeh and Lali networks, respectively. In addition, pressure-deficit conditions affected approximately 26% and 27% of hydrants in the Ziviyeh and Lali networks, respectively, under a 90% probability of occurrence. However, under limited on-demand operation, pressure deficits occurred in less than 2% of hydrants for DFI values up to 3 in the Ziviyeh network and 4.5 in the Lali network, while hydraulic reliability remained within acceptable limits. These findings demonstrate that DFI-based operational management can substantially improve delivery flexibility without requiring physical infrastructure upgrades. The proposed approach provides a practical and economically feasible transitional modernization strategy for pressurized irrigation networks operating under water-scarcity and financial constraints.